EFFECTS OF PURSED-LIPS BREATHING AND EXPIRATORY RESISTIVE LOADING IN HEALTHY-SUBJECTS

To examine the effect of pursed-lips breathing (PLB) on breathing patt ern and respiratory mechanics, we studied 11 healthy subjects breathin g with and without PLB at rest and during steady-state bicycle exercis e. Six of these subjects took part in a second study, which compared t he effects of PLB to expiratory resistive loading (ERL). PLB was found to prolong expiratory and total breath durations and to promote a slo wer and deeper breathing pattern. During exercise, the compensatory in crease that occurred in tidal volume was not sufficient to counter the reduction in breathing frequency, causing minute ventilation to be re duced. Although ERL similarly caused minute ventilation and breathing frequency to be decreased, unlike PLB, it produced no change in tidal volume and prolonged expiratory and total breath durations to a lesser extent. PLB and ERL increased the expiratory resistance to a comparab le degree, also increasing the expiratory resistive work of breathing and promoting greater expiratory rib cage and abdominal muscle recruit ment in response to the expiratory loads. End-expiratory lung volume, which was determined from inspiratory capacity maneuvers, was not alte red by PLB; however, with ERL it was increased by 0.20 and 0.24 liter during rest and exercise, respectively. Inspiratory muscle recruitment patterns were not altered by PLB at rest, although small increases in the relative contribution of the rib cage/accessory muscles in conjun ction with abdominal muscle relaxation occurred during exercise. Simil ar trends were observed with ERL. We conclude that although ERL and PL B induce comparable respiratory muscle recruitment responses, they are not equivalent with respect to breathing pattern changes and effect o n end-expiratory lung volume.