Altitude Physiology

Question 1

Structure of the atmosphere

Answer 1

Troposphere - Sea level to 26,000/53,000ft (poles vs. equator) ** mean temperature lapse rate of -1.98*C per 1000ft** (Mt. Everest is 29,000 ft high)

Stratosphere - 26,000/53,000ft to 30 miles

Mesosphere - 30 miles to 50 miles

Thermosphere - 50 miles to 435 miles

Question 2

Physiological zones of the atmosphere

Answer 2

Efficient zone - sea level to 10,000ft (760mm Hg to 523mm Hg)

Deficient zone - 10,000 to 50,000ft (523mm Hg to 87mm Hg) 30min till unconsciousness

Space equivalent zone - 50,000ft and up

63,000ft, blood boils due to gas release

Question 3

Composition of air

Answer 3

78% Nitrogen (N2)

21% Oxygen (O2)

1% other (.03% CO2)

Question 4

Barometric pressure

Answer 4

Measure of pressure on earths surface from water and gases in atmosphere (760mm or 29,92 Hg at sea level)

Question 5

Composition vs. pressure

Answer 5

Composition of atmosphere remains constant at every altitude

Pressure decreases with altitude

Question 6

Significant altitudes

Answer 6

0ft - 760mm Hg - 1atm

18,000ft - 380mm Hg - 1/2atm

34,000ft - 190mm Hg - 1/4atm

48,000ft - 95mm Hg - 1/8atm

63,000ft - 47mm Hg - 1/16atm

Question 7

Partial pressure of gases

Answer 7

O2 - 21% or 0.21 composition in atm

Ex) atmosphere pressure at 18,000ft = 380mm Hg
PO2? 0.21*380 = 79.8mm Hg partial pressure of O2 at 18,000ft

*DALTON’s LAW
Pressure total = sum of partial pressures of each gas in atm

(Pt = PO2 + PN2 + PCO2 …)

Question 8

Circulatory system

Answer 8

Oxygen/nutrients to cells

Transports waste

Assists temperature regulation

Question 9

Circulatory components

Answer 9

Arteries (oxygenated)

Veins (deoxygenated)

Capillaries - arteries to veins; transfers O2, CO2, nutrients, waste; one cell thick; gas diffusion

Question 10

Blood

Answer 10

Plasma - 55% of blood, transports nutrients, CO2 and hormone transport

WBC - no hemoglobin, fights infection/inflammation

Platelets - produced in bone marrow, coagulates blood

RBC - transport 98.5% of O2; composed of 97% hemoglobin (protein with 4 oxygen binding sites) which transports 20% of CO2 in the body

Question 11

Respiratory system

Answer 11

Intake O2

Remove CO2

Maintain heat balance

Maintain PH base balance 7-8 (slightly alkaline)

Question 12

Phases of repiration

Answer 12

Inhalation is active (diaphragm lowers)

Exhaustion is passive (diaphragm relaxes)

Question 13

Components of respiratory system

Answer 13

In relative order:

Oral-nasal passage

Oral passage

Pharynx

Larynx

Trachea

Bronchi

Bronchioles

Alveolar ducts

Alveoli (air sacs)

Pulmonary vein (where RBCs receives O2 and give CO2 by diffusion)

Diaphragm

Question 14

Law of gas diffusion

Answer 14

Gas molecules of higher pressure move in the direction of gas molecules of a lower pressure

Question 15

*Hypoxia

Answer 15

State of oxygen deficiency significant enough to cause impairment of function

Question 16

*Hypoxic hypoxia

Answer 16

Reduced PO2 in the lungs, usually due to altitude increases (lower gas pressure)

Question 17

*Hypemic Hypoxia

Answer 17

Inability of the blood to accept adequate oxygen (due to carbon monoxide [CO] or blood loss)

Question 18

*Stagnant hypoxia

Answer 18

Oxygen carrying capacity is adequate but circulation is inadequate (pressure point or G-Forces)

Question 19

Histoxic hypoxia

Answer 19

Inability of tissue to accept or use oxygen (cyanide, alcohol, narcotics)

Question 20

Symptoms of hypoxia (what you could feel)

Answer 20

Air hunger
Apprehension
Fatigue
Nausea
Headache
Dizziness
Blurred vision
Hot/cold flashes
Euphoria
Belligerence
Numbness
Tingling
Denial

Question 21

Signs of hypoxia

Answer 21

Hyperventilation
Cyanosis
Poor judgement
Lack of coordination

Question 22

Factors modifying hypoxia symptoms

Answer 22

Pressure altitude
Rate of ascent
Time at altitude
Temperature
Physical activity
Individual factors
Physical fitness
Self imposed stress (D.E.A.T.H.)

Question 23

Hypoxia prevention

Answer 23

Limit time at alt.
Pressurized cabin
Minimize stress
100% O2

Question 24

Hypoxia treatment

Answer 24

Descend to safe alt.

100% O2

Question 25

Indifferent stage of hypoxia

Answer 25

Sea level to 10,000ft O2 saturation 98% - 90% Decrease night vision to 4,000ft Acuity, color perception lessons

Question 26

Compensatory stage of hypoxia

Answer 26

10,000-15,000ft O2 at 89% - 80% Impaired efficiency, drowsiness, poor judgement, decreased coordination

Question 27

Disturbance stage of hypoxia

Answer 27

15,000 - 20,000ft O2 at 79% - 70% Decreased memory, judgement, reliability, poor understanding Happy drunk/mean drunk Blurred vision, impaired hearing, poor coordination Decreased feeling/numbness

Question 28

Critical stage of hypoxia

Answer 28

20,000ft and up O2 at 69% - 60% Loss of consciousness, convulsions, death

Question 29

Time of Useful Consciousness (TUC)

Answer 29

``` 43,000ft - 9 to 12 sec 40,000ft - 15 to 20 sec 35,000ft - 30 to 60 sec 30,000ft - 1 to 2 min 28,000ft - 2.5 to 3 min 25,000ft - 3 to 5 min 22,000ft - 8 to 10 min 18,000ft - 20-30min ``` *In a rapid decompression(RD), times are reduced by half

Question 30

Hyperventilation

Answer 30

Excessive rate of breath resulting in abnormal loss of CO2 from the blood (alkalosis)... >16 breaths/min

Question 31

Causes of hyperventilation

Answer 31

Emotional (fear, anxiety) Positive pressure breathing Hypoxia

Question 32

Symptoms of hyperventilation

Answer 32

``` Tingling Muscle spasms Hot/cold sensation Visual impairment Dizziness Unconciousness ```

Question 33

Hyperventilation corrective actions

Answer 33

Don’t panic Control your breathing Talk out loud, read a checklist Check you oxygen equipment - could be hypoxia

Question 34

Hypoxia vs. hyperventilation

Answer 34

Hypoxia - above 10,000ft; cyanosis only occurs in hypoxia Hyperventilation - below 10,000ft; muscle cramps only in hyperventilation

Question 35

Gas dysbarism

Answer 35

Types - trapped gas and evolved gas Syndrome resulting from the effects, excluding hypoxia, of a pressure differential between ambient and internal body pressures

Question 36

Boyle’s law

Answer 36

Volume of gas is inversely proportional to its pressure when temperature is constant Gas volume increases as body rises higher in altitude

Question 37

Prevention of abnormal gas

Answer 37

Avoid soda, large amounts of water Dont chew gum during ascent Keep regular bowel movement Off-gas as necessary

Question 38

Treatment of ear/sinus blocks

Answer 38

Ascent - (rare) land and refer to flight surgeon Descent - stop descent and clear by valsalva... if unable, climb and repeat. Descend slowly

Question 39

Barodentalgia

Answer 39

Tooth pain due to gas expansion on ascent Land and refer to dental

Question 40

Evolved gas dysbarism (decompression sickness)

Answer 40

Occurs due to reduction in atmospheric pressure As pressure decreases, gases dissolved in body fluid released as bubbles

Question 41

Henry’s law

Answer 41

Amount of gas dissolved in a fluid is directly proportional to the pressure on that fluid (soda bottle - evolved gas dysbarism)

Question 42

Evolved gas disorders

Answer 42

Type 1: Bends - N2 bubbles trapped in joints (painful) Skin manifestations - N2 bubbles form under skin along nerve tracts Type 2: Chokes - N2 bubbles block pulmonary vessels, burning sternum, desire to cough, sense of suffocation Central nervous system disorder - N2 bubbles trapped in brain or against spinal chord. Paralysis, disturbances, one sided tingling

Question 43

Factors influencing Evolved Gas Disorders

Answer 43

Rate of ascent Exercise Altitude Body fat Age Duration of exposure Repeated exposure

Question 44

Decompression sickness prevention

Answer 44

Denitrogenation - required for unpressurized flight above 18,000ft 30min of pure O2 decreases N2 by 30% Pressurized flight suit is a pressure at 10,000ft altitude pressure and below

Question 45

Decompression sickness treatment

Answer 45

Descend Immobilize affected area 100% O2 Land at nearest treatment available Compression > 1atm absolute *Scuba divers have 24 hours no flying