Respiratory and Airway Management Practice Questions

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

All of the above. **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.

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.

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

Sodium bicarbonate. **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.

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

Corner of the mouth to the angle of the mandible. ### 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.

Question 1

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 2

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 3

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 4

Which of the following is not a cause of bronchospasm?

Accepted Answer

Halothane

Answer

Regurgitation

Answer

Aspiration

Answer

Intubation

Question 5

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

Accepted Answer

All of the above

Answer

Respiratory arrest

Answer

Respiratory rate > 35/min

Answer

Severe acidosis < 7.25

Question 6

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 7

Laryngospasm under anesthesia can be relieved by?

Accepted Answer

Succinylcholine

Answer

Aminophylline

Answer

Salbutamol

Answer

Terbutaline

Question 8

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.

Question 9

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

Accepted Answer

Sodium bicarbonate

Answer

Atropine

Answer

Adrenaline

Answer

Lignocaine

Question 10

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

Accepted Answer

Corner of the mouth to the angle of the mandible

Answer

Incisor teeth to the tragus of the ear

Answer

Tip of the nose to the angle of the mandible

Answer

Ala of the nose to the angle of the mandible

Respiratory and Airway Management — MCQs

Respiratory and Airway Management — MCQs

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