The aim of this study was to investigate the haemodynamic and endocrinological effects of noninvasive positive pressure ventilation (NIPPV). Eleven patients with oedema and recent hypercapnic and hypoxaemic worsening of a chronic respiratory insufficiency were included. Echocardiography, cardiac radionuclide assessment, blood catecholamines, salt and water handling hormones were measured at admission and discharge (long study (LS)). To discriminate between the action of NIPPV and other treatments, measurements were performed on the fourth day, for 4 h without NIPPV and 4 h with NIPPV (short study (SS)). NIPPV entailed a correction of P(a,CO2) and an increase of P(a,O2) in LS and SS. Oedema disappeared. Body weight decreased (from 85+/-42 to 81+/-40 kg) during LS. Systolic and mean pulmonary arterial pressure decreased in LS and SS. Right ventricular ejection fraction increased in LS. Left ventricular ejection fraction did not change. Cardiac index was normal on admission and then decreased. Natriuretic peptides and catecholamines were increased on admission, whereas plasma renin activity, aldosterone and vasopressin were normal. We suggest that in these patients, oedema can occur independently of renin-angiotensin-aldosterone-vasopressin and with a normal cardiac output. Noninvasive positive pressure ventilation allowed a correction of blood gases, associated with the resolution of oedema, a decrease in pulmonary arterial pressures and an increase in right ventricular ejection fraction.