Respiratory and Airway Management — MCQs

Respiratory and Airway Management Indian Medical PG Practice Questions and MCQs

Question 101: Sellick's maneuver is:

A. Application of pressure over cricoid cartilage to occlude the esophagus
B. Aims at avoiding oxygen entry into the esophagus during mask ventilation
C. Both A and B (Correct Answer)
D. Neither A nor B

Explanation: **Explanation:** **Sellick’s Maneuver**, also known as **Cricoid Pressure**, is a fundamental technique used during Rapid Sequence Induction (RSI) to prevent pulmonary aspiration of gastric contents. 1. **Mechanism (Option A):** The maneuver involves applying firm downward pressure on the **cricoid cartilage** (the only complete cartilaginous ring in the airway). This pressure compresses the underlying esophagus against the body of the fifth or sixth cervical vertebra, effectively occluding the esophageal lumen. 2. **Function during Ventilation (Option B):** Beyond preventing regurgitation, Sellick’s maneuver is clinically used during bag-mask ventilation to prevent **gastric insufflation**. By occluding the esophagus, it ensures that the positive pressure airflow is directed into the trachea rather than the stomach, thereby reducing the risk of gastric distension and subsequent vomiting. Since both the anatomical mechanism (Option A) and the functional benefit during ventilation (Option B) are accurate descriptions of the maneuver's purpose, **Option C** is the correct answer. **Why other options are incorrect:** * **Option D** is incorrect because both A and B are standard medical definitions of the maneuver’s utility. **High-Yield Clinical Pearls for NEET-PG:** * **Pressure Required:** Approximately **10 Newtons (1kg)** when the patient is awake and **30 Newtons (3kg)** once consciousness is lost. * **Indication:** Primarily used in "Full Stomach" cases (e.g., intestinal obstruction, emergency trauma, pregnancy). * **Contraindications:** Active vomiting (risk of esophageal rupture), unstable cervical spine fractures, or laryngeal trauma. * **BURP Maneuver vs. Sellick’s:** Do not confuse Sellick's with the **BURP** maneuver (Backward, Upward, Rightward Pressure), which is applied to the *thyroid* cartilage to improve the laryngeal view during intubation.

Question 102: Which of the following is not a definitive airway?

A. Tracheostomy
B. Orotracheal tube
C. Nasotracheal tube
D. Laryngeal mask airway (Correct Answer)

Explanation: ### Explanation A **definitive airway** is defined as a tube placed in the **trachea** with the **cuff inflated below the vocal cords**, connected to an enriched oxygen source, and secured in place. The primary goal is to provide a secure channel for ventilation while protecting the lungs from aspiration. **Why Laryngeal Mask Airway (LMA) is the correct answer:** The LMA is a **supraglottic airway device**. It sits in the hypopharynx above the glottic opening. Because it does not pass through the vocal cords into the trachea, it does not provide a "watertight" seal against gastric aspiration. Therefore, it is considered an intermediate or "rescue" airway, but **not** a definitive airway. **Why the other options are incorrect:** * **Orotracheal Tube (B) & Nasotracheal Tube (C):** These are the most common definitive airways. The tube passes directly through the glottis into the trachea, and the inflated cuff prevents aspiration and allows for positive pressure ventilation. * **Tracheostomy (A):** This is a **surgical definitive airway**. It bypasses the upper airway entirely by placing a tube directly into the trachea through the neck. **High-Yield Clinical Pearls for NEET-PG:** * **Components of a Definitive Airway:** 1. In the trachea, 2. Cuff inflated, 3. Secured. * **Indications for Definitive Airway:** Apnea, inability to maintain a patent airway, protection against aspiration (e.g., GCS ≤ 8), or impending airway compromise (e.g., inhalation burns). * **Gold Standard for Confirmation:** Continuous waveform capnography ($EtCO_2$) is the most reliable method to confirm tracheal placement. * **LMA Limitation:** It is contraindicated in patients with a "full stomach" or those requiring high airway pressures.

Question 103: Armored endotracheal tube is used in which type of surgery?

A. Neurosurgery (Correct Answer)
B. Cardiac surgery
C. Liver surgery
D. Intestinal surgery

Explanation: **Explanation:** **Armored (Reinforced) Endotracheal Tubes (ETTs)** are specialized tubes containing a wire coil embedded within the silicone or PVC wall. This design makes the tube **kink-resistant**, ensuring that the airway remains patent even when the tube is bent at acute angles. **Why Neurosurgery is the Correct Answer:** In neurosurgical procedures, the patient is often placed in unconventional positions (e.g., prone, sitting, or lateral) with the head acutely flexed or rotated. Furthermore, the surgical team often works near the airway, increasing the risk of accidental tube compression or kinking. An armored tube is used because it maintains its internal diameter and prevents airway obstruction despite these extreme head positions or external pressure. **Analysis of Incorrect Options:** * **B, C, and D (Cardiac, Liver, and Intestinal Surgery):** These surgeries are typically performed in the **supine position** with the head in a neutral "sniffing" position. In these cases, a standard PVC (Murphy) ETT is sufficient, as there is minimal risk of the tube kinking due to head positioning. **High-Yield Clinical Pearls for NEET-PG:** * **The "No-Cut" Rule:** Never cut an armored tube to shorten it. If you cut it, the wire coil can unravel, or the connector may not fit securely, leading to potential airway disaster. * **Stylet Requirement:** Because armored tubes are very flexible (floppy), a **stylet** is mandatory during intubation to provide the necessary rigidity to guide the tube into the larynx. * **Biting Risk:** If a patient bites an armored tube, the wire coil can permanently deform and occlude the lumen. Therefore, a **bite block** must always be used. * **Other Indications:** Armored tubes are also frequently used in **Head and Neck surgeries** (e.g., Thyroidectomy, Parotidectomy) where the head is manipulated intraoperatively.

Question 104: What is the ideal duration for preoxygenation?

A. 3-5 minutes (Correct Answer)
B. 1-3 minutes
C. 5-8 minutes
D. 2-3 minutes

Explanation: **Explanation:** Preoxygenation (denitrogenation) is the process of replacing the nitrogen in the functional residual capacity (FRC) of the lungs with oxygen. This creates an oxygen reservoir that delays the onset of hemoglobin desaturation during periods of apnea, such as during endotracheal intubation. **Why 3–5 minutes is correct:** Under normal circumstances, breathing 100% oxygen at a normal tidal volume for **3 to 5 minutes** is the gold standard. This duration is sufficient to wash out approximately 95% of the nitrogen from the FRC. In a healthy adult, this provides approximately 8 minutes of "safe apnea time" (time until saturation drops below 90%), compared to only 1–2 minutes when breathing room air. **Analysis of incorrect options:** * **1–3 minutes & 2–3 minutes:** These durations are generally insufficient to achieve complete denitrogenation of the FRC in all patients. While 4-8 deep breaths over 30–60 seconds (vital capacity breaths) can be used in emergencies, they are not considered the "ideal" duration for elective scenarios. * **5–8 minutes:** While not harmful, extending preoxygenation beyond 5 minutes offers diminishing returns. By 5 minutes, the FRC is already maximally saturated with oxygen; further time does not significantly increase the oxygen reservoir but may delay the surgical workflow. **High-Yield Clinical Pearls for NEET-PG:** * **The Goal:** To replace Nitrogen (approx. 79% of FRC) with Oxygen. * **FRC:** The FRC acts as the primary oxygen reservoir during apnea. Conditions that decrease FRC (obesity, pregnancy, ascites) lead to faster desaturation despite adequate preoxygenation. * **Alternative Technique:** If time is limited, **8 vital capacity breaths over 60 seconds** is an acceptable alternative to 3 minutes of tidal breathing. * **Indicator of Adequacy:** Monitoring **End-tidal Oxygen (EtO2)**; a value >90% (or 0.9) indicates successful denitrogenation.

Question 105: What is the appropriate endotracheal tube size for a full-term infant?

A. 2.5 mm
B. 3.5 mm (Correct Answer)
C. 4.5 mm
D. 5.5 mm

Explanation: In pediatric anesthesiology, selecting the correct endotracheal tube (ETT) size is critical to ensure adequate ventilation while preventing subglottic stenosis or mucosal ischemia. ### **Explanation of the Correct Answer** For a **full-term infant** (typically weighing 3.0–3.5 kg), the standard internal diameter (ID) for an uncuffed ETT is **3.5 mm**. This size provides the optimal balance between airway resistance and the risk of trauma to the narrowest part of the infant's airway—the cricoid cartilage. ### **Analysis of Incorrect Options** * **A. 2.5 mm:** This size is reserved for **premature infants** (usually <1000g or <28 weeks gestation). Using this in a full-term infant would result in high airway resistance and significant air leaks. * **C. 4.5 mm:** This size is appropriate for children aged **1 to 2 years**. In a neonate, this would be too large, potentially causing pressure necrosis of the tracheal mucosa. * **D. 5.5 mm:** This size is typically used for children around **5 to 6 years** of age. ### **High-Yield Clinical Pearls for NEET-PG** 1. **Formula for Children (>2 years):** * **Uncuffed ETT size (mm) = (Age / 4) + 4** * **Cuffed ETT size (mm) = (Age / 4) + 3.5** 2. **Insertion Depth:** A quick bedside rule for ETT depth (at the lip) is **(Weight in kg + 6)** or **(ETT size × 3)**. 3. **Narrowest Point:** In children, the narrowest part of the airway is traditionally considered the **cricoid cartilage** (funnel-shaped), whereas in adults, it is the **glottis** (cylindrical). 4. **The "Leak Test":** An ideal pediatric ETT fit should allow a small air leak at an inspiratory pressure of **15–25 cm H₂O**.

Question 106: What is the major advantage of volume control ventilation?

A. Constant tidal volume (Correct Answer)
B. Variable minute ventilation
C. Improved patient comfort
D. All of the above

Explanation: In **Volume Control Ventilation (VCV)**, the clinician sets a specific tidal volume ($V_T$) and respiratory rate. The ventilator delivers this fixed volume regardless of changes in the patient’s lung mechanics (compliance or resistance). ### Why "Constant Tidal Volume" is Correct: The primary goal and major advantage of VCV is the **guaranteed delivery of a preset tidal volume**. This ensures a predictable **Minute Ventilation** ($V_E = V_T \times RR$), which is crucial for precise control of arterial $CO_2$ levels. In patients with fluctuating lung compliance (e.g., during laparoscopic surgery with pneumoperitoneum), VCV ensures the lungs do not hypoventilate. ### Why Other Options are Incorrect: * **B. Variable minute ventilation:** This is incorrect because VCV aims for a *stable* minute ventilation. Variable minute ventilation is more characteristic of pressure-supported modes where $V_T$ fluctuates based on patient effort and lung compliance. * **C. Improved patient comfort:** VCV is often associated with *decreased* patient comfort compared to Pressure Control Ventilation (PCV). In VCV, the flow rate is fixed; if a conscious patient demands more flow than the machine provides, it leads to "flow starvation" and patient-ventilator dyssynchrony. ### High-Yield Clinical Pearls for NEET-PG: * **The Trade-off:** While $V_T$ is constant in VCV, the **Peak Inspiratory Pressure (PIP)** is variable. If lung compliance decreases (e.g., bronchospasm or ARDS), PIP can rise dangerously, increasing the risk of barotrauma. * **VCV vs. PCV:** In PCV, pressure is constant but $V_T$ is variable. PCV is often preferred in ARDS to limit barotrauma and in pediatric anesthesia due to the uncuffed tubes used previously. * **Monitoring:** When using VCV, always set high-pressure alarms to prevent lung injury.

Question 107: A lightly anaesthetized patient is placed in the lithotomy position and is spontaneously breathing. Which of the following is true?

A. Marked reduction in vital capacity
B. Increased FRC
C. Normal alveolar ventilation
D. Residual volume and closing volume are equal (Correct Answer)

Explanation: ### Explanation This question tests the understanding of respiratory physiology changes induced by anesthesia and positioning. **1. Why the Correct Answer (D) is Right:** In a **lightly anesthetized** patient, there is a significant reduction in **Functional Residual Capacity (FRC)** due to the cephalad displacement of the diaphragm by abdominal contents. This effect is exacerbated by the **lithotomy position**, where the legs are elevated, further increasing intra-abdominal pressure. When FRC falls, it may reach a level equal to or below the **Closing Capacity (CC)**. Closing capacity is the volume at which small airways in the dependent parts of the lung begin to collapse. In the context of anesthesia and specific positioning, the FRC often drops to match the **Residual Volume (RV)** or approach the **Closing Volume (CV)**, leading to atelectasis and V/Q mismatch. **2. Why the Incorrect Options are Wrong:** * **Option A:** While there is a reduction in Vital Capacity (VC) in the lithotomy position (approx. 10-15%), it is generally described as **mild to moderate**, not "marked." The most significant and clinically relevant change is the reduction in FRC. * **Option B:** FRC **decreases** (not increases) in the supine and lithotomy positions due to the loss of gravitational pull on the diaphragm and increased abdominal pressure. * **Option C:** Alveolar ventilation is **not normal**. In a spontaneously breathing, anesthetized patient in lithotomy, the work of breathing increases, and the reduction in FRC leads to increased dead space and potential hypoventilation. **3. High-Yield Clinical Pearls for NEET-PG:** * **FRC vs. Position:** FRC is highest in the standing position and lowest in the Trendelenburg and Lithotomy positions. * **Anesthesia Effect:** General anesthesia alone reduces FRC by approximately 15-20% due to changes in chest wall muscle tone. * **Closing Capacity:** If CC > FRC, airway closure occurs during normal tidal breathing, leading to shunting and hypoxia. This is common in elderly patients, smokers, and those with obesity. * **Lithotomy Complication:** Beyond respiratory issues, always remember the risk of **Peroneal nerve injury** (most common) and **Compartment syndrome** of the legs in prolonged lithotomy.

Question 108: Murphy's eye is a part of which of the following devices?

A. Endotracheal tube (Correct Answer)
B. Laryngeal mask airway
C. Anesthesia face mask
D. Mapleson circuit

Explanation: **Explanation:** **Murphy’s eye** is a small oval opening or side-hole located on the side wall of an **Endotracheal Tube (ETT)**, near its distal tip. **Why Option A is correct:** The primary function of Murphy’s eye is to act as an **alternate pathway for gas exchange**. If the main distal orifice of the ETT becomes obstructed by secretions, blood clots, or if the tip abuts against the tracheal wall (carina), Murphy’s eye ensures that ventilation can still occur. Tubes featuring this opening are specifically called "Murphy-type" tubes, whereas those without it are known as "Magill-type" tubes. **Why other options are incorrect:** * **B. Laryngeal Mask Airway (LMA):** This is a supraglottic airway device. It consists of a mask and a tube but does not feature a Murphy’s eye; instead, it has aperture bars to prevent the epiglottis from obstructing the lumen. * **C. Anesthesia Face Mask:** These are used for non-invasive ventilation and do not have internal safety orifices like the ETT. * **D. Mapleson Circuit:** This is a breathing system (tubing and valves) used to deliver anesthetic gases; it does not contain an ETT-specific anatomical feature like Murphy's eye. **High-Yield Clinical Pearls for NEET-PG:** 1. **Right Mainstem Intubation:** If an ETT is inserted too deeply into the right main bronchus, Murphy’s eye may occasionally allow some ventilation to the **Right Upper Lobe**, which might otherwise be collapsed. 2. **Bevel:** The distal end of an ETT is beveled (usually to the left) to improve visualization of the vocal cords during intubation. 3. **Vocal Cord Guide:** A black line often present above the cuff to ensure correct depth of insertion. 4. **Standard Connector:** The proximal end of the ETT has a universal **15 mm connector**.

Question 109: A supraglottic airway device is contraindicated for all of the following patients except:

A. Patient with a risk of aspiration
B. Patient with poor lung compliance
C. Patient with limited mouth opening
D. Patient under general anesthesia (Correct Answer)

Explanation: **Explanation:** Supraglottic Airway Devices (SADs), such as the Laryngeal Mask Airway (LMA), are designed to sit above the glottis to maintain a patent airway. **1. Why "Patient under general anesthesia" is correct:** General anesthesia is the primary **indication** for using a SAD, not a contraindication. SADs are frequently used for elective surgical procedures under general anesthesia where tracheal intubation is not mandatory. They provide a less invasive alternative to endotracheal tubes, reducing hemodynamic stress and postoperative sore throat. **2. Why the other options are Contraindications:** * **Risk of Aspiration (Option A):** SADs do not provide a definitive seal for the trachea. In patients with a full stomach, hiatal hernia, or morbid obesity, they cannot prevent the aspiration of gastric contents. * **Poor Lung Compliance (Option B):** SADs are "low-pressure" seals. In patients with stiff lungs (e.g., ARDS, restrictive lung disease), high peak inspiratory pressures are required for ventilation. These pressures often exceed the seal pressure of the SAD, leading to significant air leaks and gastric insufflation. * **Limited Mouth Opening (Option C):** Insertion of a SAD requires adequate space to maneuver the device into the oropharynx. A patient with severe trismus or limited mouth opening (e.g., <2 cm) presents a physical barrier to successful placement. **Clinical Pearls for NEET-PG:** * **Gold Standard for Airway:** The Endotracheal Tube (ETT) remains the gold standard for protecting against aspiration. * **Difficult Airway Algorithm:** SADs (specifically the ILMA or Fastrach) play a crucial role as "rescue devices" in "cannot intubate, can ventilate" scenarios. * **Nerve Injury:** Excessive cuff inflation in an LMA can lead to pressure-induced injury of the **lingual, hypoglossal, or recurrent laryngeal nerves.**

Question 110: What complication is NOT seen with controlled ventilation?

A. Barotrauma
B. Alkalosis
C. Pulmonary embolism
D. Cardiac tamponade (Correct Answer)

Explanation: **Explanation:** Controlled ventilation involves the application of **Positive Pressure Ventilation (PPV)**, which significantly alters intrathoracic dynamics. **Why Cardiac Tamponade is the correct answer:** Cardiac tamponade is a clinical syndrome caused by the accumulation of fluid, pus, or blood in the pericardial space, leading to external compression of the heart. It is a **structural/mechanical pathology** of the pericardium and is not caused by the physiological effects of a ventilator. While PPV can mimic some hemodynamic signs of tamponade (like decreased venous return), it does not cause the condition itself. **Analysis of Incorrect Options:** * **Barotrauma:** High airway pressures during controlled ventilation can rupture alveoli, leading to pneumothorax, pneumomediastinum, or subcutaneous emphysema. * **Alkalosis:** Excessive minute ventilation (hyperventilation) during controlled breathing leads to the "blowing off" of $CO_2$. This results in **Respiratory Alkalosis**, which can shift the oxyhemoglobin dissociation curve to the left. * **Pulmonary Embolism:** While not a direct mechanical result of the breath itself, prolonged controlled ventilation (often associated with immobilization and sedation in ICU settings) significantly increases the risk of **Deep Vein Thrombosis (DVT)** and subsequent pulmonary embolism due to venous stasis. **High-Yield Clinical Pearls for NEET-PG:** * **Hemodynamic Effect:** PPV increases intrathoracic pressure, which decreases venous return (preload), leading to a potential **drop in Cardiac Output**. * **Reverse Pulsus Paradoxus:** In mechanically ventilated patients, systolic blood pressure *rises* during inspiration (the opposite of spontaneous breathing). * **VAP:** Ventilator-Associated Pneumonia is a critical infectious complication to remember for exams.

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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