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Altitude Physiology and the Stresses of Flight
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We will cover the following:
The Atmosphere Composition Structure Physiologic Zones
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GAS LAWS Universal Gas Law Boyle’s Law Charles’ Law Henry’s Law
Dalton’s Law Graham’s Law Gay-Lussac’s Law
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STRESSES OF FLIGHT
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The Atmosphere OXYGEN 21% 78% NITROGEN
1% Other 78% NITROGEN “Others” include: Argon, CO2, Neon, Helium, Krypton, Hydrogen
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The Atmosphere AT Sea Level 1,000 ft 7,000 ft 14,000 ft 30,000 ft
Atmospheric composition percentages REMAIN THE SAME regardless of the altitude. Sea Level 1,000 ft 7,000 ft 14,000 ft 30,000 ft O2 is 21% N2 is 78% Other is 1% AT With an INCREASE in altitude, there is a DECREASE in pressure:
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Alveolar 02 and Hgb Saturation Altitude Correction
ALTITUDE BAROMETRIC ALVEOLAR OXYGEN (FEET) PRESSURE OXYGEN SATURATION (mmHg) ( PAO2) % (SPO2) Sea level 10, 20, 30, 40, 50,
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Oxygen transport in the blood:
Dependent on the partial pressure of oxygen. pO2
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GAS LAWS Universal Gas Law
Gas molecules of higher pressure move in the direction of gas molecules of a lower pressure GAS LAWS PO2 = 100mmHg PO2 = 40mmHg PO2 = 74mmHg PO2 = 66mmHg
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Hemoglobin Saturation 98% Hemoglobin Saturation 75%
Blood Gas Exchange PCO2 = 46 mm PO2 = 100 mm PCO2 = 40 mm PO2 = 40 mm PO2 = mm Arterial Capillary Hemoglobin Saturation 98% O2 CO2 Venous Capillary Hemoglobin Saturation 75% Tissue Alveoli
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Physical Divisions of the Atmosphere
1200 miles EXOSPHERE 600 miles IONOSPHERE 50 miles STRATOSPHERE Tropopause TROPOSPHERE Sea level to flight level depending on temperature, latitude and season. MOUNT EVEREST ,028 FEET
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Physiological Zones of the Atmosphere
SPACE EQUIVALENT ZONE: 50,000 feet and above 63,000 ft 50,000 DEFICIENT ZONE: 10,000 to 50,000 feet 18,000 ft 10,000 EFFICIENT ZONE: Sea level to 10,000 feet
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The Principle of Atmospheric Pressure
At sea level, the weight of a one square inch column of air extending to the edge of space is called “one atmosphere”. (ATM) 1 ATM weights 14.7 lbs (760 mmHg [torr]). As you ascend the pressure becomes less (0.5 ATM or 380 mm Hg at 18,000 ft) As you dive in water you increase the forces (or weight) on your body by 1 ATM for every 33 ft you are submerged. Hence the term diving “ 1atmosphere”.
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GAS LAWS
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Boyle’s Law The volume of a gas is inversely proportional to its pressure; temperature remaining constant. GAS LAWS Robert Boyle P1 x V1 = P2 x V2
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Gas Expansion 43,000 9.5X 6.0X 4.0X 34,000 5.0X 2.5X 3.0X 25,000 1.8X 18,000 2.0X DRY GAS EXPANSION WET GAS EXPANSION SEA LEVEL
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Barotrauma and Boyle’s Law
Free air in the Chest Endotracheal Tubes Gastrointestinal Concerns NG/OG tubes Ostomies IV Fluids and Medications MAST Air Splints Dysbarisms Barotitis Media Barosinustitis Barodontalgia
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PNEUMO MEDIASTINUM This 22 y/o male presented to the ER with jaw and facial pain and neck and chest discomfort after dental work. His chest x-ray shown above demonstrates pneumomediastinum (mediastinal emphysema) and subcutaneous emphysema of the neck. Dental procedures are an uncommon cause of these findings.
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thorax PNEUMO
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PNEUMO cephalus
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PNEUMO peritoneum
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-Ostomies and Gastic Tubes
DO NOT allow air to become trapped in a closed –ostmy or NG/OG system. To include the space.
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Endotracheal/ Trach. Tubes
Air in the ET tube cuff should be replaced with sterile water/ NS prior to flight. Make sure to place in PCR and tell receiving hospital. Why? Some flight crews may elect to decrease and increase cuff pressure with ascent/decent. More prevalent in FW than RW (>1500 MSL) Greater altitude span in FW Longer exposure duration in FW Do not forget about Foley’s and NG Tubes
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MAST/ Air Splints Document pulses prior to lift off.
Monitor for decrease in circulation. Adjust pressure and document pulses at altitude as needed. Make sure to have pop-off values in place prior to take off.
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Gastrointestinal Changes
DYSBARISMS Barotitis Media Barosinusitis Barodontalgia Gastrointestinal Changes
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Barodontalgia Tooth pain due to: Gum abscess: (dull pain on ascent)
Inflamed pulp: (sharp pain on ascent) Inflamed maxillary sinus: (pain primarily on descent)
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Barotitis Media Clear Ear Block Middle Ear Cavity Tympanic Membrane
Atmospheric Pressure Clear External Ear Eustachian Tube Middle Ear Cavity Tympanic Membrane Atmospheric Pressure Ear Block External Ear Eustachian Tube Blocked / Infected
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Barosinusitis/ Sinus Blocks
Frontal Ethmoid Maxillary Sphenoid
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Treatment of Barosinusitis
Stop the descent of the aircraft and attempt to clear by valsalva. If unable to clear, climb back to altitude until clear by pressure or valsalva. Descend slowly and clear ear frequently during descent. Use nasal spray (Afrin or Neosynephrine)
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Charles’ Law At a constant pressure, the volume of a gas is directly proportional to the absolute temperature of that gas. V1/ T1 = V2/ T2
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Charles’ Law in the Aero-Medical Environment
For every 1° C temperature decreases gas volume will decrease by 1/273. Gas volume shrinks as temperature decreases. For every 1° C temperature increases gas volume will increase by 1/273. Gas volume increases as temperature increases. 1° C = V (-1/273) 1° C = V (+1/273)
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Charles’ Law in the Aero-Medical Environment
For every 1000 feet altitude increases, Temperature decreases 2 degrees centigrade Or Climb 100m = 1°C drop 1000’ Altitude 2 Degrees C
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Charles’ Law in the Aero-Medical Environment
Consider patients thermoregulatory status! Warm blankets Aircraft Heater Warmed IV Fluids Consider effects on compress gases! Oxygen/ medical air will compress/ expand due to temperature changes.
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Gay-Lussac’s Law Defines the relationship between pressure and temperature
At a constant volume, the pressure and absolute temperature of a gas are directly proportional. Example: O2/ SCBA bottles cool when opened & Heat when filling. OR That’s why if you check your bottle in the morning, you have less pressure then in the afternoon.
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Gay-Lussac’s Law Pressure Temperature Pressure Temperature
Constant Volume Pressure Temperature
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Henry’s Law The amount of gas dissolved in solution is directly proportional to the pressure of the gas over the solution.
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Decompression Sickness
Treatment Descend Immediately Compression greater than 1 atmosphere (ATM) 100% Oxygen Land at the nearest location where qualified medical assistance is available
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WARNING Evolved Gas Disorders
Evolved gas disorders are considered serious medical emergencies and require emergent specialized care
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Evolved Gas Disorders The Bends (Limb Pain)
The Chokes (Respiratory Disturbances) The Creeps (Skin Irritation) The Staggers (CNS Effects) Syncope (Cardiovascular Collapse)
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Evolved Gas Disorders N2 bubbles become trapped in the joints. Onset is mild, but eventually painful ! The Bends
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Evolved Gas Disorders The Chokes The Creeps
N2 bubbles block smaller pulmonary vessels. Burning sensation in sternum. Uncontrollable desire to cough. Sense of suffocation ensures. N2 bubbles form along nerve tracts. Burning, tingling, itchy sensation and possibly a mottled red rash.
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Evolved Gas Disorders The Staggers
N2 bubbles affect spinal cord. Visual disturbances, paralysis, one sided tingling.
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Dalton’s Law The pressure exerted by a mixture of gases is equal to the sum of the partial pressures of each gas in the mixture. Pt = P1 + P2 +…+…
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Dalton’s Gang Simply stated, the sum of the partial pressures is equal to the total pressure of a gaseous mixture. P P P P = P total
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Oxygen Correction for Dalton’s Law
%FiO2 x P1 = %FiO2 needed at altitude P2 P1= Beginning Barometric Pressure P2 = Maximum Altitude Barometric Pressure FiO2 35% x 760 (sea level) = FiO2% 51% needed 523 (10,000 ft )
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How easily it moves across the membrane.
Graham’s Law The rate of diffusion of a gas through a liquid membrane is directly proportional to the solubility of the gas and is inversely proportional to the square root of its density or gram molecular weight. How easily it moves across the membrane.
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Graham’s Law and the Aero-Medical Environment
CO2 has a solubility factor 20 times greater than O2 and will thereby, more readily diffuse across a liquid membrane.
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Questions???? The flight medic is more likely to feel the effects of altitude changes when working in this environment? Warm upper latitudes Cold upper latitudes Warm lower latitudes Cold lower latitudes When caring for the patient in the flight environment, the medic realizes that there are many flight stressors that affect the patient’s condition. Which of the following gas laws best describes the need to place supplemental oxygen on the patient during transport? Boyle’s Law Charles Law Dalton’s Law Gay-Lussac’s Law
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Questions???? Medical equipment such as MAST/ air splints, IV drip rates, and endotracheal tube cuffs are more effected by which of the following? Boyle’s Law Charles’ Law Dalton’s Law Henry’s Law Which of the following gas laws is most responsible for soft tissue swelling during flight?
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Take a 5 minute Break!
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The 8 Stressors of Flight
Hypoxia Barometric Change Thermal Change G- Forces Decrease Humidity Noise Vibration Fatigue
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Hypoxia Types of Hypoxia: Hypoxic Hypemic Histotoxic Stagnant
Hypoxia is a poor stimulus for respiration Hypercarbia is much better Types of Hypoxia: Hypoxic Hypemic Histotoxic Stagnant
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Also Called Altitude Hypoxia
Hypoxic Hypoxia Inadequate Availability of Oxygen Molecules Reduced pO2 in the lungs (high altitude) Also Called Altitude Hypoxia Reduce pO2 in the lungs due to lower availability of oxygen molecules Red blood cells Body tissue
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Inability of the blood to accept oxygen in
Hypemic Hypoxia Inability of the blood to accept oxygen in adequate amounts + Medical Conditions COPD Pneumonia Pulmonary Edema Alcohol Pulmonary Embolism Carbon monoxide
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Alcohol Histotoxic Hypoxia Inability of the cell to accept
Adequate oxygen Inability of the cell to accept or use oxygen Medical Conditions Cyanide Toxicity CO Poisoning Anaphylaxis ETOH OD Red blood cells retain oxygen Alcohol Poisoned tissue
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Stagnant Hypoxia G-Forces Reduced blood flow Adequate oxygen
Medical Conditions AMI Cadiomyopathy Cardiogenic Shock Crush Injuries Reduced blood flow Blood moving slowly Red blood cells not replenishing tissue needs fast enough G-Forces
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Hypoxia Symptoms Air Huger Apprehension Hot/ Cold Flashes Fatigue
Subjective: Feel Air Huger Apprehension Fatigue Nausea Headache Dizziness Denial Hot/ Cold Flashes Euphoria Belligerence Blurred Vision Numbness Tingling
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Hypoxia Hyperventilation Mental Confusion Cyanosis Poor Judgment
Symptoms Subjective: See Hyperventilation Mental Confusion Cyanosis Poor Judgment
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WARNING !!! Failure to recognize the signs and symptoms of HYPOXIA in flight crew members may lead to a Significant Emotional Event.
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Stages of Hypoxia Indifferent Stage Compensatory Stage
Disturbance Stage Critical Stage
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Decrease in Night Vision at 4,000 ft. MSL
Stages of Hypoxia Indifferent Stage 10,000 ft. Decrease in Night Vision at 4,000 ft. MSL Sea Level
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Impaired Efficiency Decreased Motor Skills Drowsiness Poor Judgment
Stages of Hypoxia Compensatory Stage 15,000 ft. Impaired Efficiency Decreased Motor Skills Drowsiness Poor Judgment 10,000 ft.
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Stages of Hypoxia Disturbance Stage
20,000 ft. Marked loss in vision acuity. Marked loss of sensory function Marked loss in audible acuity. Absence of memory Loss of cognitive understanding. Complete loss of judgment 15,000 ft.
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Disturbance Stage Performance Deficits
Loss of Motor Coordination Speech Degradation Loss of Handwriting Skills
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Time of Oxygen 1 Minute 2 Minutes 3 Minutes 4 Minutes 5 Minutes 6 Minutes Put Back on Oxygen
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Time of Useful Consciousness
The elapsed time from exposure to oxygen deprived environment to the point where deliberate function is lost. Protect yourself first !!!!!!! 5 minutes at 22,000 feet 18 seconds at 40,000 feet O2 required on all flights over 10’000 feet.
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Stages of Hypoxia Critical Stage Loss of Consciousness Coma Convulsion
ABOVE Loss of Consciousness Coma Convulsion Death 20,000 ft.
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WARNING WARNING When Oxygen saturation falls to below 65% serious cellular dysfunction occurs; and if prolonged, will result in DEATH !!!!
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Factors modifying hypoxia symptoms
Pressure altitude Rate of ascent Time at altitude Temperature Physical activity Individual factors Physical fitness Self-imposed stresses
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DEATH Self-Imposed Stresses Drugs Exhaustion Alcohol Tobacco
Hypoglycemia Be prepared to deal with these factors as seen in your patients!!
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1 oz. of Alcohol is physiologically equivalent to 2,000 ft.
Alcohol and Hypoxia 1 oz. of Alcohol is physiologically equivalent to 2,000 ft. 2000 ft. 1 oz.
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3 Cigarettes smoked in rapid succession is equivalent to 5,000 ft.
Tobacco and Hypoxia 3 Cigarettes smoked in rapid succession is equivalent to 5,000 ft. 5,000 ft. MSL Decreased Night Vision 3 chain smoked or ÂĽ pack in 4 hrs.
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Barometric Pressure Changes
GAS LAWS Glass Bottles PASG Air Splints/ CAST Dysbarism Barotitis Media Sinus Blocks Barodontalgia Free Air in the Chest ET Tubes Pneumocephalis GI/GU Concerns NG/OG Tubes Foley Catheters Ostomies
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Decrease in temperature produces an increase in metabolic demands.
Thermal Stress Increase in altitude produces a decrease in temperature. Decrease in temperature produces an increase in metabolic demands. What gas law covers this principle? CHARLES LAW
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Gravitational Forces
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Gravitational Forces Col. John P. Stapp, USAF
632 mph acceleration in 5 sec. Decelerated to a complete stop in 1.4 seconds
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Gravitational Forces
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Gravitational Forces and the Medical Environment
+G forces applied to Gz axis. Slow transition to horizontal flight. Little or no effect on hemodynamic status, perfusion or patient mental status Best of all options. Vertical Take Off
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Gravitational Forces and the Medical Environment
+G forces applied to Gx axis (seated) or –G axis (supine) Rapid transition to horizontal flight Significant effects on hemodynamic status, perfusion and mental status of the patient Take in consideration when deciding how to load the patient
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Patient Positioning and Gravitational Forces
Feet forward or head forward??? Cardiac patient or Neurological patient? What about the high-risk OB patient? Most patients are loaded along the long axis of the aircraft.
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Decreased Humidity An increase in altitude will produce a decrease in humidity. Oxygen should be humidified for transports lasting longer than 1 hour. In general, most patients are dehydrated as a baseline. Consider fluid replacement early.
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The Surgeon General has
WARNING WARNING Noise Pollution The Surgeon General has established 85 decibels as the maximum level of continuous unprotected exposure to steady-state noise for 8 hours
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Noise Pollution Solution
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Noise in the Aero-Medical Environment
Fixed Wing Most cabins are well insulated. Engines are placed away from patient and crew. Loudest during takeoff Does not require same protection Rotor Wing Constant high noise environment. Engines directly over patient and crew. Greatly reduced communications. Requires soft plugs and headset/ helmet
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Vibration Aircraft vibration can override the normal thermoregulatory mechanism, reducing the body’s ability to generate or disperse heat.
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Fatigue Drugs Exhaustion Alcohol Tobacco Hypoglycemia
Limit your self imposed stressors Drugs Exhaustion Alcohol Tobacco Hypoglycemia
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Questions ???? What is hypoxia?
The lack of oxygen to the tissues of the body What are the four classifications of hypoxia? Hypoxic, hypemic, stagnant, and histotoxic Give me an example of each classification of hypoxia: Hypoxic – altitude; Hypemic – anemia, carbon mon-oxide poisoning; Stagnant – “G” forces, heart failure; Histotoxic – alcohol or drugs What are the five signs (subjective) of hypoxia? Hyperventilation, cyanosis, mental confusion, poor judgment, and muscle incoordination What are the four stages of hypoxia with altitude? Indifferent 0-10,000, compensatory 10,000-15,000, disturbance 15, ,000 and critical stage 20, ,000
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Questions ???? What are the SPO2 % with the four stages of hypoxia?
Indifferent 98%-90%, compensatory 89%-80%, disturbance 79%-70%, and critical stage 69%-60% How can hypoxia be prevented? Use of oxygen, if available, or flights at lower altitudes At what altitude will crew members start losing night vision? 4,000 feet How many times will carbon monoxide bind with hemoglobin molecules of red blood cells then to oxygen? 200 to 300 times Smoking how many cigarettes in a rapid succession or how many in a 24 hour period will decrease your night vision by 20% and give a physiological altitude of 5,000 feet? 3/ 20
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This gas law states that gas expands as it rises
Lets play Jeopardy This gas law states that gas expands as it rises What is Boyles Law This gas law is responsible for decompression sickness What is Henry’s Law This gas law states that as temperature increases so will volume What is Charles’ Law Alcohol and cigarettes decrease the ability for the hemoglobin to carry oxygen. Altitude has this same effect and is an example of this law What is Dalton’s Law This law states that the rate of diffusion of gas is inversely proportional the square root of the density What is Graham’s Law (Ex: C02 is more readily diffused across cell membranes)
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SUMMARY Atmospheric Composition and Structure
Gas Laws in the Aero-Medical World Stresses Of Flight
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Thank You for your Attention!!!!
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