CCRN Acute Respiratory Failure 3 — Questions and Answers
Question 1: By the Berlin definition, ARDS is characterized by bilateral infiltrates and a PaO2/FiO2 ratio of:
- ≤ 300 mmHg with PEEP ≥ 5 (Correct answer)
- > 400 mmHg
- ≤ 500 mmHg without PEEP
- Any ratio with unilateral infiltrates
Correct answer: ≤ 300 mmHg with PEEP ≥ 5
ARDS requires a P/F ratio ≤ 300 with at least 5 cm H2O of PEEP or CPAP.
Question 2: The Berlin criteria require that ARDS-related respiratory failure is NOT fully explained by:
- Cardiac failure or fluid overload (Correct answer)
- Pneumonia
- Sepsis
- Aspiration
Correct answer: Cardiac failure or fluid overload
Hydrostatic edema from cardiac failure or volume overload must be excluded as the primary cause.
Question 3: Which lung-protective tidal volume target is recommended for a patient with ARDS?
- 6 mL/kg of predicted body weight (Correct answer)
- 12 mL/kg of actual body weight
- 15 mL/kg of predicted body weight
- 3 mL/kg of predicted body weight
Correct answer: 6 mL/kg of predicted body weight
Low tidal volume ventilation at 6 mL/kg predicted body weight reduces ventilator-induced lung injury.
Question 4: In ARDS lung-protective ventilation, plateau pressure should generally be kept below:
- 30 cm H2O (Correct answer)
- 50 cm H2O
- 60 cm H2O
- 15 cm H2O
Correct answer: 30 cm H2O
Keeping plateau pressure < 30 cm H2O limits alveolar overdistension and barotrauma.
Question 5: Which positioning intervention improves oxygenation and mortality in moderate-to-severe ARDS?
- Prone positioning (Correct answer)
- Continuous left lateral positioning
- Reverse Trendelenburg only
- Flat supine for 24 hours
Correct answer: Prone positioning
Prone positioning improves V/Q matching and recruits dorsal lung regions, reducing mortality in severe ARDS.
Question 6: Permissive hypercapnia during ARDS ventilation is acceptable as long as:
- pH remains within a tolerable range (generally > 7.20) (Correct answer)
- PaCO2 stays below 40
- Tidal volume is increased to normalize CO2
- The patient is fully awake
Correct answer: pH remains within a tolerable range (generally > 7.20)
Allowing CO2 to rise is tolerated to protect the lungs, provided pH stays in an acceptable range.
Question 7: What is the primary pathophysiologic hallmark of the exudative phase of ARDS?
- Increased alveolar-capillary membrane permeability with protein-rich edema (Correct answer)
- Pure cardiogenic pulmonary edema
- Bronchospasm and air trapping
- Pleural effusion accumulation
Correct answer: Increased alveolar-capillary membrane permeability with protein-rich edema
Diffuse alveolar damage increases capillary permeability, flooding alveoli with protein-rich fluid.
CCRN Acute Respiratory Failure 3
By the Berlin definition, ARDS is characterized by bilateral infiltrates and a PaO2/FiO2 ratio of: