Positive airway pressure improves nocturnal beat-to-beat blood pressure surges in obesity hypoventilation syndrome with obstructive sleep apnea

Abstract

Positive airway pressure (PAP) treatment has been shown to have a modest effect on ambulatory blood pressure (BP) in patients with obstructive sleep apnea (OSA). However, there is a paucity of data on the effect of PAP therapy on rapid, yet significant, BP swings during sleep, particularly in obesity hypoventilation syndrome (OHS). The present study hypothesizes that PAP therapy will improve nocturnal BP on the first treatment night (titration PAP) in OHS patients with underlying OSA, and that these improvements will become more significant with 6 wk of PAP therapy. Seventeen adults (7 men, 10 women; age 50.4 ± 10.7 years, BMI 49.3 ± 2.4 kg/m(2)) with OHS and clinically diagnosed OSA participated in three overnight laboratory visits that included polysomnography and beat-to-beat BP monitoring via finger plethysmography. Six weeks of PAP therapy, but not titration PAP, lowered mean nocturnal BP. In contrast, when nocturnal beat-to-beat BPs were aggregated into bins consisting of at least three consecutive cardiac cycles with a >10 mmHg BP surge (i.e., Δ10-20, Δ20-30, Δ30-40, and Δ>40 mmHg), titration, and 6-wk PAP reduced the number of BP surges per hour (time × bin, P < 0.05). PAP adherence over the 6-wk period was significantly correlated to reductions in nocturnal systolic (r = 0.713, P = 0.001) and diastolic (r = 0.497, P = 0.043) BP surges. Despite these PAP-induced improvements in nocturnal beat-to-beat BP surges, 6 wk of PAP therapy did not alter daytime BP. In conclusion, PAP treatment reduces nocturnal beat-to-beat BP surges in OHS patients with underlying OSA, and this improvement in nocturnal BP regulation was greater in patients with higher PAP adherence.

Keywords: hypercapnia; hypertension; hypoxemia; sleep apnea.

Fig. 1.

Changes (Δ) in mean values of nocturnal blood pressure compared with quiet wakefulness. Six weeks of positive airway pressure (PAP) therapy significantly reduced Δsystolic (SAP) and Δdiastolic (DAP). *P < 0.05 vs. baseline polysomnogram (PSG). SAP, systolic arterial pressure; MAP, mean arterial pressure; DAP, diastolic arterial pressure; HR, heart rate.

Fig. 2.

Number (#) of systolic (left) and diastolic (right) blood pressure (BP) surges per hour of nocturnal recording. The higher BP bins (i.e., 20–30, 30–40, and >40 mmHg) revealed that both titration and 6 wk of PAP therapy significantly reduced the number of hourly nocturnal BP surges compared with baseline. *P < 0.05 vs. baseline PSG.

Fig. 3.

Percentage (%) of night when systolic (left) and diastolic (right) blood pressure (BP) bins were above quiet wakefulness. The higher BP bins (i.e., 20–30, 30–40, and >40 mmHg) revealed that titration and 6 wk of positive airway pressure (PAP) therapy significantly reduced the percentage of time spent above quiet wakefulness. *P < 0.05 vs. baseline PSG.

Fig. 4.

Associations between PAP adherence and changes in the number of nocturnal surges of BP after 6 wk of PAP therapy. PAP adherence, defined as % of nights with ≥4 h of use over the 6 wk of therapy, was significantly correlated to reductions in the number of SAP and DAP nocturnal BP surges of >10 mmHg per hour. Open circles (○) denote subjects treated with average volume assured pressure support (AVAPS), while closed circles (●) denote subjects treated with bilevel PAP, and triangles (▲) denote subjects treated with continuous positive airway pressure (CPAP).