Role of spontaneous and assisted ventilation during general anaesthesia.

Spontaneous ventilation during general anaesthesia has been shown to favour atelectasis formation and decreased functional residual capacity. Therefore, general anaesthesia is commonly associated with endotracheal intubation and mechanical ventilation. Laryngeal lesions, residual curarisation, haemodynamics impairment, but most importantly, situation of cannot ventilate-cannot intubate may occur. Recently developed anaesthetic ventilators are able to detect spontaneous ventilation (triggering) and to give a pressure-limited flow cycled assisted breath (pressure support ventilation, PSV). Spontaneous ventilation assisted by PSV with laryngeal mask may avoid all the complications of endotracheal intubation and mechanical ventilation. Therefore, PSV should be a valid alternative for all patients having general anaesthesia with the exception of some contraindication. A close monitoring of tidal volume and minute ventilation is also needed.