Treatment of obstructive sleep apnoea leads to improved microvascular endothelial function in the systemic circulation

[Primary open angle glaucoma and sleep apnea syndrome: A review of the literature]

The relationship between glaucoma and Obstructive Sleep Apnea Syndrome (OSAS) has long been discussed, with conflicting study findings. OSAS appears in the most recent studies to be more of an aggravating factor than an independent risk factor for glaucoma. Patients with OSAS may develop a more rapid progression of primary open-angle glaucoma (POAG). OSAS may damage the optic nerve not only by increasing the intraocular pressure (IOP) but also by altering the blood supply to the optic nerve as shown by more recent work with OCT-Angiography. Although the systemic benefits of Continuous Positive Airway Pressure (CPAP) have been demonstrated, few studies have evaluated its effect on the optic nerve. CPAP might act on glaucomatous neuropathy by improving the blood supply to the optic nerve. The study of this mechanism of action might provide new insights into the relationship between OSAS and glaucoma.

Obstructive Sleep Apnoea and Lipid Metabolism: The Summary of Evidence and Future Perspectives in the Pathophysiology of OSA-Associated Dyslipidaemia

Obstructive sleep apnoea (OSA) is associated with cardiovascular and metabolic comorbidities, including hypertension, dyslipidaemia, insulin resistance and atherosclerosis. Strong evidence suggests that OSA is associated with an altered lipid profile including elevated levels of triglyceride-rich lipoproteins and decreased levels of high-density lipoprotein (HDL). Intermittent hypoxia; sleep fragmentation; and consequential surges in the sympathetic activity, enhanced oxidative stress and systemic inflammation are the postulated mechanisms leading to metabolic alterations in OSA. Although the exact mechanisms of OSA-associated dyslipidaemia have not been fully elucidated, three main points have been found to be impaired: activated lipolysis in the adipose tissue, decreased lipid clearance from the circulation and accelerated de novo lipid synthesis. This is further complicated by the oxidisation of atherogenic lipoproteins, adipose tissue dysfunction, hormonal changes, and the reduced function of HDL particles in OSA. In this comprehensive review, we summarise and critically evaluate the current evidence about the possible mechanisms involved in OSA-associated dyslipidaemia.

Effect of obstructive sleep apnoea syndrome and continuous positive airway pressure treatment on choroidal structure

OBJECTIVES

To evaluate the effect of obstructive sleep apnoea syndrome (OSAS) and continuous positive airway pressure (CPAP) therapy on choroidal structural changes and choroidal vascularity index (CVI) in patients with OSAS.

METHODS

Choroidal structural changes in patients with OSAS immediately after diagnosis and 12 months after CPAP treatment were evaluated and compared with healthy controls. The choroidal images on enhanced depth imaging optical coherence tomography (EDI-OCT) were binarized into luminal area (LA) and stromal area (SA) using the ImageJ software. CVI was calculated as the ratio of LA to total choroid area (TCA). The correlations between the results of polysomnography (PSG) and choroidal parameters were evaluated.

RESULTS

A total of 48 eyes of 48 patients (22 patients with OSAS, and 26 controls) were included. The mean age of the patients was 47.21 ± 8.82 (range, 30-63) years. The mean CVI values were 68.10 ± 1.80% in the OSAS group before CPAP therapy, and 69.22 ± 1.40% in the control group (p < 0.05). After 12 months of regular CPAP therapy, the mean CVI value increased significantly to 69.15 ± 1.77%, and SA decreased significantly from 0.51 ± 0.07 mm2 to 0.48 ± 0.07 mm2 in the OSAS group (p < 0.05). No statistically significant correlation was found between the results of PSG and choroidal structural parameters.

CONCLUSION

According to our results, OSAS was associated with increased stromal oedema in the choroid, which improved after 12 months of regular CPAP therapy. CVI can be an important parameter for the follow-up of patients with OSAS.

Temporal changes in coronary artery function and flow velocity reserve in mice exposed to chronic intermittent hypoxia

Study Objectives

Obstructive sleep apnea (OSA) is a chronic condition characterized by intermittent hypoxia (IH) that is implicated in an increased risk of cardiovascular disease (i.e., coronary heart disease, CHD) and associated with increased overall and cardiac-specific mortality. Accordingly, we tested the hypothesis that experimental IH progressively impairs coronary vascular function and in vivo coronary flow reserve.

Methods

Male C57BL/6J mice (8-week-old) were exposed to IH (FiO2 21% 90 s–6% 90 s) or room air (RA; 21%) 12 h/day during the light cycle for 2, 6, 16, and 28 weeks. Coronary artery flow velocity reserve (CFVR) was measured at each time point using a Doppler system. After euthanasia, coronary arteries were micro-dissected and mounted on wire myograph to assess reactivity to acetylcholine (ACh) and sodium nitroprusside (SNP).

Results

Endothelium-dependent coronary relaxation to ACh was preserved after 2 weeks of IH (80.6 ± 7.8%) compared to RA (87.8 ± 7.8%, p = 0.23), but was significantly impaired after 6 weeks of IH (58.7 ± 16.2%, p = 0.02). Compared to ACh responses at 6 weeks, endothelial dysfunction was more pronounced in mice exposed to 16 weeks (48.2 ± 5.3%) but did not worsen following 28 weeks of IH (44.8 ± 11.6%). A 2-week normoxic recovery after a 6-week IH exposure reversed the ACh abnormalities. CFVR was significantly reduced after 6 (p = 0.0006) and 28 weeks (p &lt; 0.0001) of IH when compared to controls.

Conclusion

Chronic IH emulating the hypoxia-re-oxygenation cycles of moderate-to-severe OSA promotes coronary artery endothelial dysfunction and CFVR reductions in mice, which progressively worsen until reaching asymptote between 16 and 28 weeks. Normoxic recovery after 6 weeks exposure reverses the vascular abnormalities.

Obstructive sleep apnea, chronic obstructive pulmonary disease and hypertensive microvascular disease: a cross-sectional observational cohort study

Hypertensive microvascular disease is associated with an increased risk of diastolic heart failure, vascular dementia and progressive renal impairment. This study examined whether individuals with obstructive sleep apnoea (OSA) had more retinal hypertensive microvascular disease than those with chronic obstructive pulmonary disease (COPD) and hospital controls. This was a single-centre, cross-sectional, observational study of participants recruited consecutively from a general respiratory clinic and a general medical clinic. OSA was diagnosed on overnight polysomnography study (apnoea:hypopnoea index ≥ 5), and controls with COPD had a forced expiratory volume/forced vital capacity (forced expiratory ratio) < 70%. Individuals with both OSA and COPD were excluded. Hospital controls had no COPD on respiratory function testing and no OSA on specialist physician questioning. Study participants completed a medical questionnaire, and underwent resting BP measurement, and retinal photography with a non-mydriatic camera. Images were deidentified and graded for microvascular retinopathy (Wong and Mitchell classification), and arteriole and venular calibre using a semiautomated method at a grading centre. Individuals with OSA (n = 79) demonstrated a trend to a higher mean arterial pressure than other hospital patients (n = 143) (89.2 ± 8.9 mmHg, p = 0.02), and more microvascular retinopathy (p < 0.001), and narrower retinal arterioles (134.2 ± 15.9 μm and 148.0 ± 16.2 μm respectively, p < 0.01). Microvascular retinopathy and arteriolar narrowing were still more common in OSA than hospital controls, after adjusting for age, BMI, mean arterial pressure, smoking history and dyslipidaemia (p < 0.01, p < 0.01, respectively). Individuals with OSA demonstrated a trend to a higher mean arterial pressure than those with COPD (n = 132, 93.2 ± 12.2 mmHg and 89.7 ± 12.8 mmHg respectively, p = 0.07), and more microvascular retinopathy (p = 0.0001) and narrower arterioles (134.2 ± 15.9 and 152.3 ± 16.8, p < 0.01). Individuals with OSA alone had more systemic microvascular disease than those with COPD alone or other hospital patients without OSA and COPD, despite being younger in age.

Sleep-disordered breathing in high-risk pregnancies is associated with elevated arterial stiffness and increased risk for preeclampsia

BACKGROUND

Impaired vascular function is a central feature of pathologic processes preceding the onset of preeclampsia. Arterial stiffness, a composite indicator of vascular health and an important vascular biomarker, has been found to be increased throughout pregnancy in those who develop preeclampsia and at the time of preeclampsia diagnosis. Although sleep-disordered breathing in pregnancy has been associated with increased risk for preeclampsia, it is unknown if sleep-disordered breathing is associated with elevated arterial stiffness in pregnancy.

OBJECTIVE

This prospective observational cohort study aimed to evaluate arterial stiffness in pregnant women, with and without sleep-disordered breathing and assess the interaction between arterial stiffness, sleep-disordered breathing, and preeclampsia risk.

STUDY DESIGN

Women with high-risk singleton pregnancies were enrolled at 10 to 13 weeks' gestation and completed the Epworth Sleepiness Score, Pittsburgh Sleep Quality Index, and Restless Legs Syndrome questionnaires at each trimester. Sleep-disordered breathing was defined as loud snoring or witnessed apneas (≥3 times per week). Central arterial stiffness (carotid-femoral pulse wave velocity, the gold standard measure of arterial stiffness), peripheral arterial stiffness (carotid-radial pulse wave velocity), wave reflection (augmentation index, time to wave reflection), and hemodynamics (central blood pressures, pulse pressure amplification) were assessed noninvasively using applanation tonometry at recruitment and every 4 weeks from recruitment until delivery.

RESULTS

High-risk pregnant women (n=181) were included in the study. Women with sleep-disordered breathing (n=41; 23%) had increased carotid-femoral pulse wave velocity throughout gestation independent of blood pressure and body mass index (P=.042). Differences observed in other vascular measures were not maintained after adjustment for confounders. Excessive daytime sleepiness, defined by Epworth Sleepiness Score >10, was associated with increased carotid-femoral pulse wave velocity only in women with sleep-disordered breathing (P_interaction=.001). Midgestation (first or second trimester) sleep-disordered breathing was associated with an odds ratio of 3.4 (0.9-12.9) for preeclampsia, which increased to 5.7 (1.1-26.0) in women with sleep-disordered breathing and hypersomnolence, whereas late (third-trimester) sleep-disordered breathing was associated with an odds ratio of 8.2 (1.5-39.5) for preeclampsia.

CONCLUSION

High-risk pregnant women with midgestational sleep-disordered breathing had greater arterial stiffness throughout gestation than those without. Sleep-disordered breathing at any time during pregnancy was also associated with increased preeclampsia risk, and this effect was amplified by hypersomnolence.

Effect of positive airway pressure on cardiac troponins in patients with sleep-disordered breathing: A meta-analysis

Background

Cardiac troponins are highly sensitive and specific biomarkers for cardiac injury. Previous studies evaluating the effect of positive airway pressure (PAP) on cardiac troponins in patients with sleep‐disordered breathing (SDB) have yielded conflicting results. The meta‐analysis was performed to examine the effect of PAP on cardiac troponins in SDB patients.

Methods

PubMed, Web of Science, and EMBASE before September 2021 on original English language studies were searched. The data on cardiac troponins in both baseline and post‐PAP treatment were extracted from all studies. The data on the change of cardiac troponins in both PAP and control group were extracted from randomized controlled trials. Standardized mean difference (SMD) was used to synthesize quantitative results.

Results

A total of 11 studies were included. PAP treatment was not associated with a significant change in cardiac troponin T between the baseline and post‐PAP treatment (SMD = −0.163, 95% confidence interval [CI] = −0.652 to 0.326, z = 0.65, p = .514). The pooled estimate of SMD of cardiac troponin I between the pre‐ and post‐PAP treatment was 0.287, and the 95% CI was −0.586 to 1.160 (z = 0.64, p = .519). The pooled SMD of change of cardiac troponin T between the PAP group and control group was −0.473 (95% CI = −1.198 to 0.252, z = 1.28, p = .201).

Conclusions

This meta‐analysis revealed that PAP treatment was not associated with any change of cardiac troponin in SDB patients.

The effects of exercise training on vascular function among overweight adults with obstructive sleep apnea

Obstructive sleep apnea (OSA) is associated with increased cardiovascular morbidity due, in part, to impaired vascular function. Exercise confers cardioprotection by improving vascular health. Yet, whether OSA severity affects the vascular improvements conferred with exercise training is not known. Overweight (body mass index (BMI) >27 kg/m²) adults were evaluated for OSA and enrolled in a six-week exercise intervention. Baseline assessments of brachial artery flow-mediated dilation (BAFMD), central augmentation index (AIx) and pulse wave velocity (PWV) were repeated post training. Fifty-one participants (25 men; 26 women) completed the study. Despite improved aerobic capacity (p=0.0005) and total fat mass (p=0.0005), no change in vascular function was observed. Participants were divided into two severity groups according to their baseline total apnea-hypopnea index (AHI) as either 5 to 14.9 events•hr^-1 (n= 21; Age=48 ± 7 yrs; BMI=33.7 ± 4.6kg•m^-2) or 15 ≥events•hr^-1 (n=30; Age=56 ± 13 yrs; BMI = 34.3 ± 4.2 kg•m^-2). No effect of OSA group was observed for BAFMD (p=0.82), AIx (p=0.37) or PWV (p=0.44), suggesting that OSA severity does not influence the effect of exercise on vascular function. The vascular effects of extended exercise programs of greater intensity in overweight OSA patients should be examined.

The association between sleep-related breathing disorders and pre-capillary pulmonary hypertension: A chicken and egg question

The level of knowledge about a direct link between sleep-related breathing disorders and pre-capillary pulmonary hypertension (PH) is low and there is a chicken and egg question to know which disease causes the other. On one hand, sleep-related breathing disorders are considered as a cause of group 3 PH, in the subgroup of patients with hypoxemia without lung disease. Indeed, isolated sleep-related breathing disorders can lead to mild pre-capillary PH on their own, although this is rare for obstructive sleep apnea and difficult to establish for obesity-hypoventilation syndrome, the evolution towards PH being observed especially in the presence of respiratory comorbidities. The hemodynamic improvement under treatment with continuous positive airway pressure or non-invasive ventilation also argues for a causal link between pre-capillary PH and sleep-related breathing disorders. On the other hand, patients followed for pre-capillary PH, particularly pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension, develop more sleep-related breathing disorders than the general population, especially sleep hypoxemia, central sleep apnea in patients with severe PH and obstructive sleep apnea in older patients with higher body mass index. The main objective of this article is therefore to answer two main questions, which will then lead us to discuss the bilateral link between these diseases: are sleep-related breathing disorders independent risk factors for pre-capillary PH and does pre-capillary PH induce sleep-related breathing disorders? In other words, who is the chicken and who is the egg?

The impact of continuous positive airway pressure treatment on retinal vascular changes in obstructive sleep apnea

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) was recently shown to be associated with quantifiable retinal vascular changes, which correlate with disease severity. This follow-up study examines the response of retinal vascular changes in patients with OSA receiving continuous positive airway pressure (CPAP) treatment.

METHODS

This prospective cohort study recruited adult patients undergoing diagnostic polysomnography at a tertiary sleep clinic in Sydney, Australia, stratified into 4 groups by the apnea-hypopnea index; control patients and patients with mild, moderate, and severe OSA. At baseline and follow-up approximately 24 months later, static retinal vascular calibers were derived from fundus photographs, and dynamic vascular pulsation amplitudes were measured on video fundoscopy. A proportion of patients started CPAP therapy after baseline assessment.

RESULTS

Seventy-nine patients participated in this follow-up study: 9 control patients and 18 patients with mild OSA, 21 patients with moderate OSA, and 31 patients with severe OSA. Twenty-five patients started CPAP after baseline. In the severe group, patients not on treatment showed progressive narrowing of retinal arteries from baseline, whereas those on CPAP showed a slight improvement (mean, 171.3-165.1 and 171.2-174.0 μm, respectively; P = .012). Arterio-venous ratio was also significantly reduced in the nontreatment group compared to the treatment group in those with severe OSA (0.836-0.821 and 0.837-0.855, respectively; P = .031). CPAP did not seem to have a significant impact on venous caliber or vascular pulsatility.

CONCLUSIONS

This study shows that patients with severe untreated OSA demonstrate progressive retinal arterial narrowing, whereas CPAP treatment may be protective.

The Assessment of Endothelial Dysfunction among OSA Patients after CPAP Treatment

Background and Objectives: Microcirculation dysfunction is present in patients with obstructive sleep apnea (OSA). Intermittent hypoxia generates “oxidative stress”, which contributes to chronic inflammation. The secretion of nitric oxide (NO), which is responsible for adequate regulation of the endothelium, is impaired due to a decrease in endothelial nitric oxide synthetase (eNOS) expression and an increase in endogenous eNOS inhibitors. Furthermore, nocturnal awakenings lead to the dysregulation of cortisol release and increased stimulation of the sympathetic nervous system. The non-invasive method of choice in OSA treatment is continuous positive airway pressure (CPAP). Materials and Methods: PubMed, Scopus, and Google Scholar databases were searched, and only papers published in the last 15 years were subsequently analyzed. For this purpose, we searched for keywords in article titles or contents such as “obstructive sleep apnea”, “microcirculation”, and “CPAP”. In our review, we only studied English articles that reported systemic reviews and meta-analyses, clinical studies, and case reports. Results: Endothelial dysfunction can be assessed by methods based on reactive hyperemia, such as flow-mediated dilation (FMD) measured by ultrasonography, laser-Doppler flowmetry (LDF), or capillaroscopy. In invasive techniques, intravenous administration of vasodilator substances takes place. Some surveys detected impaired microcirculation in OSA patients compared with healthy individuals. The level of dysfunction depended on the severity of OSA. CPAP treatment significantly improved endothelial function and microvascular blood flow and lowered the inflammatory mediator level. Conclusions: The first-choice treatment—CPAP—reduces the number of apneas and hypopneas during the night, induces the reversal of hypopnea and the chronic inflammatory state, and enhances activation of the sympathetic nervous system. Changes are visible as improved blood flow in both macro- and microcirculation, increased arterial elasticity, and decreased stiffness. Thus, early implementation of adequate treatment could be essential to reduce high cardiovascular risk in patients with OSA.

Hypertension as a Road to Treatment of Heart Failure with Preserved Ejection Fraction

PURPOSE OF REVIEW

Hypertension heralds the diagnosis of heart failure (HF) with preserved ejection fraction (HFpEF) in 75-85% of cases and shares many of its adverse outcomes as well as its acute and chronic symptoms. This review provides important new data about the pathophysiology and mechanisms that connect hypertension and HFpEF as well as therapy used in both conditions.

RECENT FINDINGS

The traditional model of HFpEF pathophysiology emphasizes the role of hypertension causing increased afterload on the left ventricle (LV), leading to LV hypertrophy (LVH) and subsequent LV diastolic dysfunction. Recent work has provided valuable insights into the mechanisms underlying the transition from hypertension to HFpEF, showing that the pathophysiology extends beyond LVH and diastolic dysfunction. An evolving paradigm suggests that HFpEF is inflammatory in nature with multifactorial pathophysiology, affected by age-related changes and comorbidities. Hypertension shares many of the proinflammatory mechanisms of HFpEF. Furthermore, hypertension precedes HFpEF in the majority of cases. Because of its clinically heterogeneous nature, development of standardized therapies for HFpEF has been challenging. As there are standardized approaches to hypertension, we suggest that similar approaches be used for the treatment of HFpEF, including medical and non-medical therapies. With medical therapies, a treat-to-target blood pressure (BP) strategy could be employed, such as systolic BP < 130 mmHg. With non-medical therapies, approaches to deal with physical inactivity, obesity, and sleep apnea could be used. Due to its heterogeneity, delineation of standardized therapies for HFpEF has been challenging. Focusing on the tremendous overlap of hypertensive heart disease with HFpEF, it is proposed that approaches currently used to guide therapies for hypertension be applied to the treatment of HFpEF.

Acute pulmonary embolism in patients with obstructive sleep apnea: frequency, hospital outcomes, and recurrence

STUDY OBJECTIVES

The objectives of this study were to assess the effect of obstructive sleep apnea (OSA) on the risk of acute pulmonary embolism (PE), hospital outcomes including mortality, and PE recurrence.

METHODS

We retrospectively enrolled adult patients, admitted to Mayo Clinic Hospital in Rochester, Minnesota, within a 5-year period (2009-2013). We compared frequency of PE, hospital mortality, and secondary outcomes in patients with OSA versus patients without OSA. We assessed risk of PE recurrence in relation to compliance with OSA therapy.

RESULTS

Of 25,038 patients, 3,184 (13%) had OSA and 283 (1.1%) experienced PE. Frequency of PE in patients with and without OSA was 2.4% versus 0.9% (odds ratio [OR], 2.51; 95% confidence interval [CI], 1.9-3.3; P < .001). OSA was independently associated with increased risk of PE after adjusting for demographics and comorbidities (OR, 1.44; 95% CI, 1.07-1.9; P = .017). Adjusted hospital mortality was increased in patients with PE (OR, 2.88; 95% CI, 1.7-4.9; P < .001) but not in patients with OSA (OR, 0.98; 95% CI, 0.7-1.4, P = .92). OSA was not a significant determining factor for mortality in patients who experienced a PE (OR, 0.56; 95% CI, 0.1.1-2.78; P = .47), adjusting for demographics, PE severity, and Charlson comorbidity index. Adjusted risk of PE recurrence was greater in patients with OSA compared with patients without OSA (OR, 2.21; 95% CI, 1.05-4.68; P < .04). The patients compliant with OSA therapy had a lower rate of PE recurrence (16% vs 32%; P = not significant).

CONCLUSIONS

Although OSA significantly increases risk of acute PE occurrence and recurrences, related hospital mortality was not greater in patients with OSA compared with those without OSA. OSA therapy might have a modifying effect on PE recurrence.

The Effect of Continuous Positive Airway Pressure on Vascular Function and Cardiac Structure in Diabetes and Sleep Apnea. A Randomized Controlled Trial

Rationale: Although both type 2 diabetes mellitus (T2DM) and obstructive sleep apnea (OSA) are independently recognized as risk factors for cardiovascular disease, little is known about their interaction.Objectives: We hypothesized that T2DM and OSA act synergistically to increase vascular risk, and that treatment of OSA would improve vascular reactivity in patients with T2DM plus OSA.Methods: Cross-sectional study of 141 adults with T2DM, OSA, T2DM plus OSA, and control subjects, followed by a 3-month, parallel-arm, randomized, placebo-controlled trial comparing active and sham continuous positive airway pressure (CPAP) in 53 adults with T2DM plus OSA. Endothelium-dependent macro- and microvascular reactivity (flow-mediated dilation [FMD] of the brachial artery and acetylcholine-induced dilation of forearm microvasculature, respectively) and cardiovascular magnetic resonance to assess left- and right-ventricular mass/volume.Results: Mean (±SD) FMD was 6.1 (±4.0)%, 7.3 (±3.6)%, 6.8 (±4.5)%, and 4.8 (±2.9)% in control subjects, T2DM only, OSA only, and T2DM plus OSA, respectively. We observed a significant T2DM × OSA interaction on FMD, such that the mean effect of OSA in those with T2DM was 3.1% (95% confidence interval [CI], 0.6 to 5.6) greater than the effect of OSA in those without T2DM. A total of 3 months of CPAP resulted in a mean absolute increase in FMD of 0.3% (95% CI, -1.9 to 2.5; primary endpoint), with a net improvement of 1.1% (95% CI, -1.4 to 3.6) among those with adherence of 4 h/night or greater. A significant T2DM × OSA interaction was found for both left ventricular (LV) and right ventricular end-diastolic volume, such that OSA was associated with a 22.4 ml (95% CI, 3.2 to 41.6) greater LV end-diastolic volume and 23.2 ml (95% CI, 2.6 to 43.8) greater right ventricular end-diastolic volume in those with T2DM compared with the impact of OSA in those without T2DM. We observed a net improvement in LV end-diastolic volume of 8.7 ml (95% CI, -7.0 to 24.4).Conclusions: The combination of T2DM plus OSA is associated with macrovascular endothelial dysfunction beyond that observed with either disease alone. CPAP for 3 months did not significantly improve macrovascular endothelial function in the intent-to-treat analysis; however, cardiovascular magnetic resonance results suggest that there may be a beneficial effect of CPAP on LV diastolic volume.Clinical trial registered with www.clinicaltrials.gov (NCT01629862).

GCH1 (rs841) polymorphism in the nitric oxide-forming pathway has protective effects on obstructive sleep apnea

Several studies have recently investigated the contribution of genetic factors in obstructive sleep apnea (OSA). Patients with OSA suffer from a reduction in nitric oxide (NO) serum level. This study investigated rs841, A930G p22phox, and rs1799983 polymorphisms in three critical genes involved in NO formation. A total of 94 patients with OSA and 100 healthy controls were enrolled into the study. Results showed there was no association between rs841, A930G p22phox and rs1799983 polymorphism and the risk of OSA (P = 0.51, P = 0.4 and P = 0.33, respectively). Moreover, rs841 GA genotype had a reverse relationship with the severity of OSA (P = 0.005). On the other hand, rs841 GA and A930G p22phox AA genotypes had a protective effect on daytime sleepiness in OSA patients (P = 0.01and P = 0.02, respectively). Additionally, the combination of rs841 and A930G p22phox (AG/AG and AG/AA) genotypes was significantly associated with a reduction in daytime sleepiness in OSA patients (P = 0.03 and P = 0.03, respectively). According to the results of our study, GA genotype of rs841 and GA/AA genotypes of A930G p22phox polymorphisms significantly reduced the severity of the problem and daytime sleepiness in OSA patients.

Therapy for heart failure with preserved ejection fraction: current status, unique challenges, and future directions

Heart failure (HF) with preserved ejection fraction (HFpEF) is the most common form of HF. Among elderly women, HFpEF comprises more than 80% of incident HF cases. Adverse outcomes-exercise intolerance, poor quality of life, frequent hospitalizations, and reduced survival-approach those of classic HF with reduced EF (HFrEF). However, despite its importance, our understanding of the pathophysiology of HFpEF is incomplete, and despite intensive efforts, optimal therapy remains uncertain, as most trials to date have been negative. This is in stark contrast to management of HFrEF, where dozens of positive trials have established a broad array of effective, guidelines-based therapies that definitively improve a range of clinically meaningful outcomes. In addition to providing an overview of current management status, we examine evolving data that may help explain this paradox, overcome past challenges, provide a roadmap for future success, and that underpin a wave of new trials that will test novel approaches based on these insights.

Improvement of Cognitive Function after Continuous Positive Airway Pressure Treatment for Subacute Stroke Patients with Obstructive Sleep Apnea: A Randomized Controlled Trial

Background: Obstructive sleep apnea (OSA) is common after stroke. Various studies on continuous positive airway pressure (CPAP) therapy for OSA after stroke have been published. However, there have been no studies from Korea and Asia. The present Korean study aimed to determine whether CPAP treatment during inpatient rehabilitation of stroke patients with sleep disorders, especially OSA, improves function, cognition, sleep quality, and daytime sleepiness. Methods: This single-blind randomized controlled study included 40 stroke patients with OSA between November 2017 and November 2018. The patients were divided into the CPAP treatment group (CPAP and rehabilitation; n = 20) and control group (only rehabilitation; n = 20). The intervention period was 3 weeks. The primary outcomes were function and cognition improvements, and the secondary outcomes were sleep-related improvements. Results: CPAP treatment started at an average of 4.6 ± 2.8 days after admission. Both groups showed improvements in stroke severity, function, and cognition after the 3-week intervention. However, after the intervention, the degree of change in attention and calculation was significantly higher in the CPAP treatment group than in the control group. Additionally, the improvements in sleep quality and daytime sleepiness were greater in the CPAP treatment group than in the control group. Conclusion: CPAP treatment can improve cognitive function, sleep quality, and daytime sleepiness, and it should be considered as part of the rehabilitation program for patients with stroke. Our findings might help in the treatment of stroke patients with OSA in Korea.

Intermittent hypoxia exacerbates increased blood pressure in rats with chronic kidney disease

Kidney injury and sleep apnea (SA) are independent risk factors for hypertension. Exposing rats to intermittent hypoxia (IH) to simulate SA increases blood pressure whereas adenine feeding causes persistent kidney damage to model chronic kidney disease (CKD). We hypothesized that exposing CKD rats to IH would exacerbate the development of hypertension and renal failure. Male Sprague-Dawley rats were fed a 0.2% adenine diet or control diet (Control) until blood urea nitrogen was >120 mg/dl in adenine-fed rats (14 ± 4 days, mean ± SE). After 2 wk of recovery on normal chow, rats were exposed to IH (20 exposures/h of 5% O₂-5% CO₂ 7 h/day) or control conditions (Air) for 6 wk. Mean arterial pressure (MAP) was monitored with telemeters, and plasma and urine samples were collected weekly to calculate creatinine clearance as an index of glomerular filtration rate (GFR). Prior to IH, adenine-fed rats had higher blood pressure than rats on control diet. IH treatment increased MAP in both groups, and after 6 wk, MAP levels in the CKD/IH rats were greater than those in the CKD/Air and Control/IH rats. MAP levels in the Control/Air rats were lower than those in the other three groups. Kidney histology revealed crystalline deposits, tubule dilation, and interstitial fibrosis in both CKD groups. IH caused no additional kidney damage. Plasma creatinine was similarly increased in both CKD groups throughout whereas IH alone increased plasma creatinine. IH increases blood pressure further in CKD rats without augmenting declines in GFR but appears to impair GFR in healthy rats. We speculate that treating SA might decrease hypertension development in CKD patients and protect renal function in SA patients.

Impact of continuous positive airway pressure on vascular endothelial growth factor in patients with obstructive sleep apnea: a meta-analysis

PURPOSE

Cumulative evidence supports the clear relationship of obstructive sleep apnea (OSA) with cardiovascular disease (CVD). And, adherence to continuous positive airway pressure (CPAP) treatment alleviates the risk of CVD in subjects with OSA. Vascular endothelial growth factor (VEGF), a potent angiogenic cytokine regulated by hypoxia-inducible factor, stimulates the progression of CVD. Thus, whether treatment with CPAP can actually decrease VEGF in patients with OSA remains inconclusive. The purpose of the present study was to quantitatively evaluate the impact of CPAP therapy on VEGF levels in OSA patients.

METHODS

We systematically searched Web of Science, Cochrane Library, PubMed, and Embase databases that examined the impact of CPAP on VEGF levels in OSA patients prior to May 1, 2017. Related searching terms were "sleep apnea, obstructive," "sleep disordered breathing," "continuous positive airway pressure," "positive airway pressure," and "vascular endothelial growth factor." We used standardized mean difference (SMD) to analyze the summary estimates for CPAP therapy.

RESULTS

Six studies involving 392 patients were eligible for the meta-analysis. Meta-analysis of the pooled effect showed that levels of VEGF were significantly decreased in patients with OSA before and after CPAP treatment (SMD = - 0.440, 95% confidence interval (CI) = - 0.684 to - 0.196, z = 3.53, p = 0.000). Further, results demonstrated that differences in age, body mass index, apnea-hypopnea index, CPAP therapy duration, sample size, and racial differences also affected CPAP efficacy.

CONCLUSIONS

Improved endothelial function measured by VEGF may be associated with CPAP therapy in OSA patients. The use of VEGF levels may be clinically important in evaluating CVD for OSA patients. Further large-scale, well-designed long-term interventional investigations are needed to clarify this issue.

Impact of obstructive sleep apnoea and intermittent hypoxia on cardiovascular and cerebrovascular regulation

NEW FINDINGS

What is the topic of this review? This review examines the notion that obstructive sleep apnoea (OSA) and intermittent hypoxia (IH) have hormetic effects on vascular health. What advances does it highlight? Clinical (OSA patient) and experimental animal and human models report that IH is detrimental to vascular regulation. However, mild IH and, by extension, mild OSA also have physiological and clinical benefits. This review highlights clinical and experimental animal and human data linking OSA and IH to vascular disease and discusses how hormetic effects of OSA and IH relate to OSA severity, IH intensity and duration, and patient/subject age. Obstructive sleep apnoea (OSA) is associated with increased risk of cardiovascular and cerebrovascular disease, a consequence attributed in part to chronic intermittent hypoxia (IH) resulting from repetitive apnoeas during sleep. Although findings from experimental animal, and human, models have shown that IH is detrimental to vascular regulation, the severity of IH used in many of these animal studies [e.g. inspired fraction of oxygen (FI,O2) = 2-3%; oxygen desaturation index = 120 events h^-1 ] is considerably greater than that observed in the majority of patients with OSA. This may also explain disparities between animal and recently developed human models of IH, where IH severity is, by necessity, less severe (e.g. FI,O2 = 10-12%; oxygen desaturation index = 15-30 events h^-1 ). In this review, we highlight the current knowledge regarding the impact of OSA and IH on cardiovascular and cerebrovascular regulation. In addition, we critically discuss the recent notion that OSA and IH may have hormetic effects on vascular health depending on conditions such as OSA severity, IH intensity and duration, and age. In general, data support an independent causal link between OSA and vascular disease, particularly for patients with severe OSA. However, the data are equivocal for older OSA patients and patients with mild OSA, because advanced age and short-duration, low-intensity IH have been reported to provide a degree of protection against IH and ischaemic events such as myocardial infarction and stroke, respectively. Overall, additional studies are needed to investigate the beneficial/detrimental effects of mild OSA on the various vascular beds.

Incidence, Characterization, and Predictors of Sleep Apnea in Consecutive Brain Injury Rehabilitation Admissions

OBJECTIVE

To prospectively examine the incidence and risk factors for sleep apnea in consecutive brain injury rehabilitation admissions.

SETTING

Inpatient neurorehabilitation hospital.

PARTICIPANTS

Participants (n = 86) were consecutive neurorehabilitation admissions.

DESIGN

Retrospective analysis of prospectively collected data.

MAIN MEASURES

Polysomnography.

RESULTS

Half (49%) of the sample was diagnosed with sleep apnea. For the full sample, univariate logistic regression revealed age (odds ratio: 1.08; 95% confidence interval: 1.04-1.11) and hypertension (odds ratio: 7.77; 95% confidence interval: 2.81-21.47) as significant predictors of sleep apnea diagnosis. Results of logistic regression conducted within the traumatic brain injury group revealed age (odds ratio: 1.07; 95% confidence interval: 1.02-1.13) as the only significant predictor of apnea diagnosis after adjustment for other variables. Hierarchical generalized linear regression models for the prediction of apnea severity (ie, apnea-hypopnea index found that Functional Independence Measure Cognition Score (P = .01) and age (P < .01) were significant predictors. Following adjustment for all other terms, only age (P < .01) remained significant.

CONCLUSION

Sleep apnea is prevalent in acute neurorehabilitation admissions and traditional risk profiles for sleep apnea may not effectively screen for the disorder. Given the progressive nature of obstructive sleep apnea and morbidity associated with even mild obstructive sleep apnea, early identification and intervention may address comorbidities influencing acute and long-term outcome.

The Triad of Sleep Apnea, Hypertension, and Chronic Kidney Disease: A Spectrum of Common Pathology

Obstructive sleep apnea (OSA), hypertension, and chronic kidney disease (CKD) are different entities and are generally managed individually most of the time. However, CKD, OSA, and hypertension share many common risk factors and it is not uncommon to see this complex triad together. In fact, they share similar pathophysiology and have been interlinked with each other. The common pathophysiology includes chronic volume overload, hyperaldosteronism, increased sympathetic activity, endothelial dysfunction, and increased inflammatory markers. The combination of this triad has significant negative impact on the cardiovascular health, and increases the mortality and morbidity in this complicated group of patients. On one hand, progression of CKD can lead to the worsening of OSA and hypertension; similarly, worsening sleep apnea can make the hypertension difficult to treat and enhance the progression of CKD. This review article highlights the bidirectional interlink among these apparently different disease processes which share common pathophysiological mechanisms and emphasizes the importance of treating them collectively to improve outcomes.

Continuous positive airway pressure treatment does not normalize the prolonged reflex inhibition to inspiratory loading in obstructive sleep apnea

In obstructive sleep apnea (OSA), the short-latency inhibitory reflex (IR) of inspiratory muscles to airway occlusion is prolonged in proportion to the severity of the OSA. The mechanism underlying the prolongation may relate to chronic inspiratory muscle loading due to upper airway obstruction or sensory changes due to chronic OSA-mediated inflammation. Continuous positive airway pressure (CPAP) therapy prevents upper airway obstruction and reverses inflammation. We therefore tested whether CPAP therapy normalized the IR abnormality in OSA. The IR responses of scalene muscles to brief airway occlusion were measured in 37 adult participants with untreated, mostly severe, OSA, of whom 13 were restudied after the initiation of CPAP therapy (usage >4 h/night). Participants received CPAP treatment as standard clinical care, and the mean CPAP usage between initial and subsequent studies was 6.5 h/night (range 4.1-8.8 h/night) for a mean of 19 mo (range 4–41 mo). The duration of the IR in scalene muscles in response to brief (250 ms) inspiratory loading was confirmed to be prolonged in the participants with OSA. The IR was assessed before and after CPAP therapy. CPAP treatment did not normalize the prolonged duration of the IR to airway occlusion (60 ± 21 ms pretreatment vs. 59 ± 18 ms posttreatment, means ± SD) observed in participants with severe OSA. This suggests that the prolongation of IR reflects alterations in the reflex pathway that may be irreversible, or a specific disease trait.

Hypoxia: The Force that Drives Chronic Kidney Disease

In the United States the prevalence of end-stage renal disease (ESRD) reached epidemic proportions in 2012 with over 600,000 patients being treated. The rates of ESRD among the elderly are disproportionally high. Consequently, as life expectancy increases and the baby-boom generation reaches retirement age, the already heavy burden imposed by ESRD on the US health care system is set to increase dramatically. ESRD represents the terminal stage of chronic kidney disease (CKD). A large body of evidence indicating that CKD is driven by renal tissue hypoxia has led to the development of therapeutic strategies that increase kidney oxygenation and the contention that chronic hypoxia is the final common pathway to end-stage renal failure. Numerous studies have demonstrated that one of the most potent means by which hypoxic conditions within the kidney produce CKD is by inducing a sustained inflammatory attack by infiltrating leukocytes. Indispensable to this attack is the acquisition by leukocytes of an adhesive phenotype. It was thought that this process resulted exclusively from leukocytes responding to cytokines released from ischemic renal endothelium. However, recently it has been demonstrated that leukocytes also become activated independent of the hypoxic response of endothelial cells. It was found that this endothelium-independent mechanism involves leukocytes directly sensing hypoxia and responding by transcriptional induction of the genes that encode the β2-integrin family of adhesion molecules. This induction likely maintains the long-term inflammation by which hypoxia drives the pathogenesis of CKD. Consequently, targeting these transcriptional mechanisms would appear to represent a promising new therapeutic strategy.

Effects of continuous positive airway pressure treatment on coronary vasoreactivity measured by (82)Rb cardiac PET/CT in obstructive sleep apnea patients

PURPOSE

Obstructive sleep apnea syndrome (OSA) increases the risk of cardiovascular disease. We aimed at evaluating the effect of continuous positive airway pressure (CPAP) treatment on coronary endothelium-dependent vasoreactivity in OSA patients by quantifying myocardial blood flow (MBF) response to cold pressure testing (CPT).

METHODS

In the morning after polysomnography (PSG), all participants underwent a dynamic (82)Rb cardiac positron emitting tomography/computed tomography (PET/CT) scan at rest, during CPT and adenosine stress. PSG and PET/CT were repeated at least 6 weeks after initiating CPAP treatment. OSA patients were compared to controls and according to response to CPAP. Patients' characteristics and PSG parameters were used to determine predictors of CPT-MBF.

RESULTS

Thirty-two untreated OSA patients (age 58 ± 13 years, 27 men) and 9 controls (age 62 ± 5 years, 4 men) were enrolled. At baseline, compared to controls (apnea-hypopnea index (AHI) = 5.3 ± 2.6/h), untreated OSA patients (AHI = 48.6 ± 19.7/h) tend to have a lower CPT-MBF (1.1 ± 0.2 mL/min/g vs. 1.3 ± 0.4 mL/min/g, p = 0.09). After initiating CPAP, CPT-MBF was not different between well-treated patients (AHI <10/h) and controls (1.3 ± 0.3 mL/min/g vs. 1.3 ± 0.4 mL/min/g, p = 0.83), but it was lower for insufficiently treated patients (AHI ≥10/h) (0.9 ± 0.2 mL/min/g vs. 1.3 ± 0.4 mL/min/g, p = 0.0045). CPT-MBF was also higher in well-treated than in insufficiently treated patients (1.3 ± 0.3 mL/min/g vs. 0.9 ± 0.2 mL/min/g, p = 0.001). Mean nocturnal oxygen saturation (β = -0.55, p = 0.02) and BMI (β = -0.58, p = 0.02) were independent predictors of CPT-MBF in OSA patients.

CONCLUSIONS

Coronary endothelial vasoreactivity is impaired in insufficiently treated OSA patients compared to well-treated patients and controls, confirming the need for CPAP optimization.

A novel management program for hypertension

In this article, we describe a comprehensive management program for hypertension (HTN), based on the experience of leading cardiovascular centers in China. This comprehensive approach, adhering to a number of core principles, includes diagnosis and therapeutic interventions. Therapeutic management includes lifestyle changes, risk factor management and pharmacological intervention and should allow reliable lowering blood pressure (BP). Additional paragraphs discuss the relationship between paroxysmal atrial fibrillation (PAF), and HTN.

Obstructive sleep apnoea syndrome, endothelial function and markers of endothelialization. Changes after CPAP

Study objectives

This study tries to assess the endothelial function in vivo using flow-mediated dilatation (FMD) and several biomarkers of endothelium formation/restoration and damage in patients with obstructive sleep apnoea (OSA) syndrome at baseline and after three months with CPAP therapy.

Design

Observational study, before and after CPAP therapy.

Setting and Patients

We studied 30 patients with apnoea/hypopnoea index (AHI) >15/h that were compared with themselves after three months of CPAP therapy. FMD was assessed non-invasively in vivo using the Laser-Doppler flowmetry. Circulating cell-free DNA (cf-DNA) and microparticles (MPs) were measured as markers of endothelial damage and the vascular endothelial growth factor (VEGF) was determined as a marker of endothelial restoration process.

Measurements and results

After three month with CPAP, FMD significantly increased (1072.26 ± 483.21 vs. 1604.38 ± 915.69 PU, p< 0.005) cf-DNA and MPs significantly decreased (187.93 ± 115.81 vs. 121.28 ± 78.98 pg/ml, p<0.01, and 69.60 ± 62.60 vs. 39.82 ± 22.14 U/μL, p<0.05, respectively) and VEGF levels increased (585.02 ± 246.06 vs. 641.11 ± 212.69 pg/ml, p<0.05). These changes were higher in patients with more severe disease. There was a relationship between markers of damage (r = -0.53, p<0.005) but not between markers of damage and restoration, thus suggesting that both types of markers should be measured together.

Conclusions

CPAP therapy improves FMD. This improvement may be related to an increase of endothelial restoration process and a decrease of endothelial damage.

Does airway surgery lower serum lipid levels in obstructive sleep apnea patients? A retrospective case review

Background

Obstructive sleep apnea (OSA) is tightly linked to increased cardiovascular disease. Surgery is an important method to treat OSA, but its effect on serum lipid levels in OSA patients is unknown. We aimed to evaluate the effect of upper airway surgery on lipid profiles.

Material/Methods

We performed a retrospective review of 113 adult patients with OSA who underwent surgery (nasal or uvulopalatopharyngoplasty [UPPP]) at a major, urban, academic hospital in Beijing from 2012 to 2013 who had preoperative and postoperative serum lipid profiles.

Results

Serum TC (4.86±0.74 to 4.69±0.71) and LP(a) (median 18.50 to 10.90) all decreased significantly post-operatively (P<0.01, 0.01, respectively), with no changes in serum HDL, LDL, or TG (P>0.05, all). For UPPP patients (n=51), serum TC, HDL and LP(a) improved (P=0.01, 0.01,<0.01, respectively). For nasal patients (n=62), only the serum LP(a) decreased (P<0.01). In patients with normal serum lipids at baseline, only serum LP(a) decreased (P<0.01). In contrast, in patients with isolated hypertriglyceridemia, the serum HDL, TG and LP(a) showed significant improvements (P=0.02, 0.03, <0.01, respectively). In patients with isolated hypercholesterolemia, the serum LP(a) decreased significantly (P=0.01), with a similar trend for serum TC (P=0.06). In patients with mixed hyperlipidemia, the serum TC and LDL also decreased (P=0.02, 0.03, respectively).

Conclusions

Surgery may improve blood lipid levels in patients with OSA, especially in patients with preoperative dyslipidemia, potentially yielding a major benefit in metabolism and cardiovascular sequelae. Prospective studies should examine this potential metabolic effect of airway surgery for OSA.

Beneficial effect of continuous positive airway pressure on lipid profiles in obstructive sleep apnea: a meta-analysis

Purpose

Dyslipidemia is considered as one mechanism causing cardiovascular sequelae in obstructive sleep apnea (OSA). Continuous positive airway pressure (CPAP) can reduce cardiovascular morbidities but its effect on lipid profiles is inconclusive. This study aimed to investigate the effects of CPAP on lipid profiles by a meta-analysis of the existing randomized controlled trials.

Methods

Studies were retrieved from MEDLINE/PubMed, EMBASE, CENTRAL, commercial websites, and article references up to August 2013 following the protocols (PROSPERO CRD42012002636). Randomized controlled trials investigating the CPAP effects on changes in lipid profiles in adult patients with OSA were included. Two independent researchers extracted relevant data in duplicate. The pooled effect was analyzed by fixed-effect generic inverse variance, and the heterogeneity was assessed using the I² statistic.

Results

Six trials with 348 patients and 351 controls were included. CPAP significantly lowered total cholesterol (mean, −6.23 mg/dl; 95% CI, −8.73 to –3.73; I², 0 %; p < 0.001), triglyceride (mean, −12.60 mg/dl; 95% CI, −18.80 to −6.41; I², 25 %; p < 0.001), and high-density lipoprotein (mean, −1.05 mg/dl; 95% CI, −1.69 to −0.40; I², 0 %; p = 0.001), but not low-density lipoprotein (mean, −1.01 mg/dl; 95% CI, −5.04 to 3.02; I², 0 %; p = 0.62). The lipid-lowering effects were homogeneous across the studies. By subgroup analysis, the reductions of lipid profiles were associated with the cross-over design, subtherapeutic CPAP as placebo, enrolled patients with moderate-to-severe OSA or daytime sleepiness, and CPAP treatment with short-term duration or good compliance.

Conclusions

This meta-analysis validates the observation that CPAP can reduce lipid profiles in patients with OSA.

Electronic supplementary material

The online version of this article (doi:10.1007/s11325-014-1082-x) contains supplementary material, which is available to authorized users.

Coronary endothelial function in patients with obstructive sleep apnea

OBJECTIVE

Obstructive sleep apnea (OSA) has been associated with increased risk for cardiovascular events, possibly mediated by endothelial dysfunction. The current study evaluates the association between invasive coronary endothelial dysfunction and OSA in patients with nonobstructive coronary atherosclerosis.

METHODS

All patients who had undergone both polysomnography and an invasive coronary vasomotor study at the Mayo Clinic, Rochester, Minnesota, from January 1997 to August 2011 were identified (n=143). OSA was defined as an apnea-hypopnea index of 5 or higher. Three endpoints of coronary endothelial function - percentage change in coronary artery diameter at the mid and distal left anterior descending artery to intracoronary acetylcholine and percentage change in coronary blood flow to intracoronary acetylcholine - were assessed. Differences between patients with OSA (n=102) and those without OSA (n=41) were evaluated using multivariate analysis of variance. Follow-up mortality data were collected and Kaplan-Meier curves were plotted to evaluate differences in mortality between patients with and without OSA.

RESULTS

Patients with OSA were more likely to have hypertension compared with patients without OSA. OSA was not significantly associated with coronary endothelial dysfunction on univariate analysis (P=0.23) and after adjustment for hypertension (P=0.19). Similarly, there was no significant difference in coronary endothelial function in patients who had oxygen desaturation of less than 90% during polysomnography (P=0.42). There was a trend toward higher mortality in patients with OSA compared with those without OSA, but this did not reach statistical significance (5 vs. 0% at 10 years, P=0.25).

CONCLUSION

The current study suggests that OSA is not an independent risk factor for coronary endothelial dysfunction in patients with early coronary atherosclerosis. Adverse coronary outcomes in patients with OSA may be independent of coronary endothelial dysfunction.

Adaptive servo-ventilation therapy improves long-term prognosis in heart failure patients with anemia and sleep-disordered breathing

Sleep disordered breathing (SDB) and anemia influences the progression of chronic heart failure (CHF). Adaptive servo-ventilation (ASV) is an effective therapeutic device for treatment of CHF, however, the impacts of ASV on CHF patients with or without anemia remain unclear.A total of 139 patients with CHF and SDB were divided into two groups: those treated with ASV (n = 53) and without ASV (n = 86). All patients were prospectively followed after discharge with the endpoints of cardiac death or progressive heart failure requiring rehospitalization. There were 65 patients (47%) with anemia among all subjects. The apnea hypopnea index was improved, and plasma BNP and high sensitive C-reactive protein levels were decreased in both groups with and without anemia by ASV therapy. The Kaplan-Meier survival curve demonstrated that the cardiac event-free rate in patients with ASV was significantly higher than in those without ASV in the anemia group (P = 0.008). However, in the non-anemia group, the cardiac event-free rate was similarly high in patients both with and without ASV (P = 0.664). Multivariate Cox proportional hazard analysis demonstrated that ASV use was an independent predictor of cardiac events in the anemia group (P = 0.0308), but not in the non-anemia group.ASV treatment for CHF and SDB has more favorable impacts in patients with anemia than in those without anemia.

The effect of continuous positive airway pressure therapy on arterial stiffness and endothelial function in obstructive sleep apnea: a randomized controlled trial in patients without cardiovascular disease

BACKGROUND

Obstructive sleep apnea (OSA) is associated with increased cardiovascular morbidity and mortality which may be mediated by increased arterial stiffness and endothelial dysfunction. Continuous positive airway pressure (CPAP) therapy improves excessive daytime somnolence (EDS), but its effect on vascular function in patients without preexisting cardiovascular disease (CVD) is unclear.

METHODS

Fifty-three patients with OSA defined as an apnea-hypopnea index (AHI) of ⩾15 and without CVD were recruited into a double-blind, randomized, placebo-controlled, crossover trial of 12weeks of CPAP therapy, of whom 43 participants completed the study protocol. Arterial stiffness was assessed by measuring the augmentation index (AIx) and pulse wave velocity (PWV) by applanation tonometry and cardiovascular magnetic resonance imaging to determine aortic distensibility. Endothelial function was assessed by measuring vascular reactivity after administration of salbutamol and glyceryl trinitrate.

RESULTS

CPAP therapy lowered systolic blood pressure (SBP) (126mmHg [standard deviation {SD}, 12] vs 129mmHg [SD, 14]; P=.03), with a trend towards reduced AIx (15.5 [SD, 11.9] vs 16.6 [SD, 11.7]%; P=.08) but did not modify endothelial function. When subjects with (n=24) and without (n=19) EDS were separately examined, no effect of CPAP therapy on vascular function was seen.

CONCLUSIONS

In patients without overt CVD, CPAP therapy had a nonsignificant effect on AIx and did not modify endothelial function.

Obstructive sleep apnea syndrome, vascular pathology, endothelial function and endothelial cells and circulating microparticles

Accelerated atherosclerosis and increased cardiovascular risk are frequently reported in patients with obstructive sleep apnea (OSA) syndrome. In this article the authors attempt a review of the current understanding of the relationship between vascular risk and OSA syndrome based on large cohort studies that related the disease to several cardiovascular risk factors and vascular pathologies. We also discuss the pathophysiological mechanisms that may be involved in this relationship, starting with endothelial dysfunction and its mediators. These include an increased oxidative stress and inflammation as well as several disorders of coagulation and lipid metabolism. Moreover, circulating microparticles from activated leukocytes (CD62L_MPs) are higher in patients with OSA and there is a positive correlation between circulating levels of CD62L_MPs and nocturnal hypoxemia severity. Finally, circulating level of endothelial microparticles and circulating endothelial cells seem to be increased in patients with OSA. Also, endothelial progenitor cells are reduced and plasma levels of the vascular endothelial growth factor are increased.

Effects of continuous positive airway pressure on endothelial function and circulating progenitor cells in obstructive sleep apnoea: a randomised sham-controlled study

OBJECTIVE

Obstructive sleep apnoea (OSA) is characterised by reoccurring apnoeas and hypopneas, causing repetitive hypoxia and reoxygenation, and is associated with endothelial dysfunction and reduced levels of circulating progenitor cells (CPCs). The potential to improve endothelial function and CPC levels in people with OSA by preventing hypoxic episodes with Continuous Positive Airway Pressure (CPAP) was investigated in a sham-controlled CPAP study.

METHODS

Men with moderate-to-severe OSA (mean ± SD: age=49 ± 12 y, apnoea hypopnea index (AHI)=37.6 ± 16.4 events/h, body mass index=31.5 ± 5.7 kg/m(2)) who were CPAP naïve without diabetes mellitus were randomised in a 12-week double-blind sham-controlled parallel group study to receive either active (n=25) or sham (n=21) CPAP. CPCs, isolated from blood, were measured by flow cytometry and by co-staining cultured cells (7 days) with acetylated low-density lipoprotein (acLDL) and lectin. Endothelial function was assessed by peripheral arterial tonometry (PAT).

RESULTS

Compared to sham, CPAP significantly decreased AHI (mean between-group difference -36.0 events/h; 95%CI, -49.7 to -22.3, p<0.0001) after 12 weeks. Despite this improvement in AHI, CPAP had no effect on change in CPC levels (including CD34(+)/KDR(+) (565 cells/mL; -977 to 2106, p=0.45), CD34(+)/KDR(+)/CD45(-) (37.0 cells/mL; -17.7 to 85.7, p=0.13), acLDL(+)/lectin(+) (-43.1 cells/field, -247 to 161, p=0.67)) or change in endothelial function (0.27; -0.14 to 0.67, p=0.19) compared to sham therapy.

CONCLUSIONS

Despite the improvement in OSA parameters and ablation of apnoeic events by CPAP, CPC counts and endothelial function in men with moderate-to-severe OSA were not significantly improved after 12 weeks of therapeutic CPAP when compared to sham control.

Cerebral hemodynamic changes in obstructive sleep apnea syndrome after continuous positive airway pressure treatment

BACKGROUND

Patients with obstructive sleep apnea syndrome (OSAS) are at increased risk for cerebrovascular diseases. The underlying mechanisms remain obscure. It may occur through a reduction in cerebral vascular reactivity. Continuous positive airway pressure (CPAP) is effective in reducing the occurrence of apneas. We hypothesized that treatment with CPAP improves cerebral vascular reactivity.

METHODS

This is a prospective study with OSAS patients. The apnea test (ApT) was calculated as an increase of mean artery velocity during apnea: [Artery velocity in apnea minus Resting artery velocity]/Resting artery velocity expressed as percentage. After 2 years of CPAP treatment, the test was repeated.

RESULTS

Seventy-six patients represented the study pool. After 2 years of treatment with CPAP, we were able to conduct a reassessment in 65 patients. Of the 65 patients who finished the clinical study, 56 were men, and 9 were women, with an average age of 48.1 ± 10.4 years. There was an improvement in the ApT after CPAP treatment (30.8 ± 12.1 vs 39.8 ± 15.1; p:0.000). The values of cerebral blood flow velocities, diastolic blood pressure in apnea, and basal heart rate decreased.

CONCLUSIONS

Cerebral vascular reactivity in OSAS patients measured by ApT improved after 2 years of CPAP.