Respiratory and Airway Management Practice Questions

Q: What is the appropriate size of a ProSeal Laryngeal Mask Airway (PLMA) for a 70 kg adult male patient?

5. ### Explanation The **ProSeal Laryngeal Mask Airway (PLMA)** is a second-generation supraglottic airway device designed with a gastric drainage tube and a posterior cuff to provide a better seal than the classic LMA. **Why Option C is Correct:** For the ProSeal LMA, sizing is primarily based on the patient's weight. For an adult male weighing 70 kg, **Size 5** is the recommended choice. While the Classic LMA (cLMA) guidelines often suggest Size 4 for a 70 kg adult, clinical studies and the manufacturer's guidelines for the **ProSeal** variant emphasize that a larger size (Size 5 for males, Size 4 for females) provides a better oropharyngeal leak pressure and a more effective seal, which is the primary advantage of the ProSeal design. **Analysis of Incorrect Options:** * **Option A (Size 3):** Used for children and small adolescents weighing **30–50 kg**. * **Option B (Size 4):** Recommended for adult females or small males weighing **50–70 kg**. While a 70 kg patient is on the cusp, Size 5 is preferred in males to ensure an adequate seal for positive pressure ventilation. * **Option D (Size 6):** Reserved for very large adults weighing **over 100 kg**. **High-Yield NEET-PG Pearls:** * **Maximum Intracuff Pressure:** Should not exceed **60 cm H₂O** to prevent mucosal ischemia. * **Key Feature:** The PLMA allows for the insertion of a gastric tube (to decompress the stomach) and provides a seal of up to **30 cm H₂O** (compared to ~20 cm H₂O in cLMA). * **Sizing Rule of Thumb:** * Size 3: 30–50 kg * Size 4: 50–70 kg (Standard Female) * Size 5: 70–100 kg (Standard Male)

Q: Which of the following is NOT a benefit of a supraglottic airway device compared to an endotracheal tube?

It prevents aspiration. ### Explanation The fundamental difference between a Supraglottic Airway Device (SAD), such as a Laryngeal Mask Airway (LMA), and an Endotracheal Tube (ETT) lies in the **protection of the lower airway**. **Why Option C is the correct answer:** An Endotracheal Tube (ETT) is considered the "gold standard" for airway protection because it passes through the vocal cords and utilizes an inflatable cuff to create a mechanical seal within the trachea. This prevents gastric contents, blood, or secretions from entering the lungs. In contrast, **SADs sit above the glottis** and do not provide a definitive seal against high-pressure regurgitation. Therefore, SADs **do not prevent aspiration** as effectively as an ETT and are generally contraindicated in patients with a "full stomach" or those at high risk for gastroesophageal reflux. **Analysis of Incorrect Options:** * **A. Less invasive:** SADs do not require laryngoscopy or penetration of the larynx, causing less trauma to the airway tissues. * **B. Less haemodynamic alteration:** Since SADs do not require direct laryngoscopy (which stimulates the sympathetic nervous system), there is significantly less tachycardia and hypertension during insertion compared to intubation. * **D. Less time for insertion:** SADs are easier and faster to insert, even by non-anesthetists, making them vital in "cannot intubate, cannot ventilate" scenarios. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard for Aspiration Protection:** Cuffed Endotracheal Tube. * **LMA ProSeal/Supreme:** Second-generation SADs have a gastric drainage port to reduce (but not eliminate) the risk of aspiration. * **Pressure Limit:** Standard LMAs generally allow for positive pressure ventilation up to **20 cm H₂O**; exceeding this may cause air to leak into the stomach. * **Indication:** SADs are ideal for short procedures in fasted, low-risk patients.

Q: What is the critical pH in Mendelson syndrome?

2.5. **Explanation:** **Mendelson Syndrome** (Acid Aspiration Syndrome) refers to chemical pneumonitis caused by the aspiration of acidic gastric contents into the lungs, typically occurring during the induction of general anesthesia. **1. Why Option A (2.5) is Correct:** The severity of pulmonary damage in aspiration is determined by two critical factors established by Curtis Mendelson: **pH** and **Volume**. * **Critical pH:** A gastric pH of **less than 2.5** is required to cause significant chemical burns to the pulmonary parenchyma. * **Critical Volume:** A gastric volume of **more than 0.4 mL/kg** (approximately 25 mL in an average adult) is necessary to cause widespread lung injury. When pH is <2.5, it triggers an immediate inflammatory response, leading to pulmonary edema, bronchospasm, and hypoxemia. **2. Why Other Options are Incorrect:** * **Options B, C, and D (3, 3.5, 4):** While aspiration of fluid at these pH levels can still cause mechanical airway obstruction or bacterial pneumonia, they do not typically cause the classic **chemical pneumonitis** (parenchymal destruction) associated with Mendelson syndrome. As the pH rises above 2.5, the risk of immediate acid-induced lung injury decreases significantly. **3. Clinical Pearls for NEET-PG:** * **Prophylaxis:** To prevent this, patients are given H2 blockers (Ranitidine), Proton Pump Inhibitors (Pantoprazole), or non-particulate antacids (Sodium Citrate) to increase gastric pH. * **Prokinetic:** Metoclopramide is used to decrease gastric volume. * **Management:** The priority is immediate suctioning of the oropharynx. **Steroids and prophylactic antibiotics are NOT recommended** routinely for Mendelson syndrome. * **Risk Group:** Most commonly seen in obstetric patients (due to increased intra-abdominal pressure and relaxed lower esophageal sphincter).

Q: Which endotracheal tube has a preformed bend?

RAE tube. **Explanation:** The **RAE tube** (named after its inventors Ring, Adair, and Elwyn) is specifically designed with a **preformed bend** to facilitate surgery around the head and neck. This bend allows the tube to be directed away from the surgical field, reducing the risk of kinking or accidental extubation when the patient’s head is draped. RAE tubes are available in two types: **Nasal RAE** (bends upward toward the forehead) and **Oral RAE** (bends downward toward the chin). **Analysis of Options:** * **Laser tube (Option A):** These are specialized tubes made of stainless steel or coated with laser-resistant foil. They are designed to prevent airway fires during laser surgery but do not feature a preformed bend. * **Flexometallic (Armored) tube (Option C):** These tubes contain a wire coil embedded in the wall to prevent kinking when the neck is flexed. While highly flexible, they do **not** have a preformed shape and require a stylet for insertion. * **Standard tube (Option D):** Also known as the Magill tube, it has a natural gentle curve (the Magill curve) but lacks the sharp, preformed anatomical bend characteristic of the RAE tube. **Clinical Pearls for NEET-PG:** * **Common Use:** Oral RAE tubes are most frequently used in **tonsillectomy** (fitting into the groove of a Boyle-Davis mouth gag). * **Major Limitation:** The fixed length from the bend to the tip increases the risk of **endobronchial (one-lung) intubation**, especially in pediatric patients. * **Murphy Eye:** Like standard tubes, RAE tubes usually feature a Murphy eye to provide an alternate ventilation pathway if the distal tip is occluded.

Q: During a pre-anaesthetic evaluation, with the patient's neck extended, mouth open, and tongue protruded, the uvula is not visible. How should the patient's airway be classified based on the Mallampati classification?

Mallampati class 3. ### 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. **Why Class 3 is Correct:** In **Mallampati Class 3**, the clinician can visualize the **soft palate and the base of the uvula**. The rest of the uvula is obscured by the tongue. Since the question states the "uvula is not visible" (implying only its base or the soft palate is seen), it fits the criteria for Class 3. This indicates a potentially difficult airway. **Analysis of Incorrect Options:** * **Class 1:** Full visibility of the soft palate, fauces, entire uvula, and both anterior/posterior tonsillar pillars. This suggests an easy intubation. * **Class 2:** Visualization of the soft palate, fauces, and the **upper portion (tip) of the uvula**. * **Class 4:** Only the **hard palate** is visible. Neither the soft palate nor the uvula can be seen. This indicates a very high probability of a difficult airway. **High-Yield Clinical Pearls for NEET-PG:** * **Samsoon and Young Modification:** The original Mallampati classification had 3 classes; Samsoon and Young added Class 4. * **Correct Positioning:** For an accurate assessment, the patient must be sitting upright, head in a neutral position, mouth opened maximally, and tongue protruded **without phonation** (saying "Ah" can falsely improve the grade). * **Clinical Correlation:** Mallampati Classes 3 and 4 are significant predictors of a **difficult laryngoscopy** (Cormack-Lehane Grade 3 or 4). * **Mnemonic (PUSH):** **P**illars (Class 1), **U**vula (Class 2), **S**oft Palate (Class 3), **H**ard Palate (Class 4).

Q: What is the best method for maintaining the airway during laryngectomy in a patient with carcinoma of the larynx?

Tracheostomy. **Explanation:** In a patient undergoing **laryngectomy** for carcinoma of the larynx, the primary surgical objective is the complete removal of the larynx, which involves disconnecting the upper airway from the trachea. **Why Tracheostomy is the Correct Answer:** Tracheostomy is the definitive method for airway management in this scenario for two main reasons: 1. **Surgical Access:** Since the larynx is being surgically removed, any supraglottic or trans-laryngeal device would obstruct the surgical field. 2. **Airway Security:** A tracheostomy allows the surgeon to create a permanent stoma (distal to the lesion) and insert a reinforced endotracheal tube or tracheostomy tube directly into the trachea. This ensures a secure, "shared" airway that does not interfere with the resection of the tumor. **Why the Other Options are Incorrect:** * **Laryngeal Mask Airway (LMA) & Laryngeal Tube:** These are supraglottic airway devices. They sit above the vocal cords. During a laryngectomy, the entire area where these devices reside is removed, making them physically impossible to use during the procedure. * **Combitube:** This is a double-lumen retroglottic device used primarily in emergency "cannot intubate, cannot ventilate" scenarios. It occupies the pharynx and esophagus, which would completely block the surgical site and fail to provide a definitive airway once the larynx is excised. **High-Yield Clinical Pearls for NEET-PG:** * **Shared Airway:** Laryngectomy is a classic example of a "shared airway" case where the anesthesiologist and surgeon must coordinate closely. * **Awake Fiberoptic Intubation:** If the tumor causes significant upper airway obstruction, an awake fiberoptic intubation or a tracheostomy under local anesthesia is often the safest induction strategy. * **Post-Op:** After a total laryngectomy, the patient becomes a **"total neck breather,"** as there is no longer a connection between the nose/mouth and the lungs.

Q: What is the usual suction time for a tracheostomy tube?

10-15 seconds. **Explanation:** The correct suctioning time for a tracheostomy tube is **10–15 seconds**. This duration is a critical balance between effectively clearing secretions and maintaining patient safety. **Why 10-15 seconds is correct:** Suctioning is an invasive procedure that removes not only secretions but also oxygen from the patient's airway. Limiting the duration to 15 seconds prevents significant **hypoxemia** and **atelectasis** (collapse of alveoli). Furthermore, prolonged suctioning can trigger the vagus nerve, leading to life-threatening **bradycardia** or cardiac arrhythmias. **Analysis of Incorrect Options:** * **30 seconds (Option D):** This is excessively long. Prolonged suctioning significantly increases the risk of severe hypoxia and mucosal trauma to the tracheal wall. * **45 & 60 seconds (Options B & C):** These durations are dangerous. Suctioning for a minute would lead to critical desaturation and potential respiratory or cardiac arrest in a critically ill patient. **High-Yield Clinical Pearls for NEET-PG:** * **Pre-oxygenation:** Always pre-oxygenate the patient with 100% $O_2$ for 30–60 seconds before suctioning to provide a "buffer" against hypoxia. * **Catheter Size:** The external diameter of the suction catheter should not exceed **half (50%)** of the internal diameter of the tracheostomy tube to allow air to enter around the catheter. * **Technique:** Apply suction only while **withdrawing** the catheter, using a rotating motion. Never apply suction during insertion. * **Pressure:** Standard negative pressure for adults is typically **80–120 mmHg**.

Question 1

What is the appropriate size of a ProSeal Laryngeal Mask Airway (PLMA) for a 70 kg adult male patient?

Accepted Answer

5

Answer

3

Answer

4

Answer

6

Question 2

Which of the following is NOT a benefit of a supraglottic airway device compared to an endotracheal tube?

Accepted Answer

It prevents aspiration

Answer

It is less invasive

Answer

It causes less haemodynamic alteration

Answer

It requires less time for insertion

Question 3

What is the critical pH in Mendelson syndrome?

Accepted Answer

2.5

Answer

3

Answer

3.5

Answer

4

Question 4

Which endotracheal tube has a preformed bend?

Accepted Answer

RAE tube

Answer

Laser tube

Answer

Flexometallic tube

Answer

Standard tube

Question 5

During a pre-anaesthetic evaluation, with the patient's neck extended, mouth open, and tongue protruded, the uvula is not visible. How should the patient's airway be classified based on the Mallampati classification?

Accepted Answer

Mallampati class 3

Answer

Mallampati class 1

Answer

Mallampati class 2

Answer

Mallampati class 4

Question 6

A patient presents with the following blood gas parameters: pH 7.58, pCO2 23 mm Hg, pO2 300 mm Hg, and oxygen saturation 60%. What is the most likely condition consistent with these findings?

Accepted Answer

Ventilatory malfunction

Answer

Carbon monoxide poisoning

Answer

Voluntary hyperventilation

Answer

Methyl alcohol poisoning

Question 7

What is the best method for maintaining the airway during laryngectomy in a patient with carcinoma of the larynx?

Accepted Answer

Tracheostomy

Answer

Laryngeal mask airway

Answer

Laryngeal tube

Answer

Combitube

Question 8

What is the optimal patient positioning for intubation using a Macintosh laryngoscope in an adult patient?

Accepted Answer

Flexion of the lower cervical spine and extension of the head

Answer

Shoulder elevation

Answer

Positioning flat on the bed

Answer

Hyperextension of the neck

Question 9

What is the usual suction time for a tracheostomy tube?

Accepted Answer

10-15 seconds

Answer

45 seconds

Answer

60 seconds

Answer

30 seconds

Question 10

A 72-year-old man has multiple injuries and an altered sensorium after a high-speed motor vehicle collision. He is intubated for his decreased mental status. During intubation, a large amount of gastric contents are noted in the posterior pharynx and he aspirates. What is the appropriate initial treatment?

Accepted Answer

Bronchoscopy for aspiration of particulate matter

Answer

Steroids

Answer

Prophylactic antibiotics

Answer

Inhaled nitric oxide

Respiratory and Airway Management — MCQs

Respiratory and Airway Management — MCQs

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