Patient-triggered ventilation.
During patient triggered ventilation, the infant's inspiratory efforts should occur synchronously with ventilator inflations. Such an optimal interaction, however, is dependent on the performance of the triggering device and the ventilator and the infant's lung function. Triggered ventilation (assist control, A/C), synchronous intermittent mandatory ventilation (SIMV), pressure support ventilation (PSV), volume targeted ventilation (VTV) with A/C, SIMV, PSV or proportional assist ventilation (PAV) can be delivered via the endotracheal tube or via nasal prongs. Meta-analysis of randomised trials demonstrated that the only advantage of A/C/SIMV over non-triggered positive pressure ventilation was a shorter duration of ventilation, in particular there was no significant effect on the incidence of chronic lung disease. The reduction in ventilation duration, however, was only seen if triggered ventilation is started in the recovery stage rather than in the acute phase of respiratory distress syndrome. Results from small randomised trials have suggested that A/C rather than SIMV is a better weaning mode, as reduction of the SIMV rate below 20 breaths per minute increases the work of breathing. Other small trials have highlighted triggered ventilation delivered by nasal prongs may reduce extubation failure rate. Physiological studies have demonstrated some advantages of PSV with and without VTV and PAV, whether these translate into improvements in long term clinical outcomes remains to be tested in appropriately designed randomised trials.