Respiratory and Airway Management Practice Questions

Q: What is the most important measure to avoid subglottic edema in children?

Use of appropriate size endotracheal tube. **Explanation:** The pediatric airway is anatomically unique, characterized by a funnel shape where the **cricoid cartilage** is the narrowest point. Subglottic edema in children is primarily caused by mechanical trauma and pressure-induced ischemia to the delicate subglottic mucosa. **Why Option A is correct:** Using an **appropriate size endotracheal tube (ETT)** is the most critical preventive measure. A tube that is too large exerts continuous pressure on the circumferential cricoid ring. If this pressure exceeds the capillary perfusion pressure of the mucosa (approx. 25–30 cm H₂O), it leads to edema, inflammation, and potentially subglottic stenosis. A "leak" should ideally be present at 15–20 cm H₂O inspiratory pressure to ensure the tube is not too tight. **Why other options are incorrect:** * **Option B:** While lubrication may reduce friction during insertion, it does not prevent the constant pressure necrosis caused by an oversized tube. * **Option C:** IV lidocaine is used to blunt the sympathetic response to intubation (hemodynamic stability) but has no role in preventing mechanical mucosal edema. * **Option D:** Routine IV steroids are **not** recommended for all intubations. They are reserved for high-risk cases (e.g., traumatic intubation, prolonged surgery, or known small airways) and do not substitute for proper tube sizing. **High-Yield NEET-PG Pearls:** 1. **Narrowest part of airway:** Cricoid cartilage (in children < 8 years); Glottis (in adults). 2. **Formula for Uncuffed ETT size:** (Age/4) + 4. 3. **Formula for Cuffed ETT size:** (Age/4) + 3.5. 4. **Poiseuille’s Law:** In children, even 1mm of edema reduces the cross-sectional area of the subglottic space by 75%, significantly increasing airway resistance.

Q: What are the merits of nasotracheal intubation?

Good oral hygiene. **Explanation:** Nasotracheal intubation involves passing an endotracheal tube through the nose into the trachea. This route is specifically chosen in clinical scenarios where oral access is restricted or long-term ventilation is anticipated. **Why Option A is Correct:** The primary merit of nasotracheal intubation is that it leaves the **oral cavity free**. This allows for **superior oral hygiene**, easier suctioning of secretions, and prevents the patient from biting the tube (which can happen with orotracheal tubes). It is also better tolerated in conscious patients and provides better stabilization, making it ideal for prolonged mechanical ventilation or maxillofacial surgeries. **Why Other Options are Incorrect:** * **B. Less infection:** Nasotracheal intubation is actually associated with a **higher risk of infection**, specifically **maxillary sinusitis**, due to the obstruction of the ostiomeatal complex by the tube. * **C. Less mucosal damage and bleeding:** This is incorrect. Nasal intubation carries a significant risk of **epistaxis** (bleeding) and trauma to the nasal turbinates or the posterior pharyngeal wall (adenoid trauma). * **D. More movement or displacement:** Nasotracheal tubes are generally **more stable** and less prone to accidental displacement compared to oral tubes because they are "wedged" within the nasal anatomy. **Clinical Pearls for NEET-PG:** * **Contraindications:** Avoid in patients with suspected **base of skull fractures** (risk of intracranial entry), coagulopathy, or nasal polyps. * **Preparation:** Use of vasoconstrictors (e.g., Xylometazoline) and lubricating jelly is essential to minimize bleeding. * **Tube Size:** Nasal tubes are typically **0.5 to 1.0 mm smaller** in internal diameter than oral tubes to accommodate the narrow nasal passage.

Q: Positive End Expiratory Pressure (PEEP) is useful in which of the following conditions?

All of the above. **Explanation:** Positive End-Expiratory Pressure (PEEP) is a pressure applied at the end of expiration to prevent the alveolar pressure from falling to zero. The primary physiological goal of PEEP is to **increase Functional Residual Capacity (FRC)** and prevent alveolar collapse (atelectasis), thereby improving ventilation-perfusion (V/Q) matching and oxygenation. **Why "All of the above" is correct:** * **ARDS (Option B):** This is the classic indication for PEEP. In ARDS, inflammatory exudates cause widespread alveolar collapse and shunting. PEEP "recruits" these collapsed alveoli, increasing the surface area for gas exchange and allowing for a reduction in the fraction of inspired oxygen (FiO2) to prevent oxygen toxicity. * **Pulmonary Edema (Option C):** PEEP increases intrathoracic pressure, which reduces venous return (preload) and afterload, helping a failing heart. It also shifts fluid from the alveoli back into the interstitial space, clearing the gas exchange surface. * **Pneumonia (Option A):** In severe pneumonia, localized alveolar collapse and inflammatory debris lead to hypoxemia. PEEP helps maintain patency of the airways surrounding the consolidated areas, improving oxygenation. **Clinical Pearls for NEET-PG:** * **Physiological Effects:** PEEP improves lung compliance but can decrease cardiac output due to reduced venous return. * **Complications:** High levels of PEEP can lead to **barotrauma** (pneumothorax) and increased intracranial pressure (ICP). * **Contraindication:** Absolute contraindication is an untreated tension pneumothorax. * **Auto-PEEP:** Also known as intrinsic PEEP, seen in obstructive diseases like COPD/Asthma where air trapping occurs.

Q: The Reynolds number is related to which of the following?

Laminar flow. **Explanation:** The **Reynolds number (Re)** is a dimensionless value used in fluid dynamics to predict the flow pattern of a gas or liquid. It determines the transition from **laminar flow** to **turbulent flow**. 1. **Why Option A is correct:** Laminar flow occurs when the Reynolds number is **low (< 2,000)**. In this state, gas molecules move in parallel layers, with the highest velocity in the center of the tube. When Re exceeds **4,000**, the flow becomes turbulent. The formula is $Re = (v \cdot d \cdot \rho) / \eta$ (where $v$=velocity, $d$=diameter, $\rho$=density, and $\eta$=viscosity). Crucially, laminar flow depends on **viscosity**, while turbulent flow depends on **density**. 2. **Why other options are incorrect:** * **B. Ventimask:** This device operates on the **Bernoulli principle** and the **Venturi effect**, where a pressurized gas stream creates a negative pressure that entrains room air. * **C. Dissolved oxygen in blood:** This is governed by **Henry’s Law**, which states that the amount of dissolved gas is proportional to its partial pressure. * **D. Intra-alveolar tension:** This is related to the **Law of Laplace** ($P = 2T/r$), which explains how surface tension and alveolar radius affect pressure. **High-Yield Clinical Pearls for NEET-PG:** * **Heliox Therapy:** In upper airway obstructions (turbulent flow), we use Heliox because Helium has a lower **density** than Nitrogen, which reduces the Reynolds number and converts turbulent flow back to laminar flow, decreasing the work of breathing. * **Laminar flow** is typically found in the **smaller, peripheral airways** (terminal bronchioles) where velocity is low. * **Turbulent flow** occurs in the **large airways** (trachea) and at branch points.

Question 1

What is the best method for airway maintenance in a patient experiencing cardiopulmonary arrest?

Accepted Answer

Orotracheal intubation

Answer

Bag-valve-mask ventilation

Answer

Nasotracheal intubation

Answer

Guedel airway

Question 2

Which method is best for confirming the correct placement of a double lumen tube?

Accepted Answer

Fibreoptic bronchoscopy

Answer

Clinical confirmation by auscultation

Answer

Capnography

Answer

Chest radiography

Question 3

What is the most important measure to avoid subglottic edema in children?

Accepted Answer

Use of appropriate size endotracheal tube

Answer

Lubricating endotracheal tube prior to intubation

Answer

Administer IV lidocaine for all intubations

Answer

Administer IV steroids for all intubations

Question 4

What is the Bailey maneuver in patients at high risk of laryngospasm?

Accepted Answer

The deflated LMA is placed behind the in situ ETT. The ETT is removed, and the LMA is inflated.

Answer

Laryngeal mask airway (LMA) is inserted just before reversal of anesthesia after removing the endotracheal tube (ETT).

Answer

During intubation and extubation, LMA is used, and during the intraoperative period, ETT is used.

Answer

None of the above.

Question 5

A 43-year-old trauma patient develops acute respiratory distress syndrome (ARDS) and has difficulty oxygenating despite increased concentrations of inspired O2. After the positive end-expiratory pressure (PEEP) is increased, the patient's oxygenation improves. What is the mechanism by which this occurs?

Accepted Answer

Increasing functional residual capacity

Answer

Decreasing dead-space ventilation

Answer

Decreasing the minute ventilation requirement

Answer

Increasing tidal volume

Question 6

What is the correct sequence of Cardiopulmonary Resuscitation (CPR)?

Accepted Answer

Basic CPR, Defibrillation, Advanced Cardiovascular Life Support (ACLS)

Answer

Basic CPR, Advanced Cardiovascular Life Support (ACLS), Defibrillation

Answer

Advanced Cardiovascular Life Support (ACLS), Basic CPR, Defibrillation

Answer

Defibrillation, Advanced Cardiovascular Life Support (ACLS), Basic CPR

Question 7

What are the merits of nasotracheal intubation?

Accepted Answer

Good oral hygiene

Answer

Less infection

Answer

Less mucosal damage and bleeding

Answer

More movement or displacement of endotracheal tube

Question 8

Positive End Expiratory Pressure (PEEP) is useful in which of the following conditions?

Accepted Answer

All of the above

Answer

Pneumonia

Answer

Acute Respiratory Distress Syndrome (ARDS)

Answer

Pulmonary edema

Question 9

The Reynolds number is related to which of the following?

Accepted Answer

Laminar flow

Answer

Ventimask

Answer

Dissolved oxygen in blood

Answer

Intra-alveolar tension

Question 10

A patient presents with SpO2 69%, BP 100/60 mm Hg, and HR 120 beats per minute. What should be the first step in the management of this patient?

Accepted Answer

Secure airway and O2 supplementation

Answer

Start bolus IV fluid infusion

Answer

Injection bicarbonate

Answer

Injection Epinephrine IV

Respiratory and Airway Management — MCQs

Respiratory and Airway Management — MCQs

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