Effect of continuous positive airway pressure on ambulatory blood pressure in patients with obstructive sleep apnoea

Circadian rhythms in blood pressure, heart rate, hormones, and on polysomnographic parameters in severe obstructive sleep apnea syndrome patients: effect of continuous positive airway pressure

INTRODUCTION

Seventeen male patients with severe obstructive sleep apnea syndrome (OSAS; apnea-hypopnea index>30/h) were monitored by polysomnography in the sleep lab before and after about 8 weeks of continuous positive airway pressure (CPAP). Twelve of the patients were hypertensive, but treated by antihypertensive drugs. The circadian rhythms in blood pressure (BP) and heart rate were determined by ambulatory BP monitoring and motor activity was monitored by a motion logger. As the sympathetic tone is reported to be increased in sleep apnea, the circadian rhythm in plasma norepinephrine was studied in parallel and as a marker rhythm of the biological clock plasma melatonin was determined around the clock by radioimmunoassay.

RESULTS

Level and rhythm in BP and heart rate were not significantly affected by CPAP in this group of patients, but the number of dippers increased after CPAP intervention. The high 24 h plasma values of norepinephrine were lowered by CPAP therapy. In contrast, melatonin values were disturbed in OSAS patients with a loss in nocturnal increase; this pattern was not corrected by CPAP. Sleep functions (deep sleep, slow wave sleep, rapid eye movement sleep, arousal index, apnea-hypopnea index, desaturation index) were disturbed in OSAS patients as monitored by polysomnography and were significantly improved by CPAP therapy.

CONCLUSION

The study indicates that BP-controlled hypertensive patients with OSAS can additionally benefit from CPAP therapy by increasing the number of dippers. This treatment significantly improved sleep functions and OSAS symptoms. In addition, arousal movements at night were also reduced and the high sympathetic tone during early morning hours was also decreased. However, there is still an indication of a disturbed function of the biological clock as the loss in the rhythm in plasma melatonin was not corrected by CPAP.

Sleep-time ambulatory blood pressure as a prognostic marker of vascular and other risks and therapeutic target for prevention by hypertension chronotherapy: Rationale and design of the Hygia Project

This article describes the rationale, objectives, design and conduct of the ambulatory blood pressure monitoring (ABPM)-based Hygia Project. Given the substantial evidence of the significantly better prognostic value of ABPM compared to clinic BP measurements, several international guidelines now propose ABPM as a requirement to confirm the office diagnosis of hypertension. Nonetheless, all previous ABPM outcome investigations, except the Monitorización Ambulatoria para Predicción de Eventos Cardiovasculares study (MAPEC) study, relied upon only a single, low-reproducible 24 h ABPM assessment per participant done at study inclusion, thus precluding the opportunity to explore the potential reduction in cardiovascular disease (CVD) risk associated with modification of prognostic ABPM-derived parameters by hypertension therapy. The findings of the single-center MAPEC study, based upon periodic systematic 48 h ABPM evaluation of all participants during a median follow-up of 5.6 years, constitute the first proof-of-concept evidence that the progressive reduction of the asleep systolic blood pressure (SBP) mean and correction of the sleep-time relative SBP decline toward the normal dipper BP profile, most efficiently accomplished by a bedtime hypertension treatment strategy, best attenuates the risk of CVD, stroke and development of new-onset diabetes. The Hygia Project, primarily designed to extend the use of ABPM in primary care as a requirement for diagnosis of hypertension, evaluation of response to treatment and individualized assessment of CVD and other risks, is a research network presently composed of 40 clinical sites and 292 investigators. Its main objectives are to (i) investigate whether specific treatment-induced changes in ABPM-derived parameters reduce risk of CVD events, stroke, new-onset diabetes and/or development of chronic kidney disease (CKD); and (ii) test the hypothesis that bedtime chronotherapy entailing the entire daily dose of ≥1 conventional hypertension medications exerts better ambulatory BP control and CVD, metabolic and renal risk reduction than all such medications ingested in the morning upon awakening. Between 2007 and 2015, investigators recruited 18 078 persons [9769 men/8309 women, 59.1 ± 14.3 years of age (mean ± SD)], including 15 764 with hypertension according to ABPM criteria as participants in the prospective randomized chronotherapy trial. The initial evaluation includes 48 h ABPM, detailed medical history and screening laboratory blood and urine tests. The same evaluation procedure is scheduled annually, or more frequently when treatment adjustment is required for proper ambulatory BP control, targeting a median follow-up of >5 years. The primary CVD outcome end point is the composite of CVD death, myocardial infarction, coronary revascularization, heart failure, ischemic stroke and hemorrhagic stroke. The independent Hygia Project Events Committee periodically evaluates blinded clinical reports to ascertain and certify every documented event. Beyond the potential findings resulting from testing the main hypotheses, the Hygia Project has already demonstrated, as proof of concept, that the routine diagnosis of hypertension and individualized assessment of CVD and other risks by ABPM, as currently recommended, is fully viable in the primary care setting, where most people with either hypertension, dyslipidemia, type 2 diabetes or CKD receive routine medical attention.

Treatment of Obstructive Sleep Apnea in Young and Middle-Aged Adults: Effects of Positive Airway Pressure and Compliance on Arterial Stiffness, Endothelial Function, and Cardiac Hemodynamics

Background

The cardiovascular effects of positive airway pressure (PAP) therapy in obstructive sleep apnea (OSA) patients are not clear because of confounding by comorbid conditions.

Methods and Results

Prospective interventional study of PAP therapy and withdrawal. Apnea Hypopnea Index (AHI; events/hour of sleep) was determined from polysomnography. Central aortic blood pressures (BPs), Aortic Augmentation Index (AAIx), and central (PWV_c‐f) and peripheral pulse wave (PWV_c‐r) velocities were determined by applanation tonometry. Echocardiography and brachial artery reactivity testing were performed at baseline, after 4 and 12 weeks of PAP therapy, and 1 week after PAP withdrawal. The 84 participants were mean (SD) 41.1 (7.6) years old and had 39.8 (24.5) AHI events/hour. After 4 weeks post‐PAP initiation and sustained after 12 weeks, subjects experienced decreases in central systolic BP (P=0.008), diastolic BP, mean BP, AAIx, and PWV_c‐r, and brachial artery dilation (all P<0.001), as well as improvements in left ventricular diastolic function and systemic and pulmonary vascular resistance. In adjusted models, PAP use (hours/night) predicted reductions in diastolic BP (β=−0.65 [SE, 0.32] mm Hg/hour; P=0.045), AAIx (β=−0.53 [0.27] %/hour; P=0.049) and PWV_c‐r (β=−0.13 [0.05] m·s⁻¹/hour; P=0.007), and improved brachial artery flow‐mediated dilation (β=0.31 [0.14] %/hour use; P=0.015). After 1 week of PAP withdrawal, brachial diameter, diastolic BP, mean BP, AAIx, and heart rate increased (P≤0.05).

Conclusions

PAP therapy reduces arterial tone and improves endothelial and diastolic function in young to middle‐aged adults. This positive effect is observed after 4 weeks and depends on hours of use, but reverts quickly with PAP withdrawal.

Clinical Trial Registration

URL: https://clinicaltrials.gov/. Unique identifier: NCT01317329.

Ambulatory Blood Pressure Monitoring in the Prediction of Cardiovascular Events and Effects of Chronotherapy: Rationale and Design of the MAPEC Study

Ambulatory blood pressure (BP) measurements (ABPM) correlate more closely with target organ damage and cardiovascular events than clinical cuff measurements. ABPM reveals the significant circadian variation in BP, which in most individuals presents a morning increase, small post-prandial decline, and more extensive lowering during nocturnal rest. However, under certain pathophysiological conditions, the nocturnal BP decline may be reduced (non-dipper pattern) or even reversed (riser pattern). This is clinically relevant because the non-dipper and riser circadian BP patterns constitute a risk factor for left ventricular hypertrophy, microalbuminuria, cerebrovascular disease, congestive heart failure, vascular dementia, and myocardial infarction. Hence, there is growing interest in how to best tailor and individualize the treatment of hypertension according to the specific circadian BP pattern of each patient. All previous trials that have demonstrated an increased cardiovascular risk in non-dipper as compared to dipper patients have relied on the prognostic significance of a single ABPM baseline profile from each participant without accounting for possible changes in the BP pattern during follow-up. Moreover, the potential benefit (i.e., reduction in cardiovascular risk) associated with the normalization of the circadian BP variability (conversion from non-dipper to dipper pattern) from an appropriately envisioned treatment strategy is still a matter of debate. Accordingly, the MAPEC (Monitorización Ambulatoria de la Presión Arterial y Eventos Cardiovasculares, i.e., Ambulatory Blood Pressure Monitoring and Cardiovascular Events) study was designed to investigate whether the normalization of the circadian BP profile toward more of a dipper pattern by chronotherapeutic strategies (i.e., specific timing during the 24 h of BP-lowering medications according to the 24 h BP pattern) reduces cardiovascular risk. The prospective MAPEC study investigates 3,000 diurnally active men and women >/=18 yrs of age. At inclusion, BP and wrist activity are measured for 48 h. The initial evaluation also includes a detailed medical history, an electrocardiogram, and screening laboratory blood and urine tests. The same evaluation procedure is scheduled yearly or more frequently (quarterly) if treatment adjustment is required for BP control. Cardiovascular morbidity and mortality are thus evaluated on the basis of changes in BP during follow-up. The MAPEC study, now on its fourth year of follow-up, investigates the potential decrease in cardiovascular, cerebrovascular, and renal risk from the proper modeling of the circadian BP profile by the timed administration (chronotherapy) of antihypertensive medication, beyond the reduction of clinic-determined daytime or ABPM-determined 24 h mean BP levels.

Blood pressure increase detected by ambulatory monitoring correlates with hypoxemia reflecting sleep apnea severity

Ambulatory blood pressure monitoring and parallel polysomnographic study were performed in 116 adult males divided into 6 groups. Thirty blood-pressure (BP) and polysomnographic variables were measured to test their usefulness for screening for both arterial hypertension and sleep apnea-hypopnea syndrome (SAHS). The development of severe breathing disorders and hypoxemia during sleep was attributed to SAHS, when compared with measurements in healthy controls and in patients with arterial hypertension. Such disorders manifested as an increased apnea-hypopnea index, apnea index, duration of arterial oxygen saturation of less than 85%, and decrease of average arterial oxygen saturation that correlated with nocturnal average diastolic BP (p=0.0049, p=0.0027, p=0.049 and p=0.0457, respectively). These respiratory disorders resulted in various nocturnal, rather than diurnal, and diastolic and systolic BP variables. The acute antihypertensive effect of continuous positive airway pressure therapy for SAHS significantly reduced the episodes of apnea and hypopnea and the secondary component of hypertension caused by excessive sympathetic stimulation. For the SAHS-induced, dose-dependent component of hypertension that responded to continuous positive airway pressure, the following variables, in decreasing significance, were useful: nocturnal average systolic and diastolic BP and 24-hour average systolic and diastolic BP, as well as percent time elevation and mean blood pressure load. The monitoring of these variables could contribute to early diagnostic and prognostic stratification of complications and adequate therapy of the secondary component of hypertension caused by SAHS.

Long-term effect of continuous positive airway pressure on BP in patients with hypertension and sleep apnea

OBJECTIVE

To analyze the long-term effect of continuous positive airway pressure (CPAP) on ambulatory BP in patients with obstructive sleep apnea (OSA) and hypertension, and to identify subgroups of patients for whom CPAP could be more effective.

METHODS

We conducted a prospective, long-term follow-up trial (24 months) in 55 patients with OSA and hypertension (mean CPAP use, 5.3 +/- 1.9 h/d [+/- SD]). Twenty-four-hour ambulatory BP monitoring (ABPM) was measured at baseline and after intervention with CPAP on an intention-to-treat basis. In addition, the correlation between the changes in 24-h mean arterial pressure (24hMAP) and CPAP compliance, OSA severity, and baseline ABPM was assessed.

RESULTS

At the end of follow-up, a significant decrease was shown only in diastolic BP (- 2.2 mm Hg; 95% confidence interval [CI], - 4.2 to - 0.1; p = 0.03) but not in 24hMAP or other ABPM parameters. However, a correlation between changes in 24hMAP and baseline systolic BP (r = - 0.43, p = 0.001), diastolic BP (r = - 0.38, p = 0.004), and hours of use of CPAP (r = - 0.30, p = 0.02) was observed. A significant decrease in the 24hMAP was achieved in a subgroup of patients with incompletely controlled hypertension at entry (- 4.4 mm Hg; 95% CI, - 7.9 to - 0.9 mm Hg; p = 0.01), as well as in those with CPAP compliance > 5.3 h/d (- 5.3 mm Hg; 95% CI, - 9.5 to - 1.2 mm Hg; p = 0.01). Linear regression analysis showed that baseline systolic BP and hours of CPAP were independent predictors of reductions in BP with CPAP.

CONCLUSION

Long-term CPAP reduced BP modestly in the whole sample. However, patients with higher BP at entry and good CPAP compliance achieved significant reductions in BP.

Hypertension research in sleep apnea

Obstructive sleep apnea (OSA) is characterized by repetitive partial and total collapse of the upper airway that induces stressful arousals throughout sleep to reestablish breathing. Although estimates vary, prevalence has been reported as high as 20% in the adult population. OSA is common in several chronic diseases, the most common of which is obesity. Evidence is strong that OSA increases the risk of hypertension and both fatal and nonfatal cardiovascular events. Several mechanisms linking OSA to hypertension have been proposed, with increased sympathetic activation implicated as the prime mediator. This review summarizes recent data on the influence of OSA on blood pressure, the effect of standard OSA therapy on improving blood pressure, and the potential of lifestyle modification for further decreasing hypertension risk. Challenges confronting the investigation of blood pressure outcomes in response to treatment in OSA patients are discussed.

Nondipping blood pressure patterns among individuals with essential hypertension: a review of the literature

BACKGROUND

Researchers have discovered that blood pressure (BP) varies in a diurnal manner throughout a 24-hour period, being higher during the day and lower at night. Most people have a dipping BP pattern characterized by a nighttime BP that is 10-20% lower than their daytime BP. Individuals who experience a less than 10% reduction in nighttime BP are described as having a nondipping BP pattern. Although controversial, there is a growing body of evidence suggesting that a nondipping BP pattern is associated with a greater risk of target organ damage among individuals with essential hypertension.

AIM

To review the literature on the most common factors associated with nondipping BP patterns among individuals with essential hypertension.

METHODS

CINAHL (1982-March 2006), PubMed (1950-March 2006) and Cochrane Library (1966-March 2006) databases were searched using the keywords: dipper, dipping, nondipper, nondipping, ambulatory blood pressure monitoring, ABPM, hypertension, essential hypertension, high blood pressure, blood pressure, nocturnal blood pressure, nighttime blood pressure, diurnal blood pressure, and blood pressure patterns. Published studies, abstracts, dissertations as well as the reference lists of retrieved articles were reviewed. Studies were included if they involved subjects with only treated or untreated essential hypertension or those with samples of both nomotensive and treated or untreated essential hypertensive individuals. Additionally, studies needed to evaluate 24-hour, daytime and nighttime BP patterns.

RESULTS

There is some evidence to suggest advanced age, African-American ethnicity, female sex, postmenopausal status, sodium sensitivity, sleep apnea, sleep quality, anger, hostility, depression, stress, social support, and socioeconomic status have an association with nondipping BP patterns.

CONCLUSION

Knowledge of the potential factors associated with an altered nighttime BP pattern is of importance because it can help identify persons at risk for nondipping BP patterns and potential target organ damage. Furthermore, knowledge of these factors associated with a nondipping BP profile will lay the foundation for interventions to prevent/treat alterations in nighttime BP patterns.

Effect of Continuous Positive Airway Pressure on Ambulatory BP in Patients With Sleep Apnea and Hypertension

BACKGROUND

Obstructive sleep apnea syndrome (OSAS) is an independent risk factor for arterial hypertension. Several controlled trials have investigated the effect of continuous positive airway pressure (CPAP) on BP in patients with OSAS, but its effect on hypertensive patients has not been analyzed specifically.

OBJECTIVE

To analyze the effect of CPAP on ambulatory BP in patients with OSAS and hypertension who were undergoing antihypertensive treatment.

DESIGN AND PATIENTS

We conducted a parallel, randomized, placebo-controlled trial in 68 patients with OSAS and hypertension, who were receiving treatment with antihypertensive medication. Patients were randomly allocated to either therapeutic or subtherapeutic CPAP for 4 weeks. Ambulatory BP was registered at baseline and after treatment. Antihypertensive treatment was not changed during the study. Changes in BP were assessed on an intention-to-treat basis.

RESULTS

There were no baseline differences in the apnea-hypopnea index, comorbidities, or ambulatory BP between groups. Objective compliance with CPAP was similar in both the therapeutic and subtherapeutic groups (5.0 +/- 1.4 h/d vs 4.4 +/- 1.9 h/d, respectively; p = 0.13 [mean +/- SD]). There was a small and statistically nonsignificant decrease (- 0.3 +/- 6.3 mm Hg vs - 1.1 +/- 7.9 mm Hg; difference, - 0.8 mm Hg [95% confidence interval, - 2.7 to 4.3]; p = 0.65) in 24-h mean BP (24hMBP) in both subtherapeutic and therapeutic groups after 4 weeks of treatment. No significant changes in systolic, diastolic, daytime, or nighttime BP were observed. The normal circadian dipper pattern was restored in a higher proportion of patients in the therapeutic group compared to the subtherapeutic CPAP group, although differences were not significant (11 of 32 patients vs 3 of 25 patients; odds ratio, 3.84; 95% confidence interval, 0.82 to 20.30; p = 0.10). There was no correlation between the magnitude of change in 24hMBP and CPAP compliance, OSAS severity, or number of antihypertensive drugs used.

CONCLUSION

Four weeks of CPAP did not reduce BP in patients with OSAS and hypertension who were treated with antihypertensive medication, compared to placebo group.

Sleep-disordered breathing and cardiovascular health

PURPOSE OF REVIEW

Sleep-disordered breathing is a widely prevalent condition and may have serious medical, social, and economic consequences. This review evaluates the role of sleep-disordered breathing in cardiovascular morbidity and mortality on the basis of recent literature.

RECENT FINDINGS

Epidemiologic studies, retrospective reviews, and prospective clinical trials suggest a strong association between sleep-disordered breathing and adverse cardiovascular events. Individuals with sleep-disordered breathing have a higher prevalence of hypertension, which attenuates with treatment. Furthermore, the presence of sleep-disordered breathing augurs an increased risk of coronary artery disease, cardiac arrhythmias, and heart failure.

SUMMARY

Recent research provides an emerging evidence of the role of sleep-disordered breathing as a risk factor for diverse cardiovascular disorders.