Blood Pressure Variability in Obstructive Sleep Apnoea: Data from 4 Randomised Controlled CPAP Withdrawal Trials

Abstract

Background: Increased daytime blood pressure variability (BPV) is associated with cardiovascular risk. Preliminary data suggest that obstructive sleep apnoea (OSA) might contribute to increased daytime BPV. Objective: The aim of this study was to evaluate the effect of continuous positive airway pressure (CPAP) therapy withdrawal on daytime BPV. Methods: A total of 183 patients previously diagnosed with OSA and treated with CPAP were randomised to either continue or withdraw from CPAP within 4 trials. Office morning BP was measured in triplicate at baseline and at follow-up (day 14). In addition, the participants performed BP measurements at home on a daily basis (days 1-13). The main outcome of interest was the treatment effect on within-visit BPV expressed as the standard deviation (SD) of the triplicate measurements. Additional outcomes included morning home BPV and day-to-day home BPV. Results: Within-visit variability in systolic BP significantly increased in response to recurrence of OSA in the CPAP withdrawal group (difference between groups in SD of systolic BPV, +1.14 mm Hg, 95% CI +0.20/+2.09, p = 0.02). There was no statistically significant effect on within-visit variability in diastolic BP (p = 0.38) or heart rate (p = 0.07). Neither morning home BP variability (systolic BPV, p = 0.81; diastolic BPV, p = 0.46) nor day-to-day variability in home BP measurements (systolic BPV, p = 0.61; diastolic BPV, p = 0.58) differed significantly between the groups. Conclusion: CPAP withdrawal results in a minor increase in within-visit variability in office systolic BP, but it has no effect on home BPV or day-to-day BPV. Although the treatment effect may be blunted by antihypertensives, it is unlikely that OSA contributes to cardiovascular risk via elevated daytime BPV.

Ambulatory blood pressure in relation to oxygen desaturation index as simultaneously assessed by nighttime finger pulse oximetry at home

“…This observation is in keeping with the results of several previous studies, 16,17 and may have straightforward interpretations.…”

“…ODI was assessed by overnight finger pulse oximetry in 2342 participants on the day of ambulatory BP monitoring, and calculated as the number of desaturation episodes per sleeping hour. Both BP and pulse rate increased significantly (P ≤ .006) from normal (< 5 events/h) to mildly (5)(6)(7)(8)(9)(10)(11)(12)(13)(14), moderately (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30), and severely (≥ 30 events/h) elevated ODI. The association for BP was substantially attenuated by accounting for pulse rate (partial r² from .003-.012 to .002-.006).…”

Blood-pressure variability in patients with obstructive sleep apnea: current perspectives

“… 86 Finally, a group of investigations evaluated BP variability with office or home BP measurements, and found some effect of CPAP treatment on waking systolic BP variability. 92 , 124 In summary, CPAP treatment acutely decreases nocturnal very short-term BP variability. A few weeks of CPAP treatment may convert a nondipping into a dipping 24-hour BP profile in some patients and cause some decrease in diurnal BP variability, but more data are necessary to explore these aspects better.…”

“…No effect on morning-to-morning BP was reported during CPAP withdrawal for 2 weeks, which suggested that OSA does not significantly influence midterm BP variability. 92 …”

Physiological consequences of CPAP therapy withdrawal in patients with obstructive sleep apnoea—an opportunity for an efficient experimental model

“…In addition to systemic hypertension, blood pressure variability has been suggested as an independent cardiovascular risk factor (16). However, within the CPAP withdrawal trials, randomising 183 patients to either continue therapeutic CPAP or to withdraw it, there was only a negligible increase in within-visit variability in systolic office blood pressure, whereas there was no effect of withdrawing CPAP on other short-term blood pressure variability indices (within-visit), or on intermediateterm blood pressure variability indices (visit-to-visit, day-to-day) (17). The hypothesis that OSA contributes to vascular damage via elevated daytime blood pressure variability could not be supported.…”