Weaning from respiratory support

Weaning from respiratory support - This is the process of progressively reducing and eventually removing all external ventilatory support and associated apparatus. The majority of patients require mechanical ventilatory support for only a few daysand do not need weaning; simple trials of spontaneous breathing via the endotracheal tube will usually indicate whether the patient can be successfully extubated or not. In contrast, patients who have required long-termventilatory support for severe lung disease, such as ARDS, may initially be unable to sustain even a modest degree of respiratory work because of residual decreased lung compliance and hence increased work of breathing, compounded by respiratory muscle weakness. These patients require weaning until respiratory muscle strength improves to the point that all support can be discontinued. 

Evidence-based guildines for weaning and discountinuing ventilatory support

Weaning techniques involve the patient breathing spontaneously for increasing periods of the day and a gradual reduction in the level of ventilatory support. This often involves graduation to partial support modesand then non-invasive modes of ventilatory support. The process of identifying patients able to progress to spontaneous breathing and extubation is carried out.

According to a ‘weaning protocol’. This entails deciding whether a patient can be safely subjected to a spontaneous breathing trial (Box 8.22). If the patient meets these criteria, he/she undergoes the breathing trial for 2–5 minutes. The ratio of the respiratory rate to tidal volume is calculated. If it is < 105 breaths/min/L, the patient continues the trial for a further 30-minute to 2-hour period before extubation. In the event of failure (increased respiratory rate; decreased tidal volume), gradual weaning of ventilation continues using synchronised intermittent mandatory ventilation (SIMV), pressure support ventilation (PSV) or intermittent periods of spontaneous breathing. Non-invasive ventilation via a facemask can allow earlier extubation in certain groups, such as patients with COPD,

with weaning continuing after removal of the endotracheal tube. Despite the development of objective tests and indices of the patient’s ability to sustain spontaneous ventilation, the decision to extubate and the speed of weaning from mechanical ventilation still rely largely on clinical judgement.