Altitude and Diving Physiology Practice Questions

Q: Which one of the following is a manifestation of a "negative G"?

The cerebral arterial pressure rises. ***The cerebral arterial pressure rises*** - A **negative G-force** pushes blood towards the head, causing an increase in hydrostatic pressure in the cerebral arteries. - This **elevated pressure** can lead to symptoms such as facial swelling, headache, and even petechial hemorrhages in severe cases. *The hydrostatic pressure in veins of lower limb increases* - **Negative G-forces** push blood away from the lower limbs towards the head, thereby **decreasing** hydrostatic pressure in the lower limb veins. - This is in contrast to positive G-forces, which increase hydrostatic pressure in the lower limbs. *The cardiac output decreases* - While extreme gravitational forces (both positive and negative) can impact cardiac output, a direct and common manifestation of **negative G** is not a decrease in cardiac output. - The initial effect of negative G is often increased venous return to the heart from regions below the heart, which might transiently *increase* cardiac output. *Black out occurs* - **Blackout (loss of vision followed by loss of consciousness)** is a characteristic symptom of **positive G-forces**, where blood is pulled away from the head, leading to cerebral ischemia. - In contrast, **redout** (reddening of vision due to conjunctival congestion) can occur with severe negative G-forces due to increased cerebral blood pressure.

Q: What type of narcosis is primarily associated with increased nitrogen solubility under pressure?

N2 narcosis. ***N2 narcosis*** - **Nitrogen narcosis**, also known as **inert gas narcosis** or **depth intoxication**, is caused by the increased partial pressure and resulting increased solubility of nitrogen in body tissues, particularly the brain, at depth. - This leads to altered mental states, similar to alcohol intoxication, including impaired judgment, confusion, and euphoria, posing significant risks to divers. *CO narcosis* - **Carbon monoxide (CO) narcosis** is a rare condition that would only occur if the air supply being breathed by the diver was contaminated with CO. - CO poisoning results from carbon monoxide binding to **hemoglobin** with high affinity, forming **carboxyhemoglobin** and reducing the oxygen-carrying capacity of the blood, leading to tissue hypoxia. *CO2 narcosis* - **Carbon dioxide (CO2) narcosis** occurs due to an excessive buildup of carbon dioxide in the body, which can happen if a diver hypoventilates or if breathing equipment malfunctions, leading to inadequate removal of CO2. - Symptoms include headache, confusion, drowsiness, and in severe cases, loss of consciousness; however, it is not primarily due to increased gas solubility in an inert gas context but rather an imbalance in respiratory gas exchange. *O2 toxicity* - **Oxygen toxicity** is a condition caused by breathing high partial pressures of oxygen for prolonged periods, which can lead to damage in various organ systems, including the central nervous system (CNS) and lungs. - This is a distinct phenomenon from narcosis, where the physiological effects are primarily due to the toxic effects of oxygen on cellular function rather than the inert gas properties of nitrogen dissolving in tissues.

Q: Which is a feature of high-altitude pulmonary edema?

Associated with pulmonary hypertension. ***Associated with pulmonary hypertension*** - **High-altitude pulmonary edema (HAPE)** is characterized by **exaggerated hypoxic pulmonary vasoconstriction**, leading to significantly increased pulmonary artery pressures. - This **pulmonary hypertension** drives fluid extravasation into the alveolar spaces, causing non-cardiogenic pulmonary edema. *Associated with low cardiac output* - HAPE is typically associated with **normal or elevated cardiac output** in response to hypoxia, not low cardiac output. - Low cardiac output suggests conditions like cardiogenic shock or severe myocardial dysfunction, which are not primary features of HAPE. *Exercise has no effect* - **Physical exertion at altitude** is a significant risk factor and can worsen HAPE due to increased cardiac output and pulmonary blood flow, exacerbating pulmonary hypertension. - Rest and reduced activity are crucial components of preventing and treating HAPE, indicating that exercise does indeed have an effect. *Occurs in both acclimatized and unacclimatized persons* - HAPE primarily affects **unacclimatized individuals** or those who ascend rapidly to high altitudes. - While rare, it can occur in previously acclimatized individuals returning to altitude after a period at lower elevations or in those with predisposing factors, but it is predominantly a disease of the unacclimatized.

Question 1

Which one of the following is a manifestation of a "negative G"?

Accepted Answer

The cerebral arterial pressure rises

Answer

The hydrostatic pressure in veins of lower limb increases

Answer

The cardiac output decreases

Answer

Black out occurs

Question 2

Which of the following statements about high altitude pulmonary edema (HAPE) is true?

Accepted Answer

High altitude pulmonary edema is associated with raised pulmonary capillary pressure.

Answer

High altitude pulmonary edema is caused by a combination of factors.

Answer

High altitude pulmonary edema involves leakage of proteins and white blood cells into the alveoli.

Answer

High altitude pulmonary edema is associated with increased permeability of pulmonary capillaries.

Question 3

What type of narcosis is primarily associated with increased nitrogen solubility under pressure?

Accepted Answer

N2 narcosis

Answer

CO narcosis

Answer

CO2 narcosis

Answer

O2 toxicity

Question 4

Which is a feature of high-altitude pulmonary edema?

Accepted Answer

Associated with pulmonary hypertension

Answer

Associated with low cardiac output

Answer

Exercise has no effect

Answer

Occurs in both acclimatized and unacclimatized persons

Altitude and Diving Physiology — MCQs

Altitude and Diving Physiology — MCQs

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