What is the most appropriate method for administering oxygen in patients with airway burns?
Q362
Laryngeal mask airway (LMA) is used for:
Q363
Which of the following parameters is most critical for maintaining optimal oxygenation?
Q364
Which among the following modes of ventilation has the highest risk of a patient developing respiratory alkalosis?
Respiratory and Airway Management Indian Medical PG Practice Questions and MCQs
Question 361: What is the most appropriate method for administering oxygen in patients with airway burns?
A. Elective intubation (Correct Answer)
B. Oxygen mask
C. Nasal cannula
D. Surgical airway management
Explanation: ***Elective intubation***
- **Elective intubation** is the most appropriate method because airway burns can lead to rapid **airway edema** and obstruction, making intubation extremely difficult later.
- Early intubation secures the airway before swelling progresses, preventing a potentially life-threatening emergency.
*Oxygen mask*
- An oxygen mask can provide supplemental oxygen but does not **secure the airway** or prevent potential obstruction from developing airway edema due to the burns.
- This method is insufficient for preventing **airway compromise** in patients with airway burns.
*Nasal cannula*
- A nasal cannula delivers low-flow oxygen but does not offer **airway protection** against swelling or provide adequate respiratory support for patients with compromised airways.
- This method is inadequate for ensuring a patent airway in the face of progressive **airway edema**.
*Surgical airway management*
- A surgical airway (e.g., **cricothyroidotomy** or **tracheostomy**) is a rescue procedure when intubation is impossible due to severe airway obstruction.
- It is a more invasive measure and not the primary method for initial airway management when **elective intubation** is still feasible.
Question 362: Laryngeal mask airway (LMA) is used for:
A. Maintenance of the airway (Correct Answer)
B. Removing oral secretions
C. Facilitating airway access during anesthesia
D. Reducing the risk of aspiration
Explanation: ***Maintenance of the airway***
- The primary function of a **Laryngeal Mask Airway (LMA)** is to establish and maintain an open airway for ventilation.
- It creates a seal around the laryngeal inlet, allowing for **positive pressure ventilation** and oxygen delivery.
*Facilitating airway access during anesthesia*
- While LMAs are used during anesthesia, their direct purpose is **airway maintenance**, not simply "facilitating access." Endotracheal tubes are more typically described as providing "direct access."
- They are a **supraglottic device** that sits above the larynx, rather than passing through it to provide tracheal access.
*Reducing the risk of aspiration*
- LMAs offer **less protection against aspiration** compared to an endotracheal tube because they do not seal the trachea.
- The risk of **gastric content aspiration** is a significant concern when using an LMA, especially in patients with a full stomach.
*Removing oral secretions*
- LMAs are not designed for **secretion removal**; this is typically managed by suction catheters.
- While some mild secretions might be indirectly cleared by the LMA, it is **not its intended function** or a primary benefit.
Question 363: Which of the following parameters is most critical for maintaining optimal oxygenation?
A. FiO2
B. Respiratory rate
C. PEEP (Correct Answer)
D. Tidal volume
Explanation: ***PEEP***
- **Positive End-Expiratory Pressure (PEEP)** is crucial for maintaining optimal oxygenation because it prevents **alveolar collapse** at the end of expiration, thereby increasing the **functional residual capacity** and improving gas exchange.
- By keeping alveoli open, PEEP increases the number of available alveoli for ventilation, preventing **atelectasis** and optimizing the **venous admixture** from non-ventilated lung units.
*FiO2*
- While **Fraction of Inspired Oxygen (FiO2)** is essential for providing sufficient oxygen, simply increasing FiO2 without proper alveolar recruitment and patency (often achieved with PEEP) can be less effective and potentially harmful due to **oxygen toxicity**.
- High FiO2 can improve oxygenation in cases of **hypoxemia**, but it doesn't address underlying problems like **alveolar collapse** or **ventilation-perfusion mismatch** as directly as PEEP does.
*Respiratory rate*
- **Respiratory rate** primarily affects **carbon dioxide elimination** (PaCO2) and, to some extent, alveolar ventilation.
- While an adequate respiratory rate is necessary for overall gas exchange, it is not the most direct or critical parameter for optimizing **oxygenation** compared to PEEP's role in maintaining alveolar patency.
*Tidal volume*
- **Tidal volume** also primarily affects **carbon dioxide elimination** and plays a role in overall minute ventilation.
- Excessive tidal volume can lead to **ventilator-induced lung injury (VILI)**, while insufficient tidal volume can reduce minute ventilation, but it does not directly optimize oxygenation by preventing **alveolar collapse** in the same way PEEP does.
Question 364: Which among the following modes of ventilation has the highest risk of a patient developing respiratory alkalosis?
A. Assist Control Mode (AC) (Correct Answer)
B. Controlled Mandatory Ventilation (CMV)
C. Synchronous Intermittent Mandatory Ventilation (SIMV)
D. Pressure Control Mode (PCM)
Explanation: ***Assist Control Mode (AC)***
- In AC mode, every patient-initiated breath triggers a **full mandatory breath** from the ventilator, delivering a preset tidal volume or pressure.
- If the patient has a high respiratory drive, this can lead to excessive ventilation and a significant decrease in **partial pressure of carbon dioxide (PaCO2)**, causing respiratory alkalosis.
*Controlled Mandatory Ventilation (CMV)*
- In CMV, the ventilator delivers breaths at a **preset rate and tidal volume**, independent of patient effort.
- While it can cause alkalosis if the set rate and volume are too high, it doesn't amplify patient's own respiratory efforts to the same extent as AC mode.
*Synchronous Intermittent Mandatory Ventilation (SIMV)*
- SIMV delivers **mandatory breaths** at a set rate, but also allows the patient to breathe spontaneously between these breaths.
- The patient's spontaneous breaths are *not* assisted by additional ventilator-delivered mandatory breaths, making it less likely to cause hyperventilation compared to AC mode.
*Pressure Control Mode (PCM)*
- In PCM, the ventilator delivers breaths to a **preset pressure target**, which may be either patient-triggered or time-triggered.
- While it offers consistent pressure support, the total minute ventilation is more variable than in AC mode and less likely to consistently lead to excessive minute ventilation unless the pressure settings are extremely high.
