Respiratory and Airway Management — MCQs

A patient with a known history of systemic sclerosis is scheduled for hernioplasty. During pre-operative assessment, the anesthesiologist anticipates difficult intubation based on oral examination findings. Upon laryngoscopy, only the posterior glottis is visible. What is the laryngoscopic grading of the glottis?

Q217Easy

Fink's effect is?

Q218Easy

What is the commonest sign of aspiration pneumonitis?

Q219Medium

Nasal intubation is contraindicated in which of the following conditions?

Q220Easy

What is the primary use of a laryngeal mask airway?

Respiratory and Airway Management Indian Medical PG Practice Questions and MCQs

Question 211: What is true about a laryngeal mask airway?

A. It prevents aspiration.
B. It is used in oral surgeries.
C. It is used in laryngeal surgeries.
D. It maintains the airway. (Correct Answer)

Explanation: **Explanation:** The **Laryngeal Mask Airway (LMA)** is a supraglottic airway device (SAD) designed to sit in the hypopharynx, creating a seal around the laryngeal inlet. **1. Why Option D is Correct:** The primary function of an LMA is to **maintain a patent airway** in an unconscious patient. It acts as a bridge between a face mask and an endotracheal tube (ETT). It is particularly useful for spontaneous or controlled ventilation in short surgical procedures and is a cornerstone of the **"Difficult Airway Algorithm"** when intubation or mask ventilation fails. **2. Why Other Options are Incorrect:** * **Option A:** Unlike an ETT, a standard LMA **does not prevent aspiration**. It does not seal the trachea; therefore, gastric contents can still enter the lungs if regurgitation occurs. It is contraindicated in patients with a "full stomach." * **Option B:** It is generally **not used in oral surgeries** because the device occupies significant space in the mouth, obstructing the surgeon’s access and increasing the risk of displacement. * **Option C:** It is **not used in laryngeal surgeries** because the cuff sits directly over the larynx, obscuring the surgical field. **High-Yield Clinical Pearls for NEET-PG:** * **Placement:** The tip of the LMA rests against the **upper esophageal sphincter** (cricopharyngeus muscle). * **Nerve Injury:** Excessive cuff pressure can cause injury to the **lingual, hypoglossal, or recurrent laryngeal nerves**. * **Size Selection:** Size 3 (30-50kg females), Size 4 (50-70kg males), Size 5 (>70kg large adults). * **LMA ProSeal:** A variant with a gastric drainage tube that provides a better seal and some protection against aspiration.

Question 212: In tracheotomy, what is the typical reduction in dead space?

A. 15%
B. 30-50% (Correct Answer)
C. 10%
D. 20%

Explanation: **Explanation:** **1. Understanding the Correct Answer (B: 30-50%)** Anatomical dead space refers to the volume of the conducting airways (nose, pharynx, larynx, and trachea) where no gas exchange occurs. In a healthy adult, this is approximately **2 ml/kg** (roughly 150 ml). A tracheotomy involves creating an opening in the trachea (usually between the 2nd and 4th tracheal rings) and inserting a tube, thereby bypassing the entire upper airway (nose, mouth, and pharynx). Since the upper airway accounts for a significant portion of the total anatomical dead space, bypassing it results in a **30% to 50% reduction** in dead space. This reduction decreases the work of breathing and improves alveolar ventilation, which is particularly beneficial for patients with borderline respiratory reserve or those weaning from a ventilator. **2. Why Other Options are Incorrect** * **A, C, and D (10%, 15%, 20%):** These values significantly underestimate the volume of the upper respiratory tract. The upper airway (supra-glottic and glottic regions) constitutes nearly half of the total conducting airway volume; therefore, bypassing it must result in a reduction greater than 20%. **3. Clinical Pearls for NEET-PG** * **Dead Space Calculation:** Anatomical dead space is measured using **Fowler’s Method** (Nitrogen washout). * **V/Q Relationship:** Tracheostomy reduces the **VD/VT ratio** (Dead space to Tidal volume ratio), making ventilation more efficient. * **Indications:** High-yield indications for tracheostomy include prolonged mechanical ventilation (>7-14 days), upper airway obstruction (e.g., tumors, laryngeal edema), and inability to clear secretions. * **Complication:** The most common immediate complication is hemorrhage; the most common late complication is tracheal stenosis.

Question 213: What mode of ventilation is characterized by the pressure-time graph shown?

A. Volume Controlled Ventilation (VCV)
B. Pressure Controlled Ventilation (PCV) (Correct Answer)
C. Pressure Support Ventilation (PSV)
D. Continuous Positive Airway Pressure (CPAP)

Explanation: ***Pressure Controlled Ventilation (PCV)*** - Characterized by a **square-wave pressure-time waveform** with a flat inspiratory pressure plateau, indicating constant pressure delivery throughout inspiration. - The **preset inspiratory pressure** is maintained throughout the inspiratory phase, with tidal volume varying based on lung compliance and resistance. *Volume Controlled Ventilation (VCV)* - Displays a **ramping pressure waveform** that gradually increases during inspiration to deliver the preset tidal volume. - Pressure continues to rise throughout inspiration until the **target volume** is achieved, creating an upward-sloping pressure curve. *Pressure Support Ventilation (PSV)* - Shows **patient-triggered variable pressure support** with irregular timing based on patient effort and demand. - The pressure waveform varies with each breath as it responds to the patient's **spontaneous breathing pattern** and effort. *Continuous Positive Airway Pressure (CPAP)* - Maintains a **constant baseline pressure** throughout the respiratory cycle without cyclic pressure changes. - The pressure-time graph shows a **flat horizontal line** at the set CPAP level, lacking the inspiratory pressure peaks seen in other modes.

Question 214: A throat pack is primarily used for which of the following purposes?

A. To prevent aspiration of blood and secretions into the trachea
B. To facilitate easier extubation (Correct Answer)
C. To be removed immediately after the surgical procedure
D. To provide hemostasis during pharyngeal surgery

Explanation: **Explanation:** A **throat pack** is a length of gauze or foam placed in the posterior pharynx during oral, nasal, or maxillofacial surgeries. **Why Option B is Correct:** The primary clinical objective of a throat pack is to prevent blood, secretions, and surgical debris from trickling down into the larynx and trachea. By keeping the glottic area clean, it minimizes laryngeal irritation and prevents laryngospasm upon emergence. This ensures a "smooth" and **easier extubation** process, reducing the risk of post-operative respiratory complications like coughing or aspiration during the transition from anesthesia to wakefulness. **Analysis of Incorrect Options:** * **Option A:** While it helps prevent aspiration, the *cuff* of the endotracheal tube is the definitive protection for the trachea. The throat pack is an adjunct, not the primary mechanism for tracheal protection. * **Option C:** A throat pack must be removed **before** the patient leaves the operating room, but "immediately after the procedure" is vague. The critical safety step is ensuring removal before extubation to prevent airway obstruction. * **Option D:** While it may provide minimal pressure, its purpose is not hemostasis (stopping bleeding), but rather the containment of fluids. **High-Yield Clinical Pearls for NEET-PG:** * **The "Forgotten Pack":** A retained throat pack is a "Never Event" as it can cause fatal airway obstruction. * **Safety Protocol:** Always document the time of insertion and removal. A label should be placed on the patient’s forehead or the ETT pilot balloon as a reminder. * **Complications:** Post-operative sore throat (most common) and potential uvular edema or trauma if inserted forcefully.

Question 215: Which laryngoscope is particularly used for pediatric intubation?

A. Pediatric intubation (Correct Answer)
B. Difficult airway
C. Nasal intubation
D. Rapid sequence intubation

Explanation: **Explanation:** In pediatric anesthesia, the **Miller blade** (straight blade) is the gold standard for intubation. Unlike the curved Macintosh blade used in adults, the Miller blade is designed to directly lift the epiglottis. This is crucial in infants and young children because their epiglottis is relatively longer, stiffer, and "U" or "omega" shaped, often flopping over the glottic opening. By physically pinning the epiglottis against the tongue, the Miller blade provides a superior view of the larynx. **Analysis of Options:** * **Option A (Correct):** Pediatric anatomy (high, anterior larynx and floppy epiglottis) necessitates the use of straight blades like the Miller or Seward to ensure a clear line of sight. * **Option B (Incorrect):** While specialized laryngoscopes (like the Bullard or video laryngoscopes) are used for difficult airways, the question specifically targets the standard pediatric preference. * **Option C (Incorrect):** Nasal intubation typically uses standard blades; the procedure is facilitated by Magill forceps rather than a specific type of laryngoscope blade. * **Option D (Incorrect):** Rapid Sequence Intubation (RSI) is a technique used to prevent aspiration; the choice of laryngoscope depends on the patient's age and anatomy, not the RSI protocol itself. **High-Yield Clinical Pearls for NEET-PG:** * **Macintosh Blade:** A curved blade whose tip is placed in the **vallecula** (indirectly lifting the epiglottis). * **Miller Blade:** A straight blade whose tip is placed **under the epiglottis** (directly lifting it). * **Pediatric Airway Facts:** The narrowest part of the pediatric airway is the **cricoid cartilage** (though recent studies suggest the glottis, the cricoid remains the classic exam answer). The larynx is more **cephalad** (C3-C4 level) compared to adults (C4-C5).

Question 216: A patient with a known history of systemic sclerosis is scheduled for hernioplasty. During pre-operative assessment, the anesthesiologist anticipates difficult intubation based on oral examination findings. Upon laryngoscopy, only the posterior glottis is visible. What is the laryngoscopic grading of the glottis?

A. Grade 1
B. Grade 2 (Correct Answer)
C. Grade 3
D. Grade 4

Explanation: ### Explanation The question describes the **Cormack-Lehane Classification**, which is used to grade the view obtained during direct laryngoscopy. **1. Why Grade 2 is Correct:** According to the Cormack-Lehane system, **Grade 2** is defined when only the **posterior portion of the glottis** (arytenoids and posterior commissure) or the posterior part of the vocal cords is visible. In this case, the patient’s systemic sclerosis likely caused limited mouth opening (microstomia) or stiffening of the neck tissues, resulting in this restricted view. **2. Analysis of Incorrect Options:** * **Grade 1:** Full view of the glottis (including the entire vocal cords and anterior commissure). This represents an easy intubation. * **Grade 3:** Only the **epiglottis** is visible; no part of the glottis or vocal cords can be seen. This indicates a difficult intubation. * **Grade 4:** Neither the glottis nor the epiglottis is visible; only the soft palate is seen. This represents a very difficult airway. **3. Clinical Pearls for NEET-PG:** * **Systemic Sclerosis (Scleroderma):** In anesthesia, it is associated with "Difficult Airway" due to **microstomia** (small mouth opening), decreased mandibular protrusion, and reduced neck extension. * **Modified Cormack-Lehane:** Grade 2 is often subdivided into **2a** (partial view of the glottis) and **2b** (only arytenoids/posterior commissure visible). * **Management:** For Grade 2 views, a **gum elastic bougie** is the most common and effective aid used to facilitate endotracheal intubation. * **Mallampati vs. Cormack-Lehane:** Remember that Mallampati is a *pre-operative* bedside assessment (clinical), while Cormack-Lehane is an *intra-operative* assessment (laryngoscopic).

Question 217: Fink's effect is?

A. Also called the second gas effect
B. Due to rapid uptake of nitrous oxide during induction
C. Due to rapid elimination of nitrous oxide during recovery (Correct Answer)
D. Increase in partial pressure of oxygen during recovery

Explanation: ### Explanation **Fink’s Effect**, also known as **Diffusion Hypoxia**, occurs during the recovery phase of general anesthesia. **Why Option C is Correct:** Nitrous oxide ($N_2O$) is 31 times more soluble in blood than nitrogen. When $N_2O$ administration is discontinued, it rapidly leaves the blood and floods the alveoli. This massive outpouring of $N_2O$ dilutes the concentration of both oxygen ($O_2$) and carbon dioxide ($CO_2$) within the alveoli. The resulting drop in alveolar $O_2$ partial pressure leads to arterial hypoxemia. This phenomenon is specifically termed the Fink Effect. **Analysis of Incorrect Options:** * **Option A & B:** These refer to the **Second Gas Effect**. This occurs during **induction** when the rapid uptake of a high-volume gas (like $N_2O$) concentrates a co-administered volatile anesthetic (the "second gas") in the alveoli, speeding up its onset. * **Option D:** The Fink effect causes a **decrease** (not an increase) in the partial pressure of oxygen in the alveoli. **Clinical Pearls for NEET-PG:** * **Prevention:** To prevent diffusion hypoxia, the patient should be administered **100% oxygen for 3–5 minutes** after $N_2O$ is turned off. * **Concentration Effect:** This is the counterpart to the second gas effect, where the high inspired concentration of a gas ($N_2O$) accelerates its own uptake. * **Key Difference:** * *Induction:* Concentration Effect & Second Gas Effect. * *Recovery:* Fink Effect (Diffusion Hypoxia).

Question 218: What is the commonest sign of aspiration pneumonitis?

A. Cyanosis
B. Tachypnea (Correct Answer)
C. Crepitations
D. Rhonchi

Explanation: **Explanation:** **Mendelson’s Syndrome** (aspiration pneumonitis) occurs due to the inhalation of acidic gastric contents (pH < 2.5, volume > 0.4 ml/kg). This triggers an immediate chemical burn of the pulmonary parenchyma, leading to an inflammatory response. **Why Tachypnea is the correct answer:** **Tachypnea** is the earliest and most consistent clinical sign of aspiration pneumonitis. The chemical insult causes immediate bronchospasm and a decrease in lung compliance, which triggers a compensatory increase in the respiratory rate. It is often the first warning sign observed in the post-operative period or during emergence from anesthesia. **Analysis of Incorrect Options:** * **Cyanosis:** While it occurs due to severe ventilation-perfusion (V/Q) mismatch and hypoxemia, it is a **late sign**. If a patient is cyanotic, the aspiration is likely massive or has already progressed to significant respiratory failure. * **Crepitations (Rales):** These are common as pulmonary edema develops following the inflammatory insult, but they may not be audible immediately upon aspiration. * **Rhonchi:** These may be heard if there is significant mucus production or associated large airway involvement, but they are less characteristic than tachypnea or crepitations in the acute phase of Mendelson’s Syndrome. **High-Yield Clinical Pearls for NEET-PG:** * **Mendelson’s Syndrome Criteria:** Gastric pH **< 2.5** and volume **> 25 ml** (0.4 ml/kg). * **Most common site:** The **Right Lower Lobe** (specifically the superior segment) is the most common site of aspiration due to the more vertical anatomy of the right main bronchus. * **Management:** Immediate treatment involves suctioning the oropharynx (before positive pressure ventilation) and supportive care (O2, PEEP). **Prophylactic antibiotics and steroids are NOT recommended** for chemical pneumonitis unless secondary bacterial infection occurs.

Question 219: Nasal intubation is contraindicated in which of the following conditions?

A. Cerebrospinal fluid (CSF) rhinorrhea (Correct Answer)
B. Fracture of the cervical spine
C. Fracture of the mandible
D. Shatz neck

Explanation: **Explanation:** **1. Why CSF Rhinorrhea is the Correct Answer:** CSF rhinorrhea is a hallmark sign of a **fracture of the cribriform plate** (base of the skull). In such cases, the anatomical barrier between the nasal cavity and the intracranial space is compromised. Attempting nasal intubation is strictly contraindicated because the endotracheal tube or a nasopharyngeal airway can inadvertently pass through the fracture site and enter the **cranial vault**, leading to direct brain injury, intracranial hemorrhage, or life-threatening meningitis. **2. Analysis of Incorrect Options:** * **Fracture of the Cervical Spine:** Nasal intubation (specifically fiberoptic-guided) is often a **preferred technique** here. It allows for intubation while maintaining the neck in a neutral position, avoiding the extension required for direct laryngoscopy which could worsen spinal cord injury. * **Fracture of the Mandible:** Nasal intubation is frequently indicated in mandibular fractures. It provides a clear surgical field for the maxillofacial surgeon and allows for **intermaxillary fixation** (wiring the jaws shut) post-operatively. * **Shatz Neck (Short/Stiff Neck):** While a short neck may predict a difficult airway (high Mallampati score), it is not a contraindication. In fact, if oral access is limited, nasal fiberoptic intubation may be the safest alternative. **Clinical Pearls for NEET-PG:** * **Absolute Contraindications for Nasal Intubation:** Base of skull fractures (Battle’s sign, Raccoon eyes, CSF rhinorrhea/otorrhea), severe mid-face fractures (Le Fort II and III), and coagulopathy (due to risk of epistaxis). * **Preferred Tube:** The **North Polar (Ivory) tube** is specifically designed for nasal intubation to prevent kinking. * **Vasoconstriction:** Always use topical vasoconstrictors (e.g., Xylometazoline or Oxymetazoline) to shrink nasal mucosa and minimize bleeding before insertion.

Question 220: What is the primary use of a laryngeal mask airway?

A. Airway maintenance
B. Cardiopulmonary resuscitation
C. Positive pressure ventilation
D. All of the above (Correct Answer)

Explanation: The **Laryngeal Mask Airway (LMA)** is a supraglottic airway device (SAD) designed to sit in the hypopharynx, masking the laryngeal opening. It serves as a bridge between a face mask and an endotracheal tube. ### **Explanation of the Correct Answer** The correct answer is **D (All of the above)** because the LMA is a versatile tool used in various clinical scenarios: 1. **Airway Maintenance:** It is primarily used for maintaining a patent airway during spontaneous or controlled ventilation in elective surgical procedures, especially when endotracheal intubation is not required. 2. **Cardiopulmonary Resuscitation (CPR):** In the ACLS/BLS guidelines, the LMA is a preferred rescue device for healthcare providers when they cannot achieve successful intubation. It is easier and faster to insert than an endotracheal tube. 3. **Positive Pressure Ventilation (PPV):** While originally designed for spontaneous breathing, modern LMAs (especially second-generation versions like the ProSeal or Supreme) are specifically designed to allow effective PPV with higher seal pressures. ### **Why individual options are incomplete** Options A, B, and C are all valid clinical applications of the LMA. Selecting any single one would ignore the device's broad utility in both elective anesthesia and emergency medicine. ### **High-Yield Clinical Pearls for NEET-PG** * **Classification:** It is a **Supraglottic Airway Device (SAD)**; it does not pass through the vocal cords. * **The "Difficult Airway" Algorithm:** The LMA is the "gold standard" rescue device in the **"Cannot Intubate, Cannot Ventilate" (CICV)** scenario. * **Contraindication:** The primary contraindication is a **full stomach** (risk of aspiration), as the LMA does not protect the airway from gastric contents (unlike a cuffed endotracheal tube). * **Nerve Injury:** Excessive cuff inflation or prolonged use can lead to injury of the **Lingual, Hypoglossal, or Recurrent Laryngeal nerves.** * **Size Selection:** Size 3 (30-50kg females), Size 4 (50-70kg males), Size 5 (>70kg large adults).

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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