Options for Home Oxygen Therapy Equipment: Storage and ... · able for home oxygen therapy. Each new home oxygen system has a different performance characteristic, with capabilities

Options for Home Oxygen Therapy Equipment:Storage and Metering of Oxygen in the Home

Robert W McCoy RRT FAARC

IntroductionEvolution of Home Oxygen EquipmentHome Oxygen: Equipment Economic IssuesOxygen Equipment: From Hospital to HomeHome Oxygen: Drug or Device?Home Oxygen: A Mobility SolutionSources of Oxygen for Home Use

Oxygen Produced, Stored, and Transported by a Gas Manufacturer andHome Medical Equipment Supplier

Oxygen Produced Within the Home by Oxygen ConcentratorMetering Oxygen to the Patient

Estimate of Continuous Flow FIO2From a Nasal Cannula

Equipment OptionsCompressed Oxygen CylindersLiquid Oxygen SystemsOxygen ConcentratorsIntermittent-Flow RegulatorsOxygen MonitoringPressurized OxygenPortable Oxygen Concentrators

DiscussionHome Oxygen PrescriptionsPatient AssessmentOxygen Metering

RecommendationsSummary

Home oxygen therapy equipment options have increased over the past several decades, in responseto innovations in technology, economic pressure from third-party payers, and patient demands. Thedelivery of oxygen in the home has evolved from packaged gas systems containing 99% UnitedStates Pharmacopeia oxygen provided by continuous-flow delivery to intermittent-flow delivery,with oxygen concentrators delivering < 99% oxygen purity. The majority of published papersindicating the value of long-term oxygen therapy have been based on continuous-flow delivery of99% United States Pharmacopeia oxygen. The lack of research on new home oxygen therapydevices requires more clinical involvement from physician and respiratory therapist to evaluate theperformance of oxygen devices used in the home to ensure the patient is provided adequate oxy-genation at all activity levels. New standards of care are required to address the need to haveconsistent titration of long-term oxygen therapy to meet the patient’s home needs at all activitylevels. Consistent labeling of metering devices on home oxygen equipment will need to be developed

RESPIRATORY CARE • JANUARY 2013 VOL 58 NO 1 65

by professional medical societies to be implemented by standards organizations that direct indus-trial manufacturers. Home oxygen therapy will need professionally trained respiratory therapistsreimbursed for skills and service to ensure that patients receive optimal benefits from home oxygenequipment to improve patient outcomes and prevent complications and associated costs. Key words:oxygen; equipment; home. [Respir Care 2013;58(1):65–81. © 2013 Daedalus Enterprises]

Introduction

Patients requiring long-term oxygen therapy (LTOT)must have access to clinically effective home oxygen equip-ment that is adaptable to their needs outside the hospital.Costing less and providing for a more normal lifestyle,home oxygen therapy has evolved to a standard of care forpatients experiencing chronic hypoxemia. Going beyondstationary home devices, new oxygen equipment has beendeveloped to meet the needs both of the patient who ismore mobile and of the oxygen suppliers who are strug-gling to respond to economic pressures from payers. It isimportant to keep in mind that oxygen equipment onlystores or produces oxygen in the home. Oxygen is a drugthat requires a prescription, an effective delivery system,therapeutic dosing, and monitoring for effective therapy.Economics and patient demands are a secondary consid-eration to providing effective oxygen therapy.

Oxygen therapy is the administration of oxygen at con-centrations greater than ambient air, with the intent oftreating or preventing the symptoms and manifestations ofhypoxia (Fig. 1).1 Reviews by both Kacmarek2 and Dunne3

have provided timely updates to the current available prod-ucts for LTOT. Since those reviews, in 2000 and 2009,additional products have been introduced for use in thehome with manufacturers of home oxygen equipment fo-cusing product development on both the home medicalequipment (HME) provider’s requirements to reduced op-erating expense and the patient’s needs for mobility. Theminimal research confirming the clinical benefits and ap-plications of new home oxygen equipment suggests thatclinicians are not driving the design of these new products.

Some evidence exists on the clinical capabilities and ben-efits of several new LTOT devices, yet they are tested ona limited number of patients, and are products with onlyspecific applications.4 The focus of providing home oxy-gen equipment appears to be on the availability of anoxygen system and the process of delivery and set-up ofthat system in the patient’s home. Little comparative re-search has described the variability of home oxygen prod-ucts5 related to the patient’s disease requirements with anoverall goal of ensuring adequate patient oxygenation atall activity levels. Much of the evidence-based research forLTOT does not indicate what device was selected for pa-tient use, including a description of the oxygen equip-ment’s capabilities and limitations. These variables couldimpact the consistent delivery of oxygen and the effec-tiveness of therapy.

Patient monitoring at frequent intervals is another lim-iting factor related to ensuring the clinical benefits of LTOT,again, creating an uncertainty on whether the patient isoxygenating on a specific system at all activity levelsthroughout their course of therapy. The literature for LTOTgenerally indicates that patients were placed on oxygen ata set or equivalent flow rate, with the assumption that thepatient was oxygenating at all activity levels. If oxygen isa controller medication, as indicated by Dunne,3 more em-phasis should be placed on the assessment, prescription,and monitoring of LTOT, to gain the maximum benefitsfrom oxygen products and services. This review will de-scribe the many options available for LTOT equipmentand the variability in capability and performance, suggest-ing that, when using home oxygen equipment, clinical

Mr McCoy is affiliated with Valley Inspired Products, Apple Valley,Minnesota.

Mr McCoy presented a version of this paper at the 50th RESPIRATORY

CARE Journal Conference, “Oxygen,” held April 13–14, 2012, in San Fran-cisco, California.

Mr McCoy has disclosed relationships with Breathe Technologies, CaireMedical, and Sequal.

Correspondence: Robert W McCoy RRT FAARC, Valley Inspired Prod-ucts, 15112 Galaxie Avenue, Apple Valley MN 55124. E-mail:[email protected].

DOI: 10.4187/respcare.01932

Fig. 1. Diagram of a respiratory flow cycle in relationship to con-tinuous-flow supplemental oxygen, indicating the sections of thebreathing pattern that useful oxygen is delivered.

OPTIONS FOR HOME OXYGEN THERAPY EQUIPMENT

66 RESPIRATORY CARE • JANUARY 2013 VOL 58 NO 1

intervention is critical to gaining patient benefits and toreducing complications and comorbidities.

Evolution of Home Oxygen Equipment

Initially, pressurized cylinders were the available op-tions for oxygen therapy in the home, using the sameequipment utilized in the hospital. Cylinder capabilitiesand applications were familiar to hospital-based clinicians,so understanding of performance capabilities was not anissue when prescribing and initiating home-based LTOT.In 1965, the first home based liquid oxygen (LOX) systemwas developed to provide both a stationary and portableoxygen system for patient use within the home.6 The mainadvantages of this system were the ability to refill theportable LOX system when needed, with the system weightand operating time efficiency that surpassed the capabili-ties of compressed gas cylinders. Patients could fill theirportable system whenever needed and have the advantageof a lighter weight system capable of extended use beforerefilling. Many clinicians were not familiar with the me-chanics and operation of home LOX systems, yet thesedevices were essentially equivalent to the piped oxygensystems utilized within the hospital. Stationary oxygenconcentrators became available in 1973, allowing for thegeneration of oxygen in the home by filtering nitrogenfrom the air.7 This provided an unlimited supply of oxygento the patient, as long as electricity was available and thedevice operated within specifications.

Stationary concentrators produced a different purity ofgas (90% � 5%) than hospital oxygen. Providers of hos-pital grade oxygen have strict guidelines for the produc-tion and monitoring of oxygen, and are regulated at 99%purity. Many hospital-based clinicians assume the stan-dard of oxygen purity would apply to home-based equip-ment. During the first oxygen consensus conference it wasrecommended that, for reimbursement purposes, concen-trator oxygen was considered equivalent to 99% oxygen,allowing home oxygen providers to use concentrators with-out payment issues.8 Several studies have indicated thatclinicians should consider oxygen purity when prescribingLTOT and take into consideration the device that will beused in the home when titrating a patient for therapeuticsettings.9,10 Concentrator oxygen utilization began the trendaway from the perception that home oxygen is the same ashospital oxygen, with oxygen production variability be-coming a more important issue with concentrator minia-turization.

Now there are combinations of compressed gas, LOX,concentrator, concentrators that fill compressed gas, LOXportables, and battery operated concentrator systems avail-able for home oxygen therapy. Each new home oxygensystem has a different performance characteristic, withcapabilities and applications that are unique to the product.

Clinicians need be aware of product variability in perfor-mance when prescribing and placing a home oxygen pa-tient on a specific system. Home oxygen therapy equip-ment should not be considered a commodity for which anyhome oxygen product can be used, regardless of the ther-apeutic objectives for the individual patient.

Home Oxygen: Equipment Economic Issues

The key driver that has impacted the development ofhome oxygen equipment has been the economic pressuresrelated to reimbursement for LTOT.11 Payers of home ox-ygen equipment have a different perspective related toreimbursement for LTOT, and have reduced reimburse-ment continually over the last 2 decades, focusing on theavailability of oxygen equipment as opposed to effectivepatient oxygenation. Reimbursement for professional re-spiratory therapist (RT) services in the home is not avail-able, further suggesting that equipment rather than patientoxygenation is the focus of the insurance industry. Equip-ment distribution costs and patients’ need for equipmentthat meets their lifestyle requirements have further drivenproduct design that addresses these issues, yet there hasbeen no substantial research to determine patient applica-tions, safety, or effectiveness. Several new clinically tar-geted oxygen products have been developed, yet have notgained traction, due to the lack of clinical evidence andadequate reimbursement.12,13 Clinical capabilities have notbeen a driving force from prescribing physicians, so costsand marketing advantages have been the main design con-siderations from oxygen equipment manufacturers. Oxy-gen equipment is the means to provide therapy and cannotbe considered the end point related to the effectiveness ofhome oxygen therapy.

Oxygen Equipment: From Hospital to Home

Dr Thomas Petty was instrumental in raising the aware-ness of LTOT and the benefits this therapy can provide.14,15

Equipment provided an opportunity to supply LTOT, yetalso added a variable to the therapy, with technology anda new therapy delivery environment in the home. Thehome is not the hospital, yet most testing and researchhave been conducted in a controlled institutional environ-ment that does not represent the patient’s home. Patientsbenefit from activity, and the need for oxygen during ac-tivity has stimulated the study of home oxygen therapy,which has led to new technologies. Pulmonary rehabilita-tion with LTOT determined that patients can exercise withchronic lung disease and that proper education and equip-ment can improve a patient’s quality of life and reducecomplications and mortality related to COPD.16 The Noc-turnal Oxygen Therapy Trial was the foundational researchon the benefits of LTOT, and a review of the Nocturnal



Oxygen Therapy Trial demonstrated the economic benefitsof ambulatory oxygen therapy on hospital admissions.17,18

Home Oxygen: Drug or Device?

Home oxygen equipment has evolved to address thechallenges of providing oxygen therapy in the home en-vironment with new and innovative technology and cre-ative packaging that reduces costs and improves patientadherence. A concern for the therapeutic effectiveness ofthis new home oxygen technology stimulated research thatdemonstrated the variability of products in consistentlyoxygenating patients.19 Intermittent-flow devices intro-duced to the home in 1983 started the greatest departurefrom traditional continuous-flow oxygen delivery used inthe hospital.20 Intermittent-flow devices addressed the needto improve efficiency of oxygen delivery by providingflows only when the patient was inhaling, eliminating thewaste of gas during exhalation. This efficiency has beenused with portable oxygen systems to reduce size andextend operating times, and has created ambulatory sys-tems that are patient friendly, improving adherence. Inter-mittent-flow devices have also created the greatest confu-sion related to oxygen delivery, related to prescriptions,device selection, understanding patient versus product ca-pabilities, and reimbursement for LTOT.

Home Oxygen: A Mobility Solution

Home oxygen patients need to be highly mobile to main-tain a normal lifestyle. Ambulation has been shown toimprove survival, reduce cost, and reduce complicationsassociated with chronic lung disease.21 A portable oxygensystem must be effective and efficient to gain patient ad-herence, yet must also provide therapeutic oxygen at allactivity levels. A factor that has become the most dauntingfor home oxygen therapy is the third-party payer’s will-ingness to pay for the necessary equipment. The currentpractice of payers is to continually reduce reimbursementfor LTOT products, with the assumption that LTOT costswill diminish. The reality is that those patients who do notreceive therapeutic oxygen allowing them to maintain mo-bility will increase overall cost by returning to the hospitalwith complications associated with under-oxygenation anda sedentary lifestyle.22

Sources of Oxygen for Home Use

Oxygen utilized in the home must be delivered or pro-duced. Packaged gas is created by an industrial gas pro-ducer under strict guidelines for purity and packaging.Oxygen is monitored and tracked each time it is repack-aged, with tracking systems in place to ensure the qualityof the gas. The size of a packaged gas system determines

its application and operation times between refills. Thereare many options available for both stationary and portablepackage gas systems for home oxygen utilization.

Oxygen Produced, Stored, and Transported by a GasManufacturer and Home Medical EquipmentSupplier

• Compressed gas (fractional distillation) 99% UnitedStates Pharmacopeia oxygen

• LOX (fractional distillation/refrigeration) 99% UnitedStates Pharmacopeia oxygen

• The fractional distillation process is highly regulated bythe gas industry for oxygen purity, with precision mon-itoring and documentation.

Oxygen Produced Within the Home by OxygenConcentrator

• Concentrator oxygen (pressure swing adsorption)90 � 5% purity

There is little regulation on gas production purity forpressure swing adsorption products, with no monitoringrequirements other than manufacturer recommendations.

Oxygen produced in the home is typically accomplishedwith devices that filter nitrogen from ambient air. Station-ary concentrators are well established, with a history ofreliability and performance. Portable oxygen concentrators(POCs) are newer, with performance and capabilities thatare not as well established as the larger stationary systems.Oxygen purity levels for concentrators are generally con-sidered to be between 85% and 95% fraction of deliveredoxygen (FDO2

), and some systems (yet not all) have oxy-gen monitoring capabilities. Oxygen monitoring of homeoxygen concentrators is not required by regulatory agen-cies or, more importantly, prescribing clinicians. Repack-aging of concentrator gas in the home to a cylinder orLOX system is not regulated, and each manufacturer candetermine what monitoring they will provide. Devices thatfill from a home oxygen concentrator have a proprietarycoupling system to ensure that other portable oxygen sys-tems cannot be filled from the designated stationary sys-tem. FDO2

within the portable system will be the same asthe FDO2

from the stationary source gas.Compressed gas systems have a finite capacity, depend-

ing on the size and pressurization of the cylinder. Thesesystems require a refill process with an associated serviceand cost that factor into the delivery and portable appli-cation. LOX systems are both stationary and portable andrequire a refill process, yet the portable can be filled fromthe stationary, allowing the patient control of the frequencyof refilling the portable. LOX stationary systems are re-filled at a set frequency, depending on the size of the unitand flow setting, again with a service cost. Oxygen con-



centrators create oxygen in the home, so do not requirerefilling, yet the power source (alternating current or bat-tery) becomes the determining factor for availability oftherapeutic oxygen and operating times. Stationary con-centrators can produce up to 10 L/min of 90% oxygen, andportable concentrators range from 0.4 L/min to 3 L/minproduction. Production capacity determines flow and dosecapabilities for oxygen concentrators used within the home.

Metering Oxygen to the Patient

Historically, continuous flow has been the standard ofcare in all oxygen therapy environments. With the chal-lenges of providing effective yet low cost oxygen therapyin the home, efficiency of gas utilization became a desir-able objective. Metering of home oxygen to the patientevolved from continuous-flow therapy, with the introduc-tion in 1983 of intermittent-flow delivery options. Overtime, intermittent-flow delivery systems have increasedthe number of variables that need to be considered whenproviding supplemental oxygen.

Metering of home oxygen began with continuous-flowtherapy, which was the standard in hospitals and consid-ered the gold standard for LTOT. Continuous-flow therapyis simple to administer, and the equipment necessary forapplication is typically not complicated to operate, makingit ideal for set-up in the home. Most continuous flow prod-ucts deliver flows ranging from 0.5 L/min to 5–6 L/min,with some products able to deliver up to 15 L/min. Changesin flow setting are made simply by turning a dial or press-ing a button. Patients using effective continuous-flow ther-apy are generally able to “set it and forget it.” By nature ofthe application, continuous-flow therapy has a variabledose that changes with breathing frequency and other phys-iological factors, yet even with the minute volume limita-tions of continuous flow, its application is familiar to cli-nicians and still readily accessible within most healthcareinstitutions.

Estimate of Continuous Flow FIO2From a Nasal

Cannula

Cannula flow 2 L/min (33 mL/s)Tidal volume 500 mLAnatomic reservoir 50 mL (nasal passages and naso-

pharynx)Inspiratory time 1 secondVolume of O2 inspired50 mL � 33 mL � 84 mL (amount of O2 in the inspired

air � 420 mL � 0.21)Volume of inspired oxygen � 167 mLFIO2

� 167 mL (O2)/500 mL (tidal volume) � 0.33 FIO2

The goal of oxygen therapy is to provide the necessaryamount of therapeutic oxygen to gas exchange units as

efficiently as possible to maintain oxygenation at all ac-tivity levels.23 Useful oxygen delivery occurs during aspecific time frame within the breathing cycle.24 This “sweetspot” is where the benefit of oxygen delivered to gas ex-change units within the lung is maximized. Providing ox-ygen anywhere outside this effective gas exchange area—such as during exhalation—is considered wasteful. Evenoxygen delivered during inhalation can be wasteful: gasthat remains in dead space before being exhaled is notuseful gas. The solution to eliminating wasteful oxygenwas by utilizing intermittent-flow delivery. Intermittent-flow delivery is as described: delivering oxygen in shortbursts by repeatedly alternating the delivery setting fromoff to on. The awareness of intermittent-flow oxygen de-livery technology existed prior to the introduction of acommercially available product, yet was rarely used.25 Prac-tical application of intermittent flow was achieved in theearly 1980s.

Intermittent flow products have been labeled pulse-dose,demand flow, demand oxygen delivery systems, and/oroxygen conserving devices. Intermittent-flow devices re-quire a metering method that senses, distributes, and endsdose delivery. These methods have included:

• Manually triggered/cycled: method identified in earlyresearch of the intermittent flow concept

• Pressure triggered/cycled: devices trigger on negativechange in pressure (inhalation), cycle based on positivechange in pressure (exhalation). These devices typicallyrequire a dual lumen cannula.

• Volume controlled: devices trigger on negative changein pressure (inhalation), and automatically cycle after de-livering a set volume from a chamber within the device.

• Time cycled: devices trigger on negative change in pres-sure (inhalation), and electronically control the cycletime. These devices require a power source.

Control of the dose setting by a patient on an intermit-tent-flow device has expanded from the traditional manualdialing to novel methods of changing the dose setting basedon patient needs. These methods have included:

• Manual adjustment of the intermittent flow device bythe clinician or patient

• Motion control: the intermittent-flow device sensesmovement, and, assuming the patient’s demands for ox-ygen increase with activity, increases the dose volume.The device returns to baseline when motion is not de-tected.

• Respiratory rate control: the intermittent-flow device ad-justs the dose setting based on breathing frequency. Cur-rently there is only one device that meters the dose vol-ume based on rate.26



• Oximeter control: the intermittent-flow device monitorsthe patient’s oxygen saturation and meters the dose ofoxygen based on a targeted oxygen saturation level.12,13

This type of intermittent-flow device has been describedin the literature, yet no commercially available producthas been introduced to the United States market.

Initially, intermittent-flow devices were described asequivalent to continuous-flow as a means to gain approvalfrom the federal government for a product’s release. Theseproducts were usually labeled similar to continuous-flowdevices, with numerical settings from 0.5 up to 5 or 6.Once on the market, intermittent flow products often in-cluded marketing material describing the device’s settingsas equivalent to continuous-flow delivery (eg, a setting of“3” was equivalent to 3 L/min continuous flow). However,delivering oxygen intermittently should not be consideredthe same as delivering oxygen continuously. Equivalenceof intermittent-flow delivery to continuous-flow deliveryis dependent on a number of variables, yet when one ormore of these variables change, the equivalence of anintermittent-flow delivery method to continuous-flow de-livery cannot be achieved. In early application of intermit-tent-flow therapy, this concept was not well understood,and had many people perceiving that intermittent flow andcontinuous flow, set to an equivalent setting number, werethe same.

This first misunderstanding lead to a perception thatintermittent-flow devices did not work. Manufacturers whohad labeled their devices as equivalent to continuous-flowwere also able to market the “oxygen savings ratio” thatresulted from the use of their product by comparing thevolume of oxygen delivered during continuous flow to thevolume their device delivered at an “equivalent” intermit-tent flow setting. These oxygen saving ratio values lead tomarketing claims that one device was better at conservingoxygen, and became an important factor in the selling ofoxygen conserving devices. Because of the lack of infor-mation available during early use of intermittent-flow de-livery systems, instead of considering that there may beanother intermittent-flow device that would meet the pa-tient’s needs, many clinicians assumed that all intermit-tent-flow devices would not work.

Shigeoka described the then (and remarkably currenttoday) state of oxygen conserving devices in a 1985 edi-torial27 by describing the variability of continuous-flowvolume delivery at different breathing frequencies and not-ing how conserving devices might overcome some of thecontinuous flow limitations. Also identified in that edito-rial was the fact that very limited studies were availablecomparing intermittent flow to continuous flow, and thosethat were available were conducted under laboratory con-ditions and/or generally conducted in ideal conditions bythe inventor or manufacturer.27 Studies during sleep, ex-

ercise, or in children had not been reported, and only lim-ited information is still available today.

Early recommendations for prescribing LTOT suggestedincreasing a continuous-flow setting by 1 L/min with ex-ercise and/or sleep to maintain adequate oxygenation dur-ing these activities. Interestingly, most evidence for theeffectiveness of intermittent-flow LTOT does not take intoconsideration many of the variables that are introducedwith intermittent-flow delivery, and often assume a con-sistent FIO2

throughout the investigations. Research dem-onstrating the value of LTOT in different applications (atrest, and at activity) often does not indicate how the oxy-gen therapy was monitored, if the metered flow of oxygenwas adjusted in response to changing breathing frequen-cies, and/or what system was used for the delivery ofoxygen. Many researchers appear to simply assume thatthe oxygen delivery was consistent during their study. Muchof the literature generally describes oxygen therapy as “ox-ygen was given.” Many of these studies ignore specificdetails necessary to understand how the oxygen was me-tered and delivered, meaning that the FIO2

could have var-ied considerably and may have affected the findings andconclusions.

Delivering some oxygen is better than giving no oxy-gen,28 yet providing oxygen as a therapeutic drug in amultitude of ways may change effectiveness and patientoutcomes. Intermittent-flow delivery, as described byPflug,29 introduced a more efficient method of oxygendelivery by eliminating wasteful oxygen flow. Intermit-tent-flow delivery has the ability to provide a specific doseof oxygen that can be measured and controlled to provideconsistent therapy. However, since their inception, inter-mittent-flow devices have often claimed equivalency withcontinuous-flow, which has led to confusion on the effec-tiveness of these devices.30 It is important to understandthat equivalency to continuous flow is possible based oncertain variables, like volume and breathing frequency, yeta standard for metering and labeling of intermittent-flowdevices has not been established, so any number on anintermittent-flow device should not be considered equiv-alent to continuous flow over a range of breathing fre-quencies. Even so, there is reason to believe that contin-uous 24 hour per day oxygen use, via intermittent-flow orcontinuous-flow methods, in appropriately selected patientscould produce a survival benefit even greater than thatshown in the Nocturnal Oxygen Therapy Trial.31

Equipment Options

Home oxygen equipment options have increased overthe past decades, to the point where it is difficult to knowwhat equipment is available and the capabilities and lim-itations of each device. Physicians typically prescribe aflow rate and frequency for home oxygen therapy and



expect the HME provider to supply the necessary equip-ment. This lack of involvement has relinquished control ofthe oxygen therapy equipment delivery to the HME sup-plier. The HME will balance the decision of type of equip-ment used for the patient on their available inventory,distribution economics, competition within their market,and patient demands. Effective oxygenation at all activitylevels is not a driving factor for the HME supplier, asreimbursement is not tied to documentation of oxygen-ation at all activity levels. Equipment provides the optionsfor gas storage and metering within the home; however,clinicians need to ensure that the equipment is used ther-apeutically to gain patient benefits.

Compressed Oxygen Cylinders

Oxygen cylinders were the source of oxygen for hospi-tals until the advent of piped oxygen systems, which sup-plied large volumes of gas from bulk oxygen stored incryogenic dewars. Oxygen cylinders are still the mainsource of portable oxygen within the hospital for patienttransports. Patients in the home require the lightest cylin-der that can operate for the longest period of time, to allowthe patient to do activities of daily living. The balancebetween weight and operating times was the impetus todeliver oxygen to the patient more efficiently. Aluminumcylinders replaced steel cylinders for home use, to reduceweight (Fig. 2). Aluminum regulators further reducedweight, and novel carts and carrying devices added to thepatient ease of use of cylinder gas. Composite cylindersare available that reduce weight and have the potential tobe filled to higher pressures, up to 3,000 psig. Even thoughthe potential for increased pressure operation is available,many industrial trans-filling services do not operate at over

2,000 psig, due to the need to modify equipment to fill to3,000 psig.

Large cylinders can trans-fill smaller cylinders in thehome, as an option to reduce the cost of newer equipmentand utilize readily available compressed gas systems(Fig. 3). This old concept became available again due tothe constant economic pressures from payers to reducereimbursement for home oxygen equipment

Liquid Oxygen Systems

LOX provides several advantages over cylinders. Oxy-gen in a liquid state can be stored, transported, and trans-filled more efficiently than gas systems (Fig. 4). With an860:1 expansion ratio, 1 L of LOX will expand to 860 Lof gaseous oxygen. This efficiency is utilized in the hos-pital with large cryogenic storage dewars supplying oxy-gen in large volume. In the home, stationary dewars comein a variety of sizes, with the option of determining deliv-ery cycles based on the size of the stationary dewar. Por-table LOX systems can be trans-filled in the home fromthe base dewar, which allows for a quick refill of theportable, with the further advantage of the need for onlyone portable LOX system. Small stationary dewars havebeen used when patients want to have a refill supply avail-able in the car or van during extended trips from theirhouse (Fig. 5).

High-flow LOX can provide up to 15 L/min of contin-uous flow oxygen at a purity of 99%. High-flow LOX hasan operational issue with the potential to create ice on theportable due to ambient humidity freezing on the heatexchange coils. Patients utilizing high-flow LOX usuallyhave 2 systems available, to allow one unit to de-ice while

Fig. 2. Family of products showing the variety of sizes of com-pressed gas cylinders used in home oxygen therapy. (Withpermission.)

Fig. 3. Cyl-Fil compressed oxygen trans-filling system, using largecylinders to fill smaller cylinders. (Courtesy of ResponsiveRespiratory.)



the other unit is in use. LOX is the most practical optionfor patients requiring ambulatory high-flow oxygen.

LOX production in the home is now possible with theintroduction of a commercially available product (Fig. 6).The home liquefier uses concentrator gas that is cooled tocryogenic temperatures and stored in a dewar until needed.The unit produces 3 L of LOX and has a proprietary con-nector that allows the filling of only a dedicated portableLOX system. This system allows for the benefits of a LOX

portable without the costs of delivery from a home oxygensupplier. Acquisition costs, metering gas to the patient,and the cost of electricity to the patient are still a consid-eration in the acceptance of this product.

Oxygen Concentrators

Stationary concentrators provide a convenient and reli-able source of oxygen in the home, with minimal limitingfactors, the only major consideration being the availabilityof electricity and the capabilities of the device. Oxygenconcentrators for home use are well established and thestandard of care for stationary use. These units have theability to produce 90% � 5% oxygen purity at flows rangesof 1–10 L/min (Fig. 7). The weight of current commer-cially available products is approximately 35 pounds, downfrom the initial weight in the mid 1970s of approximately80 pounds. Benefits of today’s units are lower power con-sumption, lower noise level, improved reliability, and re-duced maintenance costs. These units are used within thehome and can accept up to 100 feet of supply tubing to thepatient, to allow for mobility within the home.

A 10 L/min concentrator can address the needs of ahigher flow patient with the same benefits of a 5 L/minmodel, with only slight increase in size, weight, and elec-trical cost to operate. Oxygen concentrators that can fillcylinders have been developed to address the cost of re-supplying portable oxygen cylinders for patient ambula-

Fig. 4. Family of products showing the many options for bothstationary and portable liquid-oxygen home oxygen systems.(Courtesy of Caire Medical.)

Fig. 5. A patient trans-filling a portable liquid-oxygen containerfrom a small stationary system secured in the back of a car. (Cour-tesy of Valley Inspired Products.)

Fig. 6. HomeLOX liquid oxygen system, which creates oxygenfrom a concentrator and refrigerates the concentrator gas to aliquid state, which is stored in a small dewar to trans-fill to aliquid-oxygen portable. (Courtesy of Philips Respironics.)



tion (Fig. 8). Patients are able to refill their portable cyl-inders by mating the portable to the stationary unit, utilizinga proprietary connection. These devices can pressurize cyl-inders to 2,000 psig (2 commercially available units), andone manufacturer has a product that can pressurize a com-posite cylinder to 3,000 psig. Patients should be providedan adequate number of refill cylinders to allow for theextended refill times of the portable and for extended op-erating times away from home. Patient issues with thehome trans-filling concentrators are the availability of ex-tra cylinders, fill times of the cylinders, and a slight in-crease in electrical costs. The choice of the appropriateregulator to meter oxygen to a therapeutically effectivelevel is also a consideration for these devices.

Intermittent-Flow Regulators

Intermittent-flow regulators, either stand-alone or as anintegrated part of an oxygen system, deliver a volume ofoxygen during inhalation, with no oxygen delivery duringexhalation (Fig. 9). Unlike continuous-flow therapy, as thepatient’s breathing frequency increases, intermittent-flowdelivery systems have the capability to deliver the same

volume of oxygen per breath, no matter the breath rate.32

Some intermittent-flow devices do mimic continuous-flowdelivery using a minute volume delivery method that de-creases the dose volume as the breathing frequencies rise,often with secondary outcomes of ensuring that the devicedoes not exceed production capabilities or prolonging ox-ygen conservation. But for fixed-dose intermittent-flowdevices, in comparison to continuous flow, as breathingfrequencies increase, more oxygen can be delivered to thepatient per minute than at an “equivalent” continuous-flowsetting. A patient using 2 L/min continuous flow of 100%O2 with a 500 mL tidal volume breathing at 15 breaths/min and a 1:2 inspiratory-expiratory ratio will receive 44 mLof O2 per breath; increase the rate to 30 breaths/min withall other parameters the same and that delivered O2 vol-ume drops to 22 mL per breath and FIO2

is reduced. But onan intermittent-flow device that delivers a fixed pulse of44 mL per breath, the delivered volume does not change,and in theory the FIO2

would stay the same.There are several factors that determine just how much

of a delivered volume from an intermittent-flow device—inboth fixed-dose and minute volume delivery scenarios—actually reaches the lungs (Fig. 10). Intermittent-flow de-vices need some mechanism to turn on and turn off oxygendelivery, and to meter the dose when delivery is occurring.The ability of these devices to “trigger” is variable byproduct, and delivering earlier or later in the inhalationcycle can affect how much volume reaches gas exchangeunits in the lungs. If the intermittent-flow device is sourcedby a concentrator or other supply with � 100% oxygen,the FDO2

of the delivered oxygen will play a role in the FIO2

of the patient. The shape of the oxygen flow curve as thedose is delivered may also impact patient comfort andadherence. Down sides to higher flow and sudden on/offoxygen delivery, at least to a patient, are the sound that isproduced by the device and within the cannula during

Fig. 7. A variety of stationary oxygen concentrators, with a flowrange of 1–5 L/min. Left: 525 DS. (Courtesy of DeVilbiss Health-care.) Middle: EverFlow Q. (Courtesy of Philips Respironics.) Right:Perfecto2. (Courtesy of Invacare.)

Fig. 8. Two stationary oxygen concentrator systems that can pres-surize and fill compressed gas portable cylinders. Left: HomeFill.(Courtesy of Invacare.) Right: UltraFill. (Courtesy of PhilipsRespironics.)

Fig. 9. A variety of compressed gas oxygen regulators that provideintermittent flow. (Courtesy of Valley Inspired Products.)



delivery, and potential discomfort in the nasal cavity dueto high flow.

Oxygen Monitoring

A new device has been introduced that can monitor boththe oxygen delivery system and the patient (Fig. 11). Thisdevice connects between any oxygen system the patientwould be using and has an oximeter to monitor the pa-tient’s oxygen saturation. The unit can transmit data wire-lessly to a computer for monitoring and analysis or canstore data for extended periods of time for trending anal-ysis. This device provides the clinician with an objectivetool for determining the appropriate oxygen device for thepatient’s needs at activity plus a method of electronically

storing valuable information about the patient’s oxygenuse and benefit.

Pressurized Oxygen

Pressurized ambulatory oxygen to provide augmentedventilation has recently been introduced to address patientneeds for assisted ventilation while receiving oxygen(Fig. 12). This device uses a nasal interface similar tointerfaces used with CPAP and delivers a set volume ofgas under pressure. This pressurized oxygen will augmentventilation to reduce work of breathing and improve apatient’s capability to increase activities. The system weighs1 pound and operates at 50 psig. Standard cylinders areutilized, allowing existing HME suppliers’ inventory to beutilized. If assisted ventilation is necessary for a patient tobenefit from LTOT, this product is now an option forconsideration.

Portable Oxygen Concentrators

All LTOT patients are limited by the availability ofadequate amounts of oxygen while mobile. POCs can man-ufacture oxygen from both alternating and direct currentsources, so the capability of manufacturing adequateamounts of oxygen and electric power sources are thedetermining factor for the use of POCs. They were firstintroduced in the mid 1990s, yet have recently becomemore available, with several manufacturers introducing avariety of product options (Fig. 13). Knowing the capa-bilities of the POC, the needs of the patients, and theiractivities while using the POC are important points ofinformation for the clinician to consider when workingwith the patient to determine therapy options. POCs varyfrom traditional home oxygen products as well as betweendifferent POCs.33 Recommendations from the secondLTOT consensus conference state “Clinical evaluationshould include regular assessments of patients’ adherencewith prescribed therapy, potential complications, potential

Fig. 10. A sample of how a volume of oxygen is calculated whendetermining an intermittent flow dose. This is a hypothetical sam-ple and does not reflect a specific device.

Fig. 11. Clinical Oxygen Dose Recorder device to monitor both theoxygen device and the patient. (Courtesy of Global MedicalHoldings.)

Fig. 12. Noninvasive Open Ventilation (NIOV) device that providespressurized oxygen to augment ventilation. (Courtesy of BreatheTechnologies.)



hazards, and the need for continued education. Patientsreceiving LTOT share responsibility with the prescribingphysicians for remaining in communication with their phy-sician, in order to assure continued appropriate care fortheir condition.”34

Each POC has different oxygen production capabilitiesand dosing algorithms that can impact patient oxygen-ation. These products are being marketed with features andbenefits that are desirable to the LTOT patients, with weight,battery life, packaging, and sound being important con-sumer features. Once the patient has been tested, titrated,and ensured that the product they want keeps them prop-erly oxygenated at all activity levels, the clinician shouldfeel comfortable recommending a POC.

Larger POCs are available that can provide both 3 L/min continuous flow and a range of intermittent flowdosages. The larger production capabilities of these unitsgive more options for higher-dose, intermittent-flow vol-umes. Continuous flow is available as an option forpatients who do not consistently trigger the intermittent-flow selection, or can be used if the patient requires ahumidifier or to interface with other equipment such asa ventilator or CPAP.

Dr Petty suggested that “Practical portable concentra-tors should weigh no more than 10 pounds, produce 90%or more oxygen, and provide a least 2 L of oxygen for aminimum of 4 hours.” This suggestion came at an Amer-ican Association for Respiratory Care (AARC) JournalConference in 2000.6 A product meeting these suggestionswas introduced in January of 2012 (Fig. 14).

Intermittent-flow-only POCs produce a limited volumeof oxygen that is not practical for continuous-flow opera-tion (Fig. 15). The production capability of these systemsis typically below 1 L/min. These devices provide inter-mittent-flow-only dosing with a volume per dose set byeach manufacturer. The fixed production volume of thesedevices can be metered, with dose volume changing withbreathing frequency changes, or can have a fixed dose ofoxygen with oxygen purity reductions with higher breath-ing frequencies. With a fixed production of oxygen thesedevices cannot increase oxygen delivery beyond their pro-duction capabilities (Figs. 16–19).

The need for definitions of “portable,” “ambulatory,”and “wearable” was discussed at the 6th oxygen consensusconference, yet no agreement could be reached to catego-rize size, weight, and operating times for devices usedaway from their stationary oxygen device.35

New Issues Related to POCs. With the introduction ofPOCs, new performance variables have been introducedthat can impact effective oxygen therapy. These variables,

Fig. 13. Two options for 3 L/min continuous-flow capable portableoxygen concentrator system. Left: Eclipse 3 (Courtesy of CaireMedical). Right: Oxlife Independence. (Courtesy of O2 Concepts.)

Fig. 14. SimpleGo, a 2 L/min continuous-flow capable portableoxygen concentrator system. (Courtesy of Philips Respironics.)

Fig. 15. A family picture of intermittent-flow-only portable oxygenconcentrator systems. Left: EverGo. (Courtesy of Philips Respi-ronics.) Middle: XPO2. (Courtesy of Invacare.) Right: FreeStyle.(Courtesy of Airsep.)



most not seen in continuous-flow therapy, require clini-cian, RT, and/or patient consideration when using a POC.

Stationary concentrators typically deliver oxygen con-tinuously, at flow settings between 0.5 and 6 L/min (withsome units able to provide up to 10 L/min). Current POCson the market, which are much smaller than stationaryconcentrators, do not have this range of capability. SomePOCs are able to deliver up to 3 L/min of continuousoxygen flow (continuous-flow POCs), but a majority ofthe POCs available are able to deliver their oxygen onlyintermittently (intermittent-flow POCs). The distinction be-tween continuous-flow POCs and intermittent-flow POCsis important, if only because the oxygen production capa-bilities of these 2 types of POCs are different. Current

continuous-flow POCs produce 2,000–3,000 mL of oxy-gen per minute. Oxygen production capabilities of cur-rently available intermittent-flow POCs range from around450 mL/min up to 1,250 mL/min.

POCs have limited oxygen production capabilities and amaximum breath rate at which the device can maintainadequate FDO2

. With an intermittent flow setting on a POChaving a specific volume delivered, if a patient’s breathingfrequency—and thus the volume delivered per minute—exceeds the production capability of the POC, FDO2

willdrop. Even POCs that feature minute volume delivery,where the dose delivered at a given setting decreases withan increase in breathing frequency, have a maximum breathrate and setting at which the device can deliver oxygen

Fig. 16. The maximum FIO2of a variety of portable oxygen systems, utilizing intermittent flow at 20 breaths/min. LOX � liquid oxygen. POC �

portable oxygen concentrator.



within specification. Often these maximum breath ratesare not specified in the product literature.

Oxygen purity specifications from POC units usuallyrange from 87% to 95%. Many have O2 sensors that mon-itor oxygen purity or use internal pressure readings toindirectly gauge purity levels. However, each unit has dif-ferent methods of alerting the user to low purity, and shouldpurity levels fall below specification, some units may notdisplay a visual indicator or audible alarm for several min-utes. A reduction in FDO2

may affect patient oxygenationas a result of lower FIO2

being delivered.Triggering sensitivity is a variable that can affect whether

the device is able to detect inhalation and where in theinhalation cycle that the dose is delivered. Several POCmanufacturers advertise that their products can be usedwhile sleeping, even in intermittent-flow delivery onlymodes. Sleeping patients generally have slower breath rates

and shallower breath patterns, meaning that any differ-ences in triggering sensitivity ability across products aremagnified. Cannula placement will affect triggering sen-sitivity, so if the patient inadvertently moves their cannula,the intermittent-flow device many not trigger or triggerlater in the breathing cycle. Intermittent-flow-only POCsdo not have the ability to switch to a continuous-flowmode should breathing remain undetected. Continuous-flow POCs are able to switch to a continuous-flow modein the absence of breath detection, but some continuous-flow POCs will remain in continuous-flow mode, whileothers will cycle between intermittent flow and continuousflow until a breath is detected (which has an added benefitof conserving battery life).

When a wall or grounded power source is unavailable,the battery life of a POC becomes the determining factorfor device operating times. Battery designs and longevity

Fig. 17. The maximum oxygen dose of portable oxygen systems, utilizing intermittent flow at 20 breaths/min. LOX � liquid oxygen. POC �portable oxygen concentrator.



have improved, yet are still a consideration for a patientwho needs to be away from a power source for a substan-tial period of time. Unlike packaged gas systems, wherereplenishment of depleted oxygen is dependent on deliv-ery schedules and other factors outside of the patient’sdirect control, power availability is much greater with elec-trical sources readily available. A patient using a POC onbattery is meant to bridge the time from one power sourceto another, and reduces the patient’s fear of running out ofoxygen.

Patient education on the operation and capabilities ofPOCs is necessary, as service from the oxygen provider isdecreasing and more patients are purchasing home oxygenproducts like POCs on their own. Patients almost alwayswant the lowest weight, longest lasting POC available, yetthese products are not always able to meet their oxygen-ation needs. Advertising has enticed patients with claimsof low weight, equivalency to continuous flow, 24/7 use,and long battery life. These are factors to consider, yet any

benefit from these product variables should be secondaryto effective oxygenation at all activity levels.

Discussion

Oxygen has proven to be an effective drug in treatinghypoxemia, with a broad range of applications both in thehospital and the home. Patients with diseases causingchronic hypoxemia require supplemental oxygen continu-ously to prevent consequences and comorbidities. Homeoxygen equipment options expanded as patient and eco-nomic needs increased, without the direction of the phy-sicians and research community regarding oxygen deliv-ery capabilities, range of oxygen delivery, and oxygenpurity of home oxygen devices. Early research on new ox-ygen products showed differences in performance and capa-bilities, but the influx of new products was too fast for a

Fig. 18. The FIO2of a variety of intermittent-flow devices at 15 and

30 breaths/min.

Fig. 19. The volume of gas provided per breathe from a variety ofintermittent-flow devices at 15 and 30 breaths/min.



widespread understanding of their capabilities and outcomesto be achieved. Manufacturers and DMEs capitalized on theinterest in intermittent-flow devices, marketing products thatadded features but did not lessen growing discrepancies inproduct-to-product performance capabilities

Home oxygen therapy, once an area with a relativelyfixed amount of therapeutic options, now has a widelyvariable product base that has created noteworthy misun-derstanding and uncertainty as to the potential effective-ness of different products. Only now is there becomingwider awareness that a “2” on one device is not the sameas “2” on another, let alone not equivalent to 2 L/mincontinuous flow.

Home Oxygen Prescriptions

The assessment of clinically effective LTOT is bestachieved by the patient simulating their home activitieswith the proposed oxygen equipment. The home oxygenprescription requires detailed instructions on the dose ofoxygen the patient will have need of at all activity levelsand the oxygen equipment required to accomplish normalactivities within and outside their home. An option to tra-ditional prescriptions for home oxygen therapy would beto have the prescription indicate an oxygen saturation levelto be achieved at all activity levels, with the home oxygenprovider charged with accomplishing this objective. Thephysician will need to be actively involved to ensure thepatient is receiving the prescribed therapy. Patient needswill change throughout the course of the disease, and boththe patient’s oxygen requirements and the oxygen equip-ment capabilities will need to be monitored to ensure ef-fective and consistent therapy. Initial needs for oxygenmay be only required with exercise and sleep, then prog-ress to 24 hour therapy, so flexibility of sourcing an ef-fective device is necessary. Patient oxygen demands maychange as the disease progresses, so options for a higherdosing product to ensure patient benefits at all activitylevels outside the hospital are required. Equipment shouldbe available to the home patient based on clinical needsand not reimbursement constraints.

Technology has evolved to the point where a specificamount of oxygen can be delivered per breath, allowingfor the prescribing physician to identify a dose of oxygenas opposed to a flow. Current technology is limited inmaximum dose capabilities and oxygen purity, yet tech-nology can and should be developed to accomplish theobjective of dose volume and oxygen purity to meet thepatient’s clinical needs at all activity levels.

Patient Assessment

Patients requiring LTOT should be assessed by the pre-scribing physician for the proper oxygen dose at all ac-

tivity levels and to identify a home oxygen product thatcan accomplish the prescription. There are no standardsfor the titration of a patient for home oxygen therapy,so a standard should be developed. The 6-min walk test iswell established, yet is conducted to determine condition-ing, not oxygen prescriptions. Currently, clinicians indi-cate that they have titrated the patient for LTOT, yet with-out a standard of titration, the prescriptions can vary fromone clinician to another. Professional medical societiesshould develop a standard of titration for home oxygenpatients.

Oxygen Metering

Standardized labeling of intermittent-flow devices isneeded to help improve metering of oxygen from homeoxygen devices. Intermittent flow is not equivalent to con-tinuous flow, so the labeling of oxygen delivery deviceshould not refer to the devices as such. Intermittent flowcan reflect a specific dose of oxygen per breath, based ona determined inspiratory time. Professional medical soci-eties should focus on establishing a recommendation basedon the best therapeutic option for the patient. At this time,equipment has been developing with a broad range ofdosing capability. Labeling of existing equipment may needto change once a recommendation is established.

Recommendations

The many options for home oxygen therapy equipmentand the variability in performance capabilities of new devicesrequire a new course of action by clinicians to address agrowing problem in home oxygen therapy related to effectiveclinical care, equipment selection, and reimbursement forproducts and services. Recommendations for action needed:

• Physicians should be involved in the development of LTOTprograms and products that are capable of meeting thepatient’s needs for effective oxygen therapy at all activitylevels outside the hospital. This would include setting stan-dards for the assessment of patients requiring LTOT, stan-dards for the titration of LTOT at specific intervals to meetthe needs at all activity levels, active involvement in re-questing performance specifications for new and existingLTOT products, and standards for ongoing monitoring andassessment of patients receiving LTOT.

• Labeling of the metering devices used with LTOT shouldinclude oxygen flow with a clinically acceptable FIO2

range. Dose volume for intermittent-flow devices shouldbe labeled based on calculated volume for the first halfof inspiration, in mL, with the volume delivered in abreathing frequency range identified for specific breath-ing frequencies from 15 to 40 breaths/min.



• Oxygen purity monitoring should be available for alloxygen concentrator devices. Alarms should initiate atconcentrations below 85% purity for � 5 min. For POCdevices, alarms should initiate at breathing frequenciesthat produce oxygen purity below 85%.

• A new titration standard for oxygen prescriptions at allactivity levels should be developed by professional med-ical societies for patients receiving LTOT, to ensureadequate patient oxygenation with the devices provided.

• Prescriptions and therapy for LTOT should focus onpatient outcomes with oxygen saturations greater than90% at all activity levels, rather than the process ofhome oxygen equipment set-up and maintenance. Pre-scriptions should allow for a titration to a specific sat-uration at all activity levels.

• Appropriate and targeted reimbursement for RT profes-sional service in the home is required to ensure thateffective LTOT is provided. The RT would assist thephysician by ensuring appropriate oxygen therapy ob-jectives are met, using equipment that provides effectivepatient oxygenation at all activity levels. RTs should berecognized and reimbursed for services in the home, inaddition to the reimbursement given for the equipmentprovided.

• Reimbursement for home oxygen equipment should re-flect the cost of both products and services related to theeffective deliver of the drug oxygen. Stationary concen-trators have the lowest product and service costs, andlight-weight, longest lasting portable systems have thehighest product and service costs. Reimbursement shouldreflect these differences.

Summary

There are many equipment options available for homeoxygen therapy to meet the needs of the LTOT patient.Equipment variability in oxygen storage, oxygen produc-tion from concentrators, oxygen dosing from metering de-vices, and operating times for portable oxygen systems hascreated a need for clear labeling of an oxygen product’scapabilities, applications, and limitations. Clinician andpatient education is required to ensure the proper use andapplication of home oxygen equipment.

Patients must be tested on the equipment they will usein the home at all activity levels, to ensure adequate oxy-genation and benefits from the home oxygen therapy. Pa-tients must be monitored frequently for changes in clinicalneeds and equipment capabilities to meet those needsthroughout their lifetime use of home oxygen therapy. Anew patient assessment and titration procedure is requiredto reflect and simulate the multitude of activity levels foundin the home, to ensure oxygen equipment capabilities to

effectively oxygenate the patient to improve clinical out-comes and patient adherence to the prescribed therapy.New oxygen therapy products and procedure should bevalidated through research and peer reviewed publication.

Physicians should be actively involved in the LTOTprocess to ensure complete assessment of a patient’s ox-ygen therapy needs, including patient titration, prescription,and monitoring of effective patient oxygenation at all ac-tivity levels throughout the course of the patient’s disease.

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Discussion

Branson: When we started evaluat-ing oxygen concentrators and pulse-dose for use in mechanical ventila-tion, we observed what you describedso nicely in your presentation: that ev-ery device gives a different bolus sizeof oxygen with the same setting of 3.Should these devices have a numbersetting or the actual dose size?

McCoy: Dose volume would bebest, but it is variable based on breath-ing frequency and other variables. Thestandards organization, ASTM Inter-national [formerly American Societyfor Testing and Materials], is trying toaddress that, but they haven’t reachedconsensus because of the many vari-ables that impact dose volume. Weneed to know what the dose volume isin the range of inhalation, because,though we say 60% of the inhalationis where the therapeutic dose shouldbe, is that really true, or is it 50% or70%? Yes, we need to have millilitersper pulse, but it needs to be catego-rized so we know what the variablesare.

Branson: In my understanding, thedevice will either give a constant vol-ume no matter what, and if the breath-ing frequency is high, the purity or theFIO2

will fall, or the purity will staythe same and the pulse volume willfall. The final option is that the devicewill skip 2 out of 3 breaths, in whichcase the real delivered oxygen, FDO2

—not the FIO2

—would be unknown. Butnone of that is really important, as longas SpO2

is the target. I have a penchantfor thinking closed loop is better, andI don’t see why that technology isn’tused and hasn’t become the standardof care.

McCoy: Because of cost. Nobody’spaying for that, and nobody’s askingfor it either. If all the physicians say,“I want a saturation-controlled O2 de-livery system,” what home care pro-vider is going to deliver that system?If the decision becomes either meetthe physician’s request or providebusiness as usual, then it becomes whowants the business? Payers will needto pay for closed loop technology forit to be accepted. If the physicians man-date saturation controlled oxygen de-

livery, and effective O2 therapy be-comes a standard of care by ensuringoxygenation at all activity levels, thenno one will have a choice except toprovide effective oxygen therapy.When we say the payers are drivingthe business, it’s sort of like sayingthe payers are practicing medicine, sowhy don’t we let them have the lia-bility of the consequences of ineffec-tive therapy? If no one is going to payfor effective therapy, the physicianscan still prescribe it and let someoneelse deal with the consequences: notthe physicians.

Mangus:* With all the variables andissues about which piece of equipmentdoes what, and what the RT knows,and what the physician knows, andthe fact that we can’t seem to get ev-erybody together . . . it is a huge bodyof information to try to absorb, syn-thesize, and carry with you. The sim-ple solution that is immediately avail-able and economical is “titrate tosaturate.” Patients should have—and I

* Mark W Mangus Sr RRT RPFT FAARC,Inova Labs, Austin, Texas.



know I’m preaching to the choir—pulse oximeters, and they should usethem, just like diabetics use glucom-eters, to monitor a drug that will killthem a lot more surely than O2 evercould, and that would take care of alot of the issues of which device isbetter. It puts it back to the devicethat’s best for a patient is the one thatworks.

McCoy: A lot of physicians won’tprescribe an oximeter.

Mangus: From the few surveys thathave been done, I think RTs are re-sistant too. The resistance is greaterthan half on both sides.

McCoy: The other issue is knowingwhat you’re giving, because titratingto saturation, when you hit the highestnumber on your O2 concentrator, youneed to know whether there’s anotherdevice out there that can go higher. Ifyou’re on the maximum setting on onedevice, you need to know whether youcan go higher on another device.

Mangus: Because across the breadthof all portable O2 systems today andthe delivery technology we have, thereare points at which individual patients,depending on the severity of their dis-ease and their hypoxia, will reach themaximum capability of a given de-vice or perhaps of the maximally ca-pable device available to them. Andthey need to know when to sit andrecover or modify their activities. Anda pulse oximeter allows them to dothat.

Lewarski:† I think the intermittent-flow or pulse-dosing devices basicallyfall into the same category as otherlow-flow O2 delivery devices, whichby design are highly variable. Havingbeen involved in designing and test-ing such devices, from a design stand-

point there is no bolus number to pickthat’s always right and a match to acontinuous-flow setting. In a nasal can-nula, continuous-flow comparison, ifI evaluated 100 different patients with100 different breathing patterns, tidalvolumes, breathing frequencies, in-spiratory-expiratory ratios, deadspace, et cetera, the net effective O2

delivery and FIO2would be different

for each patient. We could pick onenumber for each setting on all pulse-dose devices, and, like a broken watch,it would be right at some point intime—meaning a perfect dose matchat some given breathing pattern fornearly all patients.

I believe that the use of intermittentflow or pulse flow devices, and themore stringent oxygenation evalua-tions often associated with their use,have revealed some of the FIO2

vari-ability weaknesses that have long ex-isted in low-flow devices. If you goback to the early LTOT consensus con-ferences, the titrate to saturate con-cept was introduced long before theuse of pulse-dosing devices, simplybecause of the known variability inbreathing patterns and oxygen demandwith exercise and sleep. Some studiesfound 40-50% of all continuous-flowpatients desaturating at night on theircontinuous flow, largely because ofchanges in their nocturnal breathingpatterns. There are probably about 35published clinical studies—though notall large or randomized and controlled,and often with different devices—andI haven’t seen one that suggested thatyou can’t adequately oxygenate a pa-tient with a conserving device or apulse-dosing device, as long as it’s ap-propriately titrated.

I think there is too much emphasisand blame on the equipment. The ISO[International Organization for Stan-dardization] and the ASTM are mov-ing toward standardized labeling anddefinitions for this class of device.Simple standardization of device per-formance would be difficult if not im-possible at this time, as there are in-tellectual property rights around these

devices, which would make it nearlyimpossible to go back and make themall do exactly the same thing. The ISOis working to standardize terms anddefinitions, but taxonomy has had aproblem, even in mechanical ventila-tion.

I saw that Chatburn’s old article1

on the topic was revisited, arguing thatwe don’t use the same terms or de-scribe features and functions the sameway when it comes to the technologythat exists in these devices. I think theend result here will be a titrate to sat-urate standard of care, which will ar-rive either through the legislative pro-cess or part of the prescription/certificate of medical necessityprocess. Most clinicians believe it isultimately what’s necessary.

The opposition to letting patientshave their own oximeters is an oldmentality that may have been drivenby many RTs, as we often think ofpulse oximetry as a lab procedure. Thiswas historically associated with the re-imbursement and CPT [Current Pro-cedural Terminology] coding rules,most of which are not relevant today.Many oxygen patients aren’t waitingfor us, and they often purchase theirown oximeters on the Internet orthrough their homecare company, so Ithink we would be better off prescrib-ing them. The use of an oximeter inmanaging LTOT is frequently com-pared to managing an insulin depen-dent diabetic patient with a glucom-eter. I admit, 10 years ago I wasn’tsure that giving patients pulse oxime-ters was a good thing, but now I thinkit’s necessary. It goes to Bob’s earlierpoints about needing more physicianinvolvement. Pulmonologists proba-bly write less than 10% of the pre-scriptions for O2 in the United States:it’s primarily a primary care physi-cian function.

Branson: Joe, I think worryingabout the FDO2

in a low-flow is a cop-out. I’m not saying everything needsto do the same thing, but if I take 3 ofthese devices and they all have set-

† Joseph S Lewarski RRT FAARC, Invacare,Elyria, Ohio.



tings of 1, 2, and 3, and I know onedevice can make only 500 mL/min andthe other one can make 1,000 mL/min,then the “3” setting is very different. Iagree that the issue is the labeling sothat users understand it. Because rightnow what they think is that 3 on thisone is the same as 3 on that one, andthat it’s equivalent to 3 L/min from awall flow meter in the hospital, butit’s not.

Lewarski: Agreed. Proponents ofstandardized labeling for these deviceswant the dose and other key charac-teristics labeled, such as the triggersensitivity, trigger response time, andtotal bolus delivery time, because thesedevices operate much more like an as-sist device than a simple flow valve.They sense breathing via pressuredrop, trigger in response, and deliveran O2 bolus at some flow rate. Allflow is volume, and the device is sim-ply converting flow to volume, deliv-ered in bolus form. How they do thismay vary by device, but if you under-stand the key performance variableswhen looking at the labels and you’reeducated on the device, then you’regoing to know if a particular devicehas a greater probability of deliveringthe FIO2

and FDO2you want.

So I completely agree. I also be-lieve you’re going to see those spec-ification disclosures, whether they arevoluntary or forced through ISO andASTM. The ISO regulation for con-servers is currently being updated, andthere is a lot of language around spec-ification disclosure and labeling.

McCoy: The unfortunate thing isthat there aren’t physicians there, ei-ther.

Lewarski: The unfortunate thing isthat not many people on the ISO stan-dards committee are experts on oxy-gen and conserving devices.

McCoy: If it’s not medically driven,it’s not going to come out the way wewant it to. Another option is the high-

dose capability from intermittent-flowdevices that could address your emer-gency medical services standpoint.We’ve never looked at doing a high-dose delivery from an intermittent-flow device, so we could have a dosevolume of 200 mL or more and pro-vide gas like a little ventilator and givean FIO2

of 0.6 to 0.8 just by givingthem that high a dose, which couldbring the concept of intermittent-flowback into the hospital to get it acceptedand be translated back into the home.So at least we’d be comparing applesto apples.

Pierson:‡ You mentioned patientsbeing on home O2 therapy for an av-erage of about 11 months before theydie. I’ve heard that figure for morethan 20 years; I think I heard it at thefirst oxygen consensus conference,2

from one of the home care folks. Youalso mentioned that now we are put-ting people on O2 earlier and they’reliving longer and therefore using it lon-ger. My question for you is, do youhave data for either of those state-ments?

McCoy: Joe would.

Lewarski: Actually, the govern-ment did it for us. In 2006 the Officeof the Inspector General published areport on home oxygen, which in-cluded data on Medicare O2 patientstay from months 1 through 36. Thiswas derived from claims data, so we’renot really looking at patient-specificinformation to see what the medicaloutcome was, such as prolonged hos-pitalization or death. Instead, we arelooking at Medicare claims data fromthe oxygen start date until the claimfor services ended, meaning that thepatient was no longer on O2. In thatstudy the median stay on home O2

was about 10.5 months, and the per-centage of patients who that stayed ontherapy for 3 years was approximately22%. The published data was limitedto a 36-month review, although it hasbeen estimated that about 5-8% of thepatients were still on O2 at the 5-yearpoint, which is a milestone from thepayer perspective, because it is whenthey start reimbursing again.

What’s interesting is that the decaycurve is very steep in the first 6 months.There are a large number of patientscoming off of O2 after relatively shortperiods of use, within that first6-12 months. It is not clear whetherthese data correlate to past beliefsabout stay for late-stage O2 patients orit reflects changes in O2 stay for ear-lier stage patients with acute-on-chronic disease and a short-term needfor O2. Late-stage patients may be ex-piring after short periods of use, andpatients with acute medical issues mayimprove to a stable, normoxic base-line at the time of follow-up with theirphysician. We don’t know the specif-ics, but we know the claims stop, andthere is a high churn rate in the first11 months.

Pierson: Are you saying that we nowhave data to substantiate Bob’s com-ment that we are placing people withCOPD on home O2 therapy earlier andthey’re on it longer?

Lewarski: No.

Pierson: Or is this just a more com-prehensive set of data to substantiatehis original statement from some timein the past?

Lewarski: I don’t know the deepermeaning of these data, other than thatthere is a regression curve or decay curverepresenting the stay on oxygen fromstart to 36 months. It also clearly iden-tifies that median stay was just shy of11 months, demonstrating that half ofMedicare patients started on O2 will beoff by the 11th month, and the remain-ing half will stay on for longer periods,

‡ David J Pierson MD FAARC, Emeritus, Di-vision of Pulmonary and Critical Care Medi-cine, Harborview Medical Center, Universityof Washington, Seattle, Washington.



with continued attrition over time. Thepurpose of the study was not clinical: itwas to identify the number of MedicareO2 patients who will still be on servicewhen the payment caps at 36 months.The government wanted to know whatthe financial liability would be post the36-month cap period. That’s where the22% comes from, which was the num-ber still on rental at month 36. Whetheror not this information correlates to whatwe thought earlier about stay and sur-vival, I don’t know.

Mangus: I would suggest the datamay be there, in the same manner Joehas described, but we probably haveto go back and look between 1990and 1995, around the time that, be-cause some pulmonary rehabilitationprograms were seeing so many patientswho did not desaturate at rest and didnot therefore previously qualify for O2

therapy, but were found to desaturate(in many cases profoundly) during ex-ercise. And by pushing Medicare wegot them to modify the “at rest” re-quirement to exhibit saturation of 88%or less and to start allowing patientswho demonstrated exertional desatu-ration or even sleep desaturation orthe combination to qualify for O2. Iwould think that before then we’d havemore data statistically looking atclaims of patients who were at-restdesaturating, representing the sickerones, and then we’d be able to see thegroup coming in with earlier use inthat era and we might be able to gleansome kind of results from there andsee if there’s an uptick.

Kallet: It seems that if you start peo-ple earlier, then, ipso facto, they’regoing to survive longer! How muchof that is cause and effect?

Lewarski: I don’t know how thisdata translates clinically. I just knowhow long they are receiving oxygenservices in the home. That’s all I cansay about the data. Anything beyondthat is opinion and theory.

Criner: I agree. To totally capsu-lize the patient’s activities at home toassess their real O2 needs would bedesirable. But how do you do that?There are some data where they sim-ulated in the lab the home circum-stances in which they are more likelyto desaturate at lower levels doingsome types of home activities than theywould with other types of home ac-tivities, but how would you assess that?The second thing would be the prob-lem of adherence in the home, and notbeing reimbursed, and the RTs can’tget paid for going there. Are there datathat show patients present to the hos-pital or have an untoward responsebecause they didn’t use their O2 cor-rectly or failed to use their O2? Arethere any claims data to substantiatethat? And what do you think the fu-ture will be for using technology tobetter assess the patient’s complianceand adherence at home, and who wouldmonitor that?

McCoy: I would suggest the use of24-hour oximetry. If we can get a pa-tient to wear an oximeter for 24 hours,we could assess their oxygenation.Next, we could have a patient do theirdaily activities at their prescribed leveland encourage the patient to adhere totheir O2 because we’re doing a test. A24-hour window that reflected the pa-tient’s normal activity might be ableto identify the dips in oxygen satura-tion and help us in prescription anddevice selection. But since no one paysfor this level of patient assessment, noone does it.

Criner: How would you assess themright now in your practice? How doyou make sure they’re optimallytreated for their daily activities? Doyou ask them, or do you mimic a homescenario in the lab?

McCoy: It takes less of a scientificapproach, and I think the people whogo into the home know this. Whenyou talk to a non-adherent patient andask why they’re not using it more, you

hear answers such as, “It’s too heavy,”or, “The cannula hurts my nose,” or “Idon’t feel any better with it.” You tryto find out their reasons for not ad-hering, and many times, to encourageadherence, you tell the patient, “Youhave to use your oxygen,” but, instead,if you take the approach of asking whythey aren’t using it and seeing if it’ssomething you can change, you cando that and the benefits are fantastic.

What do we know about readmis-sion? There are some data about thereadmission rate of COPD patients, es-pecially with the rehospitalizationproblem. I think in western Pennsyl-vania one of the home care companieswas monitoring the data and had abouta 35% COPD patient readmission. Idon’t know if that’s O2-dependent, butif you’ve got 35% coming back to thehospital in the first 30 days, that’s abig threat for a penalty from CMS[Centers for Medicare and MedicaidServices]. So what this home care com-pany is doing is reinvesting in havingRTs and technology. They’ve changedfocus from what CMS is paying, andare looking to what the future’s goingto be, so they’re investing in RTs andtechnology to oxygenate the patients,really targeting the O2, and they’veshown a 7 or 8% reduction in read-mission. Just by doing professional re-spiratory care with therapy as the endpoint, as opposed to procedural drop-ping equipment off.

Hess:§ I’ll be a bit of a contrarian.On the one hand it sounds very attrac-tive to give patients pulse oximetersand allow them to titrate their O2 totheir O2 saturation, but it may not beso simple. Here’s one of my concerns.Imagine a patient with COPD who’searly in an exacerbation and their PCO2

is rising and their O2 saturation is drop-

§ Dean R Hess PhD RRT FAARC, Editor inChief, RESPIRATORY CARE, and Department ofRespiratory Care, Massachusetts General Hos-pital, Harvard School of Medicine, Boston, Mas-sachusetts.



ping. So maybe the prudent thingwould be not be to turn up the O2 butto call the doctor or go to the emer-gency department. Or, to go back toBob Owens’s talk, the patient is de-saturating at night because they’re hav-ing OSA [obstructive sleep apnea], andthe prudent thing may not be to turnup the O2 but to put the patient onCPAP. I’d be a little careful beforesaying that every patient at home onO2 really needs a pulse oximeter, untilwe think through that carefully.

Lewarski: I’d like to support Dean’scomments. One of the questions I keepasking about closed loop feedbackmodels, and a lot of what I call “mi-cro-titration” of LTOT, is that nearlyeverything we know about LTOT out-comes is based on the Nocturnal Ox-ygen Therapy Trial and the MedicalResearch Council study and using O2

for 17 or more hours a day, which wasconsidered good adherence. The pa-tients in these studies were off oxygena good chunk of the day, and, basedon their study entrance criteria, weremoderately or severely hypoxemic onroom air. In the benchmark research,patients would likely experience mod-erate to severe hypoxemia about 30%of the day. In that population, is a short,mild desaturation clinically relevant?

If the patient walks across a park-ing lot and has a mild desaturationfrom the mid-90s to 89, and they stopand recover, then start strolling at theirnormal rate without additional desatu-rations, is that a clinically relevant de-saturation for a patient with chroniclung disease? Would responding tothat, or potentially over-responding

and making a patient wear an oxime-ter 24/7, change outcomes? I don’tthink we know the answers, but I won-der if it’s overkill. Right now we’refighting with them just to wear theirO2 or nasal cannula at least those17 hours a day, and especially whenthey ambulate. I’m not sure that weknow enough about lifestyle, ambula-tion, and O2 therapy as a whole tomake this leap simply because we havesome technology available. I don’tthink it should be about reimburse-ment, but, instead, whether this tech-nology is the right approach.

Jeff Ward: I’ll reinforce Dean’scomment. There’s a very good pro-spective randomized controlled trial byJohn Downs’s group that showed thatsupplemental O2 impedes detection ofhypercapnia in the post-anesthesia re-covery area.3 This is even more of aproblem outside the high caregiver/patient ratio area of the post-anesthe-sia recovery unit, such as the hospitalfloor or the patient’s home. Perhapsthe increased emphasis on waveformcapnography in the newest AmericanHeart Association guidelines for car-diopulmonary resuscitation4 will im-prove both awareness and technology.

McCoy: There is a correlation inthe sleep industry. In an overnightsleep study, if a patient desaturates for10 seconds, that’s an event. And ifyou have 10 events, you have an RDI[respiratory disturbance index] of 10.We throw CPAP on very fast for veryminimal desaturations. If we aggres-sively attack desaturations for veryshort periods in a sleeping patient,

shouldn’t it be the same with a COPDpatient with comorbidities kicking in?Shouldn’t the rationale for sleep bethe same as for any other disease?

Hess: I don’t know that we can saythat.

Claure: Sort of in defense of mon-itoring, I don’t think the knowledge ofthe information obtained by the mon-itors is bad for your patients. Learninghow often or how severe is the hy-poxemia or the hyperoxemia in an in-dividual patient or in a group of pa-tients may be important. The key iswhat you do with the information.Having a very sick patient titrating hisor her own O2 may not be the best useof monitors, but at least finding outhow the patient’s oxygenation is dur-ing the day or night and over timemay be important.

1. Chatburn RL, Mireles-Cabodevila E.Closed-loop control of mechanical ventila-tion: description and classification of tar-geting schemes. Respir Care 2011;56(1):85-102.

2. Problems in prescribing and supplying ox-ygen for Medicare patients. Summary of aConference on Home Oxygen Therapy heldin Denver, February 28 and March 1, 1986.Am Rev Respir Dis 1986; 134(2):340-341.

3. Fu ES, Downs JB, Schwiger JW, MiguelRV, Smith RA. Supplemental oxygen im-pairs detection of hypoventilation by pulseoximetry. Chest 2004;126(5):1552-1558.

4. Neumar RW, Otto CW, Link MS, KronickSL, et al. Part 8: Adult advanced cardio-vascular life support. 2010 American HeartAssociation guidelines for cardiopulmonaryresuscitation and emergency cardiovascu-lar care science. Circulation 2010;122(Suppl):S729-S767.

This article is approved for Continuing Respiratory Care Educationcredit. For information and to obtain your CRCE

(free to AARC members) visitwww.rcjournal.com



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