Weaning failure due to cardiac dysfunction — FFICM MCQ

Correct answer: C — Weaning-induced pulmonary oedema

The correct answer is C, weaning-induced pulmonary oedema. The abrupt onset of tachypnoea, hypertension, diaphoresis, worsening oxygenation and new B-lines with poor left ventricular contraction within minutes of switching to spontaneous ventilation is the classic pattern of cardiogenic decompensation triggered by the transition from positive to negative intrathoracic pressure. During a spontaneous breathing trial, loss of positive pressure support increases venous return (preload) and simultaneously raises left ventricular transmural pressure (afterload), unmasking latent left ventricular dysfunction and precipitating acute pulmonary oedema. This mechanism explains the rapid B-line development and echocardiographic findings far better than an infective or mechanical cause, and the slightly rising PaCO2 with falling PaO2 reflects acute ventilation-perfusion mismatch from oedema rather than airway pathology. Why the other options are wrong: A. Ventilator-associated pneumonia: this develops over hours to days with fever, purulent secretions and new infiltrates on imaging, none of which are present here (secretions minimal, temperature normal), and it would not cause an acutely failing left ventricle on ultrasound. B. Critical illness myopathy: causes generalised weakness and failure to generate adequate tidal volumes or cough, not hypertension, diaphoresis or acute echocardiographic LV dysfunction. E. Tracheal tube obstruction: would cause rising airway pressures, difficulty ventilating and often desaturation with hypercapnia from mechanical obstruction, but would not produce new B-lines or a poorly contracting ventricle on ultrasound. D. Pulmonary embolism: typically causes acute right ventricular strain and dilation rather than left ventricular failure, and would not characteristically produce diffuse B-lines from fluid extravasation. Key point: rapid tachypnoea, hypertension and new B-lines with LV dysfunction occurring within minutes of starting a spontaneous breathing trial points to weaning-induced (cardiogenic) pulmonary oedema from the abrupt rise in LV afterload and preload.

Reference: Dres M, Teboul JL, Anguel N, et al. Diaphragm dysfunction, lung aeration loss and weaning-induced pulmonary oedema in difficult-to-wean patients. Annals of Intensive Care 2021. https://annalsofintensivecare.springeropen.com/articles/10.1186/s13613-021-00886-6