ABSTRACT
OBJECTIVES: We sought to analyze exercise-derived mean pulmonary artery pressure (Mpap) - cardiac index (CI) - relationship to expand the concepts regarding its nature and to better identify pulmonary hemodynamic responders to acute oxygen breathing (AOB - 99.5%) in pulmonary hypertension (PH) - COPD patients. METHODS: mPAP/CI and extrapolated pressure (Pext) to zero flow were obtained breathing room air (BRA) and under AOB - 99.5% in 40 stable COPD patients with rest and exercise PH. Hemodynamic characteristics were analyzed for the entire cohort and separate for cases those with resting < or > 30 mmHg mPAP (cohort - A and B, respectively). RESULTS: mPAP/CI abnormal location, slope (Sp: 5.77; 95% CI: 5.02 - 6.52 mmHg/L min/m2) and Pext values (15.8 mmHg) were associated with hypoxemia/decreased mixed venous - PO2 and lung mechanics abnormalities. Hemodynamic conditions that did not change for Sp (5.47; 95% CI: 3.64 - 7.3 mmHg/L min/m2, p = 0.4) and Pext (15.7 mmHg, p = 0.2) associated with a mPAP/CI significantly decrease in parallel during AOB - 99.5%. For cohort - A, an averagemPAP decline (12.3 mmHg, p <0.004) associated with a slope decrease (from 6.02; 95% CI: 4.04 - 8 to 4.3; 95% CI: 4.11 - 4.49 mmHg/L min/m2, (p <0.008), mPAP/CI - 95% CI down-ward displacement and Pext decrease (from 8.58 ± 3 to 4.7 ± 1.4 mmHg, p <0.01) in relation to BRA were observed. For cohort-B, average-mPAP and mPAP/CI - 95% CI location did not change, Sp show a trend to decrease (p = 0.08) and Pext significantly increase (from 12 ± 2.9 to 20.6 ± 4.9 mmHg, p <0.03) in relation to BRA. Under AOB - 99.5%, significant differences for mPAP/ CI - 95% CI location, average-mPAP (A: 19.5 ± 6 vs. B: 41.2 ± 11.5 mmHg, p <0.001) and Pext (A: 4.7 ± 1.4 vs. B: 20.6 ± 4.9 mmHg, p <0.001), without Sp change between cohorts A and B were documented. CONCLUSIONS: When exercise derived mPAP/CI is analyzed, valuable information for linearpulmonary vascular resistance - (LPVR) could be obtained for PH - COPD patients. mPAP/CI abnormalities not always reflect "pure arteriolar" increased LPVR for all PH-COPD patients. Hemodynamic benefit on the pulmonary circulation and right ventricular afterload could be expected with long-term oxygen therapy in resting <30 mmHg mPAP-PH-COPD patients.
