Resource by MikeJenny


									  Flight Physiology:
Critical Care In The Air

 Bill Summerfield FP-C, EMT-P, PI, CMTE
History of Flight Medicine
• Ambulance systems first established in 1400’s
  to transport war casualties
History of Flight Medicine
• 1910-2 U.S. army officers at Ft. Barrancas, FL
  modify a biplane to carry a litter patient.
• 1915-First wartime evacuation of a wounded
  soldier by French in WWI
History of Flight Medicine
• Between 1936-1938 during Spanish civil war,
  German Luftwaffe transported thousands of war
  casualties in unpressurized Junkers over 1600
  mile routes up to altitudes of 18,000’ without
  serious complications.
History of Flight Medicine
• Feb.,1943-Graduation of first Flight Nurse Class
History of Flight Medicine
• Jan. 3, 1944-U.S.C.G. Aviation Training and
  Development Facility-Brooklyn,NY-requested to fly
  plasma from battery in N.Y.C. to a hospital in Sandy
  Hook,NJ. Several sailors injured in U.S.S. Turner
  explosion in a Sikorsky R-4.
History of Flight Medicine
• April 23, 1944- in
  the jungles of
  Mawlu, Burma,the
  first U.S. soldier
  flown to a field
  hospital by
History of Flight Medicine
• Dec. 1950- in 1
  week 4700 wounded
  marines evacuated
  from Chosin
  Reservoir during the
  Korean War.
History of Flight Medicine
• 1953- Korean War
  ends, more than
  311,000 patients
  airlifted to hospitals
  in the U.S. and
History of Flight Medicine
• 1967- First U.S. commercial
  flight program started by
  Superior Ambulance Service
  in Westland, Michigan.
History of Flight Medicine
• 1973- Vietnam War ends, more than 500,000
  patients flown.
History of Flight Medicine
              Wounded Mortality by Conflict

      Conflict          Time to Care      Mortality
World War I             12 to 18 hours        8.8 %
World War II            6 to 12 hours         5.8 %
Korea (w/ Helo)          2 to 4 hours         2.4 %
Vietnam (w/ Helo)       1 to 1.4 hours        1.7 %
Justifying Aero-medical Transport
• Expedient transport to a tertiary care facility
  for time-critical ill/injured patients.
• To access patients/extricate patients from
  isolated areas.
• To deliver persons with advanced scope of
  practice and additional treatment options to
  critically ill/injured patients.
Flight Appropriate Patients
• Trauma 1 Criteria
• Any significant blood loss resulting in
• Systolic BP less than 100 mmHg
• GCS less than 13
• Penetrating injuries to the head, neck, or
• Patients requiring intubation
Flight Appropriate Patients
• Burns
  – 2nd and 3rd degree >20% TBSA in patients <16
    or >50 years of age
  – 2nd and 3rd degree >30% in all age groups
  – Electrical, chemical, or thermal with inhalation
  – Circumferential or trauma/burn combo
Flight Appropriate Patients
• Unstable pelvis FXs
• Two or more proximal long bone FXs
• Amputation/near amputation above wrist or
• Pregnant trauma patient after 20 weeks
  gestation experiencing fetal distress, vaginal
  bleeding, or abdominal pain with significant
  mechanism of injury
Flight Appropriate Patients
• Ejection from vehicle
• Death of same car occupant
• Extrication time >20 minutes
• Fall >20’ (<15’ in children <14 y/o)
• High-speed impact
• Rollover
• Pedestrian thrown or run over
• Prolonged cold exposure
Flight Appropriate Patients
• Cerebral hemorrhage
• Pulmonary embolus
• Toxicological patients
• High-risk OB
Flight Appropriate Patients
• Septic patients
• Post cardiac arrest
• Cardiogenic shock
• Respiratory failure
Members of the Flight Crew
• RN/Paramedic                  61%
• RN/RN                          8%
• RN/EMT                         5%
• RN/Physician                   3%
• RN/Other                      18%
• Other                          5%

                 AirMed Sep-Oct 2000
Program Differences
• Crew configuration
• Required experience
• Weather minimums
• Equipment
• Flight rules
• Blood
Patient Information
• Number of patients
• Pt. weight
• Pt. age
• Airway status
• G.C.S.
• I.V. drips
• Special equipment
Patient Packaging
• In addition to assessing ABCs and a head-to-
  toe survey….
• Special consideration must be given to non-
  intubated patients who have a potential for
  airway compromise.
• Intubated patients should be assessed for
  tube placement and security.
• Ventilator settings should be
Patient Packaging
• All interventions performed prior to arrival
  should be documented and assessed for
  their effectiveness.
• Copies of x-rays and lab results need to
  accompany the patient.
• IV medication drips have to be transferred to
  aircrafts tubing and pump.
• All monitoring equipment must be
  transferred to the flight crew’s monitor.
Patient Packaging
• Flight crews should inquire as to the last
  doses of sedation, analgesia, and
  neuromuscular blockade, and anticipate
  their next needed administration.
• IV fluids given prior to arrival need to be
• Catheter bags should be assessed for the
  amount of urine, presence of blood, and
  emptied before loading the patient.
Patient Packaging
• Special consideration should be given to soft
  restraints in non-chemically restrained
• All prisoners must be in 4-way restraints with
  a key available to the pilot.
• Use of a “fluid containment bag” should be
  considered for bodily fluids.
Patient Packaging
• IV patency and appropriateness should be
• Cervical collars and splints may need to be
• The patient, IVs, and monitoring cables
  should still be readily accessible when a
  blanket is used to cover them.
• Keeping all cables and IVs untangled and
  free from straps is important.
Patient Packaging
• Before loading the patient the family should be
  addressed by the crew if time/situation permit.
• Once in the aircraft, all equipment must be
• Potentially needed equipment should be secured
  within reach.
• Patients should be briefed on normal noises and
  vibrations, how to communicate with crew,
  expected time of flight, before engine start-up.
• The patient should be given hearing protection.
Transport Modes
• Rotor wing
• Fixed wing
• Ground
American Eurocopter EC 145
• Dual engine
• Max cruise speed 145 kts.
• Useful load 3953 lbs.
• Max range 370 nm
• Rear load stretcher
• Capable of double pt. transport
Gas Laws
• Boyle’s Law
• Charles Law
• Henry’s Law
Boyle’s Law
• At a constant temperature,
  the volume of a gas is
  inversely proportional to the
  pressure exerted upon it.

                                  Sir Robert Boyle
Boyle’s Law
• As pressure doubles, volume halves.
• A balloon expands on ascent
Boyle’s Law
• Equipment affected by altitude
  – ET tube cuff
  – MAST
  – NG tube
  – Chest tube
  – Balloon Pump
  – Ventricular assist device
  – Vacuum/air splints
Charles Law
• “When pressure is
  constant, the volume of
  a gas is very nearly
  proportional to it’s
  absolute temperature.”

                            Jacques Charles
Henry’s Law
• “The quantity of gas dissolved in 1
  cm3 of a liquid is proportional to the
  partial pressure of the gas in
  contact with the liquid”

                                           William Henry
Henry’s Law

      The weight of a gas dissolved in a liquid is
      directly proportional to the weight of the gas
      above the liquid.
4 Stages of Hypoxia
• Indifferent stage
   – From sea level and extends to 10,000’
   – Body reacts to the lessened availability of
     oxygen in the air with increases in heart rate and
4 Stages of Hypoxia
• Compensatory stage
  – 10,000-15,000’
  – Body attempts to protect self against hypoxia by
    increasing blood pressure, heart rate, and
    depth/rate of respirations
  – Efficiency and performance of tasks requiring
    mental alertness become impaired
4 Stages of Hypoxia
• Disturbance stage
  – 15,000-20,000’
  – Marked by dizziness, sleepiness, tunnel vision,
    and cyanosis
  – Thinking becomes slowed and muscle
    coordination decreases
4 Stages of Hypoxia
• Critical Stage
  – 20,000-30,000’
  – Marked by mental confusion and incapacitation
    followed by unconsciousness usually within a
    few minutes
Time of Useful Consciousness
• T.U.C.
  – Refers to the elapsed time from the point of
    exposure to an oxygen-deficient environment to
    the point at which deliberate function is lost
Factors Influencing T.U.C.
• In addition to altitude:
   – Rate of ascent
   – Physical fitness
   – Physical activity
   – Temperature
   – Individual tolerance
   – Smoking
   – Drug/alcohol use
   – Rapid decompression-at altitudes above
     33,000’, an immediate reversal of oxygen flow
     in the alveoli takes place
Average T.U.C. for Non-Pressurized Aircraft
  – Altitude (in feet)    Time
  – 18,000 and lower      30 min.
  – 25,000                     3-5 min.
  – 30,000                     90 sec.
  – 35,000                     30-60 sec.
  – 40,000 and higher     15 sec. or less
Signs and Symptoms of Hypoxia
•       Objective signs         Subjective signs
•      Confusion                Confusion
•      Tachycardia              Headache
•      Tachypnea                Stupor
•      Seizures                 Insomnia
•      Dyspnea              `   Change in judgment or personality
       Bradycardia              Blurred vision
•      Restlessness             Tunnel Vision
•      Slouching                Hot/cold flashes
•      Unconsciousness          Tingling
•      Hypotension (late)       Numbness
       Cyanosis (late)          Nausea
•      Euphoria                 Euphoria
•      Belligerence             Anger

Barotitis Media (Ear Block)
• Results from failure of the middle ear space
  to ventilate when going from low to high
  atmospheric pressure.
• Pressure in the middle becomes increasingly
  negative and a partial vacuum is created.
• Tympanic membrane is depressed inward
  and becomes inflamed.
Barotitis Media (Ear Block)
• Blood and tissue fluids drawn into the
  middle ear cavity, and if equalization with
  ambient pressure does not take place,
  perforation of the tympanic membrane
• Severe pain, tinnitus, and possibly vertigo
  and nausea can accompany acute barotitis.
Barotitis Media (Ear Block)
• Treat symptoms by:
  – Valsalva maneuver
  – Administration of a vasoconstrictor spray
  – Ventilating with a B.V.M.
  – Having aircraft re-ascend
  – Having pt swallow or move jaw muscles
Barosinusitis (Sinus Block)
• Acute inflammation of one or
  more of the paranasal sinuses
  produced by the development of
  a pressure difference, usually
  negative, between the air in the
  sinus cavity and that of the
  surrounding atmosphere
Barosinusitis (Sinus Block)
• Common causes are colds and upper
  respiratory tract infections
• May vary from feeling of fullness around the
  sinuses to excruciating pain
• Treatment:Re-ascend until sinus pressure
  equalizes with cabin pressure, administer
  vasoconstrictors, and descend gradually
• A toothache that is caused by exposure to
  changing barometric pressures
• Commonly occurs on ascent involving a
  diseased tooth, with relief felt upon descent
• Crewmembers undergoing deep restorations
  should be restricted from flying for 48-72
Gastrointestinal Changes
• Gas expands on ascent
• Unless the gases of the GI tract are expelled
  by belching or passing of flatus, the
  expansion may produce pain, make
  breathing more difficult and possibly lead to
  hyperventilation and syncope
• Does not generally occur below 25,000’
Gastrointestinal Changes
• Gas expansion of 1 Liter in Volume in Gastrointestinal
  tract at Various Altitudes.
   – Altitude in feet          Amount (times) increased
   – Sea Level                 No increase
   – 9000                      1.5
   – 16,500                    2
   – 25,000                    3
   – 34,000                    5
   – 39,000                    7
   – 43,000                    9
Gastrointestinal Changes
• Example: Pediatric patient with abdominal
  distention- gas in abdomen can increase to
  raise diaphragm, lung volume and expansion
  then decreased. If expansion is large
  enough, the great blood vessels in the area
  will be compressed, altering blood supply to
  vital organs.
Thermal Changes
• Temperature decreases 1 degree C for every
• Exposure to cold and vibration stimulate
  vasoconstriction and decrease perspiration
• Exposure to whole-body vibration appears to
  interfere with humans’ normal cooling
  response in a hot environment
Decreased Humidity
• Increasing altitude decreases humidity
• May result in sore throat, hoarseness,
  chapped lips, and dehydration.
• Patients should receive humidified oxygen
  and be monitored for dehydration at high
• Communications in the form of speech and
  other auditory signals inside the aircraft may
  be degraded.
• Sense of hearing may be temporarily or
  permanently damaged.
• Noise acting as stress may interfere with
  patient care and safe transport.
• Noise may induce varying levels of fatigue.
• Aircraft noise interferes with evaluation of
  breath sounds, auscultation of blood
  pressure, or obtaining patient information.
• Crew members must rely on visual clues and
  monitors to assess patients during flight.
• When ambient noise levels exceed 80-85
  dBA, a person must shout to be heard.
• Decibels          Source
    60             normal conversation @ 3’
    80             garbage disposal
    103            jet flyover @ 1000’
    117            jet on runway in prep. for

  03/05-short flight, approached helo. 30’ from exhaust
  03/06-short flight, 30’ from exhaust during takeoff
  03/07-short flight, 30’ from exhaust during takeoff
  03/09-long flight, multiple entries/egress from ac

Poor visibility is the most common cause of
weather-related crashes in the aero-medical

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