Respiratory and Airway Management — MCQs

Respiratory and Airway Management Indian Medical PG Practice Questions and MCQs

Question 61: Which neuromuscular blocker is the drug of choice for rapid sequence induction when succinylcholine is contraindicated?

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

Explanation: **Explanation:** **Rocuronium** is the drug of choice for Rapid Sequence Induction (RSI) when Succinylcholine is contraindicated (e.g., in cases of hyperkalemia, major burns, or history of malignant hyperthermia). The primary medical concept here is **onset of action**. Rocuronium is a non-depolarizing neuromuscular blocker (NDNMB) with the fastest onset (60–90 seconds at a dose of 0.9–1.2 mg/kg), which closely mimics the rapid intubating conditions provided by Succinylcholine. **Analysis of Options:** * **Rapacuronium (Option B):** Although it had a very fast onset, it was withdrawn from the market worldwide due to a high incidence of severe bronchospasm. * **Vecuronium (Option C):** It is an intermediate-acting NDNMB but has a slower onset (approx. 3 minutes), making it unsuitable for the rapid airway control required in RSI. * **Atracurium (Option D):** It also has a slow onset (2–3 minutes). It is metabolized by Hofmann elimination, making it ideal for renal/hepatic failure, but not for emergency RSI. **High-Yield Clinical Pearls for NEET-PG:** 1. **Reversibility:** The effects of Rocuronium can be reversed immediately using **Sugammadex** (a selective relaxant binding agent), which encapsulates the drug molecule. 2. **Dosing for RSI:** While the standard intubating dose is 0.6 mg/kg, for RSI, the dose is increased to **0.9–1.2 mg/kg** to achieve faster paralysis. 3. **Duration:** Note that while Rocuronium provides fast onset, it has a much longer duration of action (30–60 mins) compared to Succinylcholine (5–10 mins).

Question 62: What is true about inhaled nitric oxide?

A. Causes generalized (systemic) vasodilation.
B. Dilates pulmonary arteries. (Correct Answer)
C. Causes hypotension and increases pulmonary artery pressure.
D. All of the above.

Explanation: **Explanation:** **Inhaled Nitric Oxide (iNO)** is a potent, selective pulmonary vasodilator. Its primary mechanism involves the activation of soluble guanylate cyclase, which increases intracellular **cyclic GMP (cGMP)**, leading to smooth muscle relaxation in the pulmonary vasculature. **Why Option B is correct:** When inhaled, nitric oxide reaches only the ventilated alveoli. It diffuses into the adjacent pulmonary capillaries, causing localized vasodilation. This improves **Ventilation-Perfusion (V/Q) matching** by redirecting blood flow to well-ventilated areas of the lung (the "Shunt-reduction" effect), thereby decreasing pulmonary artery pressure (PAP) and improving oxygenation. **Why other options are incorrect:** * **Option A & C:** iNO does **not** cause systemic vasodilation or systemic hypotension. This is because once nitric oxide enters the bloodstream, it is immediately and rapidly inactivated by binding to **hemoglobin**, forming methemoglobin. This extremely short half-life (seconds) ensures its effects are limited strictly to the pulmonary circulation. * **Option C (Part 2):** iNO *decreases* pulmonary artery pressure; it does not increase it. **High-Yield Clinical Pearls for NEET-PG:** * **Indications:** Persistent Pulmonary Hypertension of the Newborn (PPHN), ARDS (to improve oxygenation), and during cardiac surgery to manage right heart failure. * **Toxicity:** Monitor for **Methemoglobinemia** (keep levels <2%) and Nitrogen Dioxide ($NO_2$) formation, which is cytotoxic. * **Rebound Effect:** Abrupt withdrawal can cause "Rebound Pulmonary Hypertension." Always taper the dose gradually. * **Diagnostic Use:** Used in the cardiac catheterization lab to test for "Vasoreactivity" in patients with primary pulmonary hypertension.

Question 63: What is the most appropriate mode of ventilation for a patient with head injury?

A. CPAP (Continuous Positive Airway Pressure)
B. SIMV (Synchronized Intermittent Mandatory Ventilation)
C. CMV (Controlled Mechanical Ventilation) (Correct Answer)
D. AMV (Assisted Mechanical Ventilation)

Explanation: **Explanation:** In patients with severe head injury, the primary goal of mechanical ventilation is to prevent secondary brain injury by maintaining strict control over arterial carbon dioxide ($PaCO_2$) and oxygenation. **Why CMV is the correct answer:** **Controlled Mechanical Ventilation (CMV)** is the preferred mode because it allows the clinician to have absolute control over the patient’s minute ventilation. In head injury, even slight elevations in $PaCO_2$ cause cerebral vasodilation, increasing cerebral blood flow and intracranial pressure (ICP). CMV, typically combined with sedation and muscle relaxants, eliminates the patient’s work of breathing and prevents "fighting the ventilator," which can cause spikes in ICP. It ensures a stable, predictable $PaCO_2$ (ideally 30–35 mmHg) to maintain controlled cerebral vasoconstriction. **Why other options are incorrect:** * **CPAP:** This is a spontaneous breathing mode. It does not provide ventilatory support to control $PaCO_2$ and may increase intrathoracic pressure, potentially impeding venous return from the brain and increasing ICP. * **SIMV & AMV:** These modes allow for spontaneous or patient-triggered breaths. In head injury, spontaneous breathing efforts can be irregular or insufficient, leading to fluctuations in $PaCO_2$ and subsequent unstable ICP. Furthermore, the increased work of breathing associated with these modes increases cerebral oxygen consumption ($CMRO_2$). **High-Yield Clinical Pearls for NEET-PG:** * **Target $PaCO_2$:** Maintain at low-normal levels (30–35 mmHg). Aggressive hypercapnia must be avoided. * **PEEP in Head Injury:** Should be used cautiously (usually <10–12 $cmH_2O$) to avoid compromising cerebral venous drainage. * **Indication for Intubation:** A Glasgow Coma Scale (GCS) score of $\leq$ 8 is a classic indication for airway protection and mechanical ventilation in trauma patients.

Question 64: What is the recommended maximum cuff pressure for endotracheal intubation in patients requiring prolonged ventilation?

A. 20 mmHg
B. 30 mmHg (Correct Answer)
C. 40 mmHg
D. 50 mmHg

Explanation: The goal of endotracheal cuff management is to provide an effective seal for ventilation and protection against aspiration while maintaining adequate tracheal mucosal blood flow. **Explanation of the Correct Answer:** The recommended maximum cuff pressure is **30 cmH₂O (or approximately 20–22 mmHg)**. The capillary perfusion pressure of the tracheal mucosa ranges between **25–35 mmHg**. If the cuff pressure exceeds **30 cmH₂O**, it surpasses the capillary perfusion pressure, leading to mucosal ischemia, cilia destruction, and potential necrosis. Maintaining the pressure between **20–30 cmH₂O** ensures a seal that prevents micro-aspiration while preserving blood flow. **Analysis of Incorrect Options:** * **A (20 mmHg):** While 20 mmHg is roughly equivalent to 27 cmH₂O (within the safe range), the standard "maximum" threshold taught in clinical guidelines is 30 cmH₂O to avoid the onset of ischemia. * **C & D (40 & 50 mmHg):** These pressures significantly exceed the tracheal capillary perfusion pressure. Prolonged exposure to these levels leads to serious complications such as tracheal stenosis, tracheomalacia, or tracheoesophageal fistula. **High-Yield Clinical Pearls for NEET-PG:** * **The "Gold Standard" for monitoring:** Use a dedicated handheld pressure gauge (Manometer). * **Type of Cuff:** Modern practice uses **High-Volume Low-Pressure (HVLP)** cuffs to distribute pressure over a larger surface area. * **Nitrous Oxide (N₂O) Effect:** During anesthesia, N₂O can diffuse into the cuff, rapidly increasing the pressure. It should be monitored frequently during long cases. * **Minimum Pressure:** Pressure should not fall below **20 cmH₂O** to prevent the leakage of subglottic secretions, which is a major risk factor for Ventilator-Associated Pneumonia (VAP).

Question 65: Which of the following is used to prevent laryngospasm due to general anesthesia?

A. Atropine
B. Epinephrine
C. Diazepam
D. Succinylcholine (Correct Answer)

Explanation: **Explanation:** **Laryngospasm** is a protective reflex closure of the glottis due to the contraction of the laryngeal muscles (primarily the lateral cricoarytenoids and thyroarytenoids). In the context of general anesthesia, it is a life-threatening airway emergency that can lead to hypoxia and negative pressure pulmonary edema. **Why Succinylcholine is the Correct Answer:** Succinylcholine is a **depolarizing neuromuscular blocking agent** with a rapid onset (30–60 seconds). It is the "gold standard" pharmacological treatment for refractory laryngospasm because it causes immediate paralysis of the laryngeal muscles, allowing the vocal cords to relax so the clinician can ventilate the patient or perform endotracheal intubation. In emergency scenarios, it can be administered intravenously (0.25–0.5 mg/kg for spasm) or intramuscularly if IV access is lost. **Analysis of Incorrect Options:** * **Atropine (A):** An anticholinergic used to treat bradycardia or reduce secretions. While it may prevent reflex bradycardia associated with laryngospasm, it does not relax the laryngeal muscles. * **Epinephrine (B):** Used for anaphylaxis or cardiac arrest. It may reduce airway edema (racemic epinephrine) but does not stop the muscular contraction of a spasm. * **Diazepam (C):** A benzodiazepine used for sedation and anxiolysis. It lacks the rapid, potent neuromuscular blocking properties required to break an acute laryngospasm. **High-Yield Clinical Pearls for NEET-PG:** * **First-line Management:** Initial treatment for laryngospasm is **100% Oxygen** with continuous positive airway pressure (**CPAP**) and the **Larson Maneuver** (laryngospasm notch pressure). * **Succinylcholine Dose:** For laryngospasm, a sub-paralytic dose (0.1–0.5 mg/kg IV) is often sufficient, whereas 1–1.5 mg/kg is used for intubation. * **Common Triggers:** Light plane of anesthesia, blood/secretions in the oropharynx, or painful stimuli during emergence.

Question 66: In which of the following conditions is hyperbaric oxygen therapy not indicated?

A. Anemia
B. Vertigo (Correct Answer)
C. Gas gangrene
D. Compartment syndrome

Explanation: **Explanation:** Hyperbaric Oxygen Therapy (HBOT) involves breathing 100% oxygen at pressures greater than sea level (usually 2 to 3 ATA). This increases the amount of dissolved oxygen in the plasma (Henry’s Law), which is vital in conditions where hemoglobin-bound oxygen is insufficient or tissue perfusion is compromised. **Why Vertigo is the Correct Answer:** Vertigo is a symptom of vestibular dysfunction, not a primary indication for HBOT. While some studies explore HBOT for sudden sensorineural hearing loss (which may present with vertigo), **vertigo itself is not a standard indication**. In fact, oxygen toxicity at high pressures can cause CNS symptoms, and barotrauma to the middle ear during HBOT can actually *induce* vertigo. **Analysis of Incorrect Options:** * **Anemia:** Specifically, "Exceptional Blood Loss Anemia" is an indication when a patient cannot receive blood transfusions (e.g., religious reasons or cross-match incompatibility). HBOT provides enough dissolved plasma oxygen to support life temporarily. * **Gas Gangrene (Clostridial Myonecrosis):** HBOT is life-saving here. It inhibits the growth of anaerobic *Clostridium perfringens* and stops the production of alpha-toxins. * **Compartment Syndrome:** HBOT is indicated for acute traumatic ischemias and crush injuries. It causes hyperoxic vasoconstriction (reducing edema) while simultaneously increasing oxygen delivery to ischemic tissues. **High-Yield Clinical Pearls for NEET-PG:** * **Absolute Contraindication:** Untreated Tension Pneumothorax. * **Most Common Side Effect:** Middle ear barotrauma. * **Key Indications:** Carbon Monoxide (CO) poisoning, Decompression Sickness (The Bends), Air/Gas Embolism, and Chronic Non-healing wounds (Diabetic foot ulcers). * **Mechanism:** It works primarily by increasing the **dissolved oxygen** in plasma, bypassing the need for hemoglobin.

Question 67: A Guedel airway is a type of airway adjunct:

A. Oropharyngeal (Correct Answer)
B. Nasopharyngeal
C. Orotracheal
D. Nasotracheal

Explanation: ### Explanation **Correct Answer: A. Oropharyngeal** The **Guedel airway** is the most commonly used **oropharyngeal airway (OPA)**. It is a rigid, curved medical device designed to be inserted through the mouth into the posterior pharynx. Its primary function is to prevent the tongue from falling backward and obstructing the glottis in an unconscious patient by creating a patent conduit between the tongue and the posterior pharyngeal wall. **Analysis of Options:** * **B. Nasopharyngeal:** These are soft, flexible tubes (e.g., Wendel tubes) inserted through the nostril into the pharynx. Unlike Guedel airways, they can be used in patients with an intact gag reflex or trismus (locked jaw). * **C & D. Orotracheal/Nasotracheal:** These terms refer to **Endotracheal Tubes (ETT)** that pass through the vocal cords into the trachea to provide a definitive airway. A Guedel airway is a supraglottic adjunct and does not enter the trachea. **High-Yield Clinical Pearls for NEET-PG:** * **Sizing:** Measured from the **corner of the mouth to the tragus of the ear** (or the angle of the mandible). * **Insertion:** In adults, it is typically inserted "upside-down" (concavity facing the palate) and rotated 180° once halfway in to avoid pushing the tongue backward. In children, it is inserted directly using a tongue depressor to avoid palatal trauma. * **Contraindication:** Never use a Guedel airway in a **conscious or semi-conscious patient** with an intact gag reflex, as it can induce vomiting, laryngospasm, or aspiration. * **Color Coding:** Often tested; for example, Size 2 (Green), Size 3 (Yellow), Size 4 (Red).

Question 68: Which of the following devices is used for oxygen delivery regulation?

A. Oxygen tent
B. Venturi mask
C. Partial rebreather mask
D. Nasal catheter (Correct Answer)

Explanation: **Explanation:** The correct answer is **Nasal catheter**. In the context of oxygen therapy, devices are classified into those that provide a fixed concentration (High-flow) and those that provide a variable concentration (Low-flow). **Why Nasal Catheter is correct:** A nasal catheter is a low-flow oxygen delivery device. The term "regulation" in this specific clinical context refers to the ability to titrate or adjust the flow rate (typically 1–4 L/min) to achieve a desired inspiratory oxygen fraction ($FiO_2$). It is inserted into the nasal passage to the level of the uvula. While it provides a variable $FiO_2$ (24–40%), it allows for direct regulation of the flow delivered to the nasopharynx, which acts as an anatomical reservoir. **Analysis of Incorrect Options:** * **Oxygen Tent (A):** Primarily used in pediatric practice for humidification and cooling. It is highly inefficient for oxygen regulation because $FiO_2$ drops rapidly whenever the tent is opened for patient care. * **Venturi Mask (B):** This is a **fixed-performance (High-flow)** device. It uses the Bernoulli principle to deliver a precise, constant $FiO_2$ regardless of the patient’s inspiratory flow. It is the gold standard for COPD patients but is categorized as a "delivery" device rather than a simple "regulator." * **Partial Rebreather Mask (C):** A reservoir bag system that delivers high concentrations (60–80%). It does not "regulate" oxygen in the technical sense; it provides a high-concentration supply for short-term emergencies. **High-Yield Clinical Pearls for NEET-PG:** * **Flow Rates:** Nasal Cannula/Catheter (1–6 L/min), Simple Mask (5–8 L/min), Non-rebreather (10–15 L/min). * **Venturi Mask:** Best for patients where CO2 retention is a concern (COPD) because it provides a guaranteed, precise $FiO_2$. * **Rule of Fours:** For every 1 L/min increase in oxygen flow via nasal cannula, the $FiO_2$ increases by approximately 4% (starting from 21% at room air).

Question 69: What is the most appropriate size of a laryngeal mask airway for an adult weighing 30 kg?

A. 3 (Correct Answer)
B. 2.5
C. 4
D. 5

Explanation: The selection of a **Laryngeal Mask Airway (LMA)** size is primarily based on the patient’s body weight. Choosing the correct size ensures an adequate perilaryngeal seal and minimizes the risk of gastric insufflation or airway trauma. ### **Explanation of the Correct Option** * **Option A (Size 3):** According to the standard LMA sizing guidelines, **Size 3** is indicated for children and small adults weighing between **30 kg and 50 kg**. Since the patient weighs exactly 30 kg, Size 3 is the most appropriate choice to ensure a secure fit. ### **Analysis of Incorrect Options** * **Option B (Size 2.5):** This size is used for children weighing **20 kg to 30 kg**. While 30 kg is the upper limit for this size, in clinical practice and for exam purposes, the transition to Size 3 is preferred at 30 kg to ensure a better seal. * **Option C (Size 4):** This is the standard size for **average-sized adults** weighing **50 kg to 70 kg**. It would be too large for a 30 kg patient, potentially causing oropharyngeal injury. * **Option D (Size 5):** This is intended for **large adults** weighing **70 kg to 100 kg**. ### **High-Yield Clinical Pearls for NEET-PG** * **LMA Sizing Chart:** * Size 1: < 5 kg (Neonates) * Size 1.5: 5–10 kg (Infants) * Size 2: 10–20 kg (Small children) * Size 2.5: 20–30 kg (Children) * **Size 3: 30–50 kg (Small adults/Large children)** * Size 4: 50–70 kg (Average adults) * Size 5: 70–100 kg (Large adults) * **Maximum Cuff Inflation:** For Size 3, the maximum air volume is **20 ml**. * **Insertion Technique:** The LMA is inserted blindly into the hypopharynx, with the mask's aperture facing the laryngeal opening. The "index finger" technique is the most common method.

Question 70: Laryngeal mask airway size 2 is recommended for which weight range?

A. Less than 6.5 kg
B. 6.5–20 kg (Correct Answer)
C. 20–30 kg
D. 30–50 kg

Explanation: The **Laryngeal Mask Airway (LMA)** is a supraglottic airway device where sizing is strictly determined by the patient’s **ideal body weight**. Selecting the correct size is crucial to ensure an effective perilaryngeal seal and to minimize the risk of gastric insufflation or mucosal trauma. ### **Explanation of Options** * **Size 2 (6.5–20 kg):** This is the standard recommendation for infants and small children. It provides the necessary cuff volume to seal the glottic opening in this weight bracket. * **Size 1 (Less than 5–6.5 kg):** Option A is incorrect as it corresponds to Size 1 (Neonates/Infants up to 5 kg) or Size 1.5 (5–10 kg). * **Size 2.5 (20–30 kg):** Option C refers to Size 2.5, used for children who have outgrown Size 2 but are not yet large enough for adult sizes. * **Size 3 (30–50 kg):** Option D refers to Size 3, which is the transition size for large children or small adults. ### **High-Yield LMA Sizing Table for NEET-PG** | LMA Size | Patient Weight | Max Cuff Volume (Air) | | :--- | :--- | :--- | | **1** | < 5 kg | 4 ml | | **1.5** | 5 – 10 kg | 7 ml | | **2** | **10 – 20 kg** (often cited as 6.5–20 kg) | 10 ml | | **2.5** | 20 – 30 kg | 14 ml | | **3** | 30 – 50 kg | 20 ml | | **4** | 50 – 70 kg | 30 ml | | **5** | 70 – 100 kg | 40 ml | ### **Clinical Pearls** * **Rule of Thumb:** If a patient is between sizes, it is generally safer to choose the **larger size** and inflate the cuff with less air to achieve a better seal. * **Contraindication:** LMAs are contraindicated in patients with a "full stomach" (risk of aspiration) or decreased pulmonary compliance. * **Placement:** The tip of the LMA mask rests against the **upper esophageal sphincter**.

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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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