Pul 6 - Extreme Environments

Question 1

What is the difference of pressure in high altitudes?

Answer 1

1. Barometric pressure:
   - Sea-level: 760mmHg.
   - 20k feet: 349 mmHg.
2. Alveolar oxygen partial pressure:
   - Sea-level: 104mmHg.
   - 20k feet: 40mmHg.

Question 2

What are the changes the body makes to adjust to high altitudes?

Answer 2

1Ventilation is increased: more acutely and more chronically.

2. Increase in erythropoietin.
3. Increase in 2,3-BPG; helps unleash the oxygen to the tissue.
4. Mitochondria is more efficient.
5. Cells are more efficient in using Oxygen.
6. Increases renal excretion of bicarbonate.

Question 3

What is the hematocrit and hemoglobin in high altitudes?

Answer 3

Hematocrit: It is 40-45 normally; goes up to 65 in high altitudes.
Hemoglobin: it is 15 g/dL normally; goes up to 20 g/dL.

Question 4

What is the Henderson-Hasselbalch equation?

Answer 4

It is pH relative to HCO3/pCO2.

Question 5

What are drugs that we can use to help patients acclimate to high altitudes?

Answer 5

Acetosolomide.

Question 6

What is acute mountain sickness?

Answer 6

Acute mountain sickness is due to rapid descent to high altitude, and the sickness begins hours and up to two days later, showing up as headache, fatigue, acute cerebral edema in severe cases (due to hypoxia-induced vasodilation). Can also cause acute pulmonary edema (exact a cause is not known).

Question 7

What physiological changes occur during chronic mountain sickness?

Answer 7

1. Increased RBC mass and hematocrit.
2. Increased blood viscosity and decreased tissue blood flow.
3. Elevated pulmonary artery pressure.
4. Right-sided heart enlargement.
5. Peripheral artery pressure falls.
6. Congestive heart failure (CHF).

Question 8

What is G force? What does positive G and negative G do in terms of blood in the body?

Answer 8

It is the force of gravity.
Positive G moves blood from head to feet.
Negative G moves blood from feet to head.

Question 9

At what positive G-force does a visual “black-out” occur and why?

Answer 9

About 4 to 6 Gs.

1. Insufficient blood return to the heart.
2. Insufficient pumping of blood to the brain.

Question 10

What G force is achieved during a spacecraft liftoff?

Answer 10

It is 8-9 Gs, thats why the astronauts have to be in a semi-reclining position during liftoff.

Question 11

How is the body affected at zero gravity?

Answer 11

1. Decreased blood volume.
2. Decreased RBC mass.
3. Decreased in muscle strength/work capacity.
4. Decreased maximum cardiac output.
5. Loss of calcium phosphate, resulting in loss of bone mass.

Question 12

What is nitrogen narcosis?

Answer 12

1. Nitrogen dissolves into neural membrane, which causes reduced neural excitability.
2. Diver becomes jovial/careless (after an hour at 120 feet), similar to alcohol intoxication.
3. Loss of coordination and strength.

Question 13

What is Caisson disease and what happens?

Answer 13

It is decompression sickness, or “the bends”, at water depth, nitrogen dissolves in the blood, and when back at sea level, those dissolved nitrogen gases escape, making actual bubbles in the process that can occlude blood vessels.
They can cause:
1. Pain in joints and muscles of arms and legs.
2. Neurologic problems: dizziness, paralysis, syncope.
3. Chokes (2% of patients): Air bubbles seclude the lung capillaries, resulting in shortness of breath, pulmonary edema, even death.

Question 14

What is the treatment for Caisson disease?

Answer 14

Hyperbaric therapy: high-pressure rim.

Question 15

What are the uses for hyperbaric oxygen chambers?

Answer 15

1. Decompression sicknes.
2. Arterial gas emboli.
3. Carbon monoxide poisoning.
4. To get oxygen to a hard to reach place in the body.
5. Gas gangrene: clostridia.
6. Osteomyelitis (in some cases).