Unit 2 L9 Extreme Conditions

Question 1

Primary physiological response to high altitude

Answer 1

Hyperventilation, polycythemia, and pulmonary vasoconstriction

Question 2

Common pathologies of high altitude

Answer 2

Polycythemia, fatigue, reduced exercise tolerance, and hypoexmia

Question 3

How does high altitude induce hyperventilation?

Answer 3

Hypoxia drives hyperventilation, which kicks out CO2. This increases ventilation 5 fold, leading to a 5 fold decrease in PCO2

Question 4

Polycthemia

Answer 4

Increase in RBC concentration. This increases hemoglobin and O2 carrying capacity, and is stimulated by hypoxemia within days of altitude.

Question 5

Hypoxic vasoconstriction

Answer 5

Global, whole lung is experincing low oxygen. Leads to vasoconstriction in the entire pulmonary circulation, this makes the heart work harder. Leads to right heart hypertrophy, pulmonary hypertension and edema

Question 6

What are some challenges experienced if you hold your breath and dive?

Answer 6

Duration of breath hold (hypoxia)
Ability to withstand pressure
Exposure to high gas pressures

Question 7

What is the diving response?

Answer 7

Upper airway closure, stops breathing
Splenic contraction to release RBC/Hb
Bradychardia (arrhythmia) and decreased CO
Redistribution to cerebral and myocardium

Question 8

Hypoxic loss of consciousness

Answer 8

Hyperventilation prior to diving, reduces CO2 and subsequent CO2-induced drive to breathe
Leads to loss of consciousness without forewarning because the weak respiratory stimulus from hypoxia is voluntarily overriden. By the time your CO2 gets high enough to induce the drive to breathe, you’ve run out of oxygen

Question 9

Ambient pressure

Answer 9

The pressure of the surrounding medium in contact with the object. Every meter of water is +76 mmHg of ambient pressure

Question 10

Barotrauma of descent

Answer 10

Increased pressures at depth lead to air in lungs getting smaller in volume, pulling blood/fluid into the lungs. The result is lung collapse, edema, and capillary rupture

Question 11

Hypoxia of ascent

Answer 11

Dive down, partial pressure is high. Stay down there, will metabolize oxygen but still a decent PO2. Start to ascent, and PO2 can go so low, you can’t even calculate it. Will cause you to black out, as there is not enough oxygen to the lungs

Question 12

Effects of long-term O2 toxicity

Answer 12

Cellular oxidation, free radical production
Endothelial cell damage
CNS damage, causing twitching, nausea, disorientation, and irritability

Question 13

At depth, what will happen to N2

Answer 13

High pressures can force N2 into the tissues and alter conductance of neurons. All N2 in solution can now pop out during rapid ascent, leading to capillary leaks, CNS disorders, etc