New type of wasted effort during neurally adjusted ventilatory assist: A case report

In patients with dynamic hyperinflation, such as patients with chronic obstructive pulmonary disease (COPD), development of intrinsic positive end-expiratory pressure (PEEPi) complicates ventilator triggering in conventional assisted ventilation modes, such as pressure support, and causes wasted efforts. The use of extrinsic PEEP (PEEPe) can counterbalance PEEPi and as such facilitate triggering. With neurally adjusted ventilatory assist (NAVA) the ventilator is triggered by an increase in diaphragm electrical activity and does not depend on generation of inspiratory flow. Numerous studies report the absence of ‘classical’ wasted efforts with NAVA. Therefore, the widespread assumption among physicians is that wasted efforts cannot occur with NAVA. We present a 58-year-old male with an acute exacerbation of COPD in which we identify a new type of wasted effort unique to NAVA. We show that during NAVA in the presence of PEEPi it is as important to perform titration of PEEPe as with conventional modes, in order to prevent wasted efforts.