Respiratory and Airway Management — MCQs

Respiratory and Airway Management Indian Medical PG Practice Questions and MCQs

Question 41: Which of the following statements is true about the laryngeal mask airway?

A. It can be used in patients with a full stomach.
B. It is used as an alternative to endotracheal intubation.
C. It provides full protection from aspiration. (Correct Answer)
D. A difficult airway is an indication for its use.

Explanation: The Laryngeal Mask Airway (LMA) is a supraglottic airway device that sits in the hypopharynx, masking the glottic opening. **Explanation of the Correct Answer:** *Note: There appears to be a discrepancy in the provided key. In standard anesthesia practice, the LMA does **NOT** provide full protection from aspiration. However, if following specific exam-based logic where Option C is marked correct, it refers to the **ProSeal LMA** or **Second Generation LMAs**. These versions feature a gastric drain tube that allows for the venting of gastric contents and a better seal, significantly reducing (though not entirely eliminating) the risk of aspiration compared to the Classic LMA.* **Analysis of Options:** * **Option A:** Incorrect. A "full stomach" (e.g., trauma, pregnancy, intestinal obstruction) is a **contraindication** for standard LMA use because the device does not secure the trachea against regurgitated gastric contents. * **Option B:** Incorrect. While it is a "rescue" device, it is technically an **alternative to a face mask**, not a direct replacement for endotracheal intubation (ETT) in cases where a definitive airway (cuffed tube in the trachea) is required. * **Option D:** Correct (in clinical practice). A difficult airway is a primary **indication** for LMA use, especially in "cannot intubate, cannot ventilate" scenarios. (If Option C is the intended answer, it highlights the specific design evolution of the ProSeal LMA). **High-Yield Clinical Pearls for NEET-PG:** * **Nerve Injury:** The most common nerve injured due to over-inflation of the LMA cuff is the **Lingual nerve**, followed by the Hypoglossal and Recurrent Laryngeal nerves. * **Size Selection:** Size 3 (30-50kg females), Size 4 (50-70kg males), Size 5 (>70kg large adults). * **Insertion:** The LMA is inserted blindly against the hard palate; the tip rests against the **upper esophageal sphincter**. * **Gold Standard for Aspiration Protection:** Only a cuffed Endotracheal Tube provides definitive protection.

Question 42: What is the approximate oxygen concentration provided by mouth-to-mouth respiration?

A. 16% (Correct Answer)
B. 20%
C. 22%
D. 24%

Explanation: ### Explanation **Correct Option: A (16%)** The underlying medical concept is based on the **Fraction of Inspired Oxygen ($FiO_2$)** versus the **Fraction of Expired Oxygen ($FeO_2$)**. Atmospheric air contains approximately **21% oxygen**. During normal respiration, a healthy adult extracts only about 4–5% of the inhaled oxygen for cellular metabolism. Consequently, the exhaled air (which is delivered to the victim during mouth-to-mouth ventilation) contains approximately **16–17% oxygen** and about 4% carbon dioxide. This concentration is sufficient to maintain life and provide adequate oxygenation to the victim's tissues during emergency resuscitation until advanced life support is available. **Analysis of Incorrect Options:** * **B (20%):** This is nearly the concentration of oxygen in **ambient/room air (21%)**. It does not account for the oxygen consumed by the rescuer's lungs before exhalation. * **C & D (22% & 24%):** These values are higher than the concentration of oxygen in the atmosphere itself. Such concentrations can only be achieved by using supplemental oxygen devices, such as a nasal cannula (which provides ~24% at 1 L/min). **Clinical Pearls for NEET-PG:** * **Mouth-to-Mask Ventilation:** If the rescuer uses a pocket mask with supplemental oxygen at 10–15 L/min, the $FiO_2$ can increase to approximately **50%**. * **Ambu Bag (Self-inflating bag):** * Room air: **21%** * With 10–15 L/min $O_2$ (without reservoir): **40–60%** * With 10–15 L/min $O_2$ (with reservoir): **90–100%** * **Expired Air Ventilation:** While 16% $O_2$ is sufficient, the high $CO_2$ content (4%) in the rescuer's breath can theoretically stimulate the victim's respiratory center, though its clinical significance is minor compared to the oxygen delivery.

Question 43: What is the name of the curved blade of a laryngoscope as depicted?

A. McCoy blade
B. Macintosh blade (Correct Answer)
C. Miller's blade
D. Wisconsin blade

Explanation: ***Macintosh blade*** - The **Macintosh blade** is the standard **curved laryngoscope blade** designed with a gentle curve to follow the natural anatomy of the tongue and oropharynx. - It is placed in the **vallecula** (the space between the base of tongue and epiglottis) to indirectly lift the epiglottis for vocal cord visualization. *McCoy blade* - The McCoy blade is a **modified Macintosh blade** with a **hinged tip** that can be flexed to improve glottic view in difficult airways. - While it has a curved design, it is specifically distinguished by its **articulating tip mechanism**, not just being "curved." *Miller's blade* - The **Miller blade** is a **straight laryngoscope blade** designed for direct lifting of the epiglottis. - It is commonly used in **pediatric intubation** and provides better visualization in patients with **anterior larynx** positioning. *Wisconsin blade* - The **Wisconsin blade** is also a **straight blade** similar to Miller but with a slightly different tip design and curve. - It is **straight in configuration**, not curved, making it unsuitable as the answer for a curved blade.

Question 44: Opioid-induced respiratory depression can be reversed with which of the following?

A. Naloxone (Correct Answer)
B. Theophylline
C. Artificial ventilation
D. Doxapram

Explanation: **Explanation:** **Correct Option: A. Naloxone** Naloxone is a **pure competitive opioid antagonist** that has a high affinity for $\mu$, $\kappa$, and $\delta$ opioid receptors. It works by displacing opioid molecules from the receptors, specifically reversing the $\mu$-receptor-mediated effects such as respiratory depression, sedation, and miosis. It is the gold-standard treatment for acute opioid overdose. **Analysis of Incorrect Options:** * **B. Theophylline:** A methylxanthine used primarily as a bronchodilator in asthma and COPD. While it stimulates the respiratory center, it does not antagonize opioid receptors. * **C. Artificial Ventilation:** This is a **supportive measure**, not a pharmacological reversal agent. While essential for managing apnea, it does not reverse the underlying pharmacological cause. * **D. Doxapram:** A non-specific peripheral and central respiratory stimulant. It was historically used to treat post-operative respiratory depression but is rarely used now due to its narrow therapeutic index and lack of specificity for opioid receptors. **High-Yield Clinical Pearls for NEET-PG:** * **Duration of Action:** Naloxone has a short half-life (30–60 minutes). Since many opioids (e.g., Methadone, Morphine) have a longer duration of action, **"re-narcotization"** can occur. Continuous monitoring and repeat doses/infusions are often necessary. * **Side Effects:** Rapid reversal can trigger **Acute Opioid Withdrawal Syndrome**, characterized by hypertension, tachycardia, and pulmonary edema. * **Other Antagonists:** **Naltrexone** is used for long-term addiction management (oral), and **Methylnaltrexone** is used for opioid-induced constipation (does not cross the blood-brain barrier).

Question 45: A patient who faints during extraction should be positioned in which of the following positions?

A. Lateral position
B. Horizontal position
C. Trendelenburg position (Correct Answer)
D. Dorsosacral position

Explanation: ### Explanation **Correct Answer: C. Trendelenburg position** **Medical Concept:** Fainting (vasovagal syncope) during a dental extraction is primarily caused by a sudden drop in blood pressure and heart rate, leading to **transient cerebral hypoperfusion**. The **Trendelenburg position** involves placing the patient supine with the feet elevated 15–30 degrees above the head. This utilizes gravity to increase venous return to the heart (preload), thereby increasing cardiac output and restoring blood flow to the brain. In a dental chair, this is often achieved by reclining the chair back fully so the head is lower than the knees. **Analysis of Incorrect Options:** * **A. Lateral position:** While the lateral (recovery) position is excellent for maintaining a clear airway and preventing aspiration of secretions or blood, it does not prioritize the immediate restoration of cerebral perfusion as effectively as Trendelenburg. * **B. Horizontal position:** Placing a patient flat (supine) is better than sitting upright, but it lacks the gravity-assisted venous bolus provided by elevating the legs. * **D. Dorsosacral position:** Also known as the lithotomy position, this is used for gynecological or urological surgeries. While it involves leg elevation, it is impractical and unnecessary in a dental or syncopal emergency. **Clinical Pearls for NEET-PG:** * **Management of Syncope:** The first step is always to stop the procedure, position the patient (Trendelenburg), and ensure a patent airway. * **Vasovagal Syncope:** This is the most common cause of loss of consciousness in the dental office, often triggered by anxiety or pain. * **Caution:** Trendelenburg position should be avoided in patients with **congestive heart failure (CHF)** or **increased intracranial pressure**, as the increased venous return can worsen these conditions. * **Airway Protection:** If the patient vomits during syncope, they must be immediately turned to the **lateral position** to prevent aspiration.

Question 46: What is the best ventilator strategy for ARDS?

A. CPAP
B. High frequency jet ventilation
C. Assisted control mechanical ventilation (Correct Answer)
D. Synchronised intermittent mandatory ventilation

Explanation: **Explanation:** The primary goal in managing **Acute Respiratory Distress Syndrome (ARDS)** is to ensure adequate oxygenation while preventing **Ventilator-Induced Lung Injury (VILI)**. **Why Assisted Control (AC) is the Correct Answer:** The gold standard for ARDS is the **Lung Protective Ventilation Strategy (ARDSNet protocol)**. This strategy utilizes **Assist-Control (AC) mode** to deliver a low tidal volume (6 mL/kg of predicted body weight). AC mode is preferred because it ensures the patient receives a minimum minute ventilation while allowing the ventilator to support every spontaneous breath initiated by the patient with the full set tidal volume. This reduces the work of breathing and allows for precise control over pressures (keeping Plateau Pressure <30 cm H₂O), which is critical in "baby lungs" (stiff, non-compliant lungs) typical of ARDS. **Why other options are incorrect:** * **CPAP (A):** This is a non-invasive spontaneous mode. While it provides PEEP, it does not provide the inspiratory pressure support or controlled tidal volumes required to manage the severe respiratory failure and high work of breathing seen in ARDS. * **High-Frequency Jet Ventilation (B):** Once thought to be beneficial, large trials (like OSCAR and OSCILLATE) showed no survival benefit over conventional ventilation and, in some cases, increased harm. It is now reserved only as a rescue therapy. * **SIMV (D):** In SIMV, spontaneous breaths above the set rate are not supported with the full tidal volume. This often increases the patient's work of breathing and can lead to respiratory muscle fatigue in the acute phase of ARDS. **NEET-PG High-Yield Pearls:** * **Low Tidal Volume:** 6 mL/kg (based on **Predicted Body Weight**, not actual weight). * **Plateau Pressure:** Must be kept **< 30 cm H₂O** to prevent barotrauma. * **Permissive Hypercapnia:** Allowing a higher PaCO₂ (and lower pH) to avoid high airway pressures is acceptable. * **Prone Positioning:** Should be used if PaO₂/FiO₂ ratio is **< 150**.

Question 47: In which of the following conditions is hyperbaric oxygen therapy useful?

A. Osteomyelitis
B. Osteoradionecrosis
C. Gas gangrene
D. All of the above (Correct Answer)

Explanation: **Explanation:** Hyperbaric Oxygen Therapy (HBOT) involves breathing 100% oxygen at atmospheric pressures greater than 1 ATA (usually 2–3 ATA). This significantly increases the amount of dissolved oxygen in the plasma (Henry’s Law), facilitating oxygen delivery to tissues even in the presence of compromised hemoglobin or perfusion. **Why "All of the Above" is Correct:** * **Gas Gangrene (Clostridial Myonecrosis):** HBOT is life-saving here. High oxygen tension is directly bactericidal to anaerobic *Clostridium perfringens* and inhibits the production of the alpha-toxin, which is responsible for tissue destruction. * **Osteoradionecrosis (ORN):** Radiation causes "3-H" tissues (Hypocellular, Hypovascular, Hypoxic). HBOT stimulates angiogenesis and collagen synthesis, promoting healing in necrotic bone, particularly in the mandible. * **Osteomyelitis:** Specifically for **Refractory Chronic Osteomyelitis**, HBOT enhances the oxidative killing capacity of leukocytes and works synergistically with antibiotics (like aminoglycosides) to penetrate infected bone. **NEET-PG High-Yield Pearls:** 1. **Absolute Contraindication:** Untreated Tension Pneumothorax (due to risk of rapid expansion). 2. **Most Common Side Effect:** Middle ear barotrauma (due to failure to equalize pressure). 3. **Other Key Indications:** Carbon Monoxide (CO) poisoning (reduces half-life of carboxyhemoglobin), Decompression Sickness (Bends), Air/Gas Embolism, and Crush Injuries. 4. **Mechanism in CO Poisoning:** It hastens the dissociation of CO from hemoglobin and cytochrome c oxidase. **Summary:** Since HBOT addresses anaerobic infection, radiation-induced ischemia, and chronic bone infection, all three conditions listed are recognized indications.

Question 48: Which anesthetic gas is contraindicated in the presence of pneumothorax?

A. Halothane
B. Isoflurane
C. Nitrous oxide (Correct Answer)
D. Chloroform

Explanation: **Explanation** The correct answer is **Nitrous oxide ($N_2O$)**. **Mechanism of Action** The contraindication of $N_2O$ in pneumothorax is based on the **Second Gas Effect** and the difference in blood solubility between $N_2O$ and Nitrogen ($N_2$). * $N_2O$ is **34 times more soluble** in blood than Nitrogen. * When a patient has a pneumothorax, the air pocket contains mostly Nitrogen. When $N_2O$ is administered, it diffuses from the blood into the air-filled cavity much faster than Nitrogen can diffuse out. * This leads to a rapid increase in the **volume** (if the cavity is compliant) or **pressure** (if the cavity is non-compliant) of the space. In a pneumothorax, this can rapidly expand the collapse or convert a simple pneumothorax into a life-threatening **tension pneumothorax**. **Analysis of Incorrect Options** * **Halothane and Isoflurane:** These are volatile halogenated ethers/alkanes. While they affect respiratory drive, they do not significantly diffuse into closed gas spaces to cause expansion. * **Chloroform:** An obsolete anesthetic agent; like other volatile liquids, it does not share the specific solubility characteristics of $N_2O$ that lead to gas space expansion. **High-Yield NEET-PG Pearls** * **Other Contraindications for $N_2O$:** Intestinal obstruction, air embolism, middle ear surgeries (tympanoplasty), intraocular gas bubbles (sulfur hexafluoride), and Vitamin B12 deficiency (due to methionine synthase inhibition). * **Expansion Rule:** $N_2O$ at 75% concentration can double the volume of a pneumothorax in just 10 minutes. * **Diffusion Hypoxia:** Always administer 100% $O_2$ for 5–10 minutes after disconnecting $N_2O$ to prevent the rapid washout of $N_2O$ from diluting alveolar oxygen.

Question 49: In a patient with Le Fort II, Le Fort III, and nasoethmoid fractures, what is the choice of intubation?

A. Oral
B. Oral and nasal
C. Nasal
D. Submental (Correct Answer)

Explanation: **Explanation:** The management of a complex maxillofacial trauma involving **Le Fort II, Le Fort III, and nasoethmoid (NOE) fractures** presents a unique airway challenge. In these cases, the goal is to secure the airway while allowing the surgeon to establish proper dental occlusion (intermaxillary fixation) and repair midface fractures. **Why Submental Intubation is the Correct Choice:** Submental intubation involves passing an endotracheal tube through the floor of the mouth. It is the preferred choice here because: 1. **Surgical Access:** Unlike oral intubation, it keeps the oral cavity clear, allowing the surgeon to check dental occlusion. 2. **Safety:** Unlike nasal intubation, it avoids the risk of **accidental intracranial tube placement** or worsening of CSF rhinorrhea, which are high risks in Le Fort II/III and NOE fractures due to potential disruption of the **cribriform plate**. 3. **Avoidance of Tracheostomy:** It serves as a safer, less invasive alternative to a short-term tracheostomy. **Analysis of Incorrect Options:** * **Oral (A):** While safe, it interferes with the surgical requirement of achieving intermaxillary fixation (IMF) to align the jaw. * **Nasal (C):** Absolutely contraindicated in suspected base-of-skull or cribriform plate fractures (common in Le Fort II/III/NOE) due to the risk of intracranial insertion. * **Oral and Nasal (B):** Incorrect as both have the specific contraindications mentioned above. **Clinical Pearls for NEET-PG:** * **Absolute Contraindication for Nasal Intubation:** Fractures of the base of the skull, CSF rhinorrhea, and severe midface trauma. * **Submental Intubation Indication:** When long-term ventilation is not needed, but both oral and nasal routes are unsuitable due to surgical or anatomical reasons. * **Gold Standard for Long-term Airway:** If the patient requires prolonged mechanical ventilation post-surgery, **Tracheostomy** remains the definitive choice.

Question 50: In modified rapid sequence induction (RSI), which neuromuscular blocker is the drug of choice?

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

Explanation: ### Explanation **1. Why Rocuronium is the Correct Answer:** Rapid Sequence Induction (RSI) is performed to minimize the risk of gastric aspiration in patients with a "full stomach." The primary requirement for a neuromuscular blocker (NMB) in RSI is a **rapid onset of action** to facilitate tracheal intubation within 60 seconds. Traditionally, **Succinylcholine** (a depolarizing NMB) was the gold standard due to its 45–60 second onset. However, in **Modified RSI**, where Succinylcholine is contraindicated (e.g., hyperkalemia, burns, or history of malignant hyperthermia), **Rocuronium** is the drug of choice. At a dose of **0.9–1.2 mg/kg**, Rocuronium provides excellent intubating conditions in approximately 60 seconds, making it the only non-depolarizing NMB that rivals Succinylcholine's speed. **2. Analysis of Incorrect Options:** * **Vecuronium:** An intermediate-acting NMB. Even at high doses, its onset is significantly slower (approx. 120–150 seconds) than Rocuronium, making it unsuitable for RSI. * **Rapacuronium:** This was a rapid-onset non-depolarizing NMB, but it was withdrawn from the market worldwide due to a high incidence of severe bronchospasm. * **Atracurium:** An intermediate-acting NMB that undergoes Hoffmann elimination. It has a slow onset (2–3 minutes) and can cause histamine release, which is undesirable during a rapid induction sequence. **3. Clinical Pearls for NEET-PG:** * **Reversal:** The prolonged duration of high-dose Rocuronium can be immediately reversed using **Sugammadex** (a selective relaxant binding agent). * **Dose for RSI:** Rocuronium 1.2 mg/kg (2x the ED95). * **Drug of Choice (Overall):** While Succinylcholine remains the classic choice for RSI due to its short duration, Rocuronium is the **non-depolarizing drug of choice** and the preferred agent in "Modified RSI."

Practice by Chapter

Respiratory Physiology

Practice Questions

Airway Anatomy

Practice Questions

Preoxygenation Techniques

Practice Questions

Mask Ventilation

Practice Questions

Supraglottic Airway Devices

Practice Questions

Direct Laryngoscopy

Practice Questions

Video Laryngoscopy

Practice Questions

Fiberoptic Intubation

Practice Questions

Surgical Airway Management

Practice Questions

One-Lung Ventilation Techniques

Practice Questions

Ventilation Strategies During Anesthesia

Practice Questions

Extubation Criteria and Techniques

Practice Questions

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