Respiratory and Airway Management — MCQs

Respiratory and Airway Management Indian Medical PG Practice Questions and MCQs

Question 11: What is the maximum pressure allowed for positive pressure ventilation with a laryngeal mask airway?

A. 10 cm H2O
B. 20 cm H2O (Correct Answer)
C. 30 cm H2O
D. 40 cm H2O

Explanation: **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).

Question 12: What type of anesthesia is typically used in microlaryngoscopy?

A. Use of a 10 mm diameter Portex tube with heavy sedation.
B. Use of a 15 mm diameter Portex tube with topical xylocaine.
C. Use of a Portex tube with an infiltration block. (Correct Answer)
D. Heavy sedation and endotracheal intubation.

Explanation: **Explanation:** Microlaryngoscopy (MLS) requires a motionless surgical field, adequate exposure of the glottis, and a shared airway between the surgeon and the anesthesiologist. **Why the correct answer is right:** The standard approach for microlaryngoscopy involves **General Anesthesia with endotracheal intubation**. A specialized, small-diameter (usually 5.0 mm or 6.0 mm ID) **microlaryngeal tube (MLT)**, often made of polyvinyl chloride (Portex), is used to provide a clear view of the larynx while maintaining ventilation. To facilitate the procedure and suppress the intense sympathetic response (tachycardia/hypertension) caused by the laryngoscope, an **infiltration block** (topicalization or nerve blocks like the superior laryngeal nerve block) is often used as an adjunct to general anesthesia. This combination ensures hemodynamic stability and prevents coughing or laryngospasm during the procedure. **Why the incorrect options are wrong:** * **Options A & B:** A 10 mm or 15 mm diameter tube is far too large for microlaryngoscopy. These would obstruct the surgeon's view of the vocal cords and increase the risk of laryngeal trauma. Microlaryngoscopy specifically requires "small-bore" tubes. * **Option D:** While endotracheal intubation is used, "heavy sedation" alone is insufficient. MLS requires deep general anesthesia with complete muscle relaxation (neuromuscular blockade) to prevent any movement that could lead to vocal cord injury during microscopic work. **High-Yield Clinical Pearls for NEET-PG:** * **Tube Choice:** The Microlaryngeal Tube (MLT) is longer than a standard pediatric tube but has a smaller external diameter to allow surgical access. * **Laser Safety:** If a CO2 laser is used during MLS, a specialized **laser-resistant (metallic) tube** must be used to prevent airway fires. * **Alternative:** **Jet Ventilation** (Sanders Injector) is an alternative technique used when a tube would completely obstruct the surgical site. * **Reflexes:** The most common complication during induction/suspension is **autonomic stimulation**, managed by deepening anesthesia or using short-acting beta-blockers (Esmolol).

Question 13: Optimum minute ventilation is ensured by adjusting which of the following ventilation parameters?

A. PEEP and FiO2
B. Tidal volume and respiratory rate (Correct Answer)
C. PEEP and respiratory rate
D. Tidal volume and PEEP

Explanation: ### 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.

Question 14: Which of the following is not a cause of bronchospasm?

A. Regurgitation
B. Aspiration
C. Intubation
D. Halothane (Correct Answer)

Explanation: **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.

Question 15: Which of the following circumstances trigger conversion from non-invasive to invasive ventilation?

A. Respiratory arrest
B. Respiratory rate > 35/min
C. Severe acidosis < 7.25
D. All of the above (Correct Answer)

Explanation: **Explanation:** Non-invasive ventilation (NIV) is the first-line treatment for acute exacerbations of COPD and cardiogenic pulmonary edema. However, identifying **NIV failure** is critical to prevent delayed intubation, which is associated with increased mortality. The decision to convert to invasive mechanical ventilation (IMV) is based on clinical stability, gas exchange, and the patient's ability to protect their airway. * **Respiratory Arrest (Option A):** This is an absolute indication for immediate intubation. NIV requires a spontaneous respiratory effort; if the patient stops breathing, they require controlled mandatory ventilation via an endotracheal tube. * **Respiratory Rate > 35/min (Option B):** Persistent tachypnea despite NIV indicates excessive work of breathing and impending respiratory muscle fatigue. A rate >35 bpm is a recognized threshold for clinical instability. * **Severe Acidosis < 7.25 (Option C):** While NIV can manage mild-to-moderate acidosis (pH 7.30–7.35), a pH below 7.25 (especially if it does not improve within 1–2 hours of NIV) suggests profound ventilatory failure that NIV cannot overcome. **Why "All of the above" is correct:** All three parameters represent clinical or physiological failure of non-invasive measures, necessitating a definitive airway and invasive support. **High-Yield Clinical Pearls for NEET-PG:** 1. **Absolute Contraindications to NIV:** Respiratory arrest, hemodynamic instability (shock), facial trauma/burns, and high aspiration risk (impaired consciousness/GCS < 8). 2. **The "Golden Hour":** If the pH and PaCO2 do not improve within the first 60–90 minutes of NIV, the patient should be transitioned to invasive ventilation immediately. 3. **Predictor of Success:** The most reliable predictor of NIV success in COPD is an improvement in pH and a decrease in heart rate within the first hour.

Question 16: What is the advantage of the ProSeal Laryngeal Mask Airway (LMA) over the standard LMA?

A. It is easier to insert.
B. It is comparable to an endotracheal tube in preventing aspiration. (Correct Answer)
C. It can be inserted in a conscious patient.
D. It can be used for pulmonary toileting.

Explanation: The **ProSeal Laryngeal Mask Airway (PLMA)** is a second-generation supraglottic airway device designed to overcome the limitations of the classic LMA. ### **Explanation of the Correct Answer** The defining feature of the ProSeal LMA is the inclusion of a **drain tube** that runs parallel to the airway tube. This channel allows for the passage of a gastric tube to decompress the stomach and provides a bypass for regurgitated gastric contents, preventing them from entering the glottis. Additionally, the PLMA features a posterior cuff that improves the **perilaryngeal seal**, allowing for higher peak inspiratory pressures (up to 30 cm H₂O) compared to the classic LMA. These features make its protection against aspiration **comparable to an endotracheal tube (ETT)** in elective cases, although the ETT remains the gold standard for "full stomach" emergencies. ### **Why Other Options are Incorrect** * **A. Easier to insert:** The PLMA is actually **more difficult** to insert than the classic LMA because of its bulkier cuff and softer tip, which may fold over. It often requires a dedicated introducer tool or a digital technique. * **C. Inserted in a conscious patient:** Like most supraglottic devices, the PLMA requires a suppressed gag reflex (usually via general anesthesia or deep sedation) to prevent laryngospasm. * **D. Pulmonary toileting:** This refers to clearing secretions from the trachea/bronchi. Since the PLMA sits in the pharynx (supraglottic), it does not provide direct access to the lower airway for suctioning, unlike an ETT. ### **High-Yield Clinical Pearls for NEET-PG** * **Seal Pressure:** PLMA seal pressure is ~10 cm H₂O higher than the Classic LMA. * **The "Bite Block":** The PLMA has a built-in bite block to prevent airway occlusion. * **Confirmation:** Correct placement of the drain tube is often confirmed by the **"Soap Bubble Test"** or by passing a gastric tube. * **Ideal for:** Laparoscopic surgeries (where higher airway pressures are needed) and patients where intubation is difficult but aspiration risk is low-to-moderate.

Question 17: Laryngospasm under anesthesia can be relieved by?

A. Aminophylline
B. Salbutamol
C. Terbutaline
D. Succinylcholine (Correct Answer)

Explanation: **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 18: All true about airway management in obese patients except?

A. Pre-oxygenation is preferred in obese patients.
B. Positioning for laryngoscopy in these patients is preferably stacking.
C. Awake intubation is the mode of choice in morbidly obese patients. (Correct Answer)
D. Patients with a history of obstructive sleep apnea are candidates for a difficult airway.

Explanation: ### Explanation **1. Why Option C is the correct answer (The "Except" statement):** While morbid obesity is associated with a higher risk of difficult mask ventilation and laryngoscopy, **awake intubation is NOT the routine "mode of choice"** for all morbidly obese patients. The standard approach is usually a rapid sequence induction (RSI) or modified RSI with the patient in a ramped position. Awake fiberoptic intubation is reserved specifically for patients who have **predicted** difficult airways based on clinical markers (e.g., Mallampati IV, limited neck extension, or small thyromental distance), not just a high BMI alone. **2. Analysis of Incorrect Options:** * **Option A (Pre-oxygenation):** This is **true** and vital. Obese patients have a reduced Functional Residual Capacity (FRC) and increased oxygen consumption, leading to rapid desaturation during apnea. Pre-oxygenation (ideally with CPAP/PEEP) extends the "safe apnea time." * **Option B (Stacking/Ramping):** This is **true**. The "Ramped position" (stacking blankets under the upper back, neck, and head) aligns the oral, pharyngeal, and laryngeal axes by ensuring the **external auditory meatus is at the same horizontal level as the sternal notch**. * **Option D (OSA and Difficult Airway):** This is **true**. Obstructive Sleep Apnea (OSA) is a strong predictor of difficult mask ventilation and potential difficult intubation due to redundant pharyngeal tissue and narrowed upper airway. **3. Clinical Pearls for NEET-PG:** * **The "Ramped" Position:** Also known as the HELP (Head-Elevated Laryngoscopy Position). * **Safe Apnea Time:** Significantly shorter in obese patients; they desaturate at a rate of ~3-4 times faster than non-obese patients. * **Induction Agent:** Propofol dosing should be based on **Lean Body Weight (LBW)**, whereas Succinylcholine dosing is based on **Total Body Weight (TBW)**. * **Extubation:** Should always be performed when the patient is **fully awake** and in a semi-Fowler’s position to prevent immediate post-extubation airway collapse.

Question 19: Which of the following drugs is NOT recommended for intratracheal administration during cardiopulmonary resuscitation?

A. Atropine
B. Sodium bicarbonate (Correct Answer)
C. Adrenaline
D. Lignocaine

Explanation: **Explanation:** During cardiopulmonary resuscitation (CPR), when intravenous (IV) or intraosseous (IO) access is not available, certain lipid-soluble drugs can be administered via the endotracheal tube. **Why Sodium Bicarbonate is NOT recommended:** Sodium bicarbonate is a hypertonic, alkaline solution. If administered intratracheally, it causes severe damage to the alveolar-capillary membrane, leading to chemical pneumonitis and pulmonary edema. Furthermore, it is not absorbed effectively through the lungs and can deactivate concurrently administered catecholamines (like Adrenaline) due to its high pH. **Why the other options are wrong:** The mnemonic **"NAVEL"** (Naloxone, Atropine, Vasopressin/Ventolin, Epinephrine/Adrenaline, Lignocaine) represents the drugs that can be safely administered via the endotracheal route. * **Atropine:** Used for symptomatic bradycardia; it is well-absorbed via the tracheal mucosa. * **Adrenaline (Epinephrine):** The mainstay of ACLS; it is rapidly absorbed, though doses must be 2–2.5 times higher than the IV dose. * **Lignocaine:** Used for refractory VT/VF; it achieves therapeutic plasma levels when given intratracheally. **High-Yield Clinical Pearls for NEET-PG:** 1. **Dosage Rule:** For intratracheal administration, the dose is generally **2 to 2.5 times** the standard IV dose (except for Epinephrine, where some guidelines suggest up to 10x). 2. **Administration Technique:** Drugs should be diluted in 5–10 mL of sterile water or normal saline to enhance absorption. 3. **Preferred Route:** IV/IO routes are always superior to the endotracheal route because drug absorption via the lungs is unpredictable. 4. **Amiodarone:** Note that Amiodarone is **NOT** given via the endotracheal tube.

Question 20: What is the appropriate method for measuring the size of an oropharyngeal airway?

A. Incisor teeth to the tragus of the ear
B. Corner of the mouth to the angle of the mandible (Correct Answer)
C. Tip of the nose to the angle of the mandible
D. Ala of the nose to the angle of the mandible

Explanation: ### Explanation The **Oropharyngeal Airway (OPA)**, also known as the Guedel airway, is a rigid device used to maintain airway patency by preventing the tongue from obstructing the posterior pharynx in unconscious patients. **1. Why Option B is Correct:** The standard clinical method for sizing an OPA is measuring the distance from the **corner of the mouth (labial commissure) to the angle of the mandible**. Alternatively, it can be measured from the center of the maxillary incisors to the angle of the mandible. This ensures the tip of the airway reaches the base of the tongue without being so long that it causes trauma or so short that it pushes the tongue backward. **2. Analysis of Incorrect Options:** * **Option A (Incisor to Tragus):** This is an alternative measurement for OPAs in some protocols but is less standard than the angle of the mandible. * **Option C & D (Nose to Angle of Mandible/Ala):** These measurements are used for **Nasopharyngeal Airways (NPA)**. Specifically, the distance from the tip of the nose to the earlobe or the tragus is the standard for determining the length of a nasal trumpet. **3. High-Yield Clinical Pearls for NEET-PG:** * **Insertion Technique:** In adults, it is inserted "upside-down" (curve toward the palate) and rotated 180° to avoid pushing the tongue back. In pediatrics, it is inserted directly using a tongue depressor to avoid trauma to the soft palate. * **Contraindication:** Never use an OPA in a conscious or semi-conscious patient with an intact **gag reflex**, as it can induce vomiting or laryngospasm. * **Complications of Incorrect Sizing:** * **Too Large:** Can obstruct the larynx or cause epiglottic trauma. * **Too Small:** Can push the tongue posteriorly, worsening the obstruction.

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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