Respiratory and Airway Management Practice Questions

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

16%. ### 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.

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

Macintosh blade. ***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.

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

Naloxone. **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).

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

All of the above. **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.

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

Nitrous oxide. **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.

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

Submental. **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.

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

Rocuronium. ### 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."

Question 1

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

Accepted Answer

It provides full protection from aspiration.

Answer

It can be used in patients with a full stomach.

Answer

It is used as an alternative to endotracheal intubation.

Answer

A difficult airway is an indication for its use.

Question 2

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

Accepted Answer

16%

Answer

20%

Answer

22%

Answer

24%

Question 3

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

Accepted Answer

Macintosh blade

Answer

McCoy blade

Answer

Miller's blade

Answer

Wisconsin blade

Question 4

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

Accepted Answer

Naloxone

Answer

Theophylline

Answer

Artificial ventilation

Answer

Doxapram

Question 5

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

Accepted Answer

Trendelenburg position

Answer

Lateral position

Answer

Horizontal position

Answer

Dorsosacral position

Question 6

What is the best ventilator strategy for ARDS?

Accepted Answer

Assisted control mechanical ventilation

Answer

CPAP

Answer

High frequency jet ventilation

Answer

Synchronised intermittent mandatory ventilation

Question 7

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

Accepted Answer

All of the above

Answer

Osteomyelitis

Answer

Osteoradionecrosis

Answer

Gas gangrene

Question 8

Which anesthetic gas is contraindicated in the presence of pneumothorax?

Accepted Answer

Nitrous oxide

Answer

Halothane

Answer

Isoflurane

Answer

Chloroform

Question 9

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

Accepted Answer

Submental

Answer

Oral

Answer

Oral and nasal

Answer

Nasal

Question 10

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

Accepted Answer

Rocuronium

Answer

Vecuronium

Answer

Rapacuronium

Answer

Atracurium

Respiratory and Airway Management — MCQs

Respiratory and Airway Management — MCQs

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