Oxygen pulse reflects the capacity of the heart to deliver O2 per heartbeat and in patients with COPD, is often reduced at peak of an incremental exercise. In this study, we investigated the determinants of peak O2 pulse in COPD patients without concomitant cardiac diseases.
Twenty-three COPD patients (5 female, age range 47–76 years, BMI range 20–32 kg/m2) performed spirometry, muscle respiratory strength assessment and blood gas analysis. Patients carried out exercise testing using bicycle ergometry with ramp protocol (work rate increments range 5–20 W/min). Gas exchange and ventilation were measured breath by breath.
Mean(SD) values of FEV1, FEV1/VC, MIP, MEP, PaO2, PaCO2 and pH were: 54% pred (18), 50% (10), 80cmH2O (18), 110cmH2O (22), 72mmHg (8), 42mmHg (5), and 7.41(0.03), respectively. At peak of exercise, mean (SD) values of V’O2, HR and O2 pulse were 1.23 L(0.44), 130bpm(24), and 9.7ml/bpm(3). Peak O2 pulse was positively related to BMI (r=0.52, p<0.02), FEV1(r=0.59, p<0.01), FEV1/VC (r=0.70, p<0.01), MIP (r=0.53, p<0.01), and PaO2 (r=0.54, p<0.02). On the basis of regression equations by stepwise multiple regression analysis, peak O2 pulse was predicted by FEV1/VC and PaO2 (r2 = 0.66).CONCLUSIONS AND CLINICAL IMPLICATIONS: In COPD patients with moderate to severe airway obstruction and without concomitant cardiac diseases, O2 pulse at peak of an incremental exercise is determined by ventilatory limitation degree and arterial oxygen tension.
A. Chetta, None.