Extreme environments

Question 1

High altitude physiologic response

Answer 1

Increased ventilation - acutely and chronically
increased erythropoietin
-Hct 40-45 –> 65%
-Hgb 15 –> 20 g/dL
Increased 2,3 DPG - off load more O2 in tissues
Increase mitochondria - more efficent O2 use
Increased bicarb excretion to compensate loss of CO2

Question 2

Treatment of altitude sickness

Answer 2

acetazolamide

Question 3

Acute mountain sickness

Answer 3

rapid ascent to high altitudes

sx begin a few hours –> 2 days after ascent

HA - MC
fatigue
acute cerebral edema - d/t hypoxia induced vasodilation
acute pulmonary edema - extreme cases
-vasoconstriction increases capillary pressure –> local edema

Question 4

Physiologic changes in chronic mountain sickness

Answer 4

increased RBC mass and Hct
Increased blood viscosity and decreased tissue blood flow

Elevated pulmonary artery pressure –> right sided heart enlargement

Peripheral artery pressure falls

CHF, possibly death

Question 5

Positive vs Negative G forces

Answer 5

Positive blood –> feet

Negative blood –> head

Question 6

Positive G force required for visual “blackout” to occur

Answer 6

4-6 Gs

Insufficient blood return to heart, insufficient pumping of blood to brain

Question 7

G force during spacecraft lift off

Answer 7

8-9 Gs

have to be semi-reclining position at take off transverse to axis of acceleration

Question 8

Affect of zero gravity on body

Answer 8

decreased blood volume
decreased RBC mass
Decreased muscle strength/work capacity
Decreased maximum cardiac output
Loss of calcium and phosphate --> loss of bone mass

Question 9

Nitrogen narcosis

Answer 9

Nitrogen dissolves into neural membrane –> reduced neuronal excitability

Diver becomes jovial/careless –> drowsy

Loss of strength and coordination

Question 10

Decompression sickness

Answer 10

“the BENDS”, aka Caisson disease

Dissolved nitrogen –> bubbles as ascend, occluding arteries

Sx: joint/muscle pain in arms and legs
Neuro: dizziness, paralysis, syncope
2% “the Chokes” - bubbles occlude pulmonary A –> SOB, pulmonary edema, death

Prevent: surface slowly
Tx: hyperbaric O2 tx

"BEND"
Breathing problems
Extremity pain
Neuro change
Death

Question 11

Use of hyperbaric O2 treatment

Answer 11

decompensation sickness
arterial gas emboli
CO poisoning
Gas gangrene d/t Clostridia
Osteomyelitis