Respiratory and Airway Management — MCQs

Respiratory and Airway Management Indian Medical PG Practice Questions and MCQs

Question 151: Mallampati classification is used for what purpose?

A. Assessing the oral cavity before intubation (Correct Answer)
B. Determining the size of the airway
C. Selecting the size of the endotracheal tube
D. Choosing a tracheostomy tube

Explanation: ### Explanation The **Mallampati Classification** is a clinical tool used to predict the ease of endotracheal intubation by assessing the relationship between the size of the tongue and the oral cavity. **1. Why Option A is Correct:** The classification is performed by asking a seated patient to open their mouth wide and protrude the tongue without phonating. It visualizes the oropharyngeal structures (soft palate, fauces, uvula, and pillars). A large tongue relative to the oral cavity obscures these structures, indicating a potentially **difficult airway** (specifically, difficulty in visualizing the glottis during direct laryngoscopy). **2. Why Other Options are Incorrect:** * **Option B:** While it relates to the airway, Mallampati does not measure the actual anatomical "size" or diameter of the trachea or larynx; it assesses **visibility and space** within the oropharynx. * **Option C:** The size of the endotracheal tube (ETT) is determined by the patient’s age, sex, and height (or the internal diameter of the cricoid ring), not by the Mallampati score. * **Option D:** Tracheostomy tube selection depends on the depth of the neck tissues and tracheal diameter, usually assessed via palpation or imaging, not oropharyngeal visualization. **3. High-Yield Clinical Pearls for NEET-PG:** * **Modified Mallampati Classification (Samsoon & Young):** * **Class I:** Soft palate, fauces, uvula, pillars visible. * **Class II:** Soft palate, fauces, portion of uvula visible. * **Class III:** Soft palate and base of uvula visible. * **Class IV:** Only hard palate visible (highest risk of difficult intubation). * **Pillars of Airway Assessment:** Mallampati is often used alongside the **LEMON** criteria (Look, Evaluate 3-3-2, Mallampati, Obstruction, Neck mobility). * **Cormack-Lehane Grade:** This is the direct laryngoscopic view equivalent; Mallampati Class III/IV often correlates with Cormack-Lehane Grade 3/4.

Question 152: What is the recommended rate of rescue breathing for an adult?

A. 4 breaths per minute
B. 12 breaths per minute (Correct Answer)
C. 20 breaths per minute
D. 28 breaths per minute

Explanation: **Explanation:** The correct answer is **12 breaths per minute**. According to the American Heart Association (AHA) and ERC guidelines for Basic and Advanced Life Support, when an adult patient has a pulse but is not breathing normally (respiratory arrest), rescue breaths should be provided at a rate of **1 breath every 5 to 6 seconds**. This translates to approximately **10–12 breaths per minute**. **Why the other options are incorrect:** * **4 breaths per minute (Option A):** This rate is severely inadequate (bradypnea) and will lead to rapid hypercapnia (CO2 retention) and respiratory acidosis. * **20 breaths per minute (Option C):** This rate is too high for rescue breathing. Excessive ventilation increases intrathoracic pressure, which decreases venous return to the heart and can lead to gastric inflation and subsequent aspiration. * **28 breaths per minute (Option D):** This represents extreme tachypnea. Such high rates significantly impair cardiac output during resuscitation and are physiologically detrimental. **High-Yield Clinical Pearls for NEET-PG:** * **Rescue Breathing (Adult):** 1 breath every 5–6 seconds (10–12 bpm). * **Rescue Breathing (Infant/Child):** 1 breath every 2–3 seconds (20–30 bpm). * **Advanced Airway in situ:** Once an endotracheal tube or supraglottic airway is placed during CPR, asynchronous ventilations are given at **1 breath every 6 seconds** (10 bpm) while continuous chest compressions are maintained. * **Tidal Volume:** Each breath should be delivered over **1 second** with enough volume to produce a visible chest rise (approx. 500–600 mL).

Question 153: Which of the following is NOT a complication of PEEP?

A. Pulmonary edema
B. Emphysema (Correct Answer)
C. Cardiogenic shock
D. Pneumonia

Explanation: **Explanation:** Positive End-Expiratory Pressure (PEEP) is a method of ventilation that maintains airway pressure above atmospheric pressure at the end of expiration. **Why Emphysema is the correct answer:** Emphysema is a **chronic, structural lung disease** characterized by the permanent destruction of alveolar walls and loss of elastic recoil. PEEP is a dynamic physiological intervention; while it can cause acute **barotrauma** (like pneumothorax or subcutaneous emphysema) due to overdistension, it cannot "cause" the chronic pathological remodeling seen in emphysema. In fact, PEEP is often used cautiously in emphysematous patients to prevent expiratory airway collapse (dynamic hyperinflation). **Analysis of Incorrect Options:** * **Pulmonary Edema:** While PEEP is used to *treat* pulmonary edema by shifting fluid from the alveoli to the interstitium, "negative pressure pulmonary edema" can occur upon sudden withdrawal of PEEP or during upper airway obstruction. * **Cardiogenic Shock:** PEEP increases intrathoracic pressure, which decreases venous return (preload) to the right heart. In hemodynamically unstable patients, this can significantly reduce cardiac output, leading to or worsening obstructive/cardiogenic shock. * **Pneumonia:** Prolonged mechanical ventilation with PEEP is associated with Ventilator-Associated Pneumonia (VAP) due to the bypass of natural airway defenses and potential micro-aspiration. **High-Yield Clinical Pearls for NEET-PG:** * **Primary Indication:** ARDS (to improve oxygenation by recruiting collapsed alveoli and increasing FRC). * **Major Complication:** Barotrauma (Pneumothorax is the most common life-threatening respiratory complication). * **Hemodynamic Effect:** Decreases Preload, increases Right Ventricular Afterload, and may decrease Left Ventricular Afterload. * **Renal Effect:** Can decrease renal blood flow and GFR due to decreased cardiac output and altered ADH secretion.

Question 154: In controlled ventilation, which of the following statements are true?

A. Patient is active, Patient is passive, Ventilator is active
B. Patient is passive, Ventilator is active, IPPV (Correct Answer)
C. Patient is active, Ventilator is active
D. Patient is passive, IPPV

Explanation: ### Explanation **Concept Overview** Controlled ventilation (or Controlled Mechanical Ventilation - CMV) is a mode where the ventilator assumes full responsibility for the patient's minute ventilation. It is typically used in patients who are apneic, heavily sedated, or pharmacologically paralyzed (using neuromuscular blockers). **Why Option B is Correct** 1. **Patient is Passive:** In controlled mode, the patient does not initiate breaths. The respiratory muscles are at rest or paralyzed; thus, the patient is "passive." 2. **Ventilator is Active:** The machine initiates every breath based on a preset rate and volume/pressure. It performs the "work of breathing." 3. **IPPV (Intermittent Positive Pressure Ventilation):** This is the physiological mechanism used. Unlike spontaneous breathing (which relies on negative intrathoracic pressure), the ventilator pushes air into the lungs using **positive pressure**. **Analysis of Incorrect Options** * **Options A & C:** These are incorrect because the patient cannot be "active" in controlled ventilation. If the patient triggers the breath, it is termed **Assisted Ventilation** or **Assist-Control (AC)**. * **Option D:** While it mentions "Passive" and "IPPV," it is incomplete. The defining characteristic of controlled ventilation is the "Active" role of the ventilator in timing and delivering the breath. **NEET-PG High-Yield Pearls** * **Indication:** Best for patients with ARDS, crushed chest injuries, or during general anesthesia with muscle relaxants. * **Physiological Impact:** IPPV increases intrathoracic pressure, which **decreases venous return** (preload) and can lead to a drop in cardiac output and blood pressure. * **Dead Space:** Controlled ventilation increases physiological dead space compared to spontaneous breathing. * **Trigger:** In CMV, the trigger is **Time-cycled**, not patient-cycled.

Question 155: Where is the endotracheal tube inserted?

A. Right bronchus
B. Left bronchus
C. Trachea (Correct Answer)
D. Laryngopharynx

Explanation: **Explanation:** The primary objective of endotracheal intubation is to secure a patent airway and facilitate mechanical ventilation or the delivery of anesthetic gases directly into the lungs. **Why Trachea is Correct:** The endotracheal tube (ETT) is passed through the vocal cords (the narrowest part of the adult airway) and positioned within the **trachea**. The ideal position for the tip of the ETT is in the mid-trachea, approximately **3–5 cm above the carina**. This ensures equal ventilation to both lungs while preventing accidental displacement into the bronchi during neck movement. **Analysis of Incorrect Options:** * **Right and Left Bronchus (Options A & B):** If the ETT is advanced too far, it typically enters the **right main bronchus** due to its more vertical orientation, wider diameter, and shorter length compared to the left. This results in "endobronchial intubation," leading to collapse (atelectasis) of the contralateral lung and potential barotrauma to the ventilated lung. * **Laryngopharynx (Option D):** This is the region of the pharynx below the oropharynx and above the esophagus/larynx. Placing a tube here does not secure the airway and risks gastric insufflation or aspiration. **High-Yield Clinical Pearls for NEET-PG:** * **Confirmation:** The "Gold Standard" for confirming tracheal placement is **End-tidal CO2 (EtCO2)** detection (capnography). * **Narrowest Part:** The narrowest part of the airway is the **vocal cords** in adults and the **cricoid cartilage** in children (though recent literature suggests the glottis may be narrowest in both, the cricoid remains a classic exam answer for pediatrics). * **Murphy’s Eye:** The small hole at the distal end of the ETT that allows ventilation if the main tip is occluded.

Question 156: All of the following are true regarding the effect of inhalational anesthetic agents on the respiratory tract EXCEPT?

A. Volatile anesthetic agents relax airway smooth muscle.
B. They blunt respiratory drive.
C. They suppress the respiratory center.
D. They increase ciliary movement. (Correct Answer)

Explanation: **Explanation:** The correct answer is **D (They increase ciliary movement)** because inhalational anesthetic agents actually **depress or inhibit** mucociliary clearance. **1. Why Option D is the Correct Answer (The Exception):** Volatile anesthetics (like Sevoflurane, Isoflurane, and Desflurane) cause dose-dependent **inhibition of ciliary beat frequency** and alter the properties of mucus. This impairment of the mucociliary blanket leads to the pooling of secretions in the tracheobronchial tree, increasing the risk of postoperative atelectasis and pulmonary infections. **2. Why the other options are incorrect (True statements):** * **Option A (Relax airway smooth muscle):** Volatile agents are potent bronchodilators. They act by reducing intracellular calcium and inhibiting vagal pathways. **Sevoflurane** is the agent of choice for inhalational induction in patients with reactive airways (asthma/COPD) due to its non-pungency and bronchodilatory properties. * **Options B & C (Blunt respiratory drive/Suppress center):** All inhalational agents cause dose-dependent respiratory depression. They decrease the sensitivity of the medullary respiratory center to Carbon Dioxide (CO₂) and blunt the peripheral chemoreceptor response to Hypoxia. This results in a decreased tidal volume and a compensatory (but insufficient) increase in respiratory rate. **Clinical Pearls for NEET-PG:** * **Halothane** is the most potent bronchodilator but sensitizes the myocardium to catecholamines (risk of arrhythmias). * **Desflurane and Isoflurane** are pungent and can cause airway irritation (coughing, laryngospasm), making them unsuitable for smooth inhalational induction. * **Dead Space:** Inhalational agents increase the ratio of dead space to tidal volume (Vd/Vt). * **Hypoxic Pulmonary Vasoconstriction (HPV):** All volatile agents inhibit HPV, which can potentially worsen V/Q mismatch.

Question 157: Which of the following devices are used to protect the airway?

A. Laryngeal Mask Airway (LMA) and Endotracheal tube
B. Laryngeal Mask Airway (LMA), Endotracheal tube, and Ryles tube
C. Endotracheal tube and Combitube (Correct Answer)
D. Endotracheal tube, Combitube, and Sengstaken-Blakemore tube

Explanation: **Explanation:** In anesthesiology and emergency medicine, "protecting the airway" specifically refers to the prevention of **aspiration of gastric contents, blood, or secretions** into the lungs. This is achieved by creating a physical seal within the trachea. **1. Why Option C is Correct:** * **Endotracheal Tube (ETT):** This is the "gold standard" for airway protection. The inflatable cuff creates a definitive seal below the vocal cords, isolating the trachea from the esophagus. * **Combitube (Esophageal-Tracheal Double-Lumen Airway):** This is a rescue device used in difficult airways. Regardless of whether it enters the esophagus (most common) or the trachea, its dual-cuff system (pharyngeal and distal) is designed to prevent aspiration and facilitate ventilation, making it a recognized airway protection device. **2. Why Other Options are Incorrect:** * **Laryngeal Mask Airway (LMA):** Standard LMAs are **supraglottic devices**. They sit above the glottis and do not provide a definitive seal against gastric regurgitation. While newer generations (e.g., LMA ProSeal) offer better protection, they are generally not considered "definitive" airway protection compared to ETTs. * **Ryle’s Tube:** This is a nasogastric tube used for gastric decompression or feeding; it has no role in sealing the airway. * **Sengstaken-Blakemore Tube:** This is used to tamponade bleeding esophageal varices. While it has balloons, its purpose is hemostasis, not airway protection. **Clinical Pearls for NEET-PG:** * **Definitive Airway:** Defined as a tube in the trachea with the cuff inflated, connected to oxygen-enriched ventilation (e.g., ETT, Tracheostomy). * **Aspiration Risk:** Patients with a "full stomach," GCS < 8, or absent gag reflex require immediate airway protection. * **Combitube Contraindication:** Do not use in patients with an intact gag reflex or known esophageal pathology.

Question 158: Which of the following diseases is associated with resistance to succinylcholine?

A. Myasthenia gravis (Correct Answer)
B. Polymyositis
C. Lambert-Eaton myasthenic syndrome
D. Muscular dystrophy

Explanation: **Explanation:** The correct answer is **Myasthenia Gravis (MG)**. **1. Why Myasthenia Gravis is the Correct Answer:** Myasthenia Gravis is an autoimmune disorder characterized by antibodies against the **post-synaptic nicotinic acetylcholine receptors (nAChR)** at the neuromuscular junction. This results in a significant reduction in the total number of functional receptors. * **Resistance to Succinylcholine:** Because there are fewer available receptors for Succinylcholine (a depolarizing neuromuscular blocker) to bind to, a **higher dose** (usually 1.5–2.0 mg/kg) is required to achieve effective depolarization. * **Sensitivity to Non-depolarizers:** Conversely, patients with MG are **exquisitely sensitive** to non-depolarizing muscle relaxants (like Vecuronium or Atracurium) because even a small amount of blockade can incapacitate the few remaining functional receptors. **2. Analysis of Incorrect Options:** * **B. Polymyositis:** This is an inflammatory myopathy. While it causes muscle weakness, it does not typically exhibit the specific receptor-level resistance seen in MG. * **C. Lambert-Eaton Myasthenic Syndrome (LEMS):** Unlike MG, LEMS is a **pre-synaptic** defect (antibodies against voltage-gated calcium channels). Patients with LEMS are **sensitive** to both depolarizing (Succinylcholine) and non-depolarizing muscle relaxants. * **D. Muscular Dystrophy:** In conditions like Duchenne Muscular Dystrophy, Succinylcholine is strictly **contraindicated**. It can cause profound, life-threatening **hyperkalemia** and rhabdomyolysis due to the upregulation of extrajunctional receptors and fragile sarcolemma. **High-Yield Clinical Pearls for NEET-PG:** * **MG Rule of Thumb:** Resistant to Succinylcholine; Sensitive to Non-depolarizers. * **LEMS Rule of Thumb:** Sensitive to BOTH Succinylcholine and Non-depolarizers. * **Burn/Denervation/Dystrophy:** Always avoid Succinylcholine due to the risk of hyperkalemia (extrajunctional receptor proliferation). * **Anticholinesterases:** Patients on Pyridostigmine (for MG) may show a prolonged response to Succinylcholine because the drug also inhibits plasma cholinesterase.

Question 159: To minimize the effects of diffusion hypoxia during N2O-O2 analgesia, for how long should the patient be oxygenated?

A. 30 seconds to 1 minute
B. 3 to 5 minutes (Correct Answer)
C. 10 to 30 minutes
D. 30 to 45 minutes

Explanation: **Explanation:** **1. Why Option B is Correct (The Underlying Concept):** Diffusion hypoxia (the **Fink Effect**) occurs at the end of nitrous oxide (N₂O) administration. N₂O is 31 times more soluble in blood than nitrogen. When the N₂O supply is stopped and the patient breathes room air, N₂O rapidly diffuses out of the blood and into the alveoli. This massive influx of N₂O dilutes the alveolar concentration of oxygen (O₂) and carbon dioxide (CO₂). The dilution of O₂ leads to hypoxia, while the dilution of CO₂ reduces the respiratory drive. To counteract this, **100% oxygen must be administered for 3 to 5 minutes** to wash out the N₂O and maintain adequate alveolar oxygen tension. **2. Why Other Options are Wrong:** * **Option A (30s – 1 min):** This duration is insufficient to clear the large volume of N₂O exiting the blood, leaving the patient at high risk for transient hypoxemia. * **Options C & D (10 – 45 mins):** While safe, these durations are clinically unnecessary. The majority of N₂O is eliminated within the first few minutes due to its low blood-gas partition coefficient (0.47). Prolonged oxygenation unnecessarily delays recovery and room turnover. **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **Second Gas Effect:** N₂O (the "First Gas") speeds up the uptake of a companion volatile anesthetic (the "Second Gas") by creating a negative pressure in the alveoli. * **Concentration Effect:** The higher the concentration of N₂O inhaled, the more rapidly the arterial tension of the gas rises. * **Contraindications:** Avoid N₂O in cases of pneumothorax, intestinal obstruction, air embolism, or middle ear surgery, as it expands closed air-filled spaces. * **Blood-Gas Partition Coefficient:** For N₂O, it is **0.47**, explaining its rapid onset and recovery.

Question 160: What type of cuff is typically used in an Endotracheal tube?

A. Low pressure - high volume (Correct Answer)
B. High pressure - low volume
C. Variable pressure - low volume
D. Low pressure - low volume

Explanation: **Explanation:** The primary goal of an endotracheal tube (ETT) cuff is to provide a seal for positive pressure ventilation and protect the airway from aspiration while minimizing trauma to the tracheal mucosa. **1. Why "Low Pressure - High Volume" (LPHV) is correct:** Modern ETTs utilize LPHV cuffs because they have a large surface area that distributes pressure evenly against the tracheal wall. The "low pressure" refers to the intracuff pressure, which should ideally be maintained between **20–30 cm H₂O**. This range is crucial because it is high enough to prevent aspiration but lower than the **tracheal capillary perfusion pressure (approx. 30 mmHg)**. By staying below this threshold, LPHV cuffs prevent mucosal ischemia, necrosis, and subsequent tracheal stenosis. **2. Why the other options are incorrect:** * **High Pressure - Low Volume:** These were used in the past (red rubber tubes). Because they have a small contact area, they require very high pressures to create a seal, often exceeding capillary perfusion pressure, leading to a high incidence of tracheal injury. * **Variable/Low Volume options:** These do not provide an adequate seal for modern mechanical ventilation and are prone to significant air leaks or focal pressure points that damage the trachea. **Clinical Pearls for NEET-PG:** * **Critical Pressure:** Maintain cuff pressure at **20–30 cm H₂O**. Pressures >30 cm H₂O cause ischemia; <20 cm H₂O increase the risk of Microaspiration and Ventilator-Associated Pneumonia (VAP). * **Nitrous Oxide (N₂O) Effect:** N₂O can diffuse into the cuff during anesthesia, increasing the volume and pressure, which may necessitate periodic monitoring. * **Microaspiration:** Despite LPHV cuffs, "micro-channels" can form in the folds of the cuff; newer tapered-shaped or polyurethane cuffs aim to reduce this risk.

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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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