Noninvasive Tests for Responsiveness of Pulmonary Hypertension to Oxygen: Prediction of Survival in Patients with Chronic Obstructive Lung Disease and Cor Pulmonale

Abstract

Response of mean pulmonary artery pressure (PAP) to breathing oxygen for 24 hours was measured in 43 patients with chronic obstructive pulmonary disease and cor pulmonale (COPD-CP). Considering a greater than or equal to 5 mm Hg fall in PAP after breathing 28 percent oxygen for 24 hours to be a significant response to oxygen administration, 25 and 18 patients were identified as responders (R) and nonresponders (NR), respectively. Oxygen consumption at the end of a symptom-limited maximum exercise (Vo2 peak) and right (RVEF) and left ventricular (LVEF) ejection fractions by nuclide ventriculography (NVG) were also obtained, and the changes (delta) in RVEF and LVEF after 48 hours of oxygen breathing recorded. All patients were prescribed continuous long-term domiciliary oxygen therapy (CLTO) and followed up as outpatients. Thirty-three patients have completed the follow-up for three years or until their deaths. The R showed a markedly higher survival compared to the NR at 1, 2, and 3 years. A high Vo2 peak (greater than 6.5 ml min-1 kg-1) was significantly associated with R status and also predicted two- and three-year survival. A baseline EF or delta EF of right or left ventricles could not be used to predict either the response of PAP to O2 or the long-term survival, although delta LVEF was significantly higher in the R. Response of PAP to breathing O2 for 24 hours is a reliable indicator of at least three-year survival with CLTO, which can be predicted noninvasively by baseline Vo2 peak.