NBRC Mechanical Ventilation 2 — Questions and Answers
Question 1: The lung-protective ventilation strategy for ARDS recommends tidal volumes of:
- 3–4 mL/kg ideal body weight
- 6 mL/kg ideal body weight (Correct answer)
- 10–12 mL/kg ideal body weight
- 15 mL/kg ideal body weight
Correct answer: 6 mL/kg ideal body weight
The ARDSNet protocol demonstrated improved survival with tidal volumes of 6 mL/kg IBW compared to conventional 12 mL/kg volumes.
Question 2: Which waveform is characteristic of volume-controlled, constant-flow ventilation?
- Decelerating flow waveform
- Sinusoidal flow waveform
- Square (constant) flow waveform (Correct answer)
- Ascending ramp flow waveform
Correct answer: Square (constant) flow waveform
Volume control with constant flow produces a square (rectangular) flow waveform, resulting in a linearly increasing pressure waveform.
Question 3: A patient's peak airway pressure suddenly increases with no change in plateau pressure. This suggests:
- Worsening lung compliance
- Increased airway resistance (e.g., bronchospasm, secretions) (Correct answer)
- Pneumothorax
- Pulmonary edema
Correct answer: Increased airway resistance (e.g., bronchospasm, secretions)
A rise in peak pressure with unchanged plateau pressure indicates increased airway resistance because resistance affects dynamic (peak) but not static (plateau) pressure.
Question 4: Permissive hypercapnia in ARDS management allows PaCO2 to rise to reduce:
- FiO2 requirements
- Barotrauma and volutrauma from aggressive ventilation (Correct answer)
- Sedation requirements
- Cardiac afterload
Correct answer: Barotrauma and volutrauma from aggressive ventilation
Permissive hypercapnia accepts elevated PaCO2 to enable lower tidal volumes and pressures, minimizing ventilator-induced lung injury.
Question 5: Which mode is most appropriate for weaning a patient from mechanical ventilation?
- Assist-control with high PEEP
- Pressure support ventilation (PSV) with gradually reduced support (Correct answer)
- High-frequency oscillatory ventilation
- Controlled mandatory ventilation at a fixed rate
Correct answer: Pressure support ventilation (PSV) with gradually reduced support
PSV weaning allows clinicians to progressively reduce inspiratory support as the patient's spontaneous breathing strength improves, facilitating a smooth transition to extubation.
Question 6: Synchronized intermittent mandatory ventilation (SIMV) delivers mandatory breaths that are:
- Asynchronous with patient effort
- Synchronized to patient inspiratory effort when present (Correct answer)
- Only pressure-controlled
- Independent of set respiratory rate
Correct answer: Synchronized to patient inspiratory effort when present
SIMV attempts to time mandatory breaths to coincide with the patient's own inspiratory effort to reduce patient-ventilator asynchrony.
NBRC Mechanical Ventilation 2
The lung-protective ventilation strategy for ARDS recommends tidal volumes of: