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Altitude Physiology and the Stresses of Flight

Altitude Physiology and the Stresses of Flight. We will cover the following :. The Atmosphere Composition Structure Physiologic Zones. GAS LAWS. Universal Gas Law Boyle ’ s Law Charles ’ Law Henry ’ s Law Dalton ’ s Law Graham ’ s Law Gay-Lussac ’ s Law. STRESSES OF FLIGHT.

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Altitude Physiology and the Stresses of Flight

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  1. Altitude Physiology and the Stresses of Flight

  2. We will cover the following: The Atmosphere • Composition • Structure • Physiologic Zones

  3. GAS LAWS Universal Gas Law Boyle’s Law Charles’ Law Henry’s Law Dalton’s Law Graham’s Law Gay-Lussac’s Law

  4. STRESSES OF FLIGHT

  5. The Atmosphere OXYGEN 21% 1% Other 78% NITROGEN “Others” include: Argon, CO2, Neon, Helium, Krypton, Hydrogen

  6. The Atmosphere 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:

  7. ALTITUDE BAROMETRIC ALVEOLAR OXYGEN (FEET) PRESSURE OXYGEN SATURATION (mmHg) ( PAO2) % (SPO2) Sea level 760 104 99 10,000 523 67 90 20,000 349 40 70 30,000 226 21 20 40,000 141 6 5 50,000 87 1 1 Alveolar 02 and Hgb Saturation Altitude Correction

  8. Oxygen transport in the blood: Dependent on the partial pressure of oxygen. pO2

  9. 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

  10. Blood Gas Exchange Venous Capillary Hemoglobin Saturation 75% PCO2 = 46 mm PO2 = 40 mm Tissue Alveoli CO2 CO2 PO2 = 100 mm PO2 = 1 - 60 mm O2 PCO2 = 46 mm PCO2 = 40 mm O2 O2 O2 PCO2 = 40 mm PO2 = 100 mm Arterial Capillary Hemoglobin Saturation 98%

  11. Physical Divisions of the Atmosphere 1200 miles EXOSPHERE 600 miles IONOSPHERE 50 miles STRATOSPHERE Tropopause TROPOSPHERE Sea level to flight level 300 - 600 depending on temperature, latitude and season. MOUNT EVEREST 29,028 FEET

  12. 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

  13. 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”.

  14. GAS LAWS

  15. 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

  16. Gas Expansion 9.5X 43,000 6.0X 4.0X 34,000 5.0X 2.5X 3.0X 25,000 18,000 1.8X 2.0X DRY GAS EXPANSION WET GAS EXPANSION SEA LEVEL

  17. 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 Barotrauma and Boyle’s Law

  18. PNEUMO MEDIASTINUM

  19. thorax PNEUMO

  20. cephalus PNEUMO

  21. PNEUMO peritoneum

  22. -Ostomies and Gastic Tubes • DO NOT allow air to become trapped in a closed –ostmy or NG/OG system. To include the space.

  23. 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

  24. 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.

  25. DYSBARISMS Barotitis Media Barosinusitis Barodontalgia Gastrointestinal Changes

  26. Barodontalgia Tooth pain due to: • Gum abscess: (dull pain on ascent) • Inflamed pulp: (sharp pain on ascent) • Inflamed maxillary sinus: (pain primarily on descent)

  27. Barotitis Media Middle Ear Cavity Tympanic Membrane Atmospheric Pressure Clear External Ear Eustachian Tube Middle Ear Cavity Tympanic Membrane Ear Block Atmospheric Pressure External Ear Eustachian Tube Blocked / Infected

  28. Frontal Ethmoid Maxillary Sphenoid Barosinusitis/ Sinus Blocks

  29. 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)

  30. 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

  31. 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)

  32. 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

  33. 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.

  34. Gay-Lussac’s LawDefines 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.

  35. Gay-Lussac’s Law Pressure Temperature Constant Volume Pressure Temperature

  36. Henry’s Law • The amount of gas dissolved in solution is directly proportional to the pressure of the gas over the solution.

  37. Descend Immediately Compression greater than 1 atmosphere (ATM) 100% Oxygen Land at the nearest location where qualified medical assistance is available Decompression Sickness Treatment

  38. Evolved Gas Disorders • Evolved gas disorders are considered serious medical emergencies and require emergent specialized care WARNING

  39. Evolved Gas Disorders The Bends (Limb Pain) The Chokes (Respiratory Disturbances) The Creeps (Skin Irritation) The Staggers (CNS Effects) Syncope (Cardiovascular Collapse)

  40. Evolved Gas Disorders • N2 bubbles become trapped in the joints. Onset is mild, but eventually painful ! The Bends

  41. 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. Evolved Gas Disorders The Chokes The Creeps

  42. N2 bubbles affect spinal cord. Visual disturbances, paralysis, one sided tingling. Evolved Gas Disorders The Staggers

  43. 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 +…+…

  44. Dalton’s Gang Simply stated, the sum of the partial pressures is equal to the total pressure of a gaseous mixture. P1 + P2 + P3 + P4 = P total

  45. 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 )

  46. 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.

  47. 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.

  48. 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

  49. 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? • Boyle’s Law • Charles’ Law • Dalton’s Law • Henry’s Law

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