Abstract
BACKGROUND: Patients with severe chronic obstructive pulmonary disease (COPD) often have intrinsic positive end-expiratory pressure. Continuous positive airway pressure has been shown to decrease the inspiratory work of breathing and increases exercise capacity in these patients.OBJECTIVE: To determine whether continuous negative pressure (CNP) around the chest is able to bring the positive end-expiratory pressure closer to atmospheric pressure, thereby reducing the threshold load and increasing exercise capability.METHODS: A pilot study was undertaken with eight COPD patients who had been hospitalized for exacerbation and were close to discharge. For CNP, a shell (around the thorax from under the axillae to the mid abdomen) and wrap were used. Each of the eight patients was assessed with a 6 min walk test in three modes (in randomized order) with 30 min of rest in between: a control walk with no shell or wrap; a sham CNP in which the applied CNP was negligible; and CNP, with pressure chosen by the patient that provided maximal relief of dyspnea at rest.RESULTS: At the end of each of the 6 min walk tests, there was no difference in heart rate, oxygen saturation or level of dyspnea among the three test modes. Respiratory rate was reduced with CNP compared with sham. The patients walked furthest with CNP compared with control (mean ± SD) (313±66.2 m versus 257±65.2 m; P<0.01) and compared with sham.CONCLUSIONS: In the present pilot study, COPD patients improved their exercise performance with CNP.