Altitude and Diving Physiology Indian Medical PG Practice Questions and MCQs
Question 71: Which among the following is a cause of suspended animation?
- A. Rapid Blood Transfusion
- B. Severe Hypothermia (Correct Answer)
- C. Induced Coma
- D. Hyperbaric Oxygen Therapy
Explanation: ***Severe Hypothermia***
- **Severe hypothermia** significantly slows down metabolic processes, reducing the body's demand for oxygen and energy.
- This state can induce a form of **suspended animation**, where vital functions are drastically suppressed but can be restored with rewarming.
*Rapid Blood Transfusion*
- A rapid blood transfusion is a medical procedure to quickly replace lost blood volume and does not induce a state of reduced metabolic activity for suspended animation.
- While it can be life-saving in cases of severe blood loss, it does not lead to the physiological changes seen in suspended animation.
*Induced Coma*
- An induced coma is a medically controlled, temporary state of deep unconsciousness, often used to protect the brain after injury by reducing its metabolic needs.
- However, it does not lower the body's core temperature to the extent that it would result in the profound metabolic suppression characteristic of suspended animation.
*Hyperbaric Oxygen Therapy*
- Hyperbaric oxygen therapy involves breathing pure oxygen in a pressurized room, which increases oxygen delivery to tissues.
- This therapy is used to treat conditions like decompression sickness or chronic wounds and does not cause a state of suspended animation; rather, it increases metabolic activity in certain contexts.
Question 72: What type of narcosis is primarily associated with increased nitrogen solubility under pressure?
- A. CO narcosis
- B. CO2 narcosis
- C. N2 narcosis (Correct Answer)
- D. O2 toxicity
Explanation: ***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.
Question 73: Which is a feature of high-altitude pulmonary edema?
- A. Associated with low cardiac output
- B. Exercise has no effect
- C. Associated with pulmonary hypertension (Correct Answer)
- D. Occurs in both acclimatized and unacclimatized persons
Explanation: ***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.
