Respiratory and Airway Management — MCQs

Respiratory and Airway Management Indian Medical PG Practice Questions and MCQs

Question 111: Who developed the Laryngeal Mask Airway (LMA) ProSeal?

A. Bailey
B. Macewan
C. Brain (Correct Answer)
D. Magill

Explanation: **Explanation:** The **Laryngeal Mask Airway (LMA)** and its subsequent variations, including the **LMA ProSeal**, were developed by **Dr. Archie Brain**, a British anesthesiologist. He introduced the classic LMA in 1981 (commercially available in 1988), revolutionizing airway management by bridging the gap between a face mask and an endotracheal tube. The **LMA ProSeal**, introduced in 2000, is a second-generation supraglottic airway device (SAD) featuring a gastric drainage tube and a modified cuff to allow for higher seal pressures, making it suitable for controlled ventilation. **Analysis of Incorrect Options:** * **Bailey:** Known for the "Bailey Maneuver," which involves exchanging an endotracheal tube for an LMA at the end of surgery to allow for a "deep" emergence and minimize coughing/bucking. * **Macewan:** William Macewan was a pioneer in anesthesia known for performing the first recorded endotracheal intubation using a flexible metal tube (introducer) in 1878. * **Magill:** Sir Ivan Magill was a legendary anesthesiologist who developed the Magill forceps, the Magill circuit (Mapleson A), and standardized wide-bore endotracheal tubes. **High-Yield Clinical Pearls for NEET-PG:** * **LMA ProSeal vs. Classic:** The ProSeal has a **gastric port** (to vent air/drain gastric contents) and a **posterior cuff** (improving the seal up to 30 cm H₂O). * **LMA Fastrach (ILMA):** Also developed by Dr. Brain; specifically designed to facilitate blind intubation in difficult airway scenarios. * **LMA Supreme:** A single-use version that combines features of the ProSeal and Fastrach. * **Contraindication:** LMAs are generally contraindicated in patients with a "full stomach" (high risk of aspiration), though the ProSeal offers slightly better protection than the Classic.

Question 112: Which of the following is NOT a step in rapid sequence intubation?

A. Intravenous thiopental and intravenous succinylcholine are used for induction and paralysis.
B. Bag and mask ventilation is used for positive pressure ventilation. (Correct Answer)
C. Sellick’s maneuver is used to prevent aspiration.
D. Pre-oxygenation is mandatory.

Explanation: **Explanation:** The core principle of **Rapid Sequence Induction and Intubation (RSII)** is to minimize the time between the loss of protective airway reflexes and tracheal intubation to prevent the aspiration of gastric contents in "full stomach" patients. **Why Option B is the correct answer:** In classic RSII, **bag-and-mask ventilation (BMV) is avoided** after the administration of induction agents and neuromuscular blockers. Positive pressure ventilation can cause gastric insufflation, increasing intragastric pressure and the subsequent risk of regurgitation and aspiration. The patient is allowed to remain apneic until the tube is secured. **Analysis of other options:** * **Option A:** Thiopental (fast-acting induction agent) and Succinylcholine (rapid-onset, short-acting depolarizing muscle relaxant) are the traditional "gold standard" drugs for RSII due to their rapid onset of action. * **Option C:** **Sellick’s maneuver (Cricoid pressure)** is a hallmark of RSII. It involves applying downward pressure on the cricoid cartilage to occlude the esophagus against the cervical vertebrae, preventing passive regurgitation. * **Option D:** Since BMV is avoided, **Pre-oxygenation (Denitrogenation)** with 100% oxygen for 3–5 minutes is mandatory. This creates an "oxygen reservoir" in the functional residual capacity (FRC), allowing the patient to tolerate the period of apnea without desaturating. **High-Yield Clinical Pearls for NEET-PG:** * **Modified RSI:** If a patient desaturates during the procedure, gentle "low-pressure" BMV (pressure <20 cm H₂O) may be performed; this is known as modified RSI. * **Drug of Choice:** While Thiopental was traditional, **Propofol** is now commonly used. If Succinylcholine is contraindicated (e.g., hyperkalemia, burns), **Rocuronium** (1.2 mg/kg) is the alternative. * **Cricoid Pressure:** Should be released only *after* the ET tube position is confirmed and the cuff is inflated.

Question 113: The clinical use of which of the following drugs has been discontinued due to its association with severe bronchospasm?

A. Rapacuronium (Correct Answer)
B. Rocuronium
C. Atracurium
D. Mivacurium

Explanation: **Explanation:** **Rapacuronium (Option A)** is the correct answer. It was introduced as a non-depolarizing neuromuscular blocking agent (NMBA) with a rapid onset and short duration, intended to be an alternative to Succinylcholine. However, it was voluntarily withdrawn from the market worldwide in 2001 shortly after its release. The primary reason was its association with an unacceptably high incidence of **severe, life-threatening bronchospasm**, particularly in pediatric patients. The underlying mechanism is attributed to its potent **antimuscarinic effects at M2 receptors** (which normally inhibit acetylcholine release), leading to an unchecked release of acetylcholine and subsequent stimulation of M3 receptors on bronchial smooth muscle. **Why other options are incorrect:** * **Rocuronium (Option B):** Currently the most widely used rapid-onset NMBA. It does not cause significant histamine release or bronchospasm and is considered safe for asthmatic patients. * **Atracurium (Option C):** Known for causing **histamine release**, which can lead to mild bronchoconstriction, flushing, and hypotension, but it is not discontinued and remains in clinical use (metabolized by Hofmann elimination). * **Mivacurium (Option D):** A short-acting benzylisoquinolinium that also triggers histamine release. While it should be used cautiously in patients with reactive airways, it has not been discontinued. **High-Yield Clinical Pearls for NEET-PG:** * **Rapacuronium:** Remember the "Rapid" onset but "Fatal" bronchospasm. * **M2 vs. M3:** Bronchospasm in Rapacuronium is due to **M2 blockade** (presynaptic) leading to increased ACh. * **Drug of Choice for RSI:** Rocuronium is the preferred non-depolarizing agent for Rapid Sequence Induction (RSI) when Succinylcholine is contraindicated. * **Histamine Releasers:** Atracurium, Mivacurium, and Tubocurarine (the "curium/curarine" group) are the classic histamine releasers in anesthesia.

Question 114: Which of the following is the earliest and shortest-acting skeletal muscle relaxant?

A. Rocuronium
B. Vecuronium
C. Atracurium
D. Suxamethonium (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. Suxamethonium (Succinylcholine)** **Mechanism and Rationale:** Suxamethonium is the only **depolarizing neuromuscular blocker** used clinically. It works by mimicking the action of acetylcholine at the nicotinic receptors of the motor endplate, causing persistent depolarization. * **Onset:** It has the fastest onset of action (**30–60 seconds**), making it the gold standard for Rapid Sequence Induction (RSI). * **Duration:** It is the shortest-acting relaxant because it is rapidly hydrolyzed by **pseudocholinesterase (plasma cholinesterase)** in the blood. Its clinical effect lasts only **5–10 minutes**. **Analysis of Incorrect Options:** All other options belong to the **Non-depolarizing** class (competitive antagonists), which generally have a slower onset and longer duration than Suxamethonium: * **A. Rocuronium:** An aminosteroid with the fastest onset among non-depolarizers (60–90 seconds), but its duration is intermediate (30–40 minutes). * **B. Vecuronium:** An intermediate-acting aminosteroid (duration 30–40 minutes) with a slower onset (2–3 minutes) than Rocuronium. * **C. Atracurium:** An intermediate-acting benzylisoquinolinium (duration 30–45 minutes). It is unique for its metabolism via **Hofmann elimination**, making it safe in liver and kidney failure. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** For Rapid Sequence Induction (RSI) and when a "difficult airway" is anticipated (due to short duration). * **Side Effects:** Muscle fasciculations (prevented by a "pre-curarization" dose), hyperkalemia (avoid in burns/trauma), and it is a potent trigger for **Malignant Hyperthermia**. * **Prolonged Apnea:** Occurs in patients with **pseudocholinesterase deficiency** (diagnosed by a low Dibucaine Number). * **Mivacurium:** The shortest-acting *non-depolarizing* muscle relaxant, but it is still slower and longer-acting than Suxamethonium.

Question 115: Identify the pictured airway device.

A. Oropharyngeal airway
B. Nasopharyngeal airway (Correct Answer)
C. Proseal airway
D. Flexometallic LMA

Explanation: ***Nasopharyngeal airway*** - Features a **soft, flexible tube** with a **beveled distal tip** and **proximal flange with safety pin** to prevent migration into the nostril. - Designed for **nasal insertion** to maintain airway patency, particularly useful in patients with **intact gag reflex** or **oral trauma**. *Oropharyngeal airway* - Has a **rigid, curved plastic design** that follows the **natural curve of the tongue** and lacks the flexible tube structure. - Inserted through the **mouth** and requires **absence of gag reflex**, making it unsuitable for conscious patients. *Proseal airway* - A **supraglottic airway device** with an **inflatable cuff** and **gastric drainage tube** for advanced airway management. - Much **larger and more complex** than simple airway adjuncts, designed for **mechanical ventilation** under anesthesia. *Flexometallic LMA* - Features a **wire-reinforced flexible shaft** with an **inflatable laryngeal mask** at the distal end. - Designed for **supraglottic ventilation** during procedures requiring **head and neck positioning** where standard LMAs might kink.

Question 116: In a young patient with extensive soft tissue and muscle injury, which muscle relaxant used for endotracheal intubation might lead to cardiac arrest?

A. Atracurium
B. Suxamethonium (Correct Answer)
C. Vecuronium
D. Pancuronium

Explanation: **Explanation:** The correct answer is **Suxamethonium (Succinylcholine)**. **Why Suxamethonium is the correct answer:** Suxamethonium is a depolarizing neuromuscular blocker that acts by mimicking acetylcholine at the nicotinic receptors. In patients with **extensive soft tissue injury, major burns, or denervation injuries**, there is an "upregulation" of extrajunctional acetylcholine receptors. When Suxamethonium is administered, these receptors open, causing a massive efflux of potassium from the muscle cells into the extracellular fluid. This **acute hyperkalemia** can lead to severe cardiac arrhythmias and sudden **cardiac arrest**. This risk typically peaks 24–48 hours after the injury and can persist for months. **Why other options are incorrect:** * **Atracurium:** A non-depolarizing muscle relaxant (NDMR) that does not cause potassium release. It is metabolized by Hofmann elimination and is safe in renal/hepatic failure. * **Vecuronium:** An intermediate-acting NDMR with a stable cardiovascular profile; it does not cause hyperkalemia. * **Pancuronium:** A long-acting NDMR. While it may cause tachycardia (vagolytic effect), it does not trigger hyperkalemia or cardiac arrest in trauma patients. **High-Yield Clinical Pearls for NEET-PG:** * **Normal K+ rise:** In a healthy individual, Suxamethonium raises serum potassium by approximately **0.5 mEq/L**. * **Contraindications:** Avoid Suxamethonium in burns (>24 hours old), crush injuries, spinal cord injuries (paraplegia/quadriplegia), and muscular dystrophies. * **Drug of Choice for RSI:** Despite this risk, Suxamethonium remains the gold standard for Rapid Sequence Induction (RSI) due to its rapid onset and short duration, provided no contraindications exist.

Question 117: What is true about laryngoscopy and intubation?

A. Hypertension (Correct Answer)
B. Tachycardia
C. Increased intracranial pressure
D. Increased intraocular pressure

Explanation: **Explanation:** Laryngoscopy and tracheal intubation are potent stimuli that trigger a **sympathoadrenal response** due to the stimulation of epipharyngeal and tracheobronchial receptors. This results in a transient but significant increase in plasma catecholamine levels (norepinephrine and epinephrine). **1. Why Hypertension is the most characteristic response:** The primary hemodynamic response to this sympathetic surge is peripheral vasoconstriction and an increase in cardiac output, leading to a sharp rise in **systemic arterial blood pressure (Hypertension)**. While tachycardia also occurs, hypertension is often the most pronounced and clinically significant hemodynamic change monitored during induction. **2. Analysis of Other Options:** * **B. Tachycardia:** While tachycardia is a common component of the pressor response, in the context of many standardized PG exams, hypertension is prioritized as the hallmark hemodynamic change. However, it is important to note that in pediatric patients, the response may be **bradycardia** due to a dominant vagal tone. * **C & D. Increased Intracranial (ICP) and Intraocular Pressure (IOP):** Both ICP and IOP **do increase** during laryngoscopy. However, these are secondary consequences of the sympathetic surge and the mechanical stimulation (coughing/bucking). In the hierarchy of "most true" or "most characteristic" physiological responses, the systemic cardiovascular changes (hypertension) are typically the primary focus of this specific question. **High-Yield Clinical Pearls for NEET-PG:** * **Duration:** The pressor response starts within seconds, peaks at 1–2 minutes, and returns to baseline within 5–10 minutes. * **Attenuation:** To prevent these surges (especially in patients with CAD or intracranial aneurysms), clinicians use **IV Lidocaine (1.5 mg/kg)**, opioids (Fentanyl), or Beta-blockers (Esmolol) 2–3 minutes before intubation. * **Cormack-Lehane Classification:** Used to grade the view obtained during laryngoscopy (Grade I to IV).

Question 118: Tracheostomy reduces dead space by:

A. By-passing the upper airway (Correct Answer)
B. Increasing V/Q ratio
C. Raising airflow resistance
D. By all of the above mechanisms

Explanation: **Explanation:** **1. Why Option A is Correct:** The respiratory dead space consists of the **Anatomical Dead Space** (volume of the conducting airways where no gas exchange occurs). In a healthy adult, this is approximately **150 mL** (or 2 mL/kg). The upper airway (nose, pharynx, and larynx) contributes significantly to this volume. A tracheostomy involves creating a direct opening in the trachea, effectively **bypassing the upper airway**. This anatomical shortcut reduces the dead space by approximately **30% to 50%** (roughly 50–75 mL). Reducing dead space improves alveolar ventilation, making it easier for patients with respiratory compromise to clear CO2. **2. Why Other Options are Incorrect:** * **Option B (Increasing V/Q ratio):** The Ventilation/Perfusion (V/Q) ratio is a physiological measure of gas exchange efficiency at the alveolar level. While tracheostomy improves ventilation, its primary mechanical effect on dead space is anatomical, not a direct manipulation of the V/Q ratio. * **Option C (Raising airflow resistance):** This is factually incorrect. Tracheostomy actually **decreases** airflow resistance by bypassing the narrowest part of the upper airway (the glottis) and providing a shorter, wider path for air. * **Option D:** Since B and C are incorrect, this option is invalid. **High-Yield Clinical Pearls for NEET-PG:** * **Dead Space Calculation:** Anatomical dead space is measured using **Fowler’s Method** (Nitrogen washout). * **Physiological Dead Space:** Anatomical Dead Space + Alveolar Dead Space. It is measured using **Bohr’s Equation** (using $PaCO_2$ and $PeCO_2$). * **Equipment Dead Space:** In anesthesia circuits, any part of the breathing circuit where bidirectional flow occurs (e.g., the space distal to the Y-piece) increases dead space. * **Tracheostomy Benefit:** Beyond reducing dead space, it facilitates weaning from mechanical ventilation by reducing the **Work of Breathing (WOB)**.

Question 119: Generally accepted indications for mechanical ventilatory support include which of the following?

A. PaO2 of less than 70 kPa and PaCO2 of greater than 50 kPa while breathing room air
B. Alveolar-arterial oxygen tension difference of 150 kPa while breathing 100% O2
C. Vital capacity of 40-60 mL/kg
D. Respiratory rate greater than 35 breaths/min (Correct Answer)

Explanation: ### Explanation Mechanical ventilation is indicated when a patient’s spontaneous respiratory effort is insufficient to maintain adequate oxygenation, ventilation, or airway protection. The decision is based on clinical assessment and specific physiological thresholds. **1. Why Option D is Correct:** A **respiratory rate (RR) > 35 breaths/min** is a classic indication for mechanical ventilation. Such high rates significantly increase the work of breathing, leading to respiratory muscle fatigue, increased dead space ventilation, and eventual CO2 retention. It signifies impending respiratory failure. **2. Why the Other Options are Incorrect:** * **Option A:** The units and values are incorrect. A PaO2 of < 70 **mmHg** (not kPa) or a PaCO2 > 50 **mmHg** (with pH < 7.25) are typical thresholds. Note that 70 kPa is roughly 525 mmHg, which is hyperoxic. * **Option B:** The **Alveolar-arterial (A-a) oxygen gradient** indication is typically **> 350–450 mmHg** while breathing 100% O2. A difference of 150 kPa (approx. 1125 mmHg) is physiologically impossible as it exceeds the pressure of 100% oxygen at sea level. * **Option C:** A **Vital Capacity (VC) < 10–15 mL/kg** is an indication for ventilation (common in neuromuscular cases like GBS). A VC of 40–60 mL/kg is actually within the **normal range** for a healthy adult. **3. High-Yield Clinical Pearls for NEET-PG:** * **Maximum Inspiratory Force (MIF):** Ventilation is indicated if MIF is less than **-20 to -25 cm H2O**. * **Dead Space (Vd/Vt):** An indication for ventilation is a ratio **> 0.6**. * **PaO2/FiO2 Ratio:** A ratio **< 200** (suggestive of ARDS) often necessitates ventilatory support. * **Clinical Priority:** Always treat the patient, not the monitor. Tachypnea and the use of accessory muscles often precede blood gas abnormalities.

Question 120: What are the pulmonary changes in the lateral position in an anesthetized patient?

A. Dependent lung is relatively over-ventilated and over-perfused.
B. Dependent lung is relatively over-ventilated and under-perfused.
C. Dependent lung is relatively under-ventilated and over-perfused. (Correct Answer)
D. Dependent lung is relatively under-ventilated and under-perfused.

Explanation: In the lateral decubitus position under general anesthesia, significant physiological shifts occur due to the combined effects of gravity, loss of muscle tone, and mechanical ventilation. ### **Mechanism of the Correct Answer (C)** * **Perfusion (Q):** Gravity remains the primary determinant of blood flow. In the lateral position, blood preferentially flows to the **dependent (lower) lung**, making it **over-perfused**. * **Ventilation (V):** In an awake patient, the dependent lung is better ventilated due to the efficient contraction of the lower diaphragm. However, **under anesthesia and muscle paralysis**, this changes: 1. The abdominal contents push upward against the dependent diaphragm, reducing its excursion. 2. The weight of the mediastinum compresses the lower lung. 3. The non-dependent (upper) lung becomes more compliant and easier to inflate with positive pressure ventilation. Consequently, the **dependent lung is under-ventilated**, leading to a **V/Q mismatch** and an increased alveolar-arterial oxygen gradient. ### **Analysis of Incorrect Options** * **A & B:** These are incorrect because the dependent lung is **under-ventilated** under anesthesia. The loss of Functional Residual Capacity (FRC) is most pronounced in the dependent lung, often leading to atelectasis. * **D:** This is incorrect because gravity ensures the dependent lung is always **over-perfused** compared to the non-dependent lung. ### **High-Yield Clinical Pearls for NEET-PG** * **V/Q Mismatch:** The lateral position under anesthesia is a classic example of "shunt-like" physiology (perfusion without adequate ventilation). * **FRC:** General anesthesia reduces FRC in both lungs, but the reduction is most significant in the **dependent lung**. * **Mediastinal Shift:** Gravity causes the mediastinum to shift toward the dependent lung, further reducing its volume. * **One-Lung Ventilation (OLV):** During thoracic surgery, the V/Q mismatch is exacerbated as the non-dependent lung is intentionally collapsed, making the dependent lung the sole site for gas exchange.

Practice by Chapter

Respiratory Physiology

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Airway Anatomy

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Preoxygenation Techniques

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Mask Ventilation

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Supraglottic Airway Devices

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Direct Laryngoscopy

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Video Laryngoscopy

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Fiberoptic Intubation

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Surgical Airway Management

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One-Lung Ventilation Techniques

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Ventilation Strategies During Anesthesia

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Extubation Criteria and Techniques

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