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Flashcards in Extreme Conditions - Altitude and Pressure Deck (21)
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What is the pressure of water vapor at 37 C?

47 mmHg


What is the most important acclimatization response to high altitudes?



Why is hyperventilation so important for adapting to high altitudes?

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


What are the adaptations that occur at high altitudes?



How does polycythemia help to adapt to high altitudes?

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


At moderate altitudes what happens to the O2 dissociation curve?

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.


What happens to the O2 dissociation curve at higher altitudes?

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.


What occurs as a result of alveolar hypoxia?

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


In diving what happens to the pressure every 10 m?

It doubles


What is the diving response?

-Peripheral sympathetic vasoconstriction
-Vagally induced bradycardia


What is the purpose of the diving reflex?

It is meant as an O2 sparing mechanism when diving


How does the diving reflex affect the spleen?

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


What happens with hyperventilation in regards to diving?

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


What causes ascent blackout?

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


What happens with carbohydrate depletion in regards to diving?

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


What happens to the lung capacity as you dive?

It will decrease as the pressures are increasing


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

- Compression of lung (Vital Capacity)
- Redistribution of blood volume


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

- Atelectasis
- Edema
- Rupture


What is decompression sickness?

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"


What is inert gas narcosis?

At around 50 m N2 can cause euphoria


How can high O2 levels be toxic?

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.

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