skip to main content

ARDS lung-protective ventilation — ABIM Board MCQ

Instant feedback + full explanation. One question, done properly.

HardPulmonary/Critical CareARDS lung-protective ventilationABIM Board

A 48-year-old man with septic shock due to pneumonia is intubated for acute hypoxemic respiratory failure. Chest radiography shows bilateral diffuse opacities, and echocardiography shows normal left ventricular systolic function. His predicted body weight is 70 kg. He is receiving volume-control ventilation with a tidal volume of 420 mL, respiratory rate of 24/min, FiO2 of 0.80, and PEEP of 12 cm H2O. An inspiratory hold performed while he is passive demonstrates a plateau pressure of 33 cm H2O. Arterial blood gas analysis shows pH 7.25, PCO2 58 mm Hg, and PO2 62 mm Hg. Which ventilator adjustment is most appropriate?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: A — Reduce tidal volume to 5 mL/kg predicted body weight, increase respiratory rate as needed, and target plateau pressure below 30 cm H2O

This patient has severe ARDS (PaO2/FiO2 approximately 78) and an excessive plateau pressure despite an initial tidal volume of 6 mL/kg predicted body weight. Tidal volume should therefore be reduced toward 4–5 mL/kg—350 mL at 5 mL/kg—until plateau pressure is below 30 cm H2O. The respiratory rate can be increased to limit worsening respiratory acidosis; moderate permissive hypercapnia is acceptable. Increasing tidal volume would aggravate ventilator-induced lung injury. Lowering PEEP to 5 cm H2O is inappropriate given severe hypoxemia and the current preference for higher PEEP in moderate-to-severe ARDS. A pH above 7.20 does not justify maintaining an injurious plateau pressure. Routine high-frequency oscillatory ventilation is not recommended and may increase mortality.

Reference: Fan E, et al. An Official ATS/ESICM/SCCM Clinical Practice Guideline: Mechanical Ventilation in Adult Patients with Acute Respiratory Distress Syndrome, low tidal volume and inspiratory-pressure limitation recommendations, 2017. https://pubmed.ncbi.nlm.nih.gov/28459336/