High Altitude and Diving Injuries — MCQs
Which drug is given to prevent acute mountain sickness?
Immersion syndrome is also known as?
What type of narcosis is primarily associated with increased nitrogen solubility under pressure?
Which physiological adaptation does not happen at high altitudes?
Regarding Caisson's disease which statement among the following is CORRECT?
What is the most immediate hematological adaptation that occurs during high-altitude exposure to improve oxygen delivery to tissues?
What is the primary effect of acetazolamide at high altitudes?
Which of the following is seen in high altitude climbers?
In diffuse axonal injury all are true EXCEPT:
If an anesthetist at high altitude uses plenum vaporizers, what will be the delivered vapor concentration?
High Altitude and Diving Injuries Indian Medical PG Practice Questions and MCQs
Question 1: Which drug is given to prevent acute mountain sickness?
- A. Acetazolamide (Correct Answer)
- B. Diltiazem
- C. Digoxin
- D. Dexamethasone
Explanation: ***Acetazolamide*** - This drug is a **carbonic anhydrase inhibitor** that acidifies the blood and causes compensatory hyperventilation, increasing oxygenation. - It is the **first-line prophylactic agent** for acute mountain sickness (AMS) and is best started 24-48 hours before ascent. - Most effective and widely recommended for AMS prevention. *Digoxin* - This is a **cardiac glycoside** used to treat heart failure and irregular heartbeats. - Its mechanism of action is unrelated to the physiological changes that cause acute mountain sickness. *Diltiazem* - This is a **calcium channel blocker** primarily used for hypertension, angina, and certain arrhythmias. - It has no known role in the prevention or treatment of acute mountain sickness. *Dexamethasone* - While **dexamethasone** can be used for AMS prophylaxis, it is typically reserved as an **alternative agent** when acetazolamide is contraindicated or not tolerated. - It is more commonly used for **treatment** of severe altitude illness including **High Altitude Cerebral Edema (HACE)** and **High Altitude Pulmonary Edema (HAPE)**. - **Acetazolamide remains the preferred first-line prophylactic agent** due to its mechanism of action that directly addresses the underlying pathophysiology of AMS.
Question 2: Immersion syndrome is also known as?
- A. Hydrocution (Correct Answer)
- B. Wet drowning
- C. Dry drowning
- D. Secondary drowning
Explanation: ***Hydrocution*** - **Immersion syndrome**, or hydrocution, is a sudden death that occurs immediately upon immersion in cold water. - It is believed to be caused by a **vasovagal reflex** triggered by the sudden temperature change, leading to cardiac arrest. *Wet drowning* - This term refers to conventional drowning where an individual inhales water, leading to respiratory compromise and death. - It is characterized by the presence of **fluid in the lungs**, which is not the primary mechanism in immersion syndrome. *Dry drowning* - **Dry drowning** occurs when water does not enter the lungs; instead, the glottis spasms and closes, preventing air and water from entering. - This leads to suffocation, often hours after the initial water exposure, and is distinct from the immediate cardiac event of immersion syndrome. *Secondary drowning* - **Secondary drowning**, or delayed drowning, refers to complications that arise hours or days after a near-drowning incident due to inhaled water causing pulmonary edema. - It involves a delayed physiological response rather than an immediate reflex.
Question 3: 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 4: Which physiological adaptation does not happen at high altitudes?
- A. Pulmonary vasoconstriction
- B. Respiratory acidosis (Correct Answer)
- C. Hypoxia
- D. Polycythemia
Explanation: ***Respiratory acidosis*** - At high altitudes, the primary physiological response to **hypoxia** is to increase ventilation, leading to a decrease in **arterial PCO2**. - This reduction in **PCO2** causes **respiratory alkalosis**, not acidosis, as the body tries to compensate for the lower oxygen levels. *Pulmonary vasoconstriction* - This is a significant physiological response to **hypoxia** at high altitudes, leading to an increase in **pulmonary artery pressure**. - Its purpose is to divert blood flow to better-ventilated areas of the lung, but it can also contribute to **pulmonary hypertension**. *Hypoxia* - Reduced **atmospheric pressure** at high altitudes directly results in a lower partial pressure of oxygen (**PO2**), leading to **hypoxia**. - This low **PO2** is the primary trigger for most other physiological adaptations seen at high altitudes. *Polycythemia* - Prolonged exposure to **hypoxia** stimulates the kidneys to release **erythropoietin (EPO)**, which in turn increases **red blood cell production**. - This adaptive increase in **red blood cell count** and **hemoglobin concentration** aims to enhance the oxygen-carrying capacity of the blood.
Question 5: Regarding Caisson's disease which statement among the following is CORRECT?
- A. Lung damage is caused by air embolism
- B. Pain in the joints is due to nitrogen bubbles (Correct Answer)
- C. Tremors are seen due to nitrogen narcosis
- D. High pressure Nervous syndrome can be prevented by using mixtures of Oxygen & Helium
Explanation: ***Pain in the joints is due to nitrogen bubbles*** - Caisson's disease, or **decompression sickness**, is characterized by the formation of nitrogen gas bubbles in tissues and blood due to rapid depressurization. - These gas bubbles can accumulate in joints, causing **severe pain** often referred to as "the bends." *Lung damage is caused by air embolism* - While air embolism can occur due to **pulmonary barotrauma** during ascent (rapid depressurization), the primary lung damage associated with decompression sickness is not typically directly caused by an air embolism reaching the lungs from within the body. - Air embolism from pulmonary barotrauma is a distinct complication, where air from ruptured alveoli enters the arterial circulation, potentially leading to cerebral or cardiac ischemia. *Tremors are seen due to nitrogen narcosis* - **Nitrogen narcosis** is a condition that occurs at high ambient pressures when breathing compressed air, causing a reversible alteration in consciousness similar to alcohol intoxication, but it does not primarily cause tremors. - Tremors are more characteristic of other neurological conditions or high-pressure nervous syndrome, not nitrogen narcosis itself. *High pressure Nervous syndrome can be prevented by using mixtures of Oxygen & Helium* - **High-pressure nervous syndrome (HPNS)** is indeed associated with deep dives using helium-oxygen mixtures. Its symptoms include tremors. - HPNS is actually **prevented or mitigated** by adding small amounts of narcotic gases like nitrogen to the helium-oxygen mixture (e.g., trimix) to counteract the excitatory effects of helium, rather than solely using oxygen and helium.
Question 6: What is the most immediate hematological adaptation that occurs during high-altitude exposure to improve oxygen delivery to tissues?
- A. Increased red blood cell mass
- B. Reduced erythropoietin production
- C. Increased white blood cell count
- D. Increased 2,3-BPG levels (Correct Answer)
Explanation: ***Increased 2,3-BPG levels*** - **2,3-Bisphosphoglycerate (2,3-BPG)** is an organic phosphate that binds to hemoglobin, reducing its affinity for oxygen and thereby facilitating oxygen release to tissues. - This is a **rapid adaptation** in response to hypoxia at high altitudes, occurring within hours to days, providing an immediate improvement in oxygen delivery. *Increased red blood cell mass* - An increase in **red blood cell mass (polycythemia)** is a more chronic adaptation, typically taking weeks to months to develop in response to sustained hypoxia. - While it ultimately improves oxygen-carrying capacity, it is not the most immediate hematological adaptation. *Reduced erythropoietin production* - High-altitude exposure actually leads to **increased erythropoietin (EPO) production** by the kidneys due to tissue hypoxia. - This increased EPO stimulates erythropoiesis, leading to the delayed increase in red blood cell mass. *Increased white blood cell count* - An **increased white blood cell count (leukocytosis)** is primarily associated with infection, inflammation, or stress, not with the physiological response to high-altitude hypoxia for improving oxygen delivery. - It does not directly contribute to the oxygen-carrying capacity of the blood.
Question 7: What is the primary effect of acetazolamide at high altitudes?
- A. Increase CO2
- B. Decrease ventilation
- C. Elevate pH
- D. Reduce HCO3- (Correct Answer)
Explanation: ***Reduce HCO3-*** - Acetazolamide is a **carbonic anhydrase inhibitor**, which primarily acts in the renal tubules to prevent the reabsorption of bicarbonate (HCO3-). - This leads to a loss of bicarbonate in the urine, causing **metabolic acidosis**, which in turn stimulates ventilation and counteracts the effects of high altitude. *Increase CO2* - Acetazolamide's action to induce metabolic acidosis through bicarbonate excretion actually **stimulates ventilation**, leading to a *decrease* in CO2, not an increase. - An increase in CO2 would further depress respiration and worsen high-altitude symptoms. *Decrease ventilation* - The primary goal of acetazolamide at high altitude is to *increase* ventilation by inducing metabolic acidosis, which then stimulates peripheral chemoreceptors. - A decrease in ventilation would exacerbate **hypoxia** and symptoms of acute mountain sickness. *Elevate pH* - By promoting the excretion of bicarbonate (a base), acetazolamide effectively *lowers* the blood pH, creating a state of **metabolic acidosis**. - An elevated pH (alkalosis) would suppress the respiratory drive, which is counterproductive at high altitudes.
Question 8: Which of the following is seen in high altitude climbers?
- A. Hyperventilation
- B. Pulmonary edema
- C. Decreased PaCO2
- D. All of the options (Correct Answer)
Explanation: ***All of the options*** - High altitude climbers experience **hypoxia**, which triggers several physiological responses as the body tries to compensate. - **Hyperventilation**, **pulmonary edema**, and **decreased PaCO2** are all common occurrences in individuals exposed to high altitudes. *Hyperventilation* - **Hypoxia** at high altitudes stimulates the peripheral chemoreceptors, leading to an increased respiratory rate and depth. - This increased ventilation is a compensatory mechanism to try and increase **oxygen intake**. *Pulmonary edema* - **High-altitude pulmonary edema (HAPE)** is a potentially life-threatening condition caused by exaggerated hypoxic pulmonary vasoconstriction. - This leads to increased pulmonary arterial pressure, capillary leakage, and **fluid accumulation in the lungs**. *Decreased PaCO2* - The increased respiratory rate due to **hyperventilation** causes an excessive exhalation of carbon dioxide. - This results in a **decreased partial pressure of arterial carbon dioxide (PaCO2)**, leading to respiratory alkalosis.
Question 9: In diffuse axonal injury all are true EXCEPT:
- A. Seen in high energy
- B. Form of primary brain injury
- C. CT scan shows pathognomonic finding (Correct Answer)
- D. Usually causes prolonged coma
Explanation: ***CT scan shows pathognomonic finding*** - While CT scans can sometimes show petechial hemorrhages or small white matter lesions in **diffuse axonal injury (DAI)**, these findings are **not pathognomonic** and can be absent even in severe cases. - **MRI** is more sensitive for detecting microhemorrhages and white matter changes, but even MRI findings are not always definitively diagnostic of DAI, especially in milder forms. - CT scan has **low sensitivity** for DAI, often appearing normal or showing only subtle findings. *Usually causes prolonged coma* - **Diffuse axonal injury (DAI)** is a common cause of **prolonged coma** after traumatic brain injury, as widespread shearing forces disrupt neuronal connections [1]. - The severity and duration of coma correlate with the extent of axonal damage, with severe DAI typically resulting in immediate and prolonged loss of consciousness. *Seen in high energy* - DAI typically results from **high-energy acceleration-deceleration forces**, often seen in motor vehicle accidents or falls from significant heights [1]. - These forces cause differential movement between various parts of the brain, leading to **shearing and stretching of axons** [1]. *Form of primary brain injury* - DAI is considered a **primary brain injury** because the axonal damage occurs at the **moment of impact** due to mechanical forces [1]. - This contrasts with secondary brain injuries, which develop over time due to complications like edema or ischemia. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1262-1264.
Question 10: If an anesthetist at high altitude uses plenum vaporizers, what will be the delivered vapor concentration?
- A. Lower than concentration at same partial pressure
- B. Higher than the concentration at same partial pressure (Correct Answer)
- C. Lower than the concentration at lower partial pressure
- D. Higher than the original concentration at high partial pressure
Explanation: ***Higher than the concentration at same partial pressure*** - Plenum vaporizers are calibrated at **sea level** and deliver a constant *volume percent* of volatile anesthetic. At high altitude, ambient pressure is lower, meaning a given volume percent represents a **higher partial pressure** of anesthetic. - While the *anesthetic partial pressure* might be what the anesthetist aims for, the *delivered concentration* (volume percent) will be higher than the concentration that would achieve the same partial pressure at sea level because the total pressure is lower. *Lower than concentration at same partial pressure* - This statement is incorrect because a plenum vaporizer will deliver a **higher partial pressure** at altitude for a given dial setting, due to the reduced ambient pressure. - A lower partial pressure for the same set concentration would only occur if the ambient pressure were higher than calibration. *Lower than the concentration at lower partial pressure* - This option is vaguely worded and does not accurately describe the behavior of plenum vaporizers at altitude. When total pressure drops, the *partial pressure* delivered by a plenum vaporizer at a given dial setting will increase, not decrease. - A lower vapor concentration leading to a lower partial pressure is generally true, but it doesn't address the specific issue of a plenum vaporizer's performance at high altitude. *Higher than the original concentration at high partial pressure* - This option is confusing as it refers to "original concentration at high partial pressure" which isn't a standard comparison. The key is that a plenum vaporizer's *delivered volume % remains constant*, regardless of altitude. - However, this constant volume % translates to a higher *partial pressure* when the **ambient atmospheric pressure is lower**, as is the case at high altitude.
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