Airway adjuncts and Oxygen therapy

OXYGEN THERAPY

Dr.Gagan

Oxygen:

• Colourless• Odourless• Tasteless• Transparent gas• Slightly heavier than air• Constitutes 20-21% of atmospheric air• Essential for life

What is O2 Therapy ?

Oxygen therapy is the administration of oxygen at concentrations greater than that in room air to treat or prevent hypoxia.

Oxygen is available to us • Medical grade oxygen (99% or 99.5% pure) is

manufactured by fractional distillation of liquid air.• Oxygen can be stored as compressed gas at room

temperature or as liquid when refrigerated.• Oxygen cylinder

• Delivery system : Hose drops, Gas columns, Articulating arms

E-cylinder capacity

H-cylinder

Capacity

Pressure (psig at 20oC)

Color PIN index

625-700 liters

6000-8000 liters

1800-2000 Black body with white shoulder

2, 5

Anoxia No oxygen availability in tissues

Hypoxia Lack of oxygen availability in

tissues

Hypoxemia Lack of oxygen in the blood

Basics

6

Indications for Oxygen Therapy

• Hypoxemia– Inadequate amount of oxygen in the blood– SPO2 < 90%

– PaO2 < 60 mmHg

• Excessive work of breathing• Excessive myocardial workload

7

Causes of Hypoxemia• Shunt• Hypoventilation

– As carbon dioxide increases oxygen falls• V/Q mismatching (ventilation/perfusion)

– Pneumonia– Pulmonary edema– ARDS

• Increased diffusion gradient– asbestosis– Early pulmonary edema

Hypoxia

Types of hypoxia• Hypoxic hypoxia – PaO2↓

• Anaemic hypoxia – O2 content ↓, PaO2 normal

• Stagnant hypoxia

• Histotoxic hypoxia

Hypoxic hypoxia• Causes

– O2 poor air, hypoxic gas mixture– High altitude – Hypoventilation– Shunts – Septal defects – Diffusion defects - pneumonia, lobar collapse

Anaemic hypoxia• Oxygen carrying capacity of blood is

decreased. – Anemia :↓ haemoglobin– Altered haemoglobin

• CO poisoning • meth / sulph-haemoglobin

Stagnant hypoxia• Inadequate tissue perfusion• Generalized:

- Hypovolemia- Mitral stenosis- Constrictive pericerditis- Myocardial ischaemia

• Localized hypo perfusion: - Arterial obstruction, thrombus,

oedema

Histotoxic hypoxia

• Cells can not utilize the oxygen .• Electron transfer system of cytochrome

oxidase is paralysed.• e.g.

– cyanide poisoning

Benefit of O2 therapy in Hypoxia

Hypoxic hypoxia + + +Anaemic hypoxia +Stagnant hypoxia +Histotoxic hypoxia -

Effects of hypoxia• Acute hypoxia :

- Restlessness- Disorientation, confusion- In-coordination, Impaired judgment- Hyperventilation air hunger-Circulatory changes (tachycardiabrady )

• Chronic hypoxia :- fatigue, drowsiness, ↓ work capacity- inattentiveness ,apathy, delayed reaction time

Oxygen Therapy

Assessment of need• Presence of clinical indicators • Measurement of inadequate oxygen saturations

– by invasive or noninvasive methods,• Arterial blood gas• Pulse oximetry

Errors in pulse oximetry• Artificial fingernails• Dark pigmentation • Electrical interference • Intravenous dyes • Movement• Nail Polish • Pulsatile venous system• Radiated light

Types of Oxygen Therapy• Giving Oxygen more

than 21% at ambient atm pressure

• Giving Oxygen more than 21% at high atm pressure ( >1 atm)

Orthobaric Hyperbaric

Three clinical goals of O2 therapy

1. Treat hypoxia

2. Decrease work of breathing

3. Decrease myocardial Work

Oxygen therapy

1. Correcting Hypoxemia• By raising Alveolar & Blood levels of Oxygen• Easiest objective to measure

2. Decreasing symptoms of Hypoxemia• Supplemental O2 can help relieve symptoms of

hypoxia–Lessen dyspnoea/work of breathing– Improve mental function

3. Minimizing Cardiopulmonary workload• Cardiopulmonary system will compensate for Hypoxemia

by:– Increasing ventilation to get more O2 in the lungs & to the Blood– Increased work of breathing – Increasing Cardiac Output to get more oxygenated blood to tissues– Hard on the heart, especially if diseased

• Hypoxia causes Pulmonary vasoconstritcion & Pulmonary Hypertension– These cause an increased workload on the right side of heart– Over time the right heart will become more muscular & then

eventually fail (Cor Pulmonale)

• Supplemental o2 can relieve hypoxemia & relieve pulmonary vasoconstriction & Hypertension, reducing right ventricular workload!!

• Minimal acceptable saturation for post surgical patients who are cared for in non critical setup is 92%

FACTORS THAT DETERMINE WHICH SYSTEM TO USE

1. Patient comfort / acceptance 2. The level of FiO2 that is needed

3. The requirement that the FiO2 be controlled within a certain range4. The level of humidification and /or nebulization5. Minimal resistance to breathing6. Efficient & economical use of oxygen

Orthobaric Oxygen therapy

EQUIPMENT

LOW FLOW DEVICES

HIGH FLOW DEVICES

LOW FLOW OXYGEN DELIVERY

DEVICES

NASAL CANNULAHOW TO USE? disposable.

plastic devise with two protruding prongs for insertion into the nostrils, connected to an oxygen source.

- The standard nasal cannula delivers an inspiratory oxygen fraction (FIO2) of 24-44% at supply flows ranging from 1-6 L·min-1.

- The formula is FIO2 = 20% + (4 × oxygen litre flow). The FIO2 is influenced by breath rate, tidal volume and pathophysiology.

- The slower the inspiratory flow the higher the FIO2.

Delivers 24 to 44% oxygen at 1 to 6 L/min• 1 = 24 %• 2 = 28 %• 3 = 32 %• 4 = 36 %• 5 = 40 %• 6 = 44 %

FACTSADVANTAGESPatients are able to talk and eat with oxygen in place

Easily used in home setting

DISADVANTAGESmay cause irritation

to the nasal and pharyngeal mucosa

if oxygen flow rates

are above 4 liters/minute Variable FIO2

SIMPLE OXYGEN MASKSimple mask is made of clear, flexible , plastic

or rubber that can be molded to fit the face.

It is held to the head with elastic bands.

Some have a metal clip that can be bent over the bridge of the nose for a comfortable fit

O2 inlet

Exhalation ports

• Open ports for exhaled gas

• Air entrained through ports if O2 flow through does not meet peak inspiratory flow

• 5 – 10 liters per minute • < 5 liters will not flush CO2

from mask • 40 – 60% FIO2 approximately

depending on the pattern of breathing.

FACTSADVANTAGES

• Can provide increased delivery of oxygen for short period of time

• The face mask is indicated in patients with nasal irritation or epistaxis.

• It is also useful for patients who are strictly mouth breathers.

DISADVANTAGES-Tight seal required to deliver higher concentration- Difficult to keep mask in position over nose and mouth-Potential for skin breakdown due(pressure, moisture)- Uncomfortable for pt while

eating or talking.- Obtrusive, uncomfortable

and confining. - It muffles communication,

obstructs coughing.

PARTIAL REBREATHING MASK• Mask is a simple mask with a reservoir bag.• Same as the Non re-breathing bag but..without

a one way valve.• Low flow, medium concentration • 50 – 70% • 8 – 12 liters per minute • Bag should remain at least 1/3 full during

inspiration • Allow the mixture or oxygen and carbon dioxide

in the mask.

Partial Rebreather mask

Exhalationports

O2

Reservoir

• O2 directed into reservoir• Insp: draw gas from bag

& room air• Exp: first 1/3 of exhaled

gas goes into bag (dead space)

• Dead space gas mixes with ‘new’ O2 going into bag

• Deliver ~60% O2

FACTSADVANTAGES- Can inhale room air

through openings in mask if oxygen supply is briefly interrupted.

- Not as drying to mucous membranes

DISADVANTAGES- Requires tight seal

- Eating and talking difficult, uncomfortable-

NON REBREATHING MASKthe one-way valve closes and all of the expired air is

deposited into the atmosphere, not the reservoir bag.

This mask provides the highest concentration of oxygen (95-

100%) at a flow rate 8-15 L/min.

It is similar to the partial rebreather mask except two one-

way valves prevent conservation of exhaled air.

Non-Rebreathing Mask

• Valve prevents exhaled gas flow into reservoir bag

• Valve over exhalation ports prevents air entrainment

• Delivers ~100% O2, if bag does not completely collapse during inhalation

O2

Reservoir

One-way valves

Non-Rebreathing system

Reservoir

Gas sourceRoom air

Expiratorygas

To patientOne way valves

FACTSADVANTAGESDelivers the highest possible oxygen concentration

Suitable for pt breathing spontaneous with sever hypoxemia

DISADVANTAGES- Impractical for long term Therapy- Malfunction can cause CO2 buildup -- suffocation Expensive Feeling of suffocation Uncomfortable

Estimating FiO2

O2 Flow rate FiO2 O2 Flow rate FiO2 O2 Flow rate FiO2

Nasal cannula Oxygen mask Mask with reservoir1 0.24 5-6 0.4 6 0.62 0.28 6-7 0.5 7 0.73 0.32 7-8 0.6 8 0.84 0.36 9 0.80+5 0.4 10 0.80+6 0.44

HIGH FLOW

DELIVERY DEVICESOr

FIXEDDELIVERY SYSTEMS

AIR ENTRAINMENT DEVICES• High flow device (o2 concentration)• Entrains air through side ports to achieve

high flows • Variable entrainment ports and/or jets

adjust FIO2 • Air Entrainment or Venti Masks • Manufacturer recommends liter flows for

each FIO2

The Venturi SystemRoom air dilutes the oxygen entering

the tubing to a certain concentration

The amount of air drawn in is determined by the size of the orifice (jet adapter).

Applying the Bernoulli principle

VENTURI MASK

How does it work?

exhaled gas

oxygen

room air

Oxygen from 24 - 50% At liters flow of 4 to 15 L/min.The mask is so constructed that there is a

constant flow of room air blended with a fixed concentration of oxygen

Is designed with wide- bore tubing and various color - coded jet adapters.

Each color code corresponds to a precise It is high flow concentration of oxygen. Oxygen concentration and a specific liter flow.

Color FiO2 O2 Flow

Blue 24% 2 L/minWhite 28% 4 L/min

Orange 31% 6 L/minYellow 35% 8 L/min

Red 40% 10 L/minGreen 60% 15 L/min

Venturi valve

FACTSADVANTAGESDelivers most precise oxygen concentration

Doesn’t dry mucous membranes (humidity)

DISADVANTAGESuncomfortableRisk for skin irritationproduce respiratory depression in COPD patient with high oxygen concentration 50%

TRACHEOSTOMY COLLARDirected into trachea Is indicated for chronic o2 therapy need O2 flow rate 8 to 10LProvides accurate FIO2Provides good humidity.Comfortable ,more efficient Less expensive

FACTSADVANTAGES

• Delivers high concentrations of oxygen directly to the lungs.

• Stable and not moved when the patient is moved or cleaned.

• Maintains saturation levels.

DISADVANTAGES• Viscosity of secretions • Clinical status • Systemic hydration • Patient compliance • Method of humidification in use• if any of the above list remain a

problem the current method of humidification may be inadequate

Additional devices for high flow• T-PIECE ADOPTORUsed on end of ET tubeProve when weaning from ventilatoris accurate FIO2Provides good humidity

Airway adjuncts

Airway Adjuncts• Oropharyngeal Airway (OP)

– Helps prevent tongue from obstructing posterior pharynx

– Potential use in unconscious patient– Cannot use in patients with intact gag reflex– SIZING: measure from corner of mouth to angle of

jaw– PLACEMENT: direct method vs rotation method.

Airway Adjuncts• Nasopharyngeal Airway (NP)

– Unconscious or depressed mental status– SIZING: Measure from the tip of the nares to the

tragus of ear– CONTRAINDICATIONS: basilar skull fracture,

midface fractures, bleeding disorders– Relative contraindication: children < 1 year old

OXYGENATION AND VENTILATIONBag-Valve-Mask

With oxygen reservoir

Bag-Mask Ventilation• Key—ventilation volume: “enough to produce

obvious chest rise”

1-Person: difficult, less effective

2-Person:easier, more effective

OXYGENATION AND VENTILATION

Successful bag-mask ventilation depends on three things: 

• Patent airway :Airway patency can be established using basic airway maneuvers

• Adequate mask seal :In order to secure a good seal, the mask must be placed and held correctly

• Proper ventilation (ie, proper volume, rate )

LMA

• Dr. Archie Brain developed LMA in 1982 as a modification of Goldman dental mask.

• Standard of airway management , filling the niche between facemask and tracheal tubes.

• They sit outside the trachea and provide a handsfree means of gas tight airway.

• The first Supraglottic airway device was LMA-Classic(1989)

Indications Contraindications

Alternative Airway during GA Risk of aspiration

Essential part of difficult airway trolley Local pathology in pharynx , larynx or upper airway.

Cardiopulmonary resuscitaion : to secure airway

Trismus, facial or upper airway trauma

Relative indication in professional singers:To avoid trauma to vocal cords

Morbid obese, > 14 week pregnant, prior opiods medication, delayed gastric empting

Reduced lung compliance/increase work of breathing

LMA Classic

ENDOTRACHEAL TUBE

(ET Tube)

• Endotracheal tubes are curved tubes used for intubation

• Tubes were previously made up of latex (indian rubber) and those still available , currently plastic tubes (PVC) are preferred because of following advantages :

Disposable (less chances of infection) Hypoallergenic ( since latex allergy is fairly common) Transparent (easy visualization of blockage ETT due

to blood , pus , secretions

• THE ET TUBE HAS THE FOLLOWING COMPONENTS :

PROXIMAL END – 15mm adapter (connector) which fits to ventilator or AMBU bag

CENTRAL PORTION – 1. A vocal cord guide (black line ) which should be

placed at the level of the opening of the vocal cords so that the tip of the ET tube is positioned above the bifurcation if the trachea.

2. A radio-opaque marker which is essential for accurate visualization of the position of the ET tube within the trachea by means of an X-ray

3. The distance indicator (marked in centimeters) which facilitates placement of ET tube.

4. A cuff- incase of cuff ET tube DISTAL END – has Murphy’s eye (opening in

the lateral wall ) which prevents complete blockage of ET tube incase the distal end is impacted with secretion , blood , etc.

TYPES• ET tubes can be : - cuffed

- uncuffed• Cuffed ET tubes are used in children > 8 years• The cuff when inflated maintains the ET tube in proper

position and prevents aspiration of contents from GI tract into respiratory tract

• In children < 8 uncuffed ET tubes are used because the narrow subglottic area performs the function of a cuff and prevents the ET tube from slipping.

ENDOTRACHEAL TUBE / ETT

High volume Low pressure cuff

Low volume High pressure cuff

USES For Mechanical Ventilation For Intermittent Positive Pressure Ventilation

(IPPV) During resuscitation Direct suctioning of trachea in meconium

aspiration In Epiglottits & life threatening croup In tetanus (however for long term bases,

tracheostomy is preferable) In angioneurotic edema

COMPLICATIONS Mechanical trauma to tongue, teeth , palate ,

pharynx & larynx during intubation procedure Stimulation of posterior of posterior pharyngeal

wall leading to coughing , vomiting or vasovagal episode with resultant hypoxia , bradycardia.

Prolonged intubation may cause pressure necrosis of laryngeal structures leading to persistant hoarseness ( hence tracheostomy) is indicated in patients requiring long-term mechanical ventilation)

Pneumothorax,Pneumonia

Oxygen tent Hood Incubator

ENCLOSURES

OXYGEN TENTConsists of a canopy placed over

the head and shoulders or over the entire body of a patient

FiO2 – 40-50% @12-15L/minO2

Variable performance device Provides concurrent aerosol therapy Disadvantage

Expensive Cumbersome Difficult to clean Constant leakage Limits patient mobility

OXYGEN HOOD• An oxygen hood covers only the

head of the infant• O2 is delivered to hood through

either a heated entrainment nebulizer or a blending system

• Fixed performance device• Fio2 – 21-100%• Minimum Flow > 7/min to

prevent CO2 accumulation

INCUBATOR• Incubators are polymethyl

methacrylate enclosures that combine servo-controlled convection heating with supplemental O2

• Provides temperature control• FiO2 – 40-50% @ flow of 8-15

L/min• Variable performance device

Evaluation:Breathing pattern - regular and at normal rate. Color - nail beds, lips, conjunctiva of eyes -

pink No confusion, disorientation, difficulty with

cognition.Arterial oxygen concentration or hemoglobin

within normal Oxygen saturation within normal limits.

Will be explained in other class

ECMO (Extracorporeal Membrane Oxygenation )

HYPERBARIC O2 THERAPY (HBOT)

DEFINITION

• A mode of medical treatment wherein the patient breathes 100% oxygen at a

pressure greater than one Atmosphere Absolute (1 ATA)

• 1 ATA is equal to 760 mm Hg at sea level

Physiological effects of HBO

• Bubble reduction ( boyle’s law)• Hyperoxia of blood• Enhanced host immune function• Neovascularization • Vasoconstriction

INDICATIONS OF HBOTACUTE CONDITIONS CHRONIC CONDITIONS

Decompression sickness Air embolism Carbon monoxide poisoning Severe crush injuries Thermal burns Acute arterial insufficiency Clostridial gangrene Necrotizing soft-tissue

infection Ischemic skin graft or flap

• Radiation necrosis• Diabetic wounds of lower

limbs• Refratory osteomyelitis• Actinomycosis (chronic

systemic abscesses)

Hyperbaric Oxygen Contd…

Contraindications to Hyperbaric Oxygen

Condition Rationale

Claustrophobia Anxiety Pneumothorax Gas emboli, pneumomediastinum

Pneumoperitoneum Tension (pneumothorax)Subcutaneous emphysema

History of spontaneous pneumothorax

Increased lung bleb incidence (pneumothorax)

Chronic obstructive pulmonary disease

Increased oxygen intoleranceIncreased risk of seizures

Pneumocystic carinii pneumonia

Questionable fetal teratogen

Seizure disorders Barotrauma to sinus/ear/lungPregnancy Decreased threshold for oxygen-induced seizuresUpper respiratory infection

Increased hemolysis

Hyperthermia  Hereditary spherocytosis

Optic neuritis Questionable - Increased optic nerve pathologyMalignant tumors Questionable - Increased vascularity for tumorsAcidosis Decreased threshold for oxygen seizures

METHODS OF ADMINISTRATION of HBOT

Problems with HBOT

• Barotrauma– Ear/ sinus trauma– Tympanic membrane rupture– Pneumothorax

• Oxygen toxicity• Fire hazards• Clautrophobia • Sudden decompression

Long Term Oxygen Therapy

• To provide prolong and improve quality of life in hypoxic pt with COPD

• Indicated For– Pt with PaO2< 55mmHg or less– Pt with PaO2< 59mmHg or less plus

peripheral edema, hematocrit of >55% or P-pulmonale on ECG

Should be reassessed at one month

Complications of Oxygen therapy

1. Oxygen toxicity2. Depression of ventilation3. Retinopathy of Prematurity4. Absorption atelectasis5. Fire hazard

1. O2 Toxicity

• Primarily affects lung and CNS.• 2 factors: PaO2 & exposure time

• CNS O2 toxicity (Paul Bert effect) – occurs on breathing O2 at pressure > 1 atm– tremors, twitching, convulsions

Pulmonary Oxygen toxicity

C/F acute tracheobronchitis• Cough and substernal pain• ARDS like state

Pulmonary O2 Toxicity (Lorrain-Smith effect)

Mechanism: High pO2 for a prolonged period of time ↓ intracellular generation of free radicals e.g.: superoxide,H2O2 , singlet oxygen ↓ react with cellular DNA, sulphydryl proteins &lipids ↓ cytotoxicity

↓ damages capillary endothelium, ↓

Interstitial edema Thickened alveolar capillary membrane.

↓ Pulmonary fibrosis and hypertension

A Vicious Cycle

2. Depression of Ventilation

• Seen in COPD patients with chronic hypercapnia• Mechanism ↑PaO2 suppresses peripheral V/Q mismatch chemoreceptors depresses ventilatory drive ↑ dead space/tidal volume ratio ↑PaCO2

3. Retinopathy of prematurity (ROP)

• Premature or low-birth-weight infants who receive supplemental O2

• Mechanism ↑PaO2

↓ retinal vasoconstriction

↓necrosis of blood vessels

↓new vessels formation

↓ Hemorrhage → retinal detachment and blindness

To minimize the risk of ROP - PaO2 below 80 mmHg

4. Absorption atelectasis100% O2

oxygennitrogen

PO2 =673PCO2 = 40PH2O = 47

A B

A – UNDERVENTILATEDB – NORMAL VENTILATED

Denitrogenation Absorption atelectasis

The “denitrogenation” absorption atelectasis is because of collapse of underventilated alveoli (which depends on nitrogen volume to remain above critical volume )

↓ Increased physiological shunt

Take home message!!

• Oxygen is a drug, prescribe it as other drugs, i.e, amount, device and time should be specified.

• If patient’s SpO2 is not good with nasal cannula, consider changing the device instead of increasing flow rate.

• Over jealous use of oxygen is often without justification & consideration of toxic effects of oxygen therapy. So think before such unaccounted for use of oxygen.

THANK YOU