Patients grouped by surgery of thorax and upper abdomen and by surgery at "other sites" were studied during the first two postoperative days to compare inhaled volumes achieved with volume-oriented IPPB with inhaled volumes achieved voluntarily with coaching. Of the 243 patients, 59 per cent achieved at least 10 per cent more inhaled volume with IPPB than voluntarily and were termed positive responders. Of the 127 patients in the thoracic and upper abdominal surgery group, 71 per cent were positive responders to IPPB and they achieved a mean volume increase of 59 per cent with IPPB compared to voluntary effort. Of the 116 patients in the "other sites" surgery group, 44 per cent were positive responders to IPPB, achieving a mean of 48 per cent higher volume with IPPB than without it. This study demonstrates that positive responders to IPPB can greatly improve inspired volumes with mechanical assistance compared to volumes achieved by encouraged voluntary effort alone. At the same time, the volume-oriented procedure discussed herein identifies negative responders for whom benefit from IPPB is very questionable.
Powers et al. (Sun,) studied this question.