ICU · Respiratory / ventilation

Acute Severe Ventilation Weaning and Liberation from Mechanical Ventilation — Comprehensive ICU Management

Also known as Ventilator weaning · Liberation from mechanical ventilation · Spontaneous breathing trial · SBT · ABC trial · Wake up and breathe · Rapid shallow breathing index · Cuff leak test · Post-extubation stridor · ICU-acquired weakness · Weaning-induced pulmonary oedema · Difficult weaning · Protocol-directed weaning

Weaning (liberation) from mechanical ventilation is the graded withdrawal of ventilatory support once the precipitating cause of respiratory failure has resolved. Readiness is assessed daily against objective criteria — resolution of the cause, FiO2 <0.4, PEEP <8 cmH2O, haemodynamic stability, adequate cough and gag, manageable secretions, and an awake, triggering patient — followed by a spontaneous breathing trial (SBT) delivered as pressure support 5-7 cmH2O with PEEP 5, or a T-piece, for 30-120 minutes. The patient passes if respiratory rate is <35, SpO2 >90 per cent, heart rate <140, with no agitation, diaphoresis, or distress. The ABC trial (Girard, Lancet 2008) proved that pairing a daily spontaneous awakening trial (SAT, daily sedation interruption) with a daily SBT — the 'wake up and breathe' protocol — shortens ventilation time and ICU stay and saves one life for every seven patients treated. Protocol-directed (nurse or respiratory-therapist driven) weaning outperforms physician-directed weaning. Weaning is classified as simple, difficult (more than three SBT attempts or more than seven days), or prolonged (more than fourteen days); difficult and prolonged weaning demands a systematic hunt for the cause — cardiac (weaning-induced pulmonary oedema from left ventricular dysfunction unmasked by the switch to negative-pressure breathing), respiratory-muscle weakness (ICU-acquired weakness), residual respiratory load (auto-PEEP, secretions), electrolyte derangement, or delirium and agitation. The cuff leak test (leak under 130 mL or under 12 per cent of tidal volume) identifies patients at high risk of post-extubation stridor, who benefit from prophylactic steroids, who benefit from prophylactic steroids. Prophylactic non-invasive ventilation (NIV) immediately after extubation prevents reintubation in high-risk patients (COPD, hypercapnia, cardiac failure); NIV used as rescue after established extubation failure is harmful. Tracheostomy facilitates prolonged weaning, but the TracMan trial (Young, JAMA 2013) showed no mortality benefit to early (day 4) over late (day 10) placement.