Extreme Conditions - Altitude and Pressure

Question 1

What is the pressure of water vapor at 37 C?

Answer 1

47 mmHg

Question 2

What is the most important acclimatization response to high altitudes?

Answer 2

Hyperventilation

Question 3

Why is hyperventilation so important for adapting to high altitudes?

Answer 3

It lowers the PCO2 dramatically, which increases the PAO2 up to viable levels

Question 4

What are the adaptations that occur at high altitudes?

Answer 4

Hyperventilation

Polycythemia

Question 5

How does polycythemia help to adapt to high altitudes?

Answer 5

It increases the amount of RBCs which increases the Hb which increases the O2 carrying capacity of the blood

Question 6

At moderate altitudes what happens to the O2 dissociation curve?

Answer 6

It shifts to the right due to an increase in 2,3-DPG. This decreases the affinity for O2 to increase the O2 unloading to the tissues.

Question 7

What happens to the O2 dissociation curve at higher altitudes?

Answer 7

It shifts to the left because of alkalosis as a result of hyperventilation leading to an increase in pH that causes Hb to increase its affinity for O2 and load O2 better.

Question 8

What occurs as a result of alveolar hypoxia?

Answer 8

Pulmonary vasoconstriction which can result in right heart hypertrophy and pulmonary edema

Question 9

In diving what happens to the pressure every 10 m?

Answer 9

It doubles

Question 10

What is the diving response?

Answer 10

• Peripheral sympathetic vasoconstriction

- Vagally induced bradycardia

Question 11

What is the purpose of the diving reflex?

Answer 11

It is meant as an O2 sparing mechanism when diving

Question 12

How does the diving reflex affect the spleen?

Answer 12

It causes splenic contraction which enhances the Hb concentration of circulating blood

Question 13

What happens with hyperventilation in regards to diving?

Answer 13

It reduces CO2 drive to breathe which can cause the loss of consciousness without forewarning because the weak respiratory stimulus from hypoxia is voluntarily overridden

Question 14

What causes ascent blackout?

Answer 14

It is due to hypoxia as a result of the large drop in partial pressure of O2 as you go from the higher pressures deep in the water to the low pressure shallow water

Question 15

What happens with carbohydrate depletion in regards to diving?

Answer 15

It causes less CO2 production which can reduce the drive for ventilation

Question 16

What happens to the lung capacity as you dive?

Answer 16

It will decrease as the pressures are increasing

Question 17

During a dive, how is the pressure equilibrium of the lung maintained?

Answer 17

• Compression of lung (Vital Capacity)

- Redistribution of blood volume

Question 18

What happens if the pressure equilibrium is not maintained during a dive?

Answer 18

• Atelectasis
• Edema
• Rupture

Question 19

What is decompression sickness?

Answer 19

It is caused by N2 as the PN2 is high during dives and it forces the poorly soluble N2 into tissues and with rapid ascent, N2 bubble will form and cause pain in the joints known as the “bends”

Question 20

What is inert gas narcosis?

Answer 20

At around 50 m N2 can cause euphoria

Question 21

How can high O2 levels be toxic?

Answer 21

It can cause atelectasis in blocked airways leading to alveolar collapse and has been found to cause damage of endothelial cells. The threshold is around 40% O2.