Aeromedical Transportation

Aeromedical Aeromedical TransportationTransportation

Sarah McPherson & Dr. A AbbiSarah McPherson & Dr. A Abbi

November 1, 2001November 1, 2001

OutlineOutline

HistoryHistory Aviation PhysiologyAviation Physiology StructureStructure EquipmentEquipment Patient transportPatient transport CasesCases

History - a pop quizHistory - a pop quiz

When was the first documented use of areomedical transport?When was the first documented use of areomedical transport?• 1870: During the Franco-Prussian war 160 wounded soldiers and 1870: During the Franco-Prussian war 160 wounded soldiers and

civilians were evacuated by hot air balloon.civilians were evacuated by hot air balloon. When were airplanes first used for transport?When were airplanes first used for transport?

• 1910 was the first privately funded fixed wing to transport 1910 was the first privately funded fixed wing to transport patients. WW I&II saw large numbers of casulties transported to patients. WW I&II saw large numbers of casulties transported to definitive medical caredefinitive medical care

When was the helicopter invented?When was the helicopter invented?• First flight in 1939. First rescue mission in 1945.First flight in 1939. First rescue mission in 1945.

What war marked the advent of helicopters for medevac?What war marked the advent of helicopters for medevac?• The Korean warThe Korean war

When was the first hospital-based helicopter program started?When was the first hospital-based helicopter program started?• 1972, Denver, Colarado1972, Denver, Colarado

Aeromedical FactsAeromedical Facts

There are ~ 275 HEMS operating in the USAThere are ~ 275 HEMS operating in the USA ~ 4-5 in Canada~ 4-5 in Canada since 1950 estimated 1,000,000 lives have been saved since 1950 estimated 1,000,000 lives have been saved

as a result of all areomedical transportas a result of all areomedical transport STARS is 100% devoted to HEMSSTARS is 100% devoted to HEMS

Aviation PhysiologyAviation Physiology

4 laws that you need to know about:4 laws that you need to know about:

Dalton’s Law:Dalton’s Law:PPTT= P= P11 + P + P22+P+P33 … …

• the total atmospheric pressure is equal to the sum total of the total atmospheric pressure is equal to the sum total of the constituentsthe constituents

• Why does this matter? Why does this matter? – As the atmospheric pressure decreases with altitude the As the atmospheric pressure decreases with altitude the

partial pressure of oxygen also decreases.partial pressure of oxygen also decreases.– As the partial pressure of oxygen decreases, oxygen saturation As the partial pressure of oxygen decreases, oxygen saturation

also decreasesalso decreases


Boyle’s LawBoyle’s LawPP11 V V11 = P = P22 V V 22

• as pressure decreases, volume increasesas pressure decreases, volume increases• What is the significance?What is the significance?

– With ascent trapped gases will expandWith ascent trapped gases will expand– with descent gases will retract with descent gases will retract

Henry’s LawHenry’s Law• the mass of gas absorbed by a mass of liquid is directly the mass of gas absorbed by a mass of liquid is directly

proportional to the partial pressure of gas above the liquidproportional to the partial pressure of gas above the liquid• Significance? Significance?

– When diving the increased pressure forces gas into the bloodstreamWhen diving the increased pressure forces gas into the bloodstream– rapid ascent causes gas to come out of solution into the rapid ascent causes gas to come out of solution into the

bloodstreambloodstream– How would this relate to air transport?How would this relate to air transport?


Charles’ LawCharles’ LawVV11 T T22 = V = V22 T T11

• therefore temperature falls with altitudetherefore temperature falls with altitude

StructureStructure

Sponsorship of services:Sponsorship of services:• HEMS operations are costlyHEMS operations are costly• annual budgets of $700,000 - $ I.6 million (1986)annual budgets of $700,000 - $ I.6 million (1986)• hospital-basedhospital-based• private servicesprivate services• public service agenciespublic service agencies

Structure - Types of MissionsStructure - Types of Missions

Primary:Primary:• sole means of transport of patient to receiving facilitysole means of transport of patient to receiving facility

Secondary:Secondary:• transfer from a facility where some degree of stabilization transfer from a facility where some degree of stabilization

has been donehas been done

Tertiary:Tertiary:• inpatient transferinpatient transfer

Structure - types of AircraftStructure - types of Aircraft

Single engine vs. twin engineSingle engine vs. twin engine must be capable of lifting crew, equipment, fuel, must be capable of lifting crew, equipment, fuel,

reserves of fuel and oxygenreserves of fuel and oxygen center of gravity must be large enough such that center of gravity must be large enough such that

variations of persons and equipment inside the cabin variations of persons and equipment inside the cabin will not interfere with the flightwill not interfere with the flight

capability in poor weather and at night (VFR vs IFR)capability in poor weather and at night (VFR vs IFR) aircraft space - patient’s head and chest must be aircraft space - patient’s head and chest must be

accessible to 2 crew membersaccessible to 2 crew members patient loadingpatient loading

• minimal maneuveringminimal maneuvering• ability to perform load with blades turningability to perform load with blades turning

Structure - Aeromedical PersonnelStructure - Aeromedical Personnel

Variable crew compositionVariable crew composition usually 2 members; N/N, N/P, P/M, M/Musually 2 members; N/N, N/P, P/M, M/M routine physician on flight is uncommonroutine physician on flight is uncommon ~ 20% of flight have flight doc~ 20% of flight have flight doc difficult to predict which flights would benefit by having difficult to predict which flights would benefit by having

a doc on boarda doc on board

Evidence for the flight physician …..Evidence for the flight physician …..

Aeromedical Personnel - Evidence for the flight Aeromedical Personnel - Evidence for the flight physicianphysician

Lit review found 7 papers (4 trials, 1 positions paper and 2 from Lit review found 7 papers (4 trials, 1 positions paper and 2 from really obscure journals)really obscure journals)

All 2 articles dealt with trauma patients, 2 with all air transportsAll 2 articles dealt with trauma patients, 2 with all air transports all relatively small studies (n = 300-1,169)all relatively small studies (n = 300-1,169) 1 study found a positive result based on TRISS scores and 1 study found a positive result based on TRISS scores and

predicted vs actual mortalitypredicted vs actual mortality 3 studies found no difference (groups similar for patient 3 studies found no difference (groups similar for patient

demographics, severity of injury) in mortality, ICU length of stay demographics, severity of injury) in mortality, ICU length of stay or hospital length of stayor hospital length of stay

largest study only powered to detect a 10% difference in largest study only powered to detect a 10% difference in mortalitymortality

JAMAJAMA. 1987. Vol 257, no. 23, pp3246-3250. 1987. Vol 257, no. 23, pp3246-3250

J of TraumaJ of Trauma. 1991. Vol. 31, no. 4, pp 490-494. 1991. Vol. 31, no. 4, pp 490-494

Ann Emerg MedAnn Emerg Med. 1992. Vol. 21, no. 4, pp 375-378. 1992. Vol. 21, no. 4, pp 375-378

Ann Emerg Med.Ann Emerg Med. 1995. Vol. 25, no. 2, pp. 187-192 1995. Vol. 25, no. 2, pp. 187-192

Structure - CommunicationsStructure - Communications

Must have a full-time dispatch/link centerMust have a full-time dispatch/link center

Who do you need link together?Who do you need link together?• Referring agentReferring agent• referral physicianreferral physician• aircraftaircraft• flight coordination center (air traffic control)flight coordination center (air traffic control)• ground servicesground services

communication center needs to follow the flight position communication center needs to follow the flight position and give directions, distances, and scene coordinatesand give directions, distances, and scene coordinates

aircraft must be able to communicate with communication aircraft must be able to communicate with communication center, ground EMS, air traffic control, public service unitscenter, ground EMS, air traffic control, public service units

Logistical IssuesLogistical Issues

SafetySafety• 1980-1985: 47 deaths of flight crew members1980-1985: 47 deaths of flight crew members• an emphasis on safety and increased regulations has an emphasis on safety and increased regulations has

decreased “accidents”decreased “accidents”• Safety standards:Safety standards:

– crew trainingcrew training– daily craft inspectionsdaily craft inspections– impartiality of the pilot impartiality of the pilot – properly stowed equipment and secured patientproperly stowed equipment and secured patient– limits on work hourslimits on work hours

Logistical IssuesLogistical Issues

Notification:Notification:• Level of response: status, stand-by, confirmed requestLevel of response: status, stand-by, confirmed request• Preflight : accurate geographic location and possible hazardsPreflight : accurate geographic location and possible hazards• Public safety agencies to provide crowd and traffic controlPublic safety agencies to provide crowd and traffic control

Landing Zones:Landing Zones:• 60x60 foot area - day60x60 foot area - day• 100x100 foot area - night100x100 foot area - night• clear of loose debrisclear of loose debris• marked by lights/flaresmarked by lights/flares

Approaching the helicopterApproaching the helicopter• only when rotor blades at complete stoponly when rotor blades at complete stop• approach from the front NEVER the tailapproach from the front NEVER the tail• follow directions of the pilotfollow directions of the pilot

LogisticsLogistics

In general aeromedical transport is not indicated unless In general aeromedical transport is not indicated unless it decreases transport time or delivers medical expertise it decreases transport time or delivers medical expertise or equipmentor equipment

how do you know transport times?how do you know transport times?• Hopefully a chart of call existsHopefully a chart of call exists• helicopter flying time:helicopter flying time:

– ~ 120 mph~ 120 mph– double flying timedouble flying time– add 10-30 minutes at the scene add 10-30 minutes at the scene – add 5-10 minutes for dispatch timeadd 5-10 minutes for dispatch time

EquipmentEquipment

Physical Exam limitationsPhysical Exam limitations• heart sounds, breath sounds, palpation of carotid pulse very heart sounds, breath sounds, palpation of carotid pulse very

difficult difficult Communication limitationsCommunication limitations

• difficult for the crew to hear if patient has concernsdifficult for the crew to hear if patient has concerns Electronic monitoringElectronic monitoring

• cardiac monitoringcardiac monitoring• blood pressureblood pressure• endtidal CO2endtidal CO2• temperaturetemperature• oxygen saturationoxygen saturation

Therapeutic devicesTherapeutic devices• defibrillator, intraaortic balloon pump, respiratordefibrillator, intraaortic balloon pump, respirator

ETT, air splints, iv infusions, pacemakersETT, air splints, iv infusions, pacemakers

Patient TransportPatient Transport

TRAUMA PATIENTS :TRAUMA PATIENTS :

1. Scene Calls1. Scene Calls appears to be the most justifies use of helicopter transportappears to be the most justifies use of helicopter transport

early studies showed improved actual mortality vs early studies showed improved actual mortality vs predicted.predicted.• 2 major studies (N= 300, N = 1273) of helicopter vs ground2 major studies (N= 300, N = 1273) of helicopter vs ground• predicted mortality based on TRISS (TS, ISS & mechanism)predicted mortality based on TRISS (TS, ISS & mechanism)• 52% reduction in predicted mortality and 21% redcution in 52% reduction in predicted mortality and 21% redcution in

expected mortality reported (expected mortality reported (JAMA JAMA . 1983;249(22): 3047-3051 . 1983;249(22): 3047-3051 Ann Emerg Ann Emerg

Med.Med.1985; 14(9): 859-8641985; 14(9): 859-864)) hospital/ICU length of stay (use log regression to account hospital/ICU length of stay (use log regression to account

for differences in study groups)for differences in study groups)

Transport - Scene callsTransport - Scene calls

more recent studies have looked at more objective more recent studies have looked at more objective markersmarkers• larger studies (N= 20-22,000), retrospectivelarger studies (N= 20-22,000), retrospective• both found air transported patients had higher ISS, lower both found air transported patients had higher ISS, lower

TS, lower mean BP & lower GCSTS, lower mean BP & lower GCS• 1 study showed no difference in mortality but did not 1 study showed no difference in mortality but did not

comment on hospital/ICU length of stay (used log comment on hospital/ICU length of stay (used log regression to account for differences in study populations) regression to account for differences in study populations) J J of Trauma.of Trauma. 1998;45(1): 140-146 1998;45(1): 140-146

• another study found a trend toward decreased mortality another study found a trend toward decreased mortality rate in the helicopter grouprate in the helicopter group

– stat sig improvement in mortality for patients with TS 5-12 & stat sig improvement in mortality for patients with TS 5-12 & ISS 21-30 in the helicopter populationISS 21-30 in the helicopter population

J of trauma.J of trauma. 1997; 43(6): 940-946 1997; 43(6): 940-946

Trauma - Scene calls GuidelinesTrauma - Scene calls Guidelines

Should be dispatched for seriously injured patients who Should be dispatched for seriously injured patients who are salvageableare salvageable

not justified if flight does not reduce transport time not justified if flight does not reduce transport time unless providing equipment or skillsunless providing equipment or skills

patient should be transported to nearest appropriate patient should be transported to nearest appropriate hospitalhospital

should be integrated into hospital EMSshould be integrated into hospital EMS dispatched within medical guidelines established by dispatched within medical guidelines established by

regional EMSregional EMS

TransportTransport

Trauma - interfacility TransportTrauma - interfacility Transport 3 major studies:3 major studies:

1. prospective cohort , N= 200, measured actual vs predicted 1. prospective cohort , N= 200, measured actual vs predicted mortalitymortality

air transport had 25% decrease in predicted mortalityair transport had 25% decrease in predicted mortalityj of Trauma.j of Trauma. 1989; 29(6): 789-793 1989; 29(6): 789-793

2. Retrospective case series, N = 9162. Retrospective case series, N = 916

cases were reviewed and categorized into essential, helpful or “not cases were reviewed and categorized into essential, helpful or “not a factor” with respect to air transport.a factor” with respect to air transport.

~ 27% were determined to be essential/helpful~ 27% were determined to be essential/helpfulArch SurgArch Surg 1987; 122: 992-996 1987; 122: 992-996

3. Prospective cohort, N = 1,387 ( 153 by ground), end point 30 day 3. Prospective cohort, N = 1,387 ( 153 by ground), end point 30 day mortalitymortality

no difference in 30 day mortality no difference in 30 day mortality J of Trauma.J of Trauma. 1998; 45(4): 785-790 1998; 45(4): 785-790

TransportTransport

Trauma - UrbanTrauma - Urban 2 major studies:2 major studies:

1. Retrospective, N = 6061. Retrospective, N = 606

lower TS and GCS in helicopter grouplower TS and GCS in helicopter group

longer transport times within the city limits longer transport times within the city limits

mortality increased 18% vs 13% (stat sig)mortality increased 18% vs 13% (stat sig)J of Trauma.J of Trauma. 1988;28(8): 1127-1134 1988;28(8): 1127-1134

2. 2. J of Trauma.J of Trauma. 1984; 24: 946 1984; 24: 946

Patient TransferPatient Transfer

CardiacCardiac Reasons for concerns:Reasons for concerns:

• hypoxia at high altitude creates increased HR and RR and ? hypoxia at high altitude creates increased HR and RR and ? MVO2MVO2

• flight increases plasma catecholamines (flight increases plasma catecholamines (Circulation.Circulation. 1998;78(Suppl 2): 188 1998;78(Suppl 2): 188)) Numerous studies have looked at this patient groupNumerous studies have looked at this patient group

• most are case series with historical controlsmost are case series with historical controls• in general show no increased mortality en route or to hospital in general show no increased mortality en route or to hospital

dischargedischarge• ~ 12-20% have complication en route (hypotension, ~ 12-20% have complication en route (hypotension,

arrhythmia, third degree heart block)arrhythmia, third degree heart block)• no increase in bleeding complications when transported post no increase in bleeding complications when transported post

lytic (very small series)lytic (very small series)• no improved rates of outcome reportedno improved rates of outcome reported

TransportTransport

STROKESTROKE with the advent of tPA for the treatment of stroke rapid with the advent of tPA for the treatment of stroke rapid

transport is becoming an isuetransport is becoming an isue

2 studies2 studies

1. Transport of stroke patient within 24 hr of symptoms1. Transport of stroke patient within 24 hr of symptoms

n= 73n= 73

no significant deterioration of symptoms, no patient received no significant deterioration of symptoms, no patient received tPA on arrival to hospital, 93% of patient felt they benefited tPA on arrival to hospital, 93% of patient felt they benefited from HEMSfrom HEMS

2. Transport of patient after tPA 2. Transport of patient after tPA

n = 24n = 24

no neurologic or systemic complicationsno neurologic or systemic complicationsStroke.Stroke. 1999;30:2366-2368 1999;30:2366-2368 Stroke.Stroke. 1999;30:2580-2584 1999;30:2580-2584

TransportTransport

Preterm LaborPreterm Labor Air Transport not recommended if:Air Transport not recommended if:

• previous precipitous deliveryprevious precipitous delivery• cervix dilated 7cm or morecervix dilated 7cm or more• rapidly progressing labor (major change in Cx between time of rapidly progressing labor (major change in Cx between time of

dispatch and arrival of AMC)dispatch and arrival of AMC)• other medical reason not to flyother medical reason not to fly

Indications for transport:Indications for transport:• Gestational age 24-32 wkGestational age 24-32 wk• evidence of PTL with regular uterine contractionsevidence of PTL with regular uterine contractions• +/- PROM+/- PROM• NOT fully dilated/ presenting part at perineumNOT fully dilated/ presenting part at perineum• caution if Cervix caution if Cervix >> 7 cm 7 cm• patient accepted at tertiary care centerpatient accepted at tertiary care center

TransportTransport

Preterm laborPreterm labor Prior to arrival of AMC (phone orders)Prior to arrival of AMC (phone orders)

• vag exam, ? Dilation , effacement, and fetal heart tonesvag exam, ? Dilation , effacement, and fetal heart tones• Iv access and rehydrate up to 500mlIv access and rehydrate up to 500ml• indomethacin 100mg prindomethacin 100mg pr• Steroids - 24 mg IM BetamethasoneSteroids - 24 mg IM Betamethasone• iv magnesium 4 grm over 30 minutes then 2 gr/hriv magnesium 4 grm over 30 minutes then 2 gr/hr

On arrival of AMCOn arrival of AMC• repeat vag examrepeat vag exam• reconsider transport if rapidly progressing or Cx > 7 cmreconsider transport if rapidly progressing or Cx > 7 cm• Cardiac and O2 monitoringCardiac and O2 monitoring

TransportTransport

Preterm laborPreterm labor InflightInflight

• transfer with mom’s head in reartransfer with mom’s head in rear• semi-sitting ofr left lat decubsemi-sitting ofr left lat decub• O2 sat > 95%O2 sat > 95%• monitor BP : stop Mg if BP < 100 or HR < 100monitor BP : stop Mg if BP < 100 or HR < 100• if patient destas: stop Mg, sit up, lower flight altitude, give if patient destas: stop Mg, sit up, lower flight altitude, give

O2O2• monitor contractionsmonitor contractions

Imminent deliveryImminent delivery• suspect if stacking contractions, ROM en route, increased suspect if stacking contractions, ROM en route, increased

bleedingbleeding• expect a breech presentation (~ 40% of prems) expect a breech presentation (~ 40% of prems)

TransportTransport

BurnsBurns increase in fluid loss with decrease atmospheric increase in fluid loss with decrease atmospheric

humidityhumidity prone to hypothermia with decreased ambient prone to hypothermia with decreased ambient

temperaturetemperature

Decompression sicknessDecompression sickness maintain on 100% O2maintain on 100% O2 must fly at < 1000 feet to prevent further dysbarismmust fly at < 1000 feet to prevent further dysbarism

TransportTransport

General IndicationsGeneral Indications• when ground transport time is excessivewhen ground transport time is excessive• access to needed care is not accessible locally and delay in access to needed care is not accessible locally and delay in

receiving care will have adverse outcomereceiving care will have adverse outcome• local resources inappropriate for transport (ie most rural local resources inappropriate for transport (ie most rural

communities have limitted resources and BLS crews only)communities have limitted resources and BLS crews only)

ContraindicationsContraindications• patient is terminally ill with no medically treatable problempatient is terminally ill with no medically treatable problem• DNRDNR• code in progresscode in progress

TransportTransport

Relative ContraindicationsRelative Contraindications• active laboractive labor• diving within 12-24 hrdiving within 12-24 hr• violent/dangerous patientviolent/dangerous patient• gas trapping in enclosed body compartmentgas trapping in enclosed body compartment• condition overwhelms equipment or resources of the condition overwhelms equipment or resources of the

aeromedical programaeromedical program

TransportTransport

Optimal mode of transportOptimal mode of transport• urban: ground ambulanceurban: ground ambulance• rural: air or ground ambulancerural: air or ground ambulance• long range: fixed winglong range: fixed wing

TransportTransport

Comparison of groundComparison of ground

vs rotor vs fixed wingvs rotor vs fixed wing

TransportTransport

Ground AmbulanceGround Ambulance

vs rotor vs fixed wingvs rotor vs fixed wing

“ “ I always believed that the helicopter would be an I always believed that the helicopter would be an outstanding vehicle for the greatest variety of life-outstanding vehicle for the greatest variety of life-saving missions, and now, near the close of my life, I saving missions, and now, near the close of my life, I have the satisfaction of knowing that this proved to be have the satisfaction of knowing that this proved to be true”true”

- Igor Sikorsky , - Igor Sikorsky , 19721972

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Aeromedical Transportation