Altitude and Diving Physiology Practice Questions

Q: Which of the following statements regarding acute high altitude pulmonary edema is true?

Mandates immediate descent. ### Explanation **High-Altitude Pulmonary Edema (HAPE)** is a life-threatening form of non-cardiogenic pulmonary edema that occurs in unacclimatized individuals following rapid ascent to high altitudes. **1. Why Option B is Correct:** The definitive and most crucial treatment for HAPE is **immediate descent**. Because HAPE is caused by hypoxia-induced pulmonary hypertension, lowering the altitude increases the partial pressure of oxygen ($PaO_2$), which reverses pulmonary vasoconstriction. Delaying descent can lead to fatal respiratory failure. If descent is impossible, supplemental oxygen and hyperbaric bags (Gamow bags) are used as temporizing measures. **2. Why Other Options are Incorrect:** * **Option A:** HAPE is not primarily an inflammatory or infectious condition; it is a hemodynamic consequence of **hypoxic pulmonary vasoconstriction (HPV)**. While mild leukocytosis may occur, a raised ESR is not a diagnostic or characteristic feature. * **Option C:** HAPE typically occurs at altitudes above **2,500 to 3,000 meters** (approx. 8,000–10,000 feet). Waiting until 6,000 meters is incorrect, as most clinical cases manifest much lower, especially in rapid ascents. **3. Clinical Pearls for NEET-PG:** * **Pathophysiology:** Uneven hypoxic pulmonary vasoconstriction leads to increased capillary hydrostatic pressure, causing "stress failure" of the alveolar-capillary membrane. * **Drug of Choice (Prophylaxis/Treatment):** **Nifedipine** (a calcium channel blocker) helps by reducing pulmonary artery pressure. * **Key Symptom:** Early sign is decreased exercise tolerance and dry cough, progressing to tachycardia, tachypnea, and pink frothy sputum. * **Radiology:** Characteristically shows patchy, bilateral opacities (often starting in the right middle lobe).

Q: A person at a high altitude of 3000 meters complains of breathlessness. Which of the following is NOT used as a treatment for acute mountain sickness?

Intravenous Digoxin. **Explanation:** **Acute Mountain Sickness (AMS)** occurs due to hypobaric hypoxia at high altitudes (typically >2500m). The primary pathophysiology involves cerebral vasodilation and mild cerebral edema due to low arterial oxygen tension. **Why Intravenous Digoxin is the Correct Answer:** Digoxin is a cardiac glycoside used to increase myocardial contractility in heart failure or to control ventricular rate in atrial fibrillation. It has **no role** in the management of AMS. AMS is not caused by heart failure; rather, it is a neurological and respiratory response to hypoxia. Using Digoxin in this context provides no therapeutic benefit and may risk toxicity. **Analysis of Incorrect Options:** * **Immediate Descent:** This is the **most definitive treatment** for all forms of altitude sickness. Descending to a lower altitude (at least 500-1000m) rapidly increases the partial pressure of oxygen, reversing the underlying cause. * **Oxygen Supply:** Supplemental oxygen (2-4 L/min) directly corrects hypoxemia, relieves symptoms, and is a standard emergency intervention. * **Acetazolamide:** This is the **drug of choice** for both prophylaxis and treatment. It is a carbonic anhydrase inhibitor that induces metabolic acidosis by increasing bicarbonate excretion. This stimulates the respiratory center to increase ventilation (hyperventilation), thereby improving oxygenation. **High-Yield Clinical Pearls for NEET-PG:** 1. **HAPE (High Altitude Pulmonary Edema):** Characterized by pulmonary hypertension; treated with **Nifedipine** (a vasodilator). 2. **HACE (High Altitude Cerebral Edema):** The severe end of the AMS spectrum; treated with **Dexamethasone**. 3. **Gamow Bag:** A portable hyperbaric chamber used when immediate descent is not possible. 4. **Cheyne-Stokes Respiration:** Often seen during sleep at high altitudes due to unstable ventilatory drive.

Q: All are symptoms of acute mountain sickness except?

Tachycardia. **Explanation:** Acute Mountain Sickness (AMS) is a clinical syndrome that occurs in unacclimatized individuals shortly after ascending to high altitudes (usually above 2500m). It is primarily caused by **hypobaric hypoxia**, leading to cerebral vasodilation and mild cerebral edema. **Why Tachycardia is the correct answer:** While tachycardia (increased heart rate) is a common **physiological compensatory response** to hypoxia at high altitudes, it is **not** considered a diagnostic symptom of AMS itself. In the context of high-altitude medicine, tachycardia is a sign of acclimatization or a response to physical exertion, whereas AMS is defined by a specific constellation of neurological and gastrointestinal symptoms. **Analysis of Incorrect Options:** * **Headache (Option A):** This is the **hallmark symptom** and a mandatory criterion for diagnosing AMS. It is typically bilateral, throbbing, and worsens with exertion. * **Dyspnoea (Option B):** Shortness of breath on exertion is a common feature of AMS. However, dyspnoea at rest may indicate progression to High-Altitude Pulmonary Edema (HAPE). * **Light-headedness (Option D):** Dizziness and light-headedness are frequent neurological manifestations of AMS, alongside fatigue, insomnia, and anorexia. **High-Yield Clinical Pearls for NEET-PG:** * **Lake Louise Scoring System:** Used to diagnose AMS (Headache + at least one of: GI upset, fatigue, dizziness, or sleep disturbance). * **Drug of Choice (Prophylaxis):** Acetazolamide (Carbonic anhydrase inhibitor), which induces metabolic acidosis to stimulate ventilation. * **Drug of Choice (Treatment):** Dexamethasone (to reduce cerebral edema). * **Gold Standard Treatment:** Immediate descent and supplemental oxygen. * **Complications:** If untreated, AMS can progress to **HACE** (High-Altitude Cerebral Edema) or **HAPE** (High-Altitude Pulmonary Edema).

Q: Decompression sickness is seen in all of the following conditions except:

High altitude climbing. **Explanation:** The core concept behind **Decompression Sickness (DCS)**, also known as "the bends," is **Henry’s Law**, which states that the solubility of a gas in a liquid is proportional to its partial pressure. **Why High Altitude Climbing is the Correct Answer:** In high altitude climbing, the body moves from sea level (1 atm) to a lower atmospheric pressure. While this can cause hypoxia or Acute Mountain Sickness, it does **not** cause DCS. DCS requires a transition from a state of **high pressure** (where tissues are supersaturated with nitrogen) to a **lower pressure**. In climbing, the starting pressure is already low, so there is no excess nitrogen dissolved in the tissues to form bubbles upon further ascent. **Analysis of Incorrect Options:** * **Diving (A):** This is the classic cause. At high depths, the increased pressure forces nitrogen to dissolve into body tissues. If the diver ascends too rapidly, the pressure drops quickly, and nitrogen comes out of solution as bubbles in the blood and tissues. * **Aviation (B):** Pilots or passengers in unpressurized aircraft can experience DCS if they ascend rapidly from sea level to high altitudes (usually above 18,000 ft). The rapid drop from 1 atm to low atmospheric pressure causes pre-existing dissolved nitrogen to form bubbles. * **Both Diving and Aviation (C):** This is incorrect because DCS occurs in both, but not in climbing. **High-Yield Clinical Pearls for NEET-PG:** * **Henry’s Law:** Governs the pathophysiology of DCS. * **Nitrogen:** The primary gas responsible for DCS due to its high lipid solubility. * **Type I DCS:** "The Bends" (joint pain) and "The Niggles" (skin itching). * **Type II DCS:** "The Chokes" (pulmonary edema/dyspnea) and neurological deficits. * **Treatment:** 100% Oxygen and **Hyperbaric Oxygen Therapy** (recompression). * **Prevention:** Slow ascent and "decompression stops" to allow nitrogen to be exhaled gradually.

Q: What is advised for a patient with one episode of spontaneous pneumothorax?

All of the above. **Explanation:** The management of spontaneous pneumothorax (SP) involves strict lifestyle modifications to prevent recurrence and life-threatening complications like tension pneumothorax. **Why "All of the Above" is Correct:** 1. **Stop Diving (Option A):** This is the most critical contraindication. During ascent from a dive, ambient pressure decreases, causing any trapped air in the pleural space to expand (Boyle’s Law). In a patient with a history of SP, this can lead to an immediate **tension pneumothorax**, which is fatal underwater. Most guidelines (e.g., BTS) state that a history of SP is a permanent contraindication to diving unless a definitive bilateral surgical pleurectomy has been performed. 2. **Stop Smoking (Option B):** Smoking is the most significant modifiable risk factor for SP. It causes chronic airway inflammation and distal airway degradation, increasing the risk of recurrence by approximately 20-fold in men and 9-fold in women. 3. **Stop Flying (Option C):** Similar to diving, the decrease in cabin pressure at high altitudes causes trapped intrapleural air to expand. Patients are generally advised to avoid air travel until at least 1–2 weeks after a pneumothorax has completely resolved (confirmed by X-ray). **High-Yield Clinical Pearls for NEET-PG:** * **Boyle’s Law:** $P \propto 1/V$. This law explains why air expands during ascent (diving or flying), leading to tension pneumothorax. * **Recurrence Risk:** After one episode of SP, the risk of recurrence is approximately 30-50%. * **Primary Spontaneous Pneumothorax (PSP):** Typically occurs in tall, thin young males due to the rupture of subpleural apical blebs. * **Secondary Spontaneous Pneumothorax (SSP):** Occurs in patients with underlying lung disease (most commonly COPD).

Question 1

As part of a space-research program, a physiologist was asked to investigate the effect of flight-induced stress on blood pressure. The blood pressure of cosmonauts was to be measured twice: once before takeoff and once after the spacecraft entered the designated orbit around the earth. For a proper comparison, in which position should the pre-flight blood pressure be recorded?

Accepted Answer

The lying down position

Answer

The sitting position

Answer

The standing position

Answer

Any position, as long as the post-flight recording is made in the same position

Question 2

Which of the following statements regarding acute high altitude pulmonary edema is true?

Accepted Answer

Mandates immediate descent

Answer

Association with raised ESR

Answer

Usually occurs above 6000 meters height

Answer

None of the above

Question 3

A person at a high altitude of 3000 meters complains of breathlessness. Which of the following is NOT used as a treatment for acute mountain sickness?

Accepted Answer

Intravenous Digoxin

Answer

Oxygen supply

Answer

Acetazolamide

Answer

Immediate descent

Question 4

All are symptoms of acute mountain sickness except?

Accepted Answer

Tachycardia

Answer

Headache

Answer

Dyspnoea

Answer

Light headedness

Question 5

Decompression sickness is seen in all of the following conditions except:

Accepted Answer

High altitude climbing

Answer

Diving

Answer

Aviation

Answer

Both diving and aviation

Question 6

Which of the following adaptations will be most effective in increasing work capacity at high altitude?

Accepted Answer

Decreasing workload, increasing duration of exercise

Answer

Increasing workload, decreasing duration of exercise

Answer

Increasing workload, increasing duration of exercise

Answer

Decreasing workload, decreasing duration of exercise

Question 7

In high-altitude mountain sickness, which feature is characteristic of pulmonary edema?

Accepted Answer

Increased left ventricular back pressure

Answer

Decreased pulmonary capillary permeability

Answer

Increased pulmonary capillary pressure

Answer

Normal left atrial pressure

Question 8

What is advised for a patient with one episode of spontaneous pneumothorax?

Accepted Answer

All of the above

Answer

Stop diving

Answer

Stop smoking

Answer

Stop flying

Question 9

A mountaineer ascends to 18,000 feet in 2 days without supplemental oxygen. At the height of ascent, what changes are observed?

Accepted Answer

Decreased inspired O2 concentration

Answer

Increased PaCO2

Answer

Decreased barometric pressure

Answer

Decreased PaO2

Question 10

In a person who has been acclimatized to high altitude for a long time, which of the following changes is observed?

Accepted Answer

Pulmonary arterial hypertension

Answer

Increased MCHC

Answer

Irregular respiration

Answer

Increased airway resistance

Altitude and Diving Physiology — MCQs

Altitude and Diving Physiology — MCQs

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