Postural variation of the maximum inspiratory and expiratory pressures in obese patients

Evaluating whether weight is a factor responsible for the decrease of muscle force in the supine position with respect to the upright and sitting positions, we measured maximum inspiratory and expiratory pressures (PImax and PEmax) in these postures in ten obese patients (age 38.7 +/- 9.1 years; height 168.7 +/- 8.9 cm; and weight 139.3 +/- 28.4 kg) and ten normal control subjects (age 38.4 +/- 8.2 years; height 169.3 +/- 7.9 cm and weight 66.9 +/- 11.9 kg.) In both study groups, PImax and PEmax values decreased in the supine posture with respect to upright and sitting positions. Differences between pressures in the various postures were similar for both groups with the exception of PEmax in obese females. The decrease in PEmax values from the sitting to supine positions was greater in obese than control females. Weight, sex and postural changes can influence the generation of maximal expiratory force.