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 helicopter 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 Japan. 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 hypotension • Systolic BP less than 100 mmHg • GCS less than 13 • Penetrating injuries to the head, neck, or torso • 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 injury – Circumferential or trauma/burn combo Flight Appropriate Patients • Unstable pelvis FXs • Two or more proximal long bone FXs • Amputation/near amputation above wrist or ankle • 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 • AAA • AMI • 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 copied/calculated. 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 recorded. • 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 patients. • 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 assessed. • Cervical collars and splints may need to be re-applied. • 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 secured. • 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 ventilation 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 Hypertension 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 occurs. • 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 Barodontalgia • 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 hours 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 330’ • 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 altitudes. Noise • 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. Noise • 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. Noise • 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 takeoff Noise 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 Safety Poor visibility is the most common cause of weather-related crashes in the aero-medical environment.
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