Respiratory and Airway Management Practice Questions

Q: Which of the following is NOT a complication of PEEP?

Increased blood pressure. **Explanation:** Positive End-Expiratory Pressure (PEEP) increases functional residual capacity and improves oxygenation, but it exerts significant systemic effects due to the increase in **intrathoracic pressure**. **Why "Increased Blood Pressure" is the Correct Answer:** PEEP does **not** increase blood pressure; it typically **decreases** it. The mechanism is as follows: Increased intrathoracic pressure → compression of the vena cava → decreased venous return (preload) → decreased stroke volume and cardiac output → **Hypotension**. In patients who are hypovolemic, this effect is even more pronounced. **Analysis of Other Options:** * **Decreased urine output:** PEEP reduces renal blood flow and glomerular filtration rate (GFR) due to decreased cardiac output. Additionally, it triggers the release of ADH (Antidiuretic Hormone) and activates the Renin-Angiotensin-Aldosterone System (RAAS) while suppressing Atrial Natriuretic Peptide (ANP), leading to water and sodium retention. * **Increased intracranial pressure (ICP):** By increasing intrathoracic pressure, PEEP impedes venous drainage from the superior vena cava. This causes venous congestion in the cerebral vessels, leading to an increase in ICP. * **Increased intrathoracic pressure:** This is the primary physiological consequence of PEEP, as it maintains positive pressure in the airways throughout the expiratory phase. **NEET-PG High-Yield Pearls:** * **Barotrauma:** PEEP increases the risk of pneumothorax and subcutaneous emphysema. * **Dead Space:** Excessive PEEP can cause alveolar overdistension, increasing physiological dead space. * **Best PEEP:** Defined as the level of PEEP that provides maximum oxygen delivery to tissues without compromising cardiac output.

Q: What is the maximum pressure allowed for positive pressure ventilation with a laryngeal mask airway?

20 cm H2O. **Explanation:** The **Laryngeal Mask Airway (LMA)** is a supraglottic airway device that sits in the hypopharynx, creating a low-pressure seal around the laryngeal inlet. The correct answer is **20 cm H₂O** because this represents the standard "seal pressure" for a classic LMA. 1. **Why 20 cm H₂O is correct:** The LMA is not a cuffed endotracheal tube; it does not provide a high-pressure, airtight seal within the trachea. If peak inspiratory pressure (PIP) exceeds **20 cm H₂O**, the pressure overcomes the seal, leading to two major complications: **gastric insufflation** (air entering the stomach, increasing the risk of aspiration) and **oropharyngeal leak** (ineffective ventilation). 2. **Why other options are wrong:** * **10 cm H₂O:** This is too low for effective ventilation in most patients, especially those with decreased lung compliance. * **30 cm H₂O:** This exceeds the seal limit of a standard LMA. While second-generation LMAs (like the ProSeal or Supreme) can handle pressures up to 30 cm H₂O, the standard limit for general LMA use in exams is 20 cm H₂O. * **40 cm H₂O:** This pressure is likely to cause significant gastric distension and is generally the limit for safety valves in manual resuscitators, not LMAs. **High-Yield Clinical Pearls for NEET-PG:** * **Second-Generation LMAs:** Devices like the **LMA ProSeal** have a gastric drain tube and a better seal, allowing for higher pressures (up to 30 cm H₂O) and controlled ventilation. * **NPO Status:** Since the LMA does not protect against aspiration, it is generally contraindicated in non-fasted patients or those with GERD. * **Size Selection:** A common mnemonic for LMA sizes: **Size 3 (30-50kg), Size 4 (50-70kg), Size 5 (70-100kg).** * **Ideal Position:** The tip of the LMA should rest against the **upper esophageal sphincter** (cricopharyngeus muscle).

Q: Which drug is used as an alternative to succinylcholine for intubation?

Rocuronium. **Explanation:** The primary reason **Succinylcholine** is favored for emergency intubation (Rapid Sequence Induction - RSI) is its **rapid onset of action** (30–60 seconds) and **short duration** (5–10 minutes). For a drug to be considered a viable alternative, it must match this rapid onset. **1. Why Rocuronium is correct:** Rocuronium is a non-depolarizing neuromuscular blocker (NDMR) that has the fastest onset among its class. At a dose of **0.9–1.2 mg/kg**, it provides excellent intubating conditions within **60 seconds**, comparable to Succinylcholine. It is the drug of choice for RSI when Succinylcholine is contraindicated (e.g., hyperkalemia, burns, or history of malignant hyperthermia). Its action can be rapidly reversed using **Sugammadex**. **2. Why other options are incorrect:** * **A. Doxacurium:** This is a long-acting NDMR. It has a slow onset (4–6 minutes) and a very long duration of action, making it entirely unsuitable for acute intubation or RSI. * **B. Dantrolene:** This is not a neuromuscular blocker. It is a muscle relaxant that acts directly on the Ryanodine receptor (RyR1) to inhibit calcium release. It is the specific treatment for **Malignant Hyperthermia**. **Clinical Pearls for NEET-PG:** * **Drug of Choice for RSI:** Succinylcholine (Gold standard). * **Best Alternative for RSI:** Rocuronium. * **Priming Principle:** Giving a small sub-therapeutic dose of an NDMR 3 minutes before the intubating dose to slightly speed up the onset. * **Mnemonic:** "Rocks (Rocuronium) roll fast" to remember its rapid onset.

Q: Optimum minute ventilation is ensured by adjusting which of the following ventilation parameters?

Tidal volume and respiratory rate. ### Explanation **The Core Concept** Minute Ventilation ($V_E$) is the total volume of gas entering or leaving the lungs per minute. It is mathematically defined by the formula: **$V_E = \text{Tidal Volume } (V_T) \times \text{Respiratory Rate } (RR)$** To ensure optimum minute ventilation, a clinician must balance these two parameters. $V_E$ is the primary determinant of arterial carbon dioxide tension ($PaCO_2$). If minute ventilation increases, $PaCO_2$ decreases (hypocapnia); if it decreases, $PaCO_2$ increases (hypercapnia). **Analysis of Options** * **Option B (Correct):** As per the formula above, adjusting $V_T$ and $RR$ directly modifies the volume of air exchanged per minute, making them the primary controls for ventilation. * **Option A & C (Incorrect):** **PEEP** (Positive End-Expiratory Pressure) and **FiO2** (Fraction of Inspired Oxygen) are parameters used to improve **oxygenation**, not ventilation. They help keep alveoli open and increase the partial pressure of oxygen but do not directly affect the clearance of $CO_2$. * **Option D (Incorrect):** While Tidal Volume is a component of minute ventilation, PEEP is not. **High-Yield Clinical Pearls for NEET-PG** 1. **Dead Space:** Not all minute ventilation participates in gas exchange. Alveolar Ventilation ($V_A$) = $(V_T - \text{Dead Space}) \times RR$. 2. **Permissive Hypercapnia:** In ARDS, we often use low Tidal Volumes (6 mL/kg) to prevent barotrauma, intentionally allowing $V_E$ to drop and $CO_2$ to rise. 3. **Control of $PaCO_2$:** In a mechanically ventilated patient with high $CO_2$, the first step is usually to increase the Respiratory Rate or Tidal Volume. 4. **Normal Range:** For a healthy adult, the resting minute ventilation is approximately 5–8 L/min.

Q: Which of the following is not a cause of bronchospasm?

Halothane. **Explanation:** The correct answer is **Halothane** because it is a potent **bronchodilator**, not a cause of bronchospasm. In anesthesiology, Halothane (along with Sevoflurane) is frequently used for the induction of anesthesia in patients with reactive airway diseases (like asthma) because it relaxes bronchial smooth muscle and decreases airway resistance. **Why the other options are incorrect:** * **Regurgitation & Aspiration (Options A & B):** The entry of gastric contents into the tracheobronchial tree (Mendelson’s Syndrome) causes intense chemical irritation of the airway mucosa. This triggers a protective reflex resulting in severe bronchospasm and laryngospasm. * **Intubation (Option C):** Mechanical stimulation of the larynx and trachea by an endotracheal tube during a "light" plane of anesthesia is one of the most common triggers for reflex bronchospasm, mediated by the vagus nerve. **NEET-PG High-Yield Pearls:** 1. **Drug of Choice:** **Sevoflurane** is currently the preferred volatile anesthetic for mask induction in asthmatics because it is non-pungent and a potent bronchodilator. 2. **Avoid in Asthma:** **Desflurane** and **Isoflurane** are pungent and can cause airway irritation/bronchospasm, especially during induction. 3. **Intravenous Agents:** **Ketamine** is the induction agent of choice for asthmatic patients due to its sympathomimetic bronchodilatory effects. Conversely, **Thiopentone** is known to potentially worsen bronchospasm due to histamine release. 4. **Management:** The first step in intraoperative bronchospasm is increasing the concentration of volatile anesthetic (like Halothane or Sevoflurane) and providing 100% Oxygen.

Q: Laryngospasm under anesthesia can be relieved by?

Succinylcholine. **Explanation:** **Laryngospasm** is a protective but potentially life-threatening reflex closure of the vocal cords (glottic opening) mediated by the superior laryngeal nerve. It results in partial or complete airway obstruction. **Why Succinylcholine is the Correct Answer:** Succinylcholine is the "gold standard" pharmacological treatment for refractory laryngospasm. As a **depolarizing neuromuscular blocking agent**, it works by causing rapid paralysis of the skeletal muscles, including the laryngeal muscles (lateral cricoarytenoids and thyroarytenoids). This forces the vocal cords to relax, allowing for immediate ventilation or endotracheal intubation. In emergency scenarios where IV access is unavailable, it can be administered intramuscularly (IM). **Why Other Options are Incorrect:** * **Aminophylline, Salbutamol, and Terbutaline (Options A, B, C):** These are **bronchodilators**. They act on the smooth muscles of the lower airways (bronchi and bronchioles) to treat bronchospasm. Laryngospasm involves the skeletal muscles of the upper airway; therefore, bronchodilators are ineffective in opening a closed glottis. **High-Yield Clinical Pearls for NEET-PG:** * **Initial Management:** The first step in managing laryngospasm is removing the stimulus, administering 100% oxygen, and applying **CPAP (Continuous Positive Airway Pressure)**. * **Larson’s Maneuver:** Also known as the "laryngospasm notch" maneuver; applying firm pressure behind the earlobe at the styloid process can help break the spasm. * **Dosage:** For laryngospasm, a sub-paralyzing dose of Succinylcholine (0.25–0.5 mg/kg IV) is often sufficient to break the spasm without requiring full ventilatory support for a prolonged period. * **Complication:** Watch for **Negative Pressure Pulmonary Edema (NPPE)** following the resolution of a severe laryngospasm due to the intense negative intrathoracic pressure generated by the patient gasping against a closed glottis.

Question 1

Which of the following is NOT a complication of PEEP?

Accepted Answer

Increased blood pressure

Answer

Decreased urine output

Answer

Increased intracranial pressure

Answer

Increased intrathoracic pressure

Question 2

What is the maximum pressure allowed for positive pressure ventilation with a laryngeal mask airway?

Accepted Answer

20 cm H2O

Answer

10 cm H2O

Answer

30 cm H2O

Answer

40 cm H2O

Question 3

Which drug is used as an alternative to succinylcholine for intubation?

Accepted Answer

Rocuronium

Answer

Doxacurium

Answer

Dantrolene

Answer

None of the above

Question 4

What type of anesthesia is typically used in microlaryngoscopy?

Accepted Answer

Use of a Portex tube with an infiltration block.

Answer

Use of a 10 mm diameter Portex tube with heavy sedation.

Answer

Use of a 15 mm diameter Portex tube with topical xylocaine.

Answer

Heavy sedation and endotracheal intubation.

Question 5

Optimum minute ventilation is ensured by adjusting which of the following ventilation parameters?

Accepted Answer

Tidal volume and respiratory rate

Answer

PEEP and FiO2

Answer

PEEP and respiratory rate

Answer

Tidal volume and PEEP

Question 6

Which of the following is not a cause of bronchospasm?

Accepted Answer

Halothane

Answer

Regurgitation

Answer

Aspiration

Answer

Intubation

Question 7

What is the advantage of the ProSeal Laryngeal Mask Airway (LMA) over the standard LMA?

Accepted Answer

It is comparable to an endotracheal tube in preventing aspiration.

Answer

It is easier to insert.

Answer

It can be inserted in a conscious patient.

Answer

It can be used for pulmonary toileting.

Question 8

Laryngospasm under anesthesia can be relieved by?

Accepted Answer

Succinylcholine

Answer

Aminophylline

Answer

Salbutamol

Answer

Terbutaline

Question 9

All are true about classical Rapid Sequence Induction EXCEPT?

Accepted Answer

Positive pressure ventilation by bag and mask with small tidal volume.

Answer

Preoxygenation is mandatory.

Answer

Cricoid pressure is applied.

Answer

The neuromuscular blocker used is succinylcholine.

Question 10

All true about airway management in obese patients except?

Accepted Answer

Awake intubation is the mode of choice in morbidly obese patients.

Answer

Pre-oxygenation is preferred in obese patients.

Answer

Positioning for laryngoscopy in these patients is preferably stacking.

Answer

Patients with a history of obstructive sleep apnea are candidates for a difficult airway.

Respiratory and Airway Management — MCQs

Respiratory and Airway Management — MCQs

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