Effects of breathing exercises on breathing patterns in obese and non-obese subjects

Chest physiotherapy in connection with abdominal surgery includes different deep-breathing exercises to prevent post-operative pulmonary complications . The-therapy: is effective in preventing pulmonary complications, especial ly in high-risk patients such as obese persons. The mechanisms behind the e ffect is unclear, but part of the effect may be explained by the changes in breathing patterns. The aim of this study was therefore to describe and to analyse the breathing patterns in obese and non-obese subjects during thre e different breathing techniques frequently used in the treatment of post-o perative patients. Twenty-one severely obese [body mass index (BMI) > 40] a nd 21 non-obese (BMI 19-25) subjects were studied. till persons denied havi ng any lung disease and were nonsmokers. The breathing techniques investiga ted were: deep breaths without any resistance (DB), positive expiratory pre ssure (PEP) with an airway resistance of approximately +15 cmH(2)O (1.5 kPa ) during expiration, inspiratory resistance positive expiratory pressure (I R-PEP) with a pressure of approximately -10 cmH(2)O (-1.0 kPa) during inspi ration. Expiratory resistance as for PEP. Volume against time was monitored while the subjects were sitting in a body plethysmograph. Variables for vo lume and flow during the breathing cycle were determined. Tidal volume and alveolar ventilation were highest during DB, and peak inspiratory volume wa s significantly higher than during PEP and IR-PEP in the group of obese sub jects. The breathing cycles were prolonged in all techniques;but were most prolonged in PEP and IR-PEP. The functional residual capacity (FRC) was sig nificantly lower during DB than during PEP and IR-PEP in the group of obese subjects; FRC as determined-within 2 min of finishing each breathing techn ique was identical to before the breathing manoeuvres.