PULMONARY HEMODYNAMICS IN OBSTRUCTIVE SLEEP-APNEA - TIME-COURSE AND ASSOCIATED FACTORS

Changes in pulmonary artery pressure within an obstructive apnoea and elevations of transmural pulmonary artery pressure (Ppa,tm) towards th e end of apnoea are well known. The purpose of our study was to examin e which factors contribute to the increase of Ppa,tm in an apnoea, In addition, the time course of Ppa,tm and associated factors during a sl eep study was investigated. We analysed the association of changes in arterial oxygen saturation (Sa,O-2), oesophageal pressure (Poes) to es timate intrathoracic pressure, systolic blood pressure (BPsys) to esti mate left ventricular afterload, apnoea duration and the change in Ppa ,tm (Delta Ppa,tm) during the course of obstructive apnoeas, Consecuti ve apnoeas in nonrapid eye movement (NREM)-sleep at the beginning, the middle and the end of the sleep study were analysed in six patients w ith obstructive sleep apnoea, The mean systolic Ppa,tm was 28.0+/-12.1 mmHg at the beginning of apnoea and 38.6+/-15.5 mmHg at the end (Delt a Ppa,tm 10.5+/-7.4 mmHg; p<0.0001), Delta Sa,O-2 (p<0.0001; odds rati o (OR) 1.45; confidence interval (CI) 1.20-1.76) and Delta Poes (p<0.0 001; OR 1.22; CI 1.11-134) were independently associated with Delta Pp a,tm in a multiple regression analysis. Apnoea duration as well as Del ta Poes, Delta Ppa,tm and Delta Sa,O-2 were all significantly higher ( p<0.05) in apnoeas at the middle of the sleep study than at the beginn ing or the end, In conclusion, hypoxaemia and mechanical factors as an increase in negative thoracic pressure contribute to elevations of th e transmural pulmonary artery pressure during an obstructive apnoea, T he time course of pulmonary haemodynamics within a steep study reveals that the highest transmural pulmonary artery pressure occurs in the m iddle of the night with no progressive increase towards the end of the sleep study.