Eight patients (2 women and 6 men) with stable mild-to-severe COPD participated in the study (Table 1). Subjects with known cardiovascular disease, neurologic or psychiatric illness, or impaired lower extremity function or those requiring supplemental oxygen were excluded from the study. All patients received their regular treatment of inhaled bronchodilators, and none received oral steroid therapy. Four of the patients were receiving inhaled steroid therapy, and one patient was receiving oral theophylline therapy. No change in the medications was made for the purpose of the study. Patients were asked to abstain from smoking on the day of the study and to avoid eating for at least 2 h prior to undergoing testing. The study was approved by the ethics committee of the hospital, and all subjects gave written informed consent.
Protocols and Instrumentation
One week prior to the actual study, subjects underwent pulmonary function testing (system 1085; Medical Graphics Corp; St. Paul, MN) and performed an incremental exercise test on a bicycle ergometer (model 400L; Medical Fitness Equipment; Maarn, the Netherlands) to determine their maximum exercise workload (WLmax). Subjects maintained a mean (± SD) pedaling rate of 60 ± 5 revolutions per minute, and workload was increased by 10 W every minute until subjects could no longer continue. During this initial session, a physiotherapist instructed subjects on how to perform the PLB technique (ie, nasal inspiration followed by expiratory blowing against partially closed lips avoiding forceful expiration), and subjects also practiced the technique while pedaling and wearing a tight-fitting facemask in order to familiarize them with the study protocol. None of the subjects had difficulty in learning the breathing technique.