Flight Physiology & Gas Laws

Question 1

Boyle’s Law

Answer 1

As altitude increases the atmospheric pressure decreases and gas in an enclosed space will expand

P1 V1 = P2 V2

P = Pressure (Atmosphere's - ATM)
V = Volume
P,V = Inverse relationship

Question 2

Charles Law

Answer 2

Charles Law states that the relationship between temperature and volume are proportional at a constant atmospheric pressure.

As the temperature goes up, gas volume expands

As the temperature goes down, volume decreases

Question 3

Gay Lussac’s Law

Answer 3

For a given mass and constant volume of a gas, the pressure exerted on the sides of its container is directly proportional to its absolute temperature

Question 4

Dalton’s Law

Answer 4

The total pressure of a gas mixture is the sum of the partial pressures of all gases.

Also describes how a pressure is exerted by a gas at various altitudes, and how that pressure affects the partial pressure of the said gas

Question 5

Henry’s Law

Answer 5

The amount of gas dissolved in a solution is directly proportional (+:+) to the pressure of the gas over the solution

Question 6

Fick’s Law

Answer 6

The rate of diffusion of a gas across a permeable membrane is determined by:

1. The chemical nature of the membrane itself,
2. The surface areas of the membrane,
3. The partial pressure gradient of the gas across the membrane,
4. The thickness of the membrane.

Question 7

Graham’s Law

Answer 7

the rate of diffusion of a gas is inversely proportional to the square root of its molecular weight.

This means that diffusion will happen at a faster rate if the gas is thinner and at a slower rate if the gas is heavier

Question 8

Expected temperature change on ascension

Answer 8

Every 1000 feet ascended the temperature will decrease by 2^oC

Every 150 meters ascended the temperature will decrease by 1^oC

Question 9

Stressors of Flight

Answer 9

Hypoxia

Noise

Vibration

Gravitational forces

Flicker vertigo

Spatial disorientation

Fatigue

Barometric pressure

Thermal changes

Decreased humidity

Question 10

Formula for bedside PaO2

Answer 10

PaO2 = (700 torr ∗ [FiO₂ Percentage]) - 50

Question 11

Observable effects of hypoxia

Answer 11

Hyperventilation

Confusion

Poor decision making

Cyanosis (late)

Question 12

Subjective effects of hypoxia

Answer 12

Fatigue

Anxiety

Nausea

Headache

Euphoria

Numbness/Tingling

Agitation

Blurred vision

Hot/Cold flashes

Question 13

Stages of hypoxia (from least to most severe)

Answer 13

1. Indifferent Stage
2. Compensatory Stage
3. Disturbance Stage
4. Critical Stage

Question 14

Formula for FiO₂ at a new altitude

Answer 14

(%FiO₂ x P1) / (P2)

P1 = Current pressure

P2 - New pressure

Question 15

Indifferent Stage of Hypoxia

Answer 15

Occurs at altitudes 0 to 10,000 ft

SpO₂ ranges from 90% to 100%

Decrease in night vision @ 4000 ft

Question 16

Compensatory Stage of Hypoxia

Answer 16

Occurs at altitudes 10,000 to 15,000 ft

SpO₂ ranges from 80% to 90%

Night vision < 50% of usual capability

CNS symptoms start (poor judgement, decreased coordination, etc.)

Question 17

Disturbance Stage of Hypoxia

Answer 17

Occurs at altitudes of 15,000 to 20,000

SpO2 of 70% to 80%

Worsening CNS symptoms (memory loss, not understanding of speech, etc.)

Hyperventilation

Question 18

Critical Stage of Hypoxia

Answer 18

Occurs at altitudes of 20,000 to 25,000 ft

SpO₂ of 60% to 70%

Rapid unconsciousness and coma rapidly followed by death

Question 19

Seconds of useful consciousness after decompression at high (40,000’ ft +) altitudes

Answer 19

9 seconds or less

Question 20

Quick way to calculate ATM under 6000 ft

Answer 20

Every 1500’ up is 0.5 ATM loss

Question 21

What is pulmonary shunt?

Answer 21

When oxygenation fails to occur at the alveoli, leading for unoxygenated blood to be circulated

Question 22

What ventilator setting can assist with pulmonary shunt

Answer 22

Adding or increasing PEEP

Question 23

Barotrauma to consider to provider

Answer 23

Barotitis media - Ear infection causing pain on ascent and descent

Barodentalgia - Oral abscess or cavity that expands on ascent

Barobariatrauma - Displacement of nitrogen causes nitrogen narcosis

Question 24

Patient/Equipment considerations for barotrauma

Answer 24

Any cavity filled with air will expand on ascent. Will severely worsen a pneumothorax or perf a stomach filled with air

Any equipment that has air in it will expand on ascent (ex. air splints, pressure bags, etc.)

Question 25

Factors that exacerbate flight stressors of providers

Answer 25

D.E.A.T.H

Drugs (Rx or illicit)

Exhaustion

Alcohol

Tobacco

Hypoglycemia

Question 26

Atmosphere at sea level

Answer 26

760 mmHg = 760 torr

(both units are the same thing)

1 ATM

Question 27

What can cause flicker vertigo in the flight environment?

Answer 27

Sunlight rapidly flickering through moving rotors