BACKGROUND AND PURPOSE: The oxygen demand of breathing exercises and the clinical implications have not been studied in detail. In this study, the oxygen cost of 3 common breathing exercises believed to reduce oxygen cost (ie, work of breathing) was compared with that of spontaneous breathing in patients with chronic obstructive pulmonary disease (COPD). SUBJECTS: Thirty subjects with stable, moderately severe COPD participated. METHODS: Oxygen consumption (VO2) and respiratory rate (RR) during spontaneous breathing at rest (SB) were recorded for 10 minutes. Subjects then performed 3 breathing exercises in random order, with a rest between exercises: diaphragmatic breathing (DB), pursed-lip breathing (PLB), and a combination of DB and PLB (CB). Oxygen consumption and RR were measured. RESULTS: Mean VO2 (SD) was lower during the breathing exercises (165.8 +/- 22.3 mL O2/min for DB, 164.8 +/- 20.9 mL O2/min for PLB, and 167.7 +/- 20.7 mL O2/min for CB) compared with SB (174.5 +/- 25.2 mL O2/min). Correspondingly, mean RR (+/- SD) was higher during SB (17.3 +/- 4.23 breaths/min), followed by DB (15.0 +/- 4.32 breaths/min), PLB (12.8 +/- 3.53 breaths/min), and CB (11.2 +/- 2.7 breaths/min). DISCUSSION AND CONCLUSION: Given that patients do not spontaneously adopt the breathing pattern with the least O2 and the lowest RR, the results suggest that determinants of the breathing pattern other than metabolic demand warrant being a primary focus in patients with COPD.

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