ARDS with high driving pressure — FFICM MCQ

Correct answer: C — Reduce tidal volume and reassess plateau pressure

The correct answer is C, reduce tidal volume and reassess plateau pressure. This patient already has a plateau pressure of 31 cmH2O and driving pressure of 23 cmH2O, both above the thresholds associated with ventilator-induced lung injury; FICM/ICS ARDS guidance recommends low tidal volume ventilation (less than or equal to 6 ml/kg predicted body weight) with plateau pressure kept below 30 cmH2O. Falling static compliance with rising driving pressure signals worsening lung stress from the current tidal volume, so the immediate step is to trim tidal volume further (accepting permissive hypercapnia if needed) and recheck plateau pressure, before considering other interventions such as recruitment, proning or PEEP titration. This directly targets the volutrauma and barotrauma driving lung injury rather than simply optimising oxygenation numbers. Why the other options are wrong: A Increase respiratory rate and maintain tidal volume: this does not address the excessive plateau and driving pressures, and raising rate without shortening inspiratory time risks worsening dynamic hyperinflation and auto-PEEP. B Increase PEEP to 18 cmH2O immediately: a large abrupt PEEP rise without assessing recruitability will further raise plateau pressure and driving pressure, compounding barotrauma in a lung that is already poorly compliant. C Commence inhaled nitric oxide: this may transiently improve oxygenation via selective pulmonary vasodilation but has no mortality benefit and does not correct the injurious airway pressures, so it is not the priority when plateau pressure is already too high. D Convert to pressure support ventilation: a spontaneous mode is inappropriate in severe hypoxaemic respiratory failure with high driving pressure, as loss of controlled tidal volume and plateau pressure monitoring risks patient self-inflicted lung injury. Key point: when plateau and driving pressures are elevated in ARDS, the first action is to reduce tidal volume and reassess plateau pressure before adjusting PEEP or considering adjuncts.

Reference: Intensive Care Society / FICM ARDS Guideline (2018, GRADE methodology, BTS-endorsed): low tidal volume (<6 ml/kg PBW) and plateau pressure <30 cmH2O recommended. https://ics.ac.uk/resource/ards-guideline.html