Respiratory and Airway Management Practice Questions

Q: Dead space is increased by all except?

Endotracheal intubation. ### Explanation The correct answer is **D. Endotracheal intubation**. **1. Why Endotracheal Intubation is the Correct Answer:** Dead space refers to the volume of inspired air that does not participate in gas exchange. In a healthy adult, the **Anatomical Dead Space** (volume of the conducting airways) is approximately 150 ml (2 ml/kg). Endotracheal intubation involves placing a tube directly into the trachea, effectively bypassing the upper airway (nose, pharynx, and larynx). Since the volume of the endotracheal tube is significantly less than the volume of the upper airway it replaces, **endotracheal intubation decreases anatomical dead space** by approximately 30-50%. **2. Analysis of Incorrect Options:** * **Anticholinergic drugs (e.g., Atropine, Glycopyrrolate):** These drugs cause bronchodilation. By increasing the caliber of the conducting airways, they increase the volume of the anatomical dead space. * **Standing:** In the upright position, gravity leads to increased perfusion at the lung bases and decreased perfusion at the apices. This creates areas of high ventilation-perfusion (V/Q) ratio at the apices, thereby increasing **Physiological Dead Space**. * **Hyperextension of the neck:** This physical maneuver stretches and widens the upper airway structures, leading to a measurable increase in anatomical dead space. **3. Clinical Pearls for NEET-PG:** * **Formula:** Physiological Dead Space = Anatomical Dead Space + Alveolar Dead Space. * **Bohr’s Equation:** Used to measure physiological dead space ($Vd/Vt = (PaCO_2 - PeCO_2) / PaCO_2$). * **Factors decreasing dead space:** Endotracheal intubation, tracheostomy, and the supine position. * **Factors increasing dead space:** Age (due to loss of elastic recoil), PE (Pulmonary Embolism), emphysema, and positive pressure ventilation (PPV).

Q: What is the recommended ratio of chest compressions to rescue breaths for a lone rescuer performing CPR on a patient of any age?

30:2. **Explanation:** The correct answer is **30:2**. According to the American Heart Association (AHA) and International Liaison Committee on Resuscitation (ILCOR) guidelines, a compression-to-ventilation ratio of **30:2** is recommended for **lone rescuers** across all age groups (adults, children, and infants, excluding neonates). This ratio optimizes coronary perfusion pressure by minimizing interruptions in chest compressions while providing adequate oxygenation. **Analysis of Options:** * **Option A (30:2):** Correct. This is the universal ratio for single-rescuer CPR to ensure high-quality compressions and reduce the "no-flow" time. * **Option B (15:2):** This ratio is used for **two-rescuer CPR in children and infants** (to account for their higher respiratory requirements) but is not used for lone rescuers or adults. * **Option C (3:1):** This is the specific ratio used in **Neonatal Resuscitation** (90 compressions and 30 breaths per minute) because respiratory failure is the primary cause of neonatal arrest. * **Option D (30:1):** This is not a standard recommended ratio in any current basic or advanced life support guidelines. **Clinical Pearls for NEET-PG:** * **Compression Depth:** 2–2.4 inches (5–6 cm) in adults; at least 1/3rd the AP diameter of the chest in pediatrics. * **Compression Rate:** 100–120 compressions per minute. * **Hand Placement:** Lower half of the sternum. * **Advanced Airway:** Once an endotracheal tube or supraglottic airway is in place, compressions are continuous (100–120/min) with asynchronous breaths every 6 seconds (10 breaths/min). * **Chest Recoil:** Allow complete chest recoil to ensure adequate venous return and cardiac filling.

Q: Which of the following conditions requires a higher Positive End-Expiratory Pressure (PEEP) for recruiting collapsed alveoli?

Acute Respiratory Distress Syndrome. **Explanation:** **Acute Respiratory Distress Syndrome (ARDS)** is the correct answer because it is characterized by **diffuse alveolar collapse (atelectasis)**, decreased lung compliance, and intrapulmonary shunting. In ARDS, the primary pathology involves inflammatory exudates and loss of surfactant, leading to "sticky" alveoli that collapse at the end of expiration. **Positive End-Expiratory Pressure (PEEP)** is the cornerstone of management as it provides constant pressure to keep these alveoli open (recruitment), increases the Functional Residual Capacity (FRC), and improves oxygenation by reducing the shunt. **Why the other options are incorrect:** * **Asthma and Emphysema (COPD):** These are obstructive airway diseases characterized by **air trapping** and "Auto-PEEP." Adding high external PEEP can worsen dynamic hyperinflation, increase intrathoracic pressure, and lead to barotrauma or hemodynamic instability. * **Bronchiectasis:** This involves permanent dilation of the bronchi and chronic infection. While it may require bronchial hygiene and oxygen, it is not a primary "restrictive/collapsible" alveolar pathology requiring high PEEP for recruitment. **High-Yield Clinical Pearls for NEET-PG:** * **ARDS Ventilation Strategy:** Use **Low Tidal Volume (6 mL/kg)** and **High PEEP** (Open Lung Approach) to prevent Ventilator-Induced Lung Injury (VILI). * **Goal of PEEP:** To shift the pressure-volume curve above the **Lower Inflection Point** to prevent cyclic alveolar collapse and re-opening (atelectrauma). * **Side Effects of High PEEP:** Decreased venous return (reduced cardiac output) and risk of pneumothorax.

Q: Laryngeal spasm induced during intubation can be prevented by the following drugs except?

Rofecoxib. **Explanation:** Laryngospasm is a protective but potentially life-threatening reflex closure of the vocal cords mediated by the superior laryngeal nerve (afferent) and recurrent laryngeal nerve (efferent). It is typically triggered by sensory stimulation of the upper airway during light planes of anesthesia. **Why Rofecoxib is the correct answer:** Rofecoxib is a selective **COX-2 inhibitor (NSAID)** used primarily for analgesia and reducing inflammation. It has no immediate effect on airway reflexes, neuromuscular transmission, or the autonomic nervous system. Therefore, it cannot acutely prevent or treat a laryngospasm during the induction of anesthesia. **Analysis of other options:** * **Fentanyl:** As an opioid, it provides potent analgesia and suppresses airway reflexes, making the patient more tolerant of the endotracheal tube and reducing the risk of spasm. * **Local anesthetic spray (e.g., Lidocaine):** Topical application desensitizes the laryngeal mucosa, blocking the afferent limb of the reflex arc. Intravenous lidocaine (1–1.5 mg/kg) is also a standard pharmacological intervention to prevent/treat laryngospasm. * **Diltiazem:** Calcium channel blockers (CCBs) like Diltiazem can attenuate the pressor response to intubation and have a mild inhibitory effect on smooth muscle and reflex-mediated airway constriction. While not a primary treatment, they contribute to blunting the sympathetic and reflex responses during airway manipulation. **High-Yield Clinical Pearls for NEET-PG:** * **Management of Laryngospasm:** The first step is removing the stimulus and providing 100% Oxygen with continuous positive airway pressure (CPAP). * **Drug of Choice:** **Succinylcholine** (0.25–0.5 mg/kg IV) is the gold standard for breaking a severe laryngospasm that does not respond to manual maneuvers. * **Larson’s Maneuver:** Application of firm pressure at the "laryngospasm notch" (behind the earlobe) can help break the spasm.

Q: All are true about pressure control ventilation except-

There is an accelerating flow rate. In **Pressure Control Ventilation (PCV)**, the ventilator delivers a breath until a preset pressure limit is reached and maintains that pressure for a set inspiratory time. ### Why Option B is the Correct Answer (The "Except") In PCV, the flow pattern is **decelerating**, not accelerating. At the start of inspiration, the pressure gradient between the ventilator and the lungs is highest, resulting in a high initial flow. As the lungs fill and alveolar pressure approaches the set limit, the flow rate **decreases (decelerates)** to maintain the constant pressure. An accelerating flow is not a standard feature of conventional mechanical ventilation modes. ### Explanation of Incorrect Options * **A. The desired inflation pressure is preselected:** This is the defining feature of PCV. The clinician sets the Peak Inspiratory Pressure (PIP). * **C. Tidal volume can be variable:** Since pressure is fixed, the delivered Tidal Volume ($V_t$) depends on the patient's **lung compliance** and **airway resistance**. If compliance decreases (e.g., ARDS), the $V_t$ will drop. * **D. Alveolar pressure is fixed:** In PCV, the pressure waveform is "square" or "constant." The ventilator ensures that the pressure remains at the set level throughout the inspiratory phase, effectively capping the alveolar pressure and reducing the risk of barotrauma. ### High-Yield Clinical Pearls for NEET-PG * **Flow Waveforms:** PCV uses a **decelerating (ramp)** flow, while Volume Control Ventilation (VCV) typically uses a **constant (square)** flow. * **Safety:** PCV is preferred in patients with low lung compliance (e.g., ARDS) to prevent barotrauma, as it limits peak airway pressure. * **Main Disadvantage:** The primary risk in PCV is **hypoventilation** if lung compliance worsens or the patient bites the tube, as the $V_t$ is not guaranteed.

Q: What is the most important determinant of carbon dioxide elimination?

Fresh gas flow. ### Explanation The elimination of carbon dioxide ($CO_2$) in an anesthesia breathing circuit depends primarily on the **Fresh Gas Flow (FGF)** and the efficiency of the $CO_2$ absorber. In the context of Mapleson breathing systems (semi-open circuits), FGF is the single most important determinant for preventing rebreathing and ensuring $CO_2$ elimination. **Why Fresh Gas Flow is Correct:** In Mapleson circuits, the FGF "washes out" the exhaled gases (rich in $CO_2$) from the circuit before the next inspiration. If the FGF is inadequate, the patient rebreathes exhaled $CO_2$, leading to hypercapnia. For example, in a Mapleson A circuit during spontaneous respiration, the FGF must equal the minute ventilation to prevent rebreathing. **Analysis of Incorrect Options:** * **Minute Ventilation (MV):** While MV (Tidal Volume × Respiratory Rate) determines $CO_2$ removal from the *alveoli* to the circuit, it does not guarantee elimination from the *breathing system*. Without adequate FGF, increasing MV will simply cause the patient to rebreathe more $CO_2$. * **Expiratory Reserve Volume (ERV):** This is the maximum volume of air that can be exhaled after a normal tidal expiration. It relates to lung capacity but does not govern the mechanical elimination of $CO_2$ from a circuit. * **Vital Capacity (VC):** This is the maximum amount of air a person can expel from the lungs after a maximum inhalation. It is a measure of pulmonary reserve, not a determinant of gas exchange efficiency during anesthesia. **High-Yield Clinical Pearls for NEET-PG:** * **Mapleson A (Magill):** Most efficient for **Spontaneous** ventilation (FGF = MV). * **Mapleson D (Bain’s):** Most efficient for **Controlled** ventilation. * **Dead Space:** The volume of the circuit between the patient and the Y-piece (or point of FGF intake) where gas exchange does not occur. * **Soda Lime:** Used in circle systems to chemically eliminate $CO_2$, allowing for lower FGF.

Q: Which of the following is NOT an advantage of using a laryngeal mask airway?

Prevents aspiration. **Explanation:** The **Laryngeal Mask Airway (LMA)** is a supraglottic airway device that sits above the glottis. The correct answer is **B (Prevents aspiration)** because the LMA does not form a definitive, fluid-tight seal with the trachea. Unlike an endotracheal tube (ETT), which has a cuff below the vocal cords to protect the lungs from gastric contents, the LMA is a "low-pressure" seal. Therefore, it is **contraindicated in patients at high risk for aspiration** (e.g., full stomach, obesity, or hiatus hernia). **Analysis of Incorrect Options:** * **A. Easy to insert:** This is a major advantage. LMA insertion is less technically demanding than endotracheal intubation and has a high first-attempt success rate, even for non-anesthesiologists. * **C. Does not require muscle relaxant:** Unlike ETT, which often requires neuromuscular blockade for laryngoscopy and tube placement, an LMA can be inserted under deep sedation or volatile anesthesia alone. * **D. Can be used with cervical injuries:** Since LMA insertion does not require "sniffing position" or neck extension (unlike direct laryngoscopy), it is an excellent choice for managing the airway in patients with suspected or confirmed cervical spine instability. **High-Yield Pearls for NEET-PG:** * **Gold Standard for Aspiration Protection:** Endotracheal Intubation (Cuffed). * **LMA Pro-Seal:** A modified LMA with a gastric drain tube that offers *better* (but not absolute) protection against aspiration compared to the LMA Classic. * **Difficult Airway Algorithm:** The LMA is a key "rescue device" when one "cannot ventilate, cannot intubate." * **Pressure Limit:** Avoid peak airway pressures >20 cm H₂O with a standard LMA to prevent gastric insufflation.

Question 1

Dead space is increased by all except?

Accepted Answer

Endotracheal intubation

Answer

Anticholinergic drugs

Answer

Standing

Answer

Hyperextension of the neck

Question 2

Which of the following is a pure control mode of ventilation?

Accepted Answer

Pressure control ventilation

Answer

Pressure support ventilation

Answer

Synchronized intermittent mandatory ventilation

Answer

Continuous positive airway pressure

Question 3

What is the recommended ratio of chest compressions to rescue breaths for a lone rescuer performing CPR on a patient of any age?

Accepted Answer

30:2

Answer

15:2

Answer

3:1

Answer

30:1

Question 4

All of the following are relative contraindications for the use of a nasopharyngeal airway adjunct, except:

Accepted Answer

Ethmoidal fracture.

Answer

Nasoethmoidal fracture.

Answer

Nasal fracture.

Answer

None.

Question 5

Which of the following conditions requires a higher Positive End-Expiratory Pressure (PEEP) for recruiting collapsed alveoli?

Accepted Answer

Acute Respiratory Distress Syndrome

Answer

Asthma

Answer

Bronchiectasis

Answer

Emphysema

Question 6

Arterial blood gas (ABG) sampling can be performed from all of the following arteries EXCEPT:

Accepted Answer

Dorsalis pedis artery

Answer

Radial artery

Answer

Ulnar artery

Answer

Femoral artery

Question 7

Laryngeal spasm induced during intubation can be prevented by the following drugs except?

Accepted Answer

Rofecoxib

Answer

Fentanyl

Answer

Local anesthetic spray

Answer

Diltiazem

Question 8

All are true about pressure control ventilation except-

Accepted Answer

There is an accelerating flow rate

Answer

The desired inflation pressure is preselected

Answer

Tidal volume can be variable

Answer

Alveolar pressure is fixed

Question 9

What is the most important determinant of carbon dioxide elimination?

Accepted Answer

Fresh gas flow

Answer

Minute ventilation

Answer

Expiratory reserve volume

Answer

Vital capacity

Question 10

Which of the following is NOT an advantage of using a laryngeal mask airway?

Accepted Answer

Prevents aspiration

Answer

Easy to insert

Answer

Does not require muscle relaxant

Answer

Can be used with cervical injuries

Respiratory and Airway Management — MCQs

Respiratory and Airway Management — MCQs

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