Altitude Physiology & Stressors of Flight

1. Altitude Physiology & Stressors of Flight

2. Altitude Physiology Changes in altitude result in changes in barometric pressure and temperature. • Gas volumes • Partial pressures • Quantities of gases dissolved in solution

3. Altitude Physiology Earth’s Atmosphere Gas Laws Physiologic Effects of Gas Laws

4. Earth’s Atmosphere • Troposphere sea level – 26,000 ft • Stratosphere 26,000 – 158,000 ft • Mesosphere 158,000 – 264,000 ft • Thermosphere 264,000 – 435 miles

5. Earth’s Atmosphere Composition • Nitrogen 78% • Oxygen 20.9% • Other 1%

6. Earth’s Atmosphere Physiologic Zones Efficient Zone • Sea level to 10, 000 feet • Middle ear or sinus problems Deficient Zone • 10,000-50,000 feet • Trapped gas expansion and hypoxia Space Equivalent • 50,000 feet and beyond

7. Gas Laws The most important principle to understand is the overlapping relationship of temperature, pressure, and volume.

8. Gas Laws Boyle’s Law Dalton’s Law Henry’s Law Charles’ Law

9. Gas Laws Boyle’s Law (Boyles=VxP) • The inverse relationship of pressure and volume at a constant temperature • As pressure decreases, volume increases • As pressure increases, volume decreases

10. Gas Laws Boyle’s Law Dysbarism • Various manifestations of gas expansion induced by decreased barometric pressure • Trapped Gas disorders • Evolved Gas Disorders (Henry’s Law)

11. Gas Laws • Boyle’s Law • Trapped Gas Disorders • Ears • Sinuses • Gastrointestinal

12. Trapped Gas Disorders Gastrointestinal tract

13. Trapped Gas Disorders Ears

14. Trapped Gas Disorders Splints on Extremities

15. Trapped Gas Disorders Facial sinuses

16. Trapped Gas Disorders Teeth

17. Gas Laws Boyle’s Law • Mechanical Considerations • Ventilated patients • ETT balloons • Pneumothorax • Air Splints

18. Gas Laws Dalton’s Law • The pressure exerted by a mixture of non-reacting gas is equal to the sum of the pressures of its separate components. * Dalton’s law explains that the partial pressure of each gas changes with the differing altitude, but the percentage of that gas in the total gas volume remains constant.

19. Gas Laws Dalton’s Law -Partial Pressure of Oxygen states that the total pressure exerted by a gaseous mixture is equal to the sum of the partial pressures of each individual component in a gas mixture

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

21. Gas Laws Henry’s Law • Evolved – Gas Disorder • Decompression sickness (Bends) Bends-Nitrogen bubbles in joints Chokes- Nitrogen bubbles in lungs

22. Gas Laws Charles’ Law • The relationship of temperature and volume at a constant pressure • As temperature increases, volume increases • As temperature decreases, volume decreases

23. Gas Laws Charles’ Law • Considerations • Humidified Oxygen • Changes in Oxygen tank volume • Physiologic changes from temperature variations

24. 4 Types of Hypoxia Hypoxic hypoxia Hypemic hypoxia Stagnant hypoxia Histotoxic hypoxia

25. HypoxiaInsufficient O2 at the cellular level

26. Hypoxic Hypoxia Insufficient available oxygen Occurs when there is insufficient oxygen in the air that is breathed or when conditions prevent the diffusion of 02 from the lungs to the blood stream

27. Occurrences - Improper function of oxygen delivery equipment - Loss of cabin pressurization - No use of supplemental oxygen with sustained cabin altitudes above 10,000 feet - Airway obstruction

28. Hypemic Hypoxia Reduced oxygen-carrying capacity Caused by a reduction in the oxygen carrying capacity of the blood.

29. Causes • Anemia • Blood loss/donation Excessive smoking (related to CO levels)

30. Causes • Changes in hemoglobin structure • Sickle cell disease • Spherocytosis • Thalassemia • Changes in hemoglobin affinity • Carbxyhemoglobin • Methemoglobin • Cyanohemoglobin

31. Stagnant Hypoxia Inadequate circulation Occurs when the oxygen-carrying capacity of the blood is inadequate, but there is inadequate circulation. ex: heart failure, arterial spasm, blood vessel occlusion….

32. Stagnant Hypoxia • Pooling of blood causes insufficient flow of oxygenated blood to tissues • Oxygen deficiency due to lack of movement of blood within the body

33. Occurrences • Adult respiratory distress syndrome • Pulmonary embolism (blood or fat) • Pulmonary contusion

34. Histotoxic Hypoxia Interference with oxygen use by the body tissues Alcohol, narcotics, and poisons such as cyanide, interfere with the cells ability to utilize an adequate supply of oxygen.

35. Signs/Symptoms of hypoxia • General • Symptoms are the same regardless of the nature of the hypoxia • Early symptoms mimic alcohol intoxication or extreme fatigue • Each person’s symptomology will vary as tolerances to hypoxic states vary

36. Signs/symptoms of hypoxia • General d. Each crew member must be familiar with their own symptoms and must observe their coworkers for presentation of symptomology e. Hypoxia is insidious and may not be recognized until too late

37. Subjective (felt by you) • Apprehension • Blurred or double vision • Dizziness • Fatigue • Headache • Vision changes

38. Subjective (felt by you) • Hot/cold flashes • Nausea • Numbness • Tingling • Euphoria • Belligerence

39. Objective (noticed by others) • Increased rate of breathing • Cyanosis (late sign) • Impaired task force • Loss of muscle coordination • Mental confusion • Unconsciousness

40. Stages of hypoxia • Indifferent • Compensatory • Disturbance • Critical

41. Indifferent stage0 to 10,000 feet • O2 saturation - 90 - 98 % • Stage of normal operation • Symptomology may appear with higher altitudes of this range • Most persons unaware of symptoms • Most common symptoms are increase in respiratory rate and decreases in night vision

42. Compensatory stage 10,000 to 15,000 feet • O2 saturation 80 - 90 % • Symptoms advance from previous stage • Efficiency is impaired • Night vision decreases 50 %

43. Compensatory Stage Symptoms • Respiratory rate and depth increase related to air hunger • Nausea & vomiting (more pronounced in Peds) • CNS symptoms • Headache • Amnesia • Decreased level of consciousness • Belligerence • Fatigue • Apprehension

44. Compensatory Stage Symptoms • Evidenced in performance by • Poor judgment • Impaired coordination • Irritability

45. Disturbance stage 15,000 to 20,000 feet • O2 saturation - 70 - 80 % • Stage when definitely aware of symptoms • Previous symptoms increase in intensity

46. Symptoms • CNS • Slowed thinking • Impaired mental functioning • Impaired short-term memory • Impaired reaction times • Dizziness • Sleepiness • Loss of muscle coordination

47. Symptoms • Sensory • Increase in visual disturbances – mainly peripheral vision (tunnel vision) and visual acuity • Numbness • Decreased awareness of pain • Decreased sense of tough

48. Symptoms • Personality • Euphoria • Aggressive or belligerent • Depression • Over confident

49. Symptoms • Performance • Decreased coordination • Slowed speech • Impaired handwriting • Cyanosis

50. Critical stage20,000 to 30,000 feet • O2 saturation - 60 - 70 % • Symptomology • Mental confusion • Incapacitation • Unconsciousness • Seizures • Inability to remain upright • Coma and death