Abstract
BACKGROUND: Obstructive sleep apnoea (OSA) is the most common form of sleep-disordered breathing and a known risk factor for cardiovascular disease. We hypothesised that in patients with OSA the characteristics of nocturnal pulse rate (PR) are associated with changes in blood pressure and daytime sleepiness, following commencement of continuous positive airway pressure (CPAP) therapy. METHODS: Pulse oximetry data, demographics, daytime sleepiness and blood pressure were recorded at baseline and at one year follow up. Patients with OSA were grouped according to positive and negative changes in the PR (ΔPR) response during the first night of pulse oximetry before commencement of CPAP. RESULTS: A total of 115 patients (58 with OSA and 57 matched subjects without OSA) were identified and included in the analysis. The scale of improvement in daytime sleepiness could be predicted by a negative or positive ΔPR, as recorded in the initial screening pulse oximetry [ΔESS -5.8 (5.1) vs. -0.8 (7.2) points, P<0.05]. A negative correlation was observed between mean nocturnal PR and changes in systolic blood pressure (SBP) after one year of CPAP treatment (r=-0.42, P<0.05). CONCLUSIONS: Mean nocturnal PR prior to CPAP initiation was associated with changes in SBP at one year follow up. A descending nocturnal PR in patients with OSA, prior to CPAP initiation, might help to identify a symptomatic response from long term CPAP treatment.