Blood pressure responsiveness to obstructive events during sleep after chronic CPAP

The aim of this study was to investigate whether chronic continuous positive airway pressure (CPAP) affects blood pressure (BP) responsiveness to obstructive events occurring on the first night of CPAP withdrawal in obstructive sleep apnoea (OSA) after chronic treatment. Thirteen male subjects with severe OSA underwent nocturnal polysomnography with beat-by-beat BP monitoring before treatment and after 4.9±3.4 months of home CPAP (mean daily use 5.1±1.7 h). Variations in oxyhaemoglobin saturation (ΔSa,O2), systolic (ΔPs), and diastolic (ΔPd) BP within nonrapid eye movement apnoeas and hypopnoeas were measured on a sample of pre- and post-treatment events. In addition, a pretreatment sample was selected for ΔSa,O2, to match post-treatment events. The higher the mean ΔSa,O2, was in the full pretreatment sample, the more ΔSa,O2, ΔPs and ΔPd were attenuated after treatment. Mean ΔPs decreased from 47.3±8.5 in the full pretreatment sample to 42.2±6.9 in the selected pretreatment sample, to 31.5±5.9 mmHg in the post-treatment sample. The post-treatment value differed significantly from both the pretreatment values. The corresponding values for mean ΔPd were 27.0±3.5, 24.0±3.1 and 19.6±3.7 mmHg, with all values differing significantly from each other. Chronic continuous positive airway pressure is followed by a decrease in apnoea/hypopnoea-related blood pressure swings, possibly secondary to both reduced severity of event-related hypoxaemia and decreased responsiveness to obstructive events secondary to chronic prevention of nocturnal intermittent hypoxaemia.