Fixed-pressure CPAP versus auto-adjusting CPAP: comparison of efficacy on blood pressure in obstructive sleep apnoea, a randomised clinical trial

Mandibular Advancement vs CPAP for Blood Pressure Reduction in Patients With Obstructive Sleep Apnea

BACKGROUND

Hypertension guidelines recommend diagnosis and treatment of obstructive sleep apnea (OSA) in patients with hypertension. The mandibular advancement device (MAD) is an oral appliance therapy for patients who decline or cannot tolerate continuous positive airway pressure (CPAP).

OBJECTIVES

We compared the relative effectiveness of MAD vs CPAP in reducing 24-hour ambulatory blood pressure (BP).

METHODS

In an investigator-initiated, randomized, noninferiority trial (prespecified margin 1.5 mm Hg), 321 participants aged ≥40 years with hypertension and increased cardiovascular risk were recruited at 3 public hospitals for polysomnography. Of these, 220 participants with moderate-to-severe OSA (apnea-hypopnea index ≥15 events per hour) were randomized to either MAD or CPAP (1:1). The primary outcome was the difference between the 24-hour mean arterial BP at baseline and 6 months.

RESULTS

Compared with baseline, the 24-hour mean arterial BP decreased by 2.5 mm Hg (P = 0.003) at 6 months in the MAD group, whereas no change was observed in the CPAP group (P = 0.374). The between-group difference was -1.6 mm Hg (95% CI: -3.51 to 0.24, noninferiority P < 0.001). The MAD group demonstrated a larger between-group reduction in all secondary ambulatory BP parameters compared with the CPAP group, with the most pronounced effects observed in the asleep BP parameters. Both the MAD and CPAP improved daytime sleepiness, with the between-group difference similar (P = 0.384). There were no between-group differences in cardiovascular biomarkers.

CONCLUSIONS

MAD is noninferior to CPAP for reducing 24-hour mean arterial BP in participants with hypertension and increased cardiovascular risk. (Cardiosleep Research Program on Obstructive Sleep Apnea, Blood Pressure Control and Maladaptive Myocardial Remodeling-Non-inferiority Trial [CRESCENT]; NCT04119999).

Adaptive responses to chronic intermittent hypoxia: contributions from the European Sleep Apnoea Database (ESADA) Cohort

Obstructive sleep apnoea (OSA) is a common disease in the general population, and is associated with increased cardiovascular risk and several comorbidities. Obesity favours upper airway collapsibility, but other pathophysiological traits have been identified, i.e. upper airway muscle activity, modulation of the respiratory drive, and the arousal threshold. OSA causes chronic intermittent hypoxia, inflammatory activation and autonomic imbalance with diurnal and nocturnal sympathetic hyperactivity. Disentangling so many components to investigate the pathogenesis of OSA's consequences is very hard clinically. However, albeit imperfect, clinical medicine constitutes a major source of inspiration for basic research, and a mutual exchange of information is essential between clinicians and physiologists to improve our understanding of disease states. OSA is no exception, and this narrative review will summarize the results of clinical studies performed over the years by the European Sleep Apnoea Database (ESADA) Study Group, to explore the variables linked to markers of intermittent hypoxia as opposed to the traditional assessment of OSA severity based on the frequency of respiratory events during sleep (the Apnoea Hypopnoea Index). The results of the clinical studies indicate that intermittent hypoxia variables are associated with several comorbidities, although evidence of a cause-effect relationship is still missing in many cases. It is also possible that adaptive rather than maladaptive responses could be evoked by intermittent hypoxia. The intensity, duration and frequency of intermittent hypoxia episodes causing adaptive rather than maladaptive responses, and their clinical implications, deserve further investigation.

Auto-adjusted versus fixed positive airway pressure in patients with severe OSA: A large randomized controlled trial

BACKGROUND AND OBJECTIVE

Continuous positive airway pressure (CPAP) in the treatment of severe obstructive sleep apnoea (OSA) can be used in fixed CPAP or auto-adjusted (APAP) mode. The aim of this prospective randomized controlled clinical study was to evaluate the 3 month-efficacy of CPAP used either in fixed CPAP or APAP mode.

METHODS

Eight hundred one patients with severe OSA were included in twenty-two French centres. After 7 days during which all patients were treated with APAP to determine the effective pressure level and its variability, 353 and 351 patients were respectively randomized in the fixed CPAP group and APAP group. After 3 months of treatment, 308 patients in each group were analysed.

RESULTS

There was no difference between the two groups in terms of efficacy whatever the level of efficient pressure and pressure variability (p = 0.41). Exactly, 219 of 308 patients (71.1%) in the fixed CPAP group and 212 of 308 (68.8%) in the APAP group (p = 0.49) demonstrated residual apnoea hypopnoea index (AHI) <10/h and Epworth Score <11. Tolerance and adherence were also identical with a similar effect on quality of life and blood pressure evaluation.

CONCLUSION

The two CPAP modes, fixed CPAP and APAP, were equally effective and tolerated in severe OSA patients.

Comparison among three different follow-up models for obstructive sleep apnea syndrome patients: focus on the physiotherapist's role

In obstructive sleep apnea syndrome (OSAS) subjects different follow-up modalities have been proposed to improve adherence to the continuous positive airway pressure (CPAP) device. This retrospective study compares three different health professional approaches dedicated to caring OSAS patients in three consecutive follow-up periods of 15 months each. The three different follow-up models are: i) physician-oriented follow-up (P-F); ii) physiotherapist-oriented follow-up (PT-F); and iii) tele-titration plus PT-oriented follow-up (TT-PT-F). Health personal visits and actions delivered, patients' adherence, CPAP efficacy, and problems under CPAP use were considered for comparison. Data from 122 OSAS patients with a new prescription of CPAP were analyzed: 39 (32.0%) in the P-F, 38 (31.1%) in the PT-F, and 45 (36.9%) in the TT-PT-F period. We found a reduction over time (from 40.9% in P-F to 8.2% in TT-PT-F, p<0.001) in patients missing the 1-year follow-up visit. The PT-F and TT-PT-F lead to a reduction in physician visits in comparison to P-F (5.2% and 8.9% vs 100%, p<0.001) with no differences in time to the first follow-up visit, CPAP efficacy, and patients' adherence among the three periods. More device-related problems were found in the PT-F (57.8%), compared with the PF (25.6%) period (p<0.001); the most common troubles were mask problems evaluated in 26.2% of cases. In conclusion, different follow-up models offer similar efficacy and short-term adherence for CPAP leading to a significant reduction in physician visits under the PT-F with or without tele-titration, being mask problems as the most commonly treated. Further analysis should be useful to define the best cost-efficacy follow-up intervention.

Long-term outcomes of CPAP-treated sleep apnea patients: Impact of blood-pressure responses after CPAP initiation and of treatment adherence

BACKGROUND AND OBJECTIVE

In randomized controlled trials, continuous positive airway pressure (CPAP) is reported as lowering blood pressure (BP) with a mean systolic blood pressure effect size of 2.5 mmHg. These trials have a median follow-up of less than 6 months. Whether this initial BP response during the first months of CPAP treatment translates into a reduction in long-term cardiovascular events and mortality is unknown.

METHODS

This observational study addressed long-term hard cardiovascular outcomes and all-cause mortality in a well-defined population of 241 patients previously included in the AgirSASadom parallel randomized controlled trial (assessing whether fixed-pressure CPAP was superior to auto-adjusted CPAP in reducing BP (baseline evaluations 2010-2012)). Long-term outcomes were analyzed using a Cox survival model, and a logistic regression analysis was performed for long-term CPAP adherence.

RESULTS

Sixty-nine cardiovascular events occurred in 61 patients during a median follow-up of 113 months (interquartile range [102 ; 124]) giving an incidence of 26 for 1000 person-years. Twenty-one (8.7%) patients died. BP values at baseline (i.e., office and 24-h BP) was a strong predictor of incident cardiometabolic events and mortality (p < 0.01) whereas initial BP response after the first four months of CPAP was not related to outcomes. Long-term CPAP adherence above 4 h/night was associated with a reduction in all-cause mortality (Log-rank P = 0.02) but not in the occurrence of long-term cardiovascular events.

CONCLUSION

Independently of initial blood pressure response, long-term CPAP adherence is one of the prerequisites for reducing mortality.

International Consensus Statement on Obstructive Sleep Apnea

BACKGROUND

Evaluation and interpretation of the literature on obstructive sleep apnea (OSA) allows for consolidation and determination of the key factors important for clinical management of the adult OSA patient. Toward this goal, an international collaborative of multidisciplinary experts in sleep apnea evaluation and treatment have produced the International Consensus statement on Obstructive Sleep Apnea (ICS:OSA).

METHODS

Using previously defined methodology, focal topics in OSA were assigned as literature review (LR), evidence-based review (EBR), or evidence-based review with recommendations (EBR-R) formats. Each topic incorporated the available and relevant evidence which was summarized and graded on study quality. Each topic and section underwent iterative review and the ICS:OSA was created and reviewed by all authors for consensus.

RESULTS

The ICS:OSA addresses OSA syndrome definitions, pathophysiology, epidemiology, risk factors for disease, screening methods, diagnostic testing types, multiple treatment modalities, and effects of OSA treatment on multiple OSA-associated comorbidities. Specific focus on outcomes with positive airway pressure (PAP) and surgical treatments were evaluated.

CONCLUSION

This review of the literature consolidates the available knowledge and identifies the limitations of the current evidence on OSA. This effort aims to create a resource for OSA evidence-based practice and identify future research needs. Knowledge gaps and research opportunities include improving the metrics of OSA disease, determining the optimal OSA screening paradigms, developing strategies for PAP adherence and longitudinal care, enhancing selection of PAP alternatives and surgery, understanding health risk outcomes, and translating evidence into individualized approaches to therapy.

Effects of CPAP on Metabolic Syndrome in Patients With OSA: A Randomized Trial

BACKGROUND

OSA is associated with metabolic syndrome (MS), but it is unclear whether OSA treatment with CPAP can revert MS.

RESEARCH QUESTION

Does OSA treatment with CPAP per se have effects on the MS reversibility and the associated metabolic, adiposity and vascular parameters?

STUDY DESIGN AND METHODS

The TREATOSA-MS trial is a randomized placebo-controlled trial that enrolled adult patients with a recent diagnosis of MS and moderate or severe OSA (apnea-hypopnea index [AHI], ≥ 15 events/h) to undergo therapeutic CPAP or nasal dilator strips (placebo group) for 6 months. Before and after each intervention, we measured anthropometric variables, BP, glucose, and lipid profile. To control potential-related mechanisms and consequences, we also measured adiposity biomarkers (leptin and adiponectin), body composition, food intake, physical activity, subcutaneous and abdominal fat (visceral and hepatic fat), and endothelial function.

RESULTS

One hundred patients (79% men; mean age, 48 ± 9 years; BMI, 33 ± 4 kg/m²; AHI, 58 ± 29 events/h) completed the study (n = 50 per group). The mean CPAP adherence was 5.5 ± 1.5 h/night. After 6 months, most patients with OSA randomized to CPAP retained the MS diagnosis, but the rate of MS reversibility was higher than observed in the placebo group (18% vs 4%; OR, 5.27; 95% CI, 1.27-35.86; P = .04). In the secondary analysis, CPAP did not promote significant reductions in the individual components of MS, weight, hepatic steatosis, lipid profile, adiponectin, and leptin, but did promote a very modest reduction in visceral fat and improved endothelial function (all analyses were adjusted for baseline values).

INTERPRETATION

Despite the higher rate of MS reversibility after CPAP therapy as compared with placebo, most patients retained this diagnosis. The lack of significant or relevant effects on adiposity biomarkers and depots supports the modest role of OSA in modulating MS.

TRIAL REGISTRATION

ClinicalTrials.gov; No.: NCT02295202; URL: www.

CLINICALTRIALS

gov.

Modeling patient-specific desaturation patterns in sleep apnea

OBJECTIVE

The physiological mechanisms involved in cardio-respiratory responses to sleep apnea events are not yet fully elucidated. A model-based approach is proposed to analyse the acute desaturation response to obstructive apneas.

METHODS

An integrated model of cardio-respiratory interactions was proposed and parameters were identified, using an evolutionary algorithm, on a database composed of 107 obstructive apneas acquired from 10 patients (HYPNOS clinical study). Unsupervised clustering was applied to the identified parameters in order to characterize the phenotype of each response to obstructive apneas.

RESULTS

A close match was observed between simulated oxygen saturation (SaO2) and experimental SaO2 in all identifications (median RMSE = 1.3892%). Two clusters of parameters, associated with different dynamics related to sleep apnea and periodic breathing were obtained.

CONCLUSION AND SIGNIFICANCE

The proposed patient and event-specific model-based analysis provides understanding on specific desaturation patterns, consequent to apnea events, with potential applications for personalized diagnosis and treatment.

Is kidney a new organ target in patients with obstructive sleep apnea? Research priorities in a rapidly evolving field

The bidirectional relationship between sleep disordered breathing and chronic kidney disease (CKD) has recently gained a lot of interest. Several lines of evidence suggest the high prevalence of coexistent obstructive sleep apnea (OSA) in patients with CKD and end-stage renal disease (ESRD). In addition, OSA seems to result in loss of kidney function in some patients, especially in those with cardio-metabolic comorbidities. Treatment of CKD/ESRD and OSA can alter the natural history of each other; still better phenotyping with selection of appropriate treatment approaches is urgently needed. The aim of this narrative review is to provide an update of recent studies on epidemiological associations, pathophysiological interactions, and management of patients with OSA and CKD or ESRD.

CPAP Therapeutic Options for Obstructive Sleep Apnea

Introduction

There are many options available to patients who are placed on constant positive airway pressure (CPAP) for obstructive sleep apnea. Despite the success of CPAP in correcting apnea, a significant number of patients have difficulty with the therapy. A large number of those patients who have difficulty stop therapy and are often labeled as "CPAP Failure". Non-sleep specialists may view CPAP therapy as a singular course of treatment, but there are many ways CPAP may be ordered for a patient. Each patient experiences a unique set of options that constitute a unique order set.

Methods

In order to demonstrate the magnitude of the possible options, estimates of the number of unique order sets were calculated. The author chose individual order options and the number of selections possible within each option. The calculated sets included a "Generous, Limited and Minimal" number of selections for each option. Calculations were done separately for standard CPAP and for auto-adjusting CPAP. Additional calculations were performed using the number of commercially available masks in the United States.

Results

The maximum number of unique order sets was seen using a standard CPAP combined with commercially available masks: 49,152 unique order sets. The fewest number of unique order sets were seen with the auto-adjusting CPAP and the "Minimal" selections: 288 unique order sets.

Discussion

There are a large number of unique CPAP orders that a patient may experience. CPAP treatment is not a singular or simple therapy. When evaluating obstructive sleep apnea patients with histories of CPAP failure or prior difficulty with CPAP, paying close attention to the patient's treatment experiences may help explain a significant number of those patients' CPAP therapy problems.

Clinical side effects of continuous positive airway pressure in patients with obstructive sleep apnoea

CPAP is considered the gold standard treatment in OSA and is highly efficacious in controlling OSA symptoms. However, treatment effectiveness is limited because of many factors including low adherence due to side effects. This review highlights the range of side effects associated with CPAP therapy in patients with OSA. This information is important for the initiation of patients onto CPAP as well as their continued care while on treatment, given the increase in non-medically supervised CPAP care models in use globally.

Pressure modification or humidification for improving usage of continuous positive airway pressure machines in adults with obstructive sleep apnoea

BACKGROUND

Obstructive sleep apnoea (OSA) is the repetitive closure of the upper airway during sleep. This results in disturbed sleep and excessive daytime sleepiness. It is a risk factor for long-term cardiovascular morbidity. Continuous positive airway pressure (CPAP) machines can be applied during sleep. They deliver air pressure by a nasal or oronasal mask to prevent the airway from closing, reducing sleep disturbance and improving sleep quality. Some people find them difficult to tolerate because of high pressure levels and other symptoms such as a dry mouth. Switching to machines that vary the level of air pressure required to reduce sleep disturbance could increase comfort and promote more regular use. Humidification devices humidify the air that is delivered to the upper airway through the CPAP circuit. Humidification may reduce dryness of the throat and mouth and thus improve CPAP tolerability. This updated Cochrane Review looks at modifying the delivery of positive pressure and humidification on machine usage and other clinical outcomes in OSA.

OBJECTIVES

To determine the effects of positive pressure modification or humidification on increasing CPAP machine usage in adults with OSA.

SEARCH METHODS

We searched Cochrane Airways Specialised Register and clinical trials registries on 15 October 2018.

SELECTION CRITERIA

Randomised parallel group or cross-over trials in adults with OSA. We included studies that compared automatically adjusting CPAP (auto-CPAP), bilevel positive airway pressure (bi-PAP), CPAP with expiratory pressure relief (CPAPexp), heated humidification plus fixed CPAP, automatically adjusting CPAP with expiratory pressure relief, Bi-PAP with expiratory pressure relief, auto bi-PAP and CPAPexp with wakefulness detection with fixed pressure setting.

DATA COLLECTION AND ANALYSIS

We used standard methods expected by Cochrane. We assessed the certainty of evidence using GRADE for the outcomes of machine usage, symptoms (measured by the Epworth Sleepiness Scale (ESS)), Apnoea Hypopnoea Index (AHI), quality of life measured by Functional Outcomes of Sleep Questionnaire (FOSQ), blood pressure, withdrawals and adverse events (e.g. nasal blockage or mask intolerance). The main comparison of interest in the review is auto-CPAP versus fixed CPAP.

MAIN RESULTS

We included 64 studies (3922 participants, 75% male). The main comparison of auto-CPAP with fixed CPAP is based on 36 studies with 2135 participants from Europe, USA, Hong Kong and Australia. The majority of studies recruited participants who were recently diagnosed with OSA and had not used CPAP previously. They had excessive sleepiness (ESS: 13), severe sleep disturbance (AHI ranged from 22 to 59), and average body mass index (BMI) of 35 kg/m2. Interventions were delivered at home and the duration of most studies was 12 weeks or less. We judged that studies at high or unclear risk of bias likely influenced the effect of auto-CPAP on machine usage, symptoms, quality of life and tolerability, but not for other outcomes. Primary outcome Compared with average usage of about five hours per night with fixed CPAP, people probably use auto-CPAP for 13 minutes longer per night at about six weeks (mean difference (MD) 0.21 hours/night, 95% confidence interval (CI) 0.11 to 0.31; 31 studies, 1452 participants; moderate-certainty evidence). We do not have enough data to determine whether auto-CPAP increases the number of people who use machines for more than four hours per night compared with fixed CPAP (odds ratio (OR) 1.16, 95% CI 0.75 to 1.81; 2 studies, 346 participants; low-certainty evidence). Secondary outcomes Auto-CPAP probably reduces daytime sleepiness compared with fixed CPAP at about six weeks by a small amount (MD -0.44 ESS units, 95% CI -0.72 to -0.16; 25 studies, 1285 participants; moderate-certainty evidence). AHI is slightly higher with auto-CPAP than with fixed CPAP (MD 0.48 events per hour, 95% CI 0.16 to 0.80; 26 studies, 1256 participants; high-certainty evidence), although it fell with both machine types from baseline values in the studies. Ten per cent of people in auto-CPAP and 11% in the fixed CPAP arms withdrew from the studies (OR 0.90, 95% CI 0.64 to 1.27; moderate-certainty evidence). Auto-CPAP and fixed CPAP may have similar effects on quality of life, as measured by the FOSQ but more evidence is needed to be confident in this result (MD 0.12, 95% CI -0.21 to 0.46; 3 studies, 352 participants; low-certainty evidence). Two studies (353 participants) provided data on clinic-measured blood pressure. Auto-CPAP may be slightly less effective at reducing diastolic blood pressure compared to fixed CPAP (MD 2.92 mmHg, 95% CI 1.06 to 4.77 mmHg; low-certainty evidence). The two modalities of CPAP probably do not differ in their effects on systolic blood pressure (MD 1.87 mmHg, 95% CI -1.08 to 4.82; moderate-certainty evidence). Nine studies (574 participants) provided information on adverse events such as nasal blockage, dry mouth, tolerance of treatment pressure and mask leak. They used different scales to capture these outcomes and due to variation in the direction and size of effect between the studies, the comparative effects on tolerability outcomes are uncertain (very low-certainty evidence).  The evidence base for other interventions is smaller, and does not provide sufficient information to determine whether there are important differences between pressure modification strategies and fixed CPAP on machine usage outcomes, symptoms and quality of life. As with the evidence for the auto-CPAP, adverse events are measured disparately.

AUTHORS' CONCLUSIONS

In adults with moderate to severe sleep apnoea starting positive airway pressure therapy, auto-CPAP probably increases machine usage by about 13 minutes per night. The effects on daytime sleepiness scores with auto-CPAP are not clinically meaningful. AHI values are slightly lower with fixed CPAP. Use of validated quality of life instruments in the studies to date has been limited, although where they have been used the effect sizes have not exceeded proposed clinically important differences. The adoption of a standardised approach to measuring tolerability would help decision-makers to balance benefits with harms from the different treatment options available. The evidence available for other pressure modification strategies does not provide a reliable basis on which to draw firm conclusions. Future studies should look at the effects of pressure modification devices and humidification in people who have already used CPAP but are unable to persist with treatment.

Impact of CPAP treatment on leptin and adiponectin in adults with coronary artery disease and nonsleepy obstructive sleep apnoea in the RICCADSA trial

BACKGROUND

Increased leptin and decreased adiponectin levels are reported in coronary artery disease (CAD) as well as in obstructive sleep apnoea (OSA). Less is known regarding the impact of continuous positive airway pressure (CPAP) on these biomarkers. We aimed to determine variables associated with leptin and adiponectin in adults with CAD and nonsleepy OSA, and evaluate the effect of CPAP adjusted for confounding factors.

METHODS

This was one of the secondary outcomes of the RICCADSA trial, conducted in Sweden between 2005 and 2013. From 244 revascularized CAD and OSA patients (apnoea-hypopnoea index >15/h) without excessive daytime sleepiness (Epworth Sleepiness Scale score <10), 196 with blood samples at baseline, after 3, and 12 months were included in the randomized controlled trial arm; of those, 98 were allocated to auto-titrating CPAP, and 98 to no-CPAP.

RESULTS

No significant changes in leptin and adiponectin levels were observed during follow-up, whereas Body-Mass-Index and waist circumference increased in both CPAP and no-CPAP groups with no significant between-group differences. Alterations in plasma leptin were determined by changes in waist circumference (beta coefficient 2.47; 95% confidence interval 0.77-4.40), whereas none of the analyzed parameters was predictive for changes in adiponectin levels. No association was found with CPAP adherence.

CONCLUSIONS

CPAP had no significant effect on leptin and adiponectin in this cohort of nonsleepy OSA patients. An increase in waist circumference predicted an increase in plasma levels of leptin after 12 months, suggesting that lifestyle modifications should be given priority in adults with CAD and OSA regardless of CPAP treatment.

Comparison of Auto- and Fixed-Continuous Positive Airway Pressure on Air Leak in Patients with Obstructive Sleep Apnea: Data from a Randomized Controlled Trial

Auto-CPAP may cause sleep fragmentation due to variations in pressure and unintentional leaks. The aim of this study was to compare air leak between fixed-CPAP and auto-CPAP after 4 months of CPAP treatment. This study is an ancillary analysis of a randomized, double-blind, parallel, controlled trial over 4 months, comparing fixed- and auto-CPAP in newly diagnosed patients with OSA. The following data were extracted from the CPAP devices: mean and 90th percentile pressure, residual apnea-hypopnea index, mean CPAP use, and amount of leak. Within each arm, patients were also randomly allocated to use of one of the three different brands of devices. Since the leak was reported differently for each device, median leak value was determined for each brand and leaks were classified as “above the median” or “below the median”. Data from 269 patients were analyzed. The univariate analysis showed that tobacco consumption, CPAP level, and oronasal masks were associated with leaks above the median value but not the type of CPAP. The multivariate analysis showed that only CPAP level and oronasal masks were associated with leaks below the median. There were no differences in the types of mask used between fixed- and auto-CPAP. There was no impact of the type of CPAP on leaks or the type of interface used. We used a method based on the median leak value to standardize comparisons across devices which report leaks with different definitions.

Obstructive sleep apnea and chronic kidney disease

PURPOSE OF REVIEW

Obstructive sleep apnea (OSA) is highly prevalent in patients with chronic kidney disease (CKD). The relationship between OSA and CKD is likely to be bi-directional. On one hand, the presence of OSA leads to intermittent hypoxia, sympathetic nervous system activity, and hypertension, all of which may have deleterious effects on kidney function. On the other hand, in patients with end-stage renal disease (ESRD), intensification of renal replacement therapy has been shown to attenuate sleep apnea severity, suggesting that the renal disease itself contributes to the pathogenesis of OSA. The present review describes our current understanding of the bi-directional relationship between OSA and CKD.

RECENT FINDINGS

Studies suggest that the presence of OSA and nocturnal hypoxia may lead to worsening of kidney function. One potential mechanism is activation of the renin-angiotensin system by OSA, an effect which may be attenuated by CPAP therapy. In ESRD, fluid overload plays an important role in the pathogenesis of OSA and fluid removal by ultrafiltration leads to marked improvements in sleep apnea severity.

SUMMARY

OSA is associated with accelerated loss of kidney function. In patients with ESRD, fluid overload plays an important role in the pathogenesis of OSA.

Chronic kidney disease in patients with obstructive sleep apnea. A narrative review

Prevalence of both chronic kidney disease (CKD) and obstructive sleep apnea (OSA) is continuously increasing. Moreover, the prevalence of OSA increases as kidney function declines and is higher among patients with end-stage renal disease (ESRD). In addition, OSA is recognized as a potential nontraditional risk factor for development and progression of CKD. Continuous positive airway pressure (CPAP) plays a pivotal role in the management of OSA, eliminating patients' symptoms and improving their quality of life. Recent studies suggested that CPAP treatment may have beneficial effects on kidney function among patients with OSA. This narrative review summarizes the existing knowledge on the association between CKD and OSA, with emphasis on the epidemiology, the pathophysiology of the development of CKD in OSA and vice versa, as well as the effect of CPAP on renal function.

Reduction in sympathetic tone in patients with obstructive sleep apnoea: is fixed CPAP more effective than APAP? A randomised, parallel trial protocol

INTRODUCTION

Obstructive sleep apnoea (OSA) is a prevalent disease associated with cardiovascular events. Hypertension is one of the major intermediary mechanisms leading to long-term cardiovascular adverse events. Intermittent hypoxia and hypercapnia associated with nocturnal respiratory events stimulate chemoreflexes, resulting in sympathetic overactivity and blood pressure (BP) elevation. Continuous positive airway pressure (CPAP) is the primary treatment for OSA and induces a small but significant reduction in BP. The use of auto-adjusting positive airway pressure (APAP) has increased in the last years and studies showed different ranges of BP reduction when comparing both modalities. However, the pathophysiological mechanisms implicated are not fully elucidated. Variations in pressure through the night inherent to APAP may induce persistent respiratory efforts and sleep fragmentation that might impair sympathovagal balance during sleep and result in smaller decreases in BP. Therefore, this double-blind randomised controlled trial aims to compare muscle sympathetic nerve activity (MSNA) assessed by microneurography (reference method for measuring sympathetic activity) after 1 month of APAP versus fixed CPAP in treatment-naive OSA patients. This present manuscript describes the design of our study, no results are presented herein. and is registered under the below reference number.

METHODS AND ANALYSIS

Adult subjects with newly diagnosed OSA (Apnoea-Hypopnoea Index >20/hour) will be randomised for treatment with APAP or fixed CPAP. Measurements of sympathetic activity by MSNA, heart rate variability and catecholamines will be obtained at baseline and after 30 days. The primary composite outcome will be the change in sympathetic tone measured by MSNA in bursts/min and bursts/100 heartbeats. Sample size calculation was performed with bilateral assumption. We will use the Student's t-test to compare changes in sympathetic tone between groups.

ETHICS AND DISSEMINATION

The protocol was approved by The French Regional Ethics Committee. The study started in March 2018 with primary completion expected to March 2019. Dissemination plans of the results include presentations at conferences and publication in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT03428516; Pre-results.

Treatment of Adult Obstructive Sleep Apnea With Positive Airway Pressure: An American Academy of Sleep Medicine Systematic Review, Meta-Analysis, and GRADE Assessment

INTRODUCTION

The purpose of this systematic review is to provide supporting evidence for the clinical practice guideline for the treatment of obstructive sleep apnea (OSA) in adults using positive airway pressure (PAP).

METHODS

The American Academy of Sleep Medicine commissioned a task force of experts in sleep medicine. A systematic review was conducted to identify studies that compared the use of PAP with no treatment as well as studies that compared different PAP modalities. Meta-analyses were performed to determine the clinical significance of using PAP in several modalities (ie, continuous PAP, auto-adjusting PAP, and bilevel PAP), to treat OSA in adults. In addition, meta-analyses were performed to determine the clinical significance of using an in-laboratory versus ambulatory strategy for the initiation of PAP, educational and behavioral interventions, telemonitoring, humidification, different mask interfaces, and flexible or modified pressure profile PAP in conjunction with PAP to treat OSA in adults. Finally, the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) process was used to assess the evidence for making recommendations.

RESULTS

The literature search resulted in 336 studies that met inclusion criteria; 184 studies provided data suitable for meta-analyses. The data demonstrated that PAP compared to no treatment results in a clinically significant reduction in disease severity, sleepiness, blood pressure, and motor vehicle accidents, and improvement in sleep-related quality of life in adults with OSA. In addition, the initiation of PAP in the home demonstrated equivalent effects on patient outcomes when compared to an in-laboratory titration approach. The data also demonstrated that the use of auto-adjusting or bilevel PAP did not result in clinically significant differences in patient outcomes compared with standard continuous PAP. Furthermore, data demonstrated a clinically significant improvement in PAP adherence with the use of educational, behavioral, troubleshooting, and telemonitoring interventions. Systematic reviews for specific PAP delivery method were also performed and suggested that nasal interfaces compared to oronasal interfaces have improved adherence and slightly greater reductions in OSA severity, heated humidification compared to no humidification reduces some continuous PAP-related side effects, and pressure profile PAP did not result in clinically significant differences in patient outcomes compared with standard continuous PAP.

Challenges and perspectives in obstructive sleep apnoea

Obstructive sleep apnoea (OSA) is a major challenge for physicians and healthcare systems throughout the world. The high prevalence and the impact on daily life of OSA oblige clinicians to offer effective and acceptable treatment options. However, recent evidence has raised questions about the benefits of positive airway pressure therapy in ameliorating comorbidities.

An international expert group considered the current state of knowledge based on the most relevant publications in the previous 5 years, discussed the current challenges in the field, and proposed topics for future research on epidemiology, phenotyping, underlying mechanisms, prognostic implications and optimal treatment of patients with OSA.

The group concluded that a revision to the diagnostic criteria for OSA is required to include factors that reflect different clinical and pathophysiological phenotypes and relevant comorbidities (e.g.nondipping nocturnal blood pressure). Furthermore, current severity thresholds require revision to reflect factors such as the disparity in the apnoea–hypopnoea index (AHI) between polysomnography and sleep studies that do not include sleep stage measurements, in addition to the poor correlation between AHI and daytime symptoms such as sleepiness. Management decisions should be linked to the underlying phenotype and consider outcomes beyond AHI.

Fixed But Not Autoadjusting Positive Airway Pressure Attenuates the Time-dependent Decline in Glomerular Filtration Rate in Patients With OSA

BACKGROUND

The impact of treating OSA on renal function decline is controversial. Previous studies usually included small samples and did not consider specific effects of different CPAP modalities. The aim of this study was to evaluate the respective influence of fixed and autoadjusting CPAP modes on estimated glomerular filtration rate (eGFR) in a large sample of patients derived from the prospective European Sleep Apnea Database cohort.

METHODS

In patients of the European Sleep Apnea Database, eGFR prior to and after follow-up was calculated by using the Chronic Kidney Disease-Epidemiology Collaboration equation. Three study groups were investigated: untreated patients (n = 144), patients receiving fixed CPAP (fCPAP) (n = 1,178), and patients on autoadjusting CPAP (APAP) (n = 485).

RESULTS

In the whole sample, eGFR decreased over time. The rate of eGFR decline was significantly higher in the subgroup with eGFR above median (91.42 mL/min/1.73 m²) at baseline (P < .0001 for effect of baseline eGFR). This decline was attenuated or absent (P < .0001 for effect of treatment) in the subgroup of patients with OSA treated by using fCPAP. A follow-up duration exceeding the median (541 days) was associated with eGFR decline in the untreated and APAP groups but not in the fCPAP group (P < .0001 by two-way ANOVA for interaction between treatment and follow-up length). In multiple regression analysis, eGFR decline was accentuated by advanced age, female sex, cardiac failure, higher baseline eGFR, and longer follow-up duration, whereas there was a protective effect of fCPAP.

CONCLUSIONS

fCPAP but not APAP may prevent eGFR decline in OSA.

Kinesthetic stimulation for obstructive sleep apnea syndrome: An "on-off" proof of concept trial

Obstructive sleep apnea (OSA) occurs when the upper airway narrows or collapses due to the loss of upper airway muscle activation at sleep onset. This study investigated the effectiveness of triggered kinesthetic stimulation in patients with OSA. This proof-of-concept, open-label, multicenter prospective study was conducted on 24 patients with severe OSA. During a one night evaluation, kinesthetic stimulation was intermittently delivered in 30 minute periods. The duration of apneas and hypopneas during Stim _on and Stim _off periods were compared. Five hospital-based university centers in France participated. Sleep studies were evaluated by a single scorer at a core laboratory (CHU Grenoble). Results show that during the Stim _on phases, statistically significant decreases in durations of apneas and hypopneas were observed in 56% and 46% of patients, respectively. Overall, 75% of patients showed an improvement in apneas or hypopneas durations. The mean reduction in durations for patients with a significant decrease was 4.86 seconds for apneas and 6.00 seconds for hypopneas. This proof of concept study is the first to identify kinesthetic stimulation as a potentially effective therapy for OSA. These data justify evaluation in a controlled study.

Which place of pharmacological approaches beyond continuous positive airway pressure to treat vascular disease related to obstructive sleep apnea?

Obstructive sleep apnea (OSA) is characterized by recurrent episodes of partial or complete upper airway obstruction, occurring during sleep, leading to chronic intermittent hypoxia (IH), which harms the cardiovascular system. OSA is associated with both functional and structural vascular alterations that contribute to an increased prevalence of fatal and non-fatal cardiovascular events. OSA is a heterogeneous disease with respect to the severity of hypoxia, the presence of daytime symptoms, obesity, and cardiovascular comorbidities. Various clusters of OSA phenotypes have been described leading to more highly personalized treatment. The aim of this review is to describe the various therapeutic strategies including continuous positive airway pressure (CPAP), oral appliances, surgery, weight loss, and especially pharmacological interventions that have been evaluated to reduce vascular alterations in both OSA patients and preclinical animal models. Conventional therapies, predominantly CPAP, have a limited impact on vascular alterations in the presence of co-morbidities. A better knowledge of pharmacological therapies targeting IH-induced vascular alterations will facilitate the use of combined therapies and is crucial for designing clinical trials in well-defined OSA phenotypes.

Autoadjusted versus fixed CPAP for obstructive sleep apnoea: a multicentre, randomised equivalence trial

Background

The obstructive sleep apnoea syndrome (OSAS) is conventionally treated by continuous positive airway pressure set at a fixed level (fCPAP). Automatic mask pressure adjustment (autoCPAP) is increasingly used during home therapy. We investigated whether autoCPAP is equivalent to fCPAP in improving sleepiness in patients with OSAS in the long-term.

Methods

In this multicentre equivalence trial, 208 patients with OSAS, with median Epworth sleepiness score (ESS) 13, apnoea/hypopnoea index 48.4/hour, were randomised to treatment with autoCPAP (5–15 mbar) or fCPAP (pressure set at the 90th percentile applied by autoCPAP during 2–4 weeks adaptation). Coprimary outcomes were changes in subjective and objective sleepiness from baseline to 2 years after treatment. Equivalence ranges were ±2 points in ESS and ±3 min sleep resistance time evaluated by recording responses to light signals.

Results

At 2 years, in the intention to treat analysis, the reduction in sleepiness versus pretreatment baseline was similar in patients using autoCPAP (n=113, mean ESS-change −6.3, 95% CI −7.1 to −5.5; sleep resistance time +8.3 min, +6.9 to +9.7) and fCPAP (n=95, mean ESS-change −6.2, 95% CI −7.0 to −5.3; sleep resistance time +6.3 min, +4.7 to +7.8). The 95% CI of difference in ESS-reduction between autoCPAP and fCPAP was −0.9 to +1.4 and the 95% CI of difference in increase in sleep resistance time was −2.6 to +1.0 min. Blood pressure reduction and OSAS-related costs were similar between groups.

Conclusions

AutoCPAP and fCPAP are equivalent within prespecified ranges in improving subjective and objective sleepiness in patients with OSAS over the course of 2 years. Costs of these treatments are similar.

Trial registration number

ClinicalTrials.gov NCT00280800.

Verifying the Relative Efficacy between Continuous Positive Airway Pressure Therapy and Its Alternatives for Obstructive Sleep Apnea: A Network Meta-analysis

Obstructive sleep apnea (OSA) is a common breathing disorder, and continuous positive airway pressure (CPAP) therapy together with its alternatives has been developed to treat this disease. This network meta-analysis (NMA) was aimed to compare the efficacy of treatments for OSA. Cochrane Library, MEDLINE, and Embase were searched for eligible studies. A conventional and NMA was carried out to compare all therapies. Sleeping characteristics, including Apnea–Hypopnea Index (AHI), Epworth Sleepiness Scale (ESS), arterial oxygen saturation, and arousal index (AI), and changes of blood pressure were selected as outcomes. A total of 84 studies were finally included after rigorous screenings. For the primary outcomes of AHI and ESS, the value of auto-adjusting positive airway pressure (APAP), CPAP, and oral appliance (OA) all showed statistically reduction compared with inactive control (IC). Similar observation was obtained in AI, with treatments of the three active interventions. A lower effect of IC in SaO₂ was exhibited when compared with APAP, CPAP, and OA. Similar statistically significant results were presented in 24 h systolic blood pressure and 24 h DBP when comparing with CPAP. Our NMA identified CPAP as the most efficacious treatment for OSA patients after the evaluation of sleeping characteristics and blood pressures. In addition, more clinical trials are needed for further investigation due to the existence of inconsistency observed in this study.