Effectiveness of continuous positive airway pressure in lowering blood pressure in patients with obstructive sleep apnea: a critical review of the literature

Obstructive sleep apnea and hypertension; critical overview

Obstructive sleep apnea (OSA) and hypertension are two important modifiable risk factors for cardiovascular disease and mortality. Numerous studies have highlighted the interplay between these two conditions. We provide a critical review of the current literature on the role of the OSA as a risk factor for hypertension and its effect on blood pressure (BP). We discuss several key topics: the effect of OSA on nocturnal BP, BP response to continuous positive airway pressure (CPAP) treatment, CPAP effect on BP in refractory hypertension, the role of OSA in BP variability (BPV), and maladaptive cardiac remodeling mediated by OSA's effect on BP. Finally, we discuss the unique aspects of ethnicity and social determinants of health on OSA with a focus on Asian populations and the disparity in BP control and cardiovascular outcomes.

Heterologous mRNA-protein vaccination with Tc24 induces a robust cellular immune response against Trypanosoma cruzi, characterized by an increased level of polyfunctional CD8+ T-cells

Tc24 is a Trypanosoma cruzi-derived flagellar protein that, when formulated with a TLR-4 agonist adjuvant, induces a balanced immune response in mice, elevating IgG2a antibody titers and IFN-γ levels. Furthermore, vaccination with the recombinant Tc24 protein can reduce parasite levels and improve survival during acute infection. Although some mRNA vaccines have been proven to elicit a stronger immune response than some protein vaccines, they have not been used against T. cruzi. This work evaluates the immunogenicity of a heterologous prime/boost vaccination regimen using protein and mRNA-based Tc24 vaccines. Mice (C57BL/6) were vaccinated twice subcutaneously, three weeks apart, with either the Tc24-C4 protein + glucopyranosyl A (GLA)-squalene emulsion, Tc24 mRNA Lipid Nanoparticles, or with heterologous protein/mRNA or mRNA/protein combinations, respectively. Two weeks after the last vaccination, mice were euthanized, spleens were collected to measure antigen-specific T-cell responses, and sera were collected to evaluate IgG titers and isotypes. Heterologous presentation of the Tc24 antigen generated antigen-specific polyfunctional CD8+ T cells, a balanced Th1/Th2/Th17 cytokine profile, and a balanced humoral response with increased serum IgG, IgG1 and IgG2c antibody responses. We conclude that heterologous vaccination using Tc24 mRNA to prime and Tc24-C4 protein to boost induces a broad and robust antigen-specific immune response that was equivalent or superior to two doses of a homologous protein vaccine, the homologous mRNA vaccine and the heterologous Tc24-C4 Protein/mRNA vaccine.

Chagas Disease in Pregnant Women from Endemic Regions Attending the Hospital General de Mexico, Mexico City

Trypanosoma cruzi infection leads to Chagas disease (CD), a neglected tropical infection of significant public health importance in South and Central America and other, non-endemic, countries. Pregnant women and their children are of particular importance to screen as T. cruzi can be transmitted vertically. The objective of this study was to screen for T. cruzi infection among pregnant women from endemic areas seen at the Hospital General de Mexico for prenatal care, so that they and their children may be quickly connected to CD treatment. Pregnant women were recruited through the hospital prenatal clinic and screened for T. cruzi infection using a series of serological and molecular tests. Of 150 screened patients, mean age 26.8 (SD 6.4), 30 (20.0%) were positive by at least one diagnostic test. Of these, only nine (6%) were positive as determined by PCR. Diagnosis of chronic CD is difficult in endemic places like Mexico due to the limitations of current commercially available diagnostic tests. Further evaluation of diagnostic performance of various assays could improve current CD diagnostic algorithms and proper care management in these regions. Genetic variability in the parasite may also play a role in the differing assay performances seen in this study, and this may be a valuable avenue of further research.

Six Months of Inspiratory Muscle Training to Lower Blood Pressure and Improve Endothelial Function in Middle-Aged and Older Adults With Above-Normal Blood Pressure and Obstructive Sleep Apnea: Protocol for the CHART Clinical Trial

Background: Cardiovascular disease is a major global health concern and prevalence is high in adults with obstructive sleep apnea (OSA). Lowering blood pressure (BP) can greatly reduce cardiovascular disease risk and physical activity is routinely prescribed to achieve this goal. Unfortunately, many adults with OSA suffer from fatigue, daytime sleepiness, and exercise intolerance—due to poor sleep quality and nocturnal hypoxemia—and have difficulty initiating and maintaining an exercise program. High-resistance inspiratory muscle strength training (IMST) is a simple, time-efficient breathing exercise consistently reported to reduce BP in small, selective groups of both healthy and at-risk adults. Herein we present the study protocol for a randomized clinical trial to determine the long-term efficacy of IMST performed regularly for 24 weeks in middle-aged and older adults with OSA. The primary outcome is casual systolic BP. Secondary outcomes are 24-h systolic BP and circulating plasma norepinephrine concentration. Other outcomes include vascular endothelial function (endothelial-dependent and -independent dilation), aortic stiffness, casual and 24-h diastolic BP, and the influence of circulating factors on endothelial cell nitric oxide and reactive oxygen species production. Overall, this trial will establish efficacy of high-resistance IMST for lowering BP and improving cardiovascular health in middle-aged and older adults with OSA.

Methods: This is a single-site, double-blind, randomized clinical trial. A minimum of 92 and maximum of 122 male and female adults aged 50–80 years with OSA and above-normal BP will be enrolled. After completion of baseline assessments, subjects will be randomized in a 1:1 ratio to participate in either high-resistance or sham (low-resistance) control IMST, performed at home, 5 min/day, 5 days/week, for 24 weeks. Repeat assessments will be taken after the 24-week intervention, and after 4 and 12 weeks of free living.

Discussion: This study is designed to assess the effects of 24 weeks of IMST on BP and vascular function. The results will characterize the extent to which IMST can reduce BP when performed over longer periods (i.e., 6 months) than have been assessed previously. Additionally, this study will help to determine underlying mechanisms driving IMST-induced BP reductions that have been reported previously.

Clinical Trial Registration: This trial is registered with ClinicalTrials.gov (Registration Number: NCT04932447; Date of registration June 21, 2021).

The effect of continuous positive airway pressure on blood pressure in patients with obstructive sleep apnea and uncontrolled hypertension - Study design and challenges during the COVID-19 pandemic

OBJECTIVES

To describe the MORPHEOS (Morbidity in patients with uncontrolled HTN and OSA) trial, and describe the challenges imposed by the COVID-19 pandemic.

METHODS

MORPHEOS is a multicenter (n=6) randomized controlled trial designed to evaluate the blood pressure (BP) lowering effects of treatment with continuous positive airway pressure (CPAP) or placebo (nasal strips) for 6 months in adult patients with uncontrolled hypertension (HTN) and moderate-to-severe obstructive sleep apnea (OSA). Patients using at least one antihypertensive medication were included. Uncontrolled HTN was confirmed by at least one abnormal parameter in the 24-hour ABPM and ≥80% medication adherence evaluated by pill counting after the run-in period. OSA was defined by an apnea-hypopnea index ≥15 events/hours. The co-primary endpoints are brachial BP (office and ambulatory BP monitoring, ABPM) and central BP. Secondary outcomes include hypertension-mediated organ damage (HMOD) to heart, aorta, eye, and kidney. We pre-specified several sub-studies from this investigation. Visits occur once a week in the first month and once a month thereafter. The programmed sample size was 176 patients but the pandemic prevented this final target. A post-hoc power analysis will be calculated from the final sample. ClinicalTrials.gov: NCT02270658.

RESULTS

The first 100 patients are predominantly males (n=69), age: 52±10 years, body mass index: 32.7±3.9 kg/m2 with frequent co-morbidities.

CONCLUSIONS

The MORPHEOS trial has a unique study design including a run-in period; pill counting, and detailed analysis of hypertension-mediated organ damage in patients with uncontrolled HTN that will allow clarification of the impact of OSA treatment with CPAP.

Obstructive sleep apnea and ambulatory blood pressure monitoring: current evidence and research gaps

Obstructive Sleep Apnea (OSA) is a common condition characterized by intermittent collapse of the upper airway during sleep, resulting in partial (hypopnoeas) and total obstructions (apneas). These respiratory events observed in OSA may trigger multiple pathways involved in the blood pressure (BP) instability during the night and potentially influencing daytime BP as well (carry-over effects). This review provides an update about the impact of OSA and its treatments on 24-h BP control. Overall, there is growing evidence suggest that OSA is associated with higher frequency of nondipping BP pattern and nocturnal hypertension in a dose-dependent manner. The presence of nondiping BP (especially the reverse pattern) is independently associated with OSA regardless of sleep-related symptoms suggesting a potential tool for screening OSA in patients with clinical indication for performing ABPM. Beyond dipping BP, preliminary evidence associated OSA with white-coat effect and higher frequency of masked hypertension and BP variability than the control group (no OSA). Unfortunately, most of the evidence on the evidence addressing the impact of OSA treatment on BP was limited to office measurements. In the last years, data from observational and randomized studies pointed that CPAP is able to promote 24-h BP decrease especially in patients with resistant and refractory hypertension. A randomized trial suggests that CPAP is able to decrease the rate of masked hypertension as compared to no treatment in patients with severe OSA. Interestingly, nondipping BP is a good predictor of BP response to CPAP making ABPM an interesting tool for better OSA management.

Preliminary Characterization of Triatomine Bug Blood Meals on the Island of Trinidad Reveals Opportunistic Feeding Behavior on Both Human and Animal Hosts

Chagas disease is a neglected tropical disease caused by infection with Trypanosoma cruzi. The parasite is endemic to the Americas, including the Caribbean, where it is vectored by triatomine bugs. Although Chagas disease is not considered a public health concern in the Caribbean islands, studies in Trinidad have found T. cruzi-seropositive humans and T. cruzi-infected triatomine bugs. However, little is known about triatomine bug host preferences in Trinidad, making it difficult to evaluate local risk of vector-borne T. cruzi transmission to humans. To investigate this question, we collected triatomine bugs in Trinidad and diagnosed each one for T. cruzi infection (microscopy and PCR). We then carried out a blood meal analysis using DNA extracted from each bug (PCR and sequencing). Fifty-five adult bugs (54 Panstrongylus geniculatus and one Rhodnius pictipes) were collected from five of 21 sample sites. All successful collection sites were residential. Forty-six out of the 55 bugs (83.6%) were infected with T. cruzi. Fifty-three blood meal hosts were successfully analyzed (one per bug), which consisted of wild birds (7% of all blood meals), wild mammals (17%), chickens (19%), and humans (57%). Of the 30 bugs with human blood meals, 26 (87%) were from bugs infected with T. cruzi. Although preliminary, our results align with previous work in which P. geniculatus in Trinidad had high levels of T. cruzi infection. Furthermore, our findings suggest that P. geniculatus moves between human and animal environments in Trinidad, feeding opportunistically on a wide range of species. Our findings highlight a critical need for further studies of Chagas disease in Trinidad in order to estimate the public health risk and implement necessary preventative and control measures.

Inspiratory muscle strength training lowers blood pressure and sympathetic activity in older adults with OSA: a randomized controlled pilot trial

Previous work has shown lowered casual blood pressure after just 6 wk of inspiratory muscle strength training (IMST), suggesting IMST as a potential therapeutic in the prevention/treatment of hypertension. In this study, we assessed the effects of IMST on cardiovascular parameters in older, overweight adults diagnosed with moderate and severe obstructive sleep apnea (OSA). Subjects were randomly assigned to one of two interventions 1) high-intensity IMST (n = 15, 75% maximal inspiratory pressure), or 2) a control intervention (n = 10, 15% maximum inspiratory pressure). Subjects in both groups trained at home completing 30 training breaths/day, 5 days/wk for 6 wk. Pre- and posttraining measures included maximal inspiratory pressure, casual and ambulatory blood pressures, spontaneous cardiac baroreflex sensitivity, and muscle sympathetic nerve activity. Men and women in the high-intensity IMST group exhibited reductions in casual systolic (SBP), diastolic (DBP), and mean arterial blood pressures (MAP) [SBP: -8.82 ± 4.98 mmHg; DBP: -4.69 ± 2.81 mmHg; and MAP: -6.06 ± 1.03 mmHg; P < 0.002] and nighttime SBP (pre: -12.00 ± 8.20 mmHg; P < 0.01). Muscle sympathetic nerve activities also were lower (-6.97 ± 2.29 bursts/min^-1; P = 0.01 and -9.55 ± 2.42 bursts/100 heartbeats; P = 0.002) by week 6. Conversely, subjects allocated to the control group showed no change in casual blood pressure or muscle sympathetic nerve activity and a trend toward higher overnight blood pressures. A short course of high-intensity IMST may offer significant respiratory and cardiovascular benefits for older, overweight adults with OSA. For Clinical Trial Registration, see https://www.clinicaltrials.gov (Identifier: NCT02709941).NEW & NOTEWORTHY Older, obese adults with moderate-severe obstructive sleep apnea who perform 5 min/day high-intensity inspiratory muscle strength training (IMST) exhibit lowered casual and nighttime systolic blood pressure and sympathetic nervous outflow. In contrast, adults assigned to a control (low-intensity) intervention exhibit no change in casual blood pressure or muscle sympathetic nerve activity and a trend toward increased overnight blood pressure. Remarkably, adherence to IMST even among sleep-deprived and exercise-intolerant adults is high (96%).

Reducing Coronary Heart Disease Risk Through Treatment of Insomnia Using Web-Based Cognitive Behavioral Therapy for Insomnia: A Methodological Approach

Objective: Observational data demonstrate increased risk of recurrent acute coronary syndrome in patients with comorbid insomnia. We conducted a pragmatic randomized controlled pilot study to address knowledge gaps and inform future large-scale randomized trials to test the impact of Web-based cognitive behavioral therapy for insomnia (wCBT-I) on coronary heart disease (CHD) outcomes. Participants: Thirty-five adults recruited from Brigham and Women's and Cleveland Clinic Hospitals with insomnia, defined by Insomnia Severity Index (ISI) score ≥ 10 and symptoms of at least 3 months, and comorbid CHD identified from medical records. Methods: We randomized 34 patients to either general sleep education coupled with wCBT-I or general sleep education alone followed by an opportunity for treatment after the study (a wait-list control) to evaluate feasibility and uptake of insomnia treatment in patients with heart disease. Participants completed the ISI at baseline and 6 weeks to assess insomnia severity. Results: Twenty-nine adults completed the trial, yielding an 85% retention rate, and adherence rate in the treatment arm was 80%. Mean age was 71.6 ± 9.5 years, 75% were male, and mean body mass index (BMI) was 29 ± 4.5 kg/m². Baseline ISI scores were 15.6. There was a 6.2 ± 5.3 point reduction in ISI scores in the intervention arm and a 3.3 ± 5.1 reduction in the control arm (p value 0.1). Conclusion: Web-based CBT-I intervention was feasible in an older sample with prevalent CHD and resulted in clinically meaningful improvement in insomnia severity, though statistical significance was limited by lack of power.

Resistant Hypertension: Time to Consider the Best Fifth Anti-Hypertensive Treatment

PURPOSE OF REVIEW

Resistant hypertension (RH) is a growing clinical condition worldwide associated with target-organ damage and poor prognosis compared to non-resistant counterparts. The purpose of this review is to perform a critical evaluation of preferable drug choices for managing RH highlighting the evidence that significant proportion of patients remained uncontrolled despite using four anti-hypertensive drugs.

RECENT FINDINGS

Until recently, the fourth drug therapy was main derived from personal opinion or small interventional studies. The recent data derived from two multicentric randomized trials, namely PATHWAY-2 and ReHOT, pointed spironolactone as the preferable fourth drug therapy in patients with confirmed RH as compared to bisoprolol and doxazosin (PATHWAY-2) as well as clonidine (ReHOT). However, significant proportion of patients (especially observed in ReHOT trial that used 24-h ambulatory blood pressure monitoring) did not achieve optimal blood pressure with the fourth drug. This finding underscores the need of new approaches and treatment options in this important research area. The current evidence pointed that significant proportion of RH patients are requiring more than four drugs for controlling BP. This statement is particularly true considering the new criteria proposed by the 2017 Guidelines for diagnosing RH (> 130 × 80 mmHg). New combinations, drugs, or treatments should be tested aiming to reduce the RH burden. Based on the aforementioned multicentric trials, we proposed the first five preferable anti-hypertensive classes in the overall context of RH.

Investigation of the binding mode of a novel cruzain inhibitor by docking, molecular dynamics, ab initio and MM/PBSA calculations

Chagas disease remains a major health problem in South America, and throughout the world. The two drugs clinically available for its treatment have limited efficacy and cause serious adverse effects. Cruzain is an established therapeutic target of Trypanosoma cruzi, the protozoan that causes Chagas disease. Our group recently identified a competitive cruzain inhibitor (compound 1) with an IC₅₀ = 15 µM that is also more synthetically accessible than the previously reported lead, compound 2. Prior studies, however, did not propose a binding mode for compound 1, hindering understanding of the structure-activity relationship and optimization. Here, the cruzain binding mode of compound 1 was investigated using docking, molecular dynamics (MD) simulations with ab initio derived parameters, ab initio calculations, and MM/PBSA. Two ligand protonation states and four binding poses were evaluated. A careful ligand parameterization method was employed to derive more physically meaningful parameters than those obtained by automated tools. The poses of unprotonated 1 were unstable in MD, showing large conformational changes and diffusing away from the binding site, whereas the protonated form showed higher stability and interaction with negatively charged residues Asp161 and Cys25. MM/PBSA also suggested that these two residues contribute favorably to binding of compound 1. By combining results from MD, ab initio calculations, and MM/PBSA, a binding mode of 1 is proposed. The results also provide insights for further optimization of 1, an interesting lead compound for the development of new cruzain inhibitors.

Obstructive Sleep Apnea-Induced Hypertension: Role of the Gut Microbiota

PURPOSE OF REVIEW

Obstructive sleep apnea (OSA) is a significant risk factor for systemic hypertension and other cardiovascular diseases. While this relationship has been firmly established, a detailed understanding of how OSA leads to hypertension is lacking. This review will examine the emerging idea that the gut microbiota plays a role in the development of hypertension, including that associated with OSA.

RECENT FINDINGS

Disruption of the normal composition of the gut microbiota, termed dysbiosis, has been identified in a number of metabolic and cardiovascular diseases, including diabetes, obesity, and atherosclerosis. Recently, a number of studies have demonstrated gut dysbiosis in various animal models of hypertension as well as in hypertensive patients. Evidence is now emerging that gut dysbiosis plays a causal role in the development of OSA-induced hypertension. In this review, we will examine the evidence that gut dysbiosis plays a role in OSA-induced hypertension. We will discuss potential mechanisms linking OSA to gut dysbiosis, examine how gut dysbiosis may be linked to hypertension, and highlight how this understanding may be utilized for the development of future therapeutics.

Sleep Apnea and Cardiovascular Disease: Lessons From Recent Trials and Need for Team Science

Emerging research highlights the complex interrelationships between sleep-disordered breathing and cardiovascular disease, presenting clinical and research opportunities as well as challenges. Patients presenting to cardiology clinics have a high prevalence of obstructive and central sleep apnea associated with Cheyne-Stokes respiration. Multiple mechanisms have been identified by which sleep disturbances adversely affect cardiovascular structure and function. Epidemiological research indicates that obstructive sleep apnea is associated with increases in the incidence and progression of coronary heart disease, heart failure, stroke, and atrial fibrillation. Central sleep apnea associated with Cheyne-Stokes respiration predicts incident heart failure and atrial fibrillation; among patients with heart failure, it strongly predicts mortality. Thus, a strong literature provides the mechanistic and empirical bases for considering obstructive sleep apnea and central sleep apnea associated with Cheyne-Stokes respiration as potentially modifiable risk factors for cardiovascular disease. Data from small trials provide evidence that treatment of obstructive sleep apnea with continuous positive airway pressure improves not only patient-reported outcomes such as sleepiness, quality of life, and mood but also intermediate cardiovascular end points such as blood pressure, cardiac ejection fraction, vascular parameters, and arrhythmias. However, data from large-scale randomized controlled trials do not currently support a role for positive pressure therapies for reducing cardiovascular mortality. The results of 2 recent large randomized controlled trials, published in 2015 and 2016, raise questions about the effectiveness of pressure therapies in reducing clinical end points, although 1 trial supported the beneficial effect of continuous positive airway pressure on quality of life, mood, and work absenteeism. This review provides a contextual framework for interpreting the results of recent studies, key clinical messages, and suggestions for future sleep and cardiovascular research, which include further consideration of individual risk factors, use of existing and new multimodality therapies that also address adherence, and implementation of trials that are sufficiently powered to target end points and to support subgroup analyses. These goals may best be addressed through strengthening collaboration among the cardiology, sleep medicine, and clinical trial communities.

The Role of Metabolic Surgery on Blood Pressure Control

Obesity and hypertension are growing epidemics in the modern world. Lifestyle changes and medical treatment for obesity have disappointing long-term results and albeit drugs for hypertension are usually very effective, the necessity of multiple pills and frequent side effects make the adherence to treatment a huge challenge for healthcare systems. Bariatric/metabolic surgery is a very effective treatment and an exponential number of studies have been showing its positive impact beyond weight loss, mainly on type 2 diabetes. There is also growing evidence suggesting that bariatric/metabolic surgery is associated with reduced incidence of cardiovascular events, but the impact on hypertension and other components of metabolic syndrome usually derive from trials' secondary end points. Taking this limitation in mind, bariatric/metabolic surgery action on blood pressure is reaching a significant proportion of hypertension resolution or improvement. In this review, we discussed the current evidence on the impact of bariatric/metabolic surgery on blood pressure control and pointed out perspectives in this research area.

The Complement System: A Prey of Trypanosoma cruzi

Trypanosoma cruzi is a protozoan parasite known to cause Chagas disease (CD), a neglected sickness that affects around 6-8 million people worldwide. Originally, CD was mainly found in Latin America but more recently, it has been spread to countries in North America, Asia, and Europe due the international migration from endemic areas. Thus, at present CD represents an important concern of global public health. Most of individuals that are infected by T. cruzi may remain in asymptomatic form all lifelong, but up to 40% of them will develop cardiomyopathy, digestive mega syndromes, or both. The interaction between the T. cruzi infective forms and host-related immune factors represents a key point for a better understanding of the physiopathology of CD. In this context, the complement, as one of the first line of host defense against infection was shown to play an important role in recognizing T. cruzi metacyclic trypomastigotes and in controlling parasite invasion. The complement consists of at least 35 or more plasma proteins and cell surface receptors/regulators, which can be activated by three pathways: classical (CP), lectin (LP), and alternative (AP). The CP and LP are mainly initiated by immune complexes or pathogen-associated molecular patterns (PAMPs), respectively, whereas AP is spontaneously activated by hydrolysis of C3. Once activated, several relevant complement functions are generated which include opsonization and phagocytosis of particles or microorganisms and cell lysis. An important step during T. cruzi infection is when intracellular trypomastigotes are release to bloodstream where they may be target by complement. Nevertheless, the parasite uses a sequence of events in order to escape from complement-mediated lysis. In fact, several T. cruzi molecules are known to interfere in the initiation of all three pathways and in the assembly of C3 convertase, a key step in the activation of complement. Moreover, T. cruzi promotes secretion of plasma membrane-derived vesicles from host cells, which prevent the activity of C3 convertase C4b2a and thereby may hinder complement. In this review, we aim to present an overview on the strategies used by T. cruzi in order to circumvent the activation of complement and, consequently, its biological effects.

Obstructive Sleep Apnea-Induced Hypertension: Role of the Gut Microbiota

PURPOSE OF REVIEW

Obstructive sleep apnea (OSA) is a significant risk factor for systemic hypertension and other cardiovascular diseases. While this relationship has been firmly established, a detailed understanding of how OSA leads to hypertension is lacking. This review will examine the emerging idea that the gut microbiota plays a role in the development of hypertension, including that associated with OSA.

RECENT FINDINGS

Disruption of the normal composition of the gut microbiota, termed dysbiosis, has been identified in a number of metabolic and cardiovascular diseases, including diabetes, obesity, and atherosclerosis. Recently, a number of studies have demonstrated gut dysbiosis in various animal models of hypertension as well as in hypertensive patients. Evidence is now emerging that gut dysbiosis plays a causal role in the development of OSA-induced hypertension. In this review, we will examine the evidence that gut dysbiosis plays a role in OSA-induced hypertension. We will discuss potential mechanisms linking OSA to gut dysbiosis, examine how gut dysbiosis may be linked to hypertension, and highlight how this understanding may be utilized for the development of future therapeutics.