Sleep during proportional-assist ventilation with load-adjustable gain factors in critically ill patients.

BACKGROUND

Proportional-assist ventilation with load-adjustable gain factors (PAV+) automatically adjusts the flow and volume assist to represent constant fractions of resistance and elastance of the respiratory system, respectively. Resistance and elastance are calculated at random intervals of 4-10 breaths, by applying a 300 ms pause maneuver at the end of selected inspirations.

OBJECTIVES

To determine whether the large number of end-inspiratory occlusions during PAV+ operation influences sleep quality in critically ill patients who exhibited good patient-ventilator synchrony during pressure support (PS, baseline).

METHODS

One and two nights' polysomnography was performed in sedated (protocol A, n=11) and non-sedated (protocol B, n=9) patients, respectively, while respiratory variables were continuously recorded. In each protocol the patients were ventilated with PAV+ and PS at two levels of assist (baseline and high).

RESULTS

In both protocols sleep quality did not differ between the modes of support or the assist levels. In sedated patients sleep efficiency was slightly but significantly higher with PAV+ than with high PS, while it did not differ between modes in non-sedated patients. The two modes of support had comparable effects on respiratory variables. Independent of the mode of support and particularly at high assist, a significant proportion of patients developed periodic breathing during sleep (27% in protocol A and 44% in protocol B).

CONCLUSION

In patients exhibiting good patient-ventilator synchrony during PS, the large number of short-term end-inspiratory occlusions with PAV+ operation did not adversely influence sleep quality. With both modes high assist may cause unstable breathing during sleep.