1. Gas Laws
   1. Boyle's Law
      1. Law
         1. "If the temperature remains constant, the volume of a given mass of gas is inversely proportional to the absolute pressure."
      2. Formula
         1. P₁ × V₁ = P₂ × V₂
            1. V₁ = The initial volume V₂ = The final volume P₁ = The initial pressure P₂ = The final pressure
      3. Significance
         1. As we ascend, the air in an enclosed space will expand.
            1. The enclosed space could be a pneumothorax.
            2. This would rapidly turn into a tension pneumothorax on ascent.
   2. Dalton's Law
      1. Law
         1. "The total pressure of a gas mixture is the sum of the partial pressures of each individual gas in the mixture."
      2. Formula
         1. P₁ = F₁ × P
            1. P₁ = The partial pressure of gas 1 F₁ = The fractional concentration of gas 1 P = The total pressure of the gas mixture
      3. Significance
         1. Barometric Pressure × Gas concentration = Gas partial pressure 760 mm Hg × 21% O₂ = 159.6 mm Hg PO₂ @ Sea Level
         2. Oxygen remains @ 21%, regardless of altitude.
            1. Oxygen availability decreases with altitude because the oxygen molecules are farther apart.
            2. This can result in hypoxia!!!
   3. Charles' Law
      1. Law
         1. "The volume of a gas is very nearly proportional to its absolute temperature when the pressure is kept constant."
      2. Formula
         1. V₁ ÷ T₁ = V₂ ÷ T₂
            1. V₁ = The initial volume V₂ = The final volume T₁ = The initial absolute temperature T₂ = The final absolute temperature
      3. Significance
   4. Gay-Lussac's Law
      1. Law
         1. "The density of an ideal gas at constant pressure varies inversely with the absolute temperature of the gas."
      2. Formula
         1. P₁ ÷ T₁ = P₂ ÷ T₂
            1. P₁ = The initial pressure P₂ = The final pressure T₁ = The initial absolute temperature T₂ = The final absolute temperature
      3. Significance
   5. Henry's Law
      1. Law
         1. "The quantity of gas dissolved in a liquid is proportional to its partial pressure in contact with that liquid."
      2. Significance
         1. If the gas is N and the liquid is blood... ...and we decrease the pressure rapidly... ...we get acute decompression illness!
         2. What happens if we fly this patient? We decrease the pressure more... ...making the decompression illness worse!
            1. Don’t fly high with divers!!!
   6. Graham's Law
      1. Law
         1. "The rate of diffusion of a gas through a liquid medium is directly proportional to the solubility of the gas and inversely proportional to the square of its density"
      2. Significance
         1. This means that gases will go from a higher pressure or concentration to a region of lower pressure or concentration.
            1. This is the basis for gas exchange at the cellular level.
2. Stresses of Transport
   1. Decreased Partial Pressure of Oxygen
      1. Terminology
         1. Hypoxia
            1. A state of low tissue oxygenation.
         2. Hypoxemia
            1. A state of low arterial blood oxygen tension.
         3. Hypercapnia
            1. A state of increased amount of carbon dioxide in the blood.
      2. Hypoxia
         1. The four stages of hypoxia
            1. Indifferent stage
            2. The physiologic zone for this stage starts at sea level and extends to FL100. [10,000 ft :: 3,000 m]
            3. Body reacts to hypoxia at this stage with a slight increase in RR & HR.
            4. Night vision loss occurs at FL50. [5,000 ft :: 1,500 m]
            5. Compensatory stage
            6. The physiologic zone for this stage is FL100-150. [10,000-15,000 ft :: 3,000-4,500 m]
            7. At this stage the body attempts to protect itself from hypoxia.
            8. BR, RR, and HR increase. Quality of respirations becomes deeper.
            9. Efficiency and performance of mental tasks requiring alertness become impaired.
            10. Disturbance stage
            11. The physiologic zone for this stage is FL150-200. [15,000-20,000 ft :: 4,500-5,000 m]
            12. This stage is characterized by dizziness, sleepiness, tunnel vision, and cyanosis.
            13. Thinking becomes slow and muscle coordination decreases.
            14. Critical stage
            15. The physiologic zone for this stage is FL200-300. [20,000-30,000 ft :: 6,000-9,000 m]
            16. This stage is characterized marked mental confusion and incapacitation.
            17. Unconsciousness usually follows within a few minutes.
            18. Death is imminent!
         2. The four types of hypoxia
            1. Hypoxic hypoxia
            2. Interferes with gas exchange in two phases of respiration, ventilation and diffusion.
            3. Manifests as a deficiency of alveolar oxygen exchange.
            4. Caused by a reduction in PO₂ in inspired air, or a reduction in the effective gas exchange area of the lung.
            5. Often referred to a altitude hypoxia.
            6. During the ventilation phase, a reduction in PaO₂ may occur. Specific causes include reduced barometric pressure, respiratory arrest, severe asthma, hypoventilation, breathing gas mixtures with insufficient PO₂, and malfunctioning oxygen equipment at altitude.
            7. Causes of reduction in the gas exchange area include pneumonia, drowning, atelectasis, emphysema, pneumothorax, pulmonary embolism, congenital defects, and physiologic shunting.
            8. Hypemic hypoxia
            9. Interferes in the transportation phase of respiration, caused by a reduction in oxygen-carrying capacity of the blood.
            10. Mainly caused by anemia, hemorrhage, or intake of chemicals (CO, cyanide).
            11. Can be a risk to air-medical crews since they are around exhaust fumes.
            12. Stagnant hypoxia
            13. Interferes in the transportation phase of respiration, caused by a reduction in systemic blood flow.
            14. Specific causes include heart failure, shock, G-forces, and pulmonary embolism.
            15. A reduction in regional or local blood flow can be caused by blood clots, tourniquets, and extremes of environmental temperatures.
            16. Histotoxic hypoxia
            17. Interferes with the utilization phase of respiration, caused by metabolic disorders or poisoning of cytochrome oxidase enzyme system resulting in a cell’s inability to use molecular oxygen.
            18. Common causes include CO, cyanide, and alcohol poisoning.
            19. Also caused by respiratory enzyme poisoning or degradation.
         3. EPT & TUC
            1. Effective Performance Time [EPT]
            2. Time that crew member can perform his duties in a satisfactory manner.
            3. Time of Useful Consciousness [TUC]
            4. Time that crew member can mantain consciousness.
            5. TUC in Non-Pressurized Aircraft
            6. 18,000 ft :: 5,500 m and lower -> 30 min or more
            7. 25,000 ft :: 7,600 m -> 3-5 min
            8. 30,000 ft :: 9,150 m -> 90 sec
            9. 35,000 ft :: 10,650 m -> 30-60 sec
            10. 40,000 ft :: 12,200 m -> 15 sec or less
         4. Causes of Hypoxia
            1. High altitude
            2. Hypoventilation
            3. Pathologic condition of the lung
         5. Characteristics of Hypoxia
         6. Signs and Symptoms of Hypoxia
            1. Objective signs
            2. Confusion Tachycardia Tachypnea Seizures Dyspnea Hypertension Bradycardia Arrhythmias Restlessness Slouching Unconsciousness Hypotension (late) Cyanosis (late) Euphoria Belligerence
            3. Subjective symptoms
            4. Confusion Headache Stupor Insomnia Change in judgement or personality Dizziness Blurred vision Tunnel vision Hot and cold flashes Tingling Numbness Nausea Euphoria Anger
         7. Treatment of Hypoxia
            1. Administer supplemental oxygen under pressure
            2. Monitor breathing
            3. Monitor equipment
            4. Descend
      3. Hyperventilation
         1. Signs and Symptoms of Hyperventilation
         2. Treatment of Hyperventilation
   2. Barometric Pressure
      1. Middle Ear
      2. Barosinusitis
      3. Barodontalgia
      4. GI Changes
   3. Thermal Changes
   4. Decreased Humidity
   5. Noise
   6. Vibration
   7. Fatigue
   8. Gravitational Forces
3. Cabin Pressurization
   1. Pressurization Zones
   2. Decompression
      1. Slow Decompression
      2. Rapid Decompression
         1. Noise
         2. Flying debris
         3. Fog
      3. Decompression Sickness
4. Additional Stresses of Transport
   1. Spatial Disorientation
   2. Flicker Vertigo
   3. Fuel Vapors