Systemic hypertension and obstructive sleep apnoea

Assessing the importance and safety of hypoxia conditioning for patients with occupational pulmonary diseases: A recent clinical perspective

Occupational pulmonary diseases (OPDs) pose a significant global health challenge, contributing to high mortality rates. This review delves into the pathophysiology of hypoxia and the safety of intermittent hypoxic conditioning (IHC) in OPD patients. By examining sources such as PubMed, Relemed, NLM, Scopus, and Google Scholar, the review evaluates the efficacy of IHC in clinical outcomes for OPD patients. It highlights the complexities of cardiovascular and respiratory regulation dysfunctions in OPDs, focusing on respiratory control abnormalities and the impact of intermittent hypoxic exposures. Key areas include the physiological effects of hypoxia, the role of hypoxia-inducible factor-1 alpha (HIF-1α) in occupational lung diseases, and the links between brain ischemia, stroke, and OPDs. The review also explores the interaction between intermittent hypoxic exposures, mitochondrial energetics, and lung physiology. The potential of IHE to improve clinical manifestations and underlying pathophysiology in OPD patients is thoroughly examined. This comprehensive analysis aims to benefit molecular pathologists, pulmonologists, clinicians, and physicians by enhancing understanding of IHE's clinical benefits, from research to patient care, and improving clinical outcomes for OPD patients.

Validity of Modified STOP-Bang Questionnaire as a Screening Tool for Obstructive Sleep Apnea

OBJECTIVES

The aim of this study was to evaluate the validity of a modified STOP-Bang questionnaire with different body mass index reference as a screening tool for obstructive sleep apnea in Korean population.

METHODS

The medical records of 1417 participants who underwent overnight Level I polysomnography were retrospectively analyzed. Predictive parameters were calculated for each of the 3 groups classified by obstructive sleep apnea severity with a cut-off value of 3 or 4. Responses to modified and traditional questionnaires were comparatively analyzed by receiver-operator characteristic curves and area under the receiver-operator characteristic curves.

RESULTS

The optimal cut-off values of the modified and traditional questionnaires were both 3.5. The area under the receiver-operator characteristic curve of modified STOP-Bang questionnaire for any obstructive sleep apnea group was 0.786 ± 0.018, which was significantly higher than that of the traditional questionnaire. The modified STOP-Bang questionnaire with a cut-off value ≥4 showed significantly higher sensitivity than the traditional one for any obstructive sleep apnea group. The diagnostic accuracy of the modified questionnaire was also significantly higher for the any obstructive sleep apnea group when the cut-off value was 4.

CONCLUSION

The modified STOP-Bang questionnaire, with a cut-off value of 4, can be used as an alternative to the traditional screening tool for the Korean population.

Excessive Daytime Sleepiness in Patients With Hypertension: A Systematic Review

We must remember that there are many subclinical cases of obstructive sleep apnea (OSA), even if the patient or family members typically become aware of it through symptoms such as snoring and excessive daytime sleepiness (EDS). EDS is a common symptom among hypertensive patients. This interesting and remarkable systematic review aims to comprehensively survey the current literature on the prevalence and association of EDS among hypertensive patients. PubMed, SCOPUS, Web of Science, and Science Direct were systematically searched for relevant literature. Rayyan QRCI (Rayyan Systems Inc., Cambridge, MA) was employed throughout this comprehensive process. This review included nine studies with a total of 58,517 patients, and 34,398 (58.8%) were males. EDS prevalence among hypertensive patients ranged from 12.1% to 88.3%. This review stated that individuals with hypertension (HTN) had EDS that was worse than that of patients with normotension. In one of the studies included in this analysis, sympathovagal imbalance was noted alongside EDS and HTN. Older age, primary education, being overweight, working, obesity, depression, and having had the condition for longer are all associated with EDS in HTN patients.

The relation of dietary components with severity of obstructive sleep apnea in Cypriot patients: A randomized, stratified epidemiological study

Background

Obstructive Sleep Apnea (OSA) is considered a public health problem and its prevalence is increasing at an epidemic rate. The aim of this study was to examine whether individual nutrients (macronutrients, antioxidant vitamins) rather than energy restriction may potentially affect OSA severity in a representative population of Cyprus.

Methods

A total sample of 303 adults (>18 years old) with Cypriot citizenship and permanently residing in Cyprus were randomly selected. Selected patients have completed the food frequency questionnaire, and a physical activity questionnaire and underwent a sleep study to assess OSA severity.

Results

Overall, 303 patients were included in this study, 169 (55.8%) had mild OSA (apnea-hypopnea index—AHI <15) and the remaining 83 (27.4%) had moderate to severe OSA (AHI>15). The mean age of all patients was 55.7 years old. Patients with moderate to severe OSA had significant higher BMI levels, higher consumption of calories, higher hip circumference, waist circumference, waist-hip ratio and neck circumference and higher consumption of folic acid compared with the patients with mild OSA (p<0.05).

Conclusions

The findings suggest that increased energy intake regardless diet macronutrient composition is positively associated with OSA severity whereas higher folic acid intake seems to have a protective role.

Diagnostic accuracy of screening questionnaires for obstructive sleep apnoea in adults in different clinical cohorts: a systematic review and meta-analysis

PURPOSE

The majority of individuals with clinically significant obstructive sleep apnoea (OSA) are undiagnosed and untreated. A simple screening tool may support risk stratification, identification, and appropriate management of at-risk patients. Therefore, this systematic review and meta-analysis evaluated and compared the accuracy and clinical utility of existing screening questionnaires for identifying OSA in different clinical cohorts.

METHODS

We conducted a systematic review and meta-analysis of observational studies assessing the diagnostic value of OSA screening questionnaires. We identified prospective studies, validated against polysomnography, and published to December 2020 from online databases. To pool the results, we used random effects bivariate binomial meta-analysis.

RESULTS

We included 38 studies across three clinical cohorts in the meta-analysis. In the sleep clinic cohort, the Berlin questionnaire's pooled sensitivity for apnoea-hypopnoea index (AHI) ≥ 5, ≥ 15, and ≥ 30 was 85%, 84%, and 89%, and pooled specificity was 43%, 30%, and 33%, respectively. The STOP questionnaire's pooled sensitivity for AHI ≥ 5, ≥ 15, and ≥ 30 was 90%, 90%, and 95%, and pooled specificity was 31%, 29%, and 21%. The pooled sensitivity of the STOP-Bang questionnaire for AHI ≥ 5, ≥ 15, and ≥ 30 was 92%, 95%, and 96%, and pooled specificity was 35%, 27%, and 28%. In the surgical cohort (AHI ≥ 15), the Berlin and STOP-Bang questionnaires' pooled sensitivity were 76% and 90% and pooled specificity 47% and 27%.

CONCLUSION

Among the identified questionnaires, the STOP-Bang questionnaire had the highest sensitivity to detect OSA but lacked specificity. Subgroup analysis considering other at-risk populations was not possible. Our observations are limited by the low certainty level in available data.

Mandibular Advancement Devices for OSA: An Alternative to CPAP?

Obstructive sleep apnea (OSA) is a prevalent condition causing unrefreshing sleep and excessive daytime sleepiness. It has individual socioeconomic impacts and, through association with increased risk of road traffic accidents, diabetes, and cardiovascular disease, OSA is a public health issue. Continuous positive airway pressure (CPAP) is the first-line treatment for moderate-to-severe OSA. It is effective in improving excessive daytime sleepiness and quality of life. There is also evidence that CPAP therapy has cardiovascular benefits although nature and extent remain uncertain. Despite its benefits, a significant proportion of patients are unable to tolerate CPAP. There are also patients with mild but symptomatic disease, for whom CPAP is usually not available or appropriate, so there is a need for other treatment options. Mandibular advancement devices (MADs) offer an effective alternative to CPAP and can improve daytime symptoms and quality of life. There are many devices available, representing a range of complexity and cost. It is challenging to properly evaluate the effectiveness of this ever-evolving range. The more basic MADs are cheaper and more accessible but are less well tolerated. More complex devices are better tolerated and may be more effective. However, they are more expensive and often require dental expertise, so access is more limited. Efforts continue to try to improve accessibility to effective MAD therapy. Alongside increasing awareness, this may be facilitated by developing and refining devices that could be fitted by non-dental clinicians, and potentially by patients themselves. Research efforts need to focus on determining how to efficiently identify patients who are likely to respond to MAD therapy, so as to improve clinical and cost-effectiveness of OSA therapy overall.

Examination of the Relationship Between Metabolic Syndrome and Obstructive Sleep Apnea in Iranian Patients with Type 2 Diabetes: A Case-Control Study

INTRODUCTION

Obstructive sleep apnea (OSA) is a common risk factor for metabolic syndrome (MS) that increases the chance of cardiovascular disease, stroke, and mortality. Many studies have been conducted on this matter, but the results are still conflicting. The aim of the present study was to examine the relationship between metabolic syndrome (MS) and obstructive sleep apnea (OSA) in Iranian patients with type 2 diabetes (T2D).

PATIENTS AND METHODS

This matched case-control study was conducted with 190 patients with T2D in Sanandaj, Iran. The data were selected using the demographic questionnaire, clinical and anthropometric measures, the Berlin Questionnaire (BQ), and the National Cholesterol Education Program's Adult Treatment Panel III (NCEP-ATP III). Participants were divided into two groups of high risk of OSA (experimental) and low risk of OSA (control). The data were analyzed using Stata, version 14.

RESULTS

The frequency of MS was higher in the OSA group than the control group (81.1% vs 70.5%), but the group difference was not statistically significant (p=0.127). The results of crude and age-sex adjusted logistic regression analysis revealed no significant association between OSA and the other variables under study (P>0.05). Sensitivity analysis and external adjustment for BMI showed no significant relationship between OSA and the other variables under study (P=0.319).

CONCLUSION

In the present study, no significant association was found between metabolic syndrome (MS) and obstructive sleep apnea (OSA) in patients with T2D; therefore, more studies should be conducted on this subject.

Dietary and cardio-metabolic risk factors in patients with Obstructive Sleep Apnea: cross-sectional study

BACKGROUND

Little is known about the role of dietary intake in obstructive sleep apnea (OSA), which could prove important in improving clinical outcomes for people with obesity and/or cardiovascular disease within these populations. Reduction in energy intake typically results in weight loss, markedly improving metabolic parameters and ameliorating OSA severity. The aim of this study was to evaluate the association of dietary and cardio-metabolic risk factors with OSA severity.

METHODS

This was a cross-sectional study. A total of 75 volunteers at risk of OSA were recruited from 153 patients suffering from sleep disturbance at the Department of Pulmonology, Allergology and Respiratory Oncology at the Poznan University of Medical Sciences. Polysomnography was used for OSA diagnosis. Sleep quality was assessed by the Pittsburgh Sleep Quality Index. Blood pressure, parameters of glucose (fasting glucose, glucose tolerance test) and lipid metabolism (TC, LDL-C, HDL-C, TG) were assessed using routine enzymatic methods. Dietary intake was evaluated by 24-hr dietary recalls and Food Frequency Questionnaire. Ordinal logistic regression models were used for association of background characteristics and dietary intake with OSA severity. All analyses were adjusted for age, sex, BMI, smoking and alcohol intake.

RESULTS

A higher percentage of smokers were observed in patients with mild OSA, while alcohol intake was the highest in severe OSA patients. Approximately 60% of the studied patients were self-reported poor sleepers. Results from ordinal logistic regression models showed that higher intakes of alcohol intake were associated with increased odds of severe OSA; whereas higher HDL-C levels were associated with lower odds (OR 0.01; 95% CI [0.0003-0.55]). Significantly higher odds of high OSA severity were observed in patients with disturbed sleep stages and obstructive sleep apnea. Moreover, the investigation of nutrient intake in relation to OSA severity showed that a higher intake of dietary fiber was associated with decreased OSA severity (OR 0.84; 95% CI [0.71-0.98]).

CONCLUSIONS

The severity of OSA is related to higher alcohol consumption and disturbed sleep. The significantly lower dietary fiber intake in patients with severe OSA is of particular importance for dietary consulting in clinical practice, which may positively influence cardiometabolic outcomes.

A new predictive model for continuous positive airway pressure in the treatment of obstructive sleep apnea

BACKGROUND

Numerous mathematical formulas have been developed to determine continuous positive airway pressure (CPAP) without an in-laboratory titration study. Recent studies have shown that style of CPAP mask can affect the optimal pressure requirement. However, none of the current models take mask style into account. Therefore, the goal of this study was to develop new predictive models of CPAP that take into account the style of mask interface.

METHODS

Data from 200 subjects with attended CPAP titrations during overnight polysomnograms using nasal masks and 132 subjects using oronasal masks were randomized and split into either a model development or validation group. Predictive models were then created in each model development group and the accuracy of the models was then tested in the model validation groups.

RESULTS

The correlation between our new oronasal model and laboratory determined optimal CPAP was significant, r = 0.61, p < 0.001. Our nasal formula was also significantly related to laboratory determined optimal CPAP, r = 0.35, p < 0.001. The oronasal model created in our study significantly outperformed the original CPAP predictive model developed by Miljeteig and Hoffstein, z = 1.99, p < 0.05. The predictive performance of our new nasal model did not differ significantly from Miljeteig and Hoffstein's original model, z = -0.16, p < 0.90. The best predictors for the nasal mask group were AHI, lowest SaO2, and neck size, whereas the top predictors in the oronasal group were AHI and lowest SaO2.

CONCLUSION

Our data show that predictive models of CPAP that take into account mask style can significantly improve the formula's accuracy. Most of the past models likely focused on model development with nasal masks (mask style used for model development was not typically reported in previous investigations) and are not well suited for patients using an oronasal interface. Our new oronasal CPAP prediction equation produced significantly improved performance compared to the well-known Miljeteig and Hoffstein formula in patients titrated on CPAP with an oronasal mask and was also significantly related to laboratory determined optimal CPAP.

The association between obstructive sleep apnea and metabolic syndrome: a systematic review and meta-analysis

Background

Obstructive sleep apnea (OSA) is characterized by repeated episodes of obstruction of the upper airway. Numerous studies have indicated a relationship between OSA and metabolic syndrome (MS), but the results remain debatable. We aimed to perform a systematic review and meta-analysis to evaluate the association between OSA and MS.

Methods

We searched electronic databases (PubMed, EMBASE, and ISO Web of Knowledge) up to September 2014 with English-language restriction. Cross-sectional, case–control, and cohort studies in which the presence of OSA was assessed by objective measurements, the exposure of interest was OSA, and the outcome of interest was the presence (or incidence) of MS were included. The adjusted odds ratios (ORs) (or relative risk) and 95 % confidence intervals (CIs) were extracted and pooled. Sensitivity analyses were conducted, and heterogeneity and publication bias were assessed.

Results

Overall, 15 cross-sectional (2456 patients with OSA and 1705 subjects without OSA), five case–control (1156 OSA patients and 404 controls), and no cohort studies were included. The pooled ORs of MS in individuals with OSA for cross-sectional and case–control studies were 2.87 (95 % CI: 2.41–3.42) and 2.56 (95 % CI: 1.98–3.31), respectively. There was clinically unimportant (I² = 20 %) and moderate (I² = 35 %) between-study heterogeneity of the analysis. The pooled crude ORs of MS in individuals with mild and moderate-to-severe OSA was 2.39 (95 % CI: 1.65–3.46) and 3.45 (95 % CI: 2.33–5.12), respectively, and there was substantial heterogeneity in the meta-analyses (I² = 53 % and I² = 63 %, respectively). However, no evidence of publication bias was detected.

Conclusions

OSA is shown to be associated with MS, although causality between these two factors has not been demonstrated yet. Future cohort and randomized controlled studies are needed.

Electronic supplementary material

The online version of this article (doi:10.1186/s12890-015-0102-3) contains supplementary material, which is available to authorized users.

Comparison of the upper airway dynamics of oronasal and nasal masks with positive airway pressure treatment using cine magnetic resonance imaging

PURPOSE

It is known that oronasal masks are not as effective at opening the upper airway compared to nasal only continuous positive airway pressure (CPAP) masks in patients with sleep-disordered breathing. However, the physiological mechanism for this difference in efficacy is not known; although, it has been hypothesized to involve the retroglossal and/or retropalatal region of the upper airway. The objective of this study was to investigate differences in retroglossal and retropalatal anterior-posterior space with the use of oronasal vs. nasal CPAP masks using real-time cine magnetic resonance imaging (cMRI).

METHODS

Ten subjects (eight men, two women) with obstructive sleep apnea (OSA) were given cMRI with both nasal and oronasal CPAP masks. Each subject was imaged with each interface at pressures of 5, 10, and 15 cm of H2O, while in the supine position along the sagittal plane.

RESULTS

The oronasal mask produced significantly less airway opening in the retropalatal region of the upper airway compared to the nasal mask interface. During exhalation, mask style had a significant effect on anterior-posterior distance p = 0.016. No differences were found in the retroglossal region between mask styles.

CONCLUSIONS

Our study confirmed previous findings showing differences in treatment efficacy between oronasal and nasal mask styles. We have shown anatomic evidence that the nasal mask is more effective in opening the upper airway compared to the oronasal mask in the retropalatal region.

Therapeutic potential of intermittent hypoxia: a matter of dose

Intermittent hypoxia (IH) has been the subject of considerable research in recent years, and triggers a bewildering array of both detrimental and beneficial effects in multiple physiological systems. Here, we review the extensive literature concerning IH and its impact on the respiratory, cardiovascular, immune, metabolic, bone, and nervous systems. One major goal is to define relevant IH characteristics leading to safe, protective, and/or therapeutic effects vs. pathogenesis. To understand the impact of IH, it is essential to define critical characteristics of the IH protocol under investigation, including potentially the severity of hypoxia within episodes, the duration of hypoxic episodes, the number of hypoxic episodes per day, the pattern of presentation across time (e.g., within vs. consecutive vs. alternating days), and the cumulative time of exposure. Not surprisingly, severe/chronic IH protocols tend to be pathogenic, whereas any beneficial effects are more likely to arise from modest/acute IH exposures. Features of the IH protocol most highly associated with beneficial vs. pathogenic outcomes include the level of hypoxemia within episodes and the number of episodes per day. Modest hypoxia (9-16% inspired O2) and low cycle numbers (3-15 episodes per day) most often lead to beneficial effects without pathology, whereas severe hypoxia (2-8% inspired O2) and more episodes per day (48-2,400 episodes/day) elicit progressively greater pathology. Accumulating evidence suggests that "low dose" IH (modest hypoxia, few episodes) may be a simple, safe, and effective treatment with considerable therapeutic potential for multiple clinical disorders.

Nonarteritic anterior ischemic optic neuropathy and obstructive sleep apnea

BACKGROUND

To evaluate the obstructive sleep apnea syndrome (OSAS) in patients with nonarteritic anterior ischemic optic neuropathy (NAION).

METHODS

We recruited 27 patients with NAION and 27 age-matched and sex-matched controls who also were similar for systemic risk factors such as diabetes mellitus, hypertension, and hypercholesterolemia. All patients and controls underwent overnight polysomnography for the diagnosis of OSAS and calculation of apnea-hypopnea index (AHI).

RESULTS

Patients and controls were statistically similar in terms of age, sex, gender, smoking, systemic risk factors, neck circumference, and body mass index. The subjects with AHI ≥ 20 were accepted as OSAS. Fifteen of 27 patients (55.6%) with NAION and 6 of 27 controls (22.2%) had OSAS (P < 0.05).

CONCLUSION

The prevalence of OSAS was higher in patients with NAION, and the difference between patient and control groups was statistically significant (P < 0.05). This result supports prior series suggesting the association between NAION and OSAS.

Normal-tension glaucoma and obstructive sleep apnea syndrome: a prospective study

BACKGROUND

Today, identified risk factors for normal-tension glaucoma (NTG) include abnormal ocular blood flow, abnormal blood coagulation, systemic hypotension, ischemic vascular disorders, and autoimmune diseases. However, pathogenesis of the condition remains unclear. On the other hand, there are also a few studies suggesting that the obstructive sleep apnea syndrome (OSAS) may compromise optic nerve head perfusion and cause glaucomatous optic neuropathy by creating transient hypoxemia and increasing vascular resistance. In this study, we evaluated the possible association between OSAS and NTG.

METHODS

We recruited 24 patients with NTG and 24 age and sex matched controls who were also similar for systemic risk factors such as diabetes mellitus (DM), hypertension (HT) and hypercholesterolemia. All patients and controls underwent over-night polysomnography (PSG) for the diagnosis of OSAS and calculation of Apnea-Hypopnea Index (AHI).

RESULTS

Patients and controls were statistically similar in terms of age, sex, gender, smoking, systemic risk factors, neck circumference and body mass index. The subjects with AHI ≥ 20 were accepted as OSAS. Ten (41.7%) of 24 patients with NTG and 3 (12.5%) of 24 controls had OSAS (p < 0.05).

CONCLUSIONS

The prevalence of OSAS was higher in patients with NTG and the difference between patient and control groups was statistically significant (p < 0.05).

A randomised controlled trial on the effect of mask choice on residual respiratory events with continuous positive airway pressure treatment

INTRODUCTION

It has been found that mask style can affect the amount of continuous positive airway pressure (CPAP) required to reduce an apnoea/hyponoea index (AHI) to < 5/h on a titration study. However, it was not previously known whether switching from one CPAP mask style to another post titration could affect the residual AHI with CPAP. The purpose of this study was to investigate the differences in residual AHI with CPAP treatment between oronasal and nasal masks.

METHODS

Twenty-one subjects (age mean (M)=62.9, body mass index (BMI) M=29.6 kg/m2) were randomised (14 subjects completed the protocol) to undergo an in-laboratory CPAP titration with either a nasal mask or an oronasal mask. Subjects were then assigned this mask for 3weeks of at-home CPAP use with the optimal treatment pressure determined on the laboratory study (CPAP M=8.4 cm of H2O). At the end of this 3-week period, data were collected from the CPAP machine and the subject was given the other mask to use with the same CPAP settings for the next 3weeks at home (if the nasal mask was given initially, the oronasal one was given later and vice versa). On completion of the second 3-week period, data on residual AHI were again collected and compared with the first 3-week period on CPAP.

RESULTS

A Wilcoxon Signed-Rank Test (two-tailed) revealed that residual AHI with CPAP treatment was significantly higher with the oronasal compared with the nasal mask (z = -3.296, p<0.001). All 14 subjects had a higher residual AHI with the oronasal versus nasal mask, and 50% of the subjects had a residual AHI >10/h in the oronasal mask condition, even though all of these subjects were titrated to an AHI of < 5/h in the laboratory.

CONCLUSION

A higher residual AHI was seen in all patients with the use of an oronasal mask compared with a nasal mask. Switching to an oronasal mask post titration results in an increase in residual AHI with CPAP treatment, and pressure adjustment may be warranted.

High levels of inflammation and insulin resistance in obstructive sleep apnea patients with hypertension

Hypertension induced by obstructive sleep apnea (OSA) may be multifactorial in origin, and systemic inflammation is one of the major factors. However, OSA patients do not always have the identical probability with hypertension even in patients with the same history and degree of OSA. The aim of this study was to compare the levels of inflammation and insulin resistance in two groups of patients who had the same degree as well as the same long history of OSA, but with/without hypertension. OSA patients (Apnea Hyponea Index, AHI ≥ 40/h, n = 70) were examined by polysomnography and blood analysis for the measurements of fasting plasma glucose, serum insulin (FINS), high-sensitivity C-reactive protein (CRP), peptide C,TNF-α, IL-6, and IL-10. Patients with hypertension (n = 40) had higher level of LDL-C and lower HDL-C levels than patients without hypertension. Almost half (16/40) of OSA patients with hypertension had family history of hypertension. Moreover in OSA patients with hypertension, the levels of TNF-α, IL-6, and CRP were higher, but IL-10 was lower than those without hypertension. FINS, peptide C, HOMA-IR, and HOMA-islet were also higher in OSA patients with hypertension. OSA patients with hypertension have higher level of inflammation and insulin resistance. Systemic inflammation and insulin resistance are both important factors for the development of hypertension in OSA patients.

The efficacy of three different mask styles on a PAP titration night

BACKGROUND

This study compared the efficacy of three different masks, nasal pillows, nasal masks and full face (oronasal) masks, during a single night of titration with continuous positive airway pressure (CPAP).

METHODS

Fifty five subjects that included men (n=33) and women (n=22) were randomly assigned to one of three masks and underwent a routine titration with incremental CPAP applied through the different masks.

RESULTS

CPAP applied through the nasal pillows and nasal mask was equally effective in treating mild, moderate, and severe sleep apnea. However, CPAP applied through the oronasal mask required a significantly higher pressure compared to nasal masks to treat moderately severe (2.8 cm of H(2)O ± 2.1 SD) and severe (6.0 cm of H(2)O ± 3.2 SD) obstructive sleep apnea.

CONCLUSION

CPAP applied with either nasal mask was effective in treating mild, moderate, and severe sleep apnea. The oronasal mask required significantly higher pressures in subjects with moderate to severe disease. Therefore, when changing from a nasal to an oronasal mask, a repeat titration is required to ensure effective treatment of sleep apnea, especially in patients with moderate to severe disease.

Epworth Sleepiness Scale may be an indicator for blood pressure profile and prevalence of coronary artery disease and cerebrovascular disease in patients with obstructive sleep apnea

OBJECTIVE

This study seeks to determine whether scores of a short questionnaire assessing subjective daytime sleepiness (Epworth Sleepiness Scale [ESS]) are associated with blood pressure (BP) level, BP profile, and prevalence of related coronary artery disease (CAD) and cerebrovascular disease (CVD) in obstructive sleep apnea (OSA) patients diagnosed by polysomnography (PSG).

METHODS

Twenty university hospital sleep centers in China mainland were organized by the Chinese Medical Association to participate in this study. Between January 2004 and April 2006, 2,297 consecutive patients (aged 18-85 years; 1,981 males and 316 females) referred to these centers were recruited. BP assessments were evaluated at four time points (daytime, evening, nighttime, and morning) under standardized conditions. Anthropometric measurements, medical history of hypertension, CAD, and CVD were collected. ESS score was calculated for each participant and at the night of BP assessment, nocturnal PSG was performed and subjects were classified into four groups based on the apnea-hypopnea index (AHI) from PSG as follows: control group (control, n = 213) with AHI < 5; mild sleep apnea (mild, n = 420) with AHI ≥ 5 and <15; moderate sleep apnea (moderate, n = 460) with AHI ≥ 15 and <30; and severe sleep apnea (severe, n = 1,204) with AHI ≥ 30. SPSS 11.5 software package was used for the relationships between ESS and BP profile and prevalence of CAD and CVD.

RESULTS

ESS is correlated positively with average daytime, nighttime, evening, and morning BP before and even after controlling for confounding effects of age, sex, BMI, AHI, and nadir nocturnal oxygen saturation (before--r = 0.182, 0.326, 0.245, and 0.329, respectively, all P values < 0.001; after--r = 0.069, 0.212, 0.137, and 0.208, respectively, all P values < 0.001). In the severe group, nighttime, evening, morning average BPs (ABPs), the ratio of nighttime/daytime average BP (ratio of nighttime average BP to daytime average BP), and prevalence of hypertension, drug-resistant hypertension (R-HTN), isolated nighttime hypertension (IN-HTN), CAD, and CVD in excessive daytime sleepiness (EDS, ESS ≥ 11) subjects are higher than those in non-EDS (ESS 0-10; t/χ(2) = -8.388, -6.207, -8.607, -5.901, 12.742, 38.980, 16.343, 59.113, and 67.113, respectively; all P values < 0.05). For EDS subjects in the moderate group but not in the control and mild group, nighttime ABP and the ratio of nighttime/daytime average BP are higher (t = -2.086 and -3.815, respectively, all P values < 0.05). Linear fitting with ESS and the ratio of nighttime/daytime average BP shows a positive correlation (r(2) = 0.049, P < 0.001).

CONCLUSIONS

In severe OSA patients with comparable AHI, EDS may identify a subset of individuals with OSA at higher risk of hypertension, R-HTN, IN-HTN, CAD, and CVD. Overall, nighttime ABP seems to be more sensitive to be influenced by EDS than other ABP parameters. Future studies should investigate the potential dose-effect relationship between EDS and hypertension and the possibility that diagnosis and treatment of EDS could aid in BP reduction and ultimately in decreased morbidity and mortality from cardiovascular and cerebrovascular complications (TMUIRB20010002 at www.clinicaltrials.gov ).

Polymorphisms in α- and β-Adrenergic Receptor Genes, Hypertension, and Obstructive Sleep Apnea: The Skaraborg Sleep Study

The sympathetic nervous system and the adrenergic receptors play an important role in regulation of blood pressure. This study explored the associations between functional polymorphisms of the α(2B)-, β(1)-, and β(2)-adrenergic receptor genes and obstructive sleep apnea (OSA) in hypertensive patients and hypertension in patients with OSA in a populationbased sample of 157 hypertensive patients and 181 healthy control subjects. Only the Arg389Gly polymorphism of the β(1)-adrenergic receptor gene was associated with increased risk for mild OSA in hypertensive patients (Arg/Arg versus Gly/Arg/Gly/Gly, 2.1, 95% CI, 1.02-4.7). Hypertensive men carrying the Arg389Arg genotype had higher crude and age-adjusted AHI than carriers of the Arg389Gly/Gly389Gly genotypes. When adjusted also for BMI this difference became borderline significant. This difference was not observed in women. The risk of hypertension in mild OSA was associated with increasing number of Arg-alleles (Arg/Arg OR 5.4, 95% CI 1.4-21.2).

Randomized controlled trial of variable-pressure versus fixed-pressure continuous positive airway pressure (CPAP) treatment for patients with obstructive sleep apnea/hypopnea syndrome (OSAHS)

STUDY OBJECTIVE

To determine whether fixed-pressure or variable-pressure CPAP was preferred by patients and gave better outcomes in patients with the obstructive sleep apnea/hypopnea syndrome (OSAHS).

DESIGN

Randomized blinded cross-over trial with 6 weeks of fixed and 6 weeks of variable-pressure CPAP.

SETTING

Sleep center.

PATIENTS

200 consecutive consenting CPAP naïve patients with daytime sleepiness and > 15 apneas + hypopneas/h after an attended auto-CPAP titration night.

INTERVENTIONS

CPAP therapy using the same device (Autoset Spirit) set for 6 weeks in fixed pressure mode and for 6 weeks in variable pressure mode, the order of therapies being randomized.

MEASUREMENTS AND RESULTS

All measurements were recorded at the end of each limb by a researcher blind to treatment. These included symptoms, Epworth Score, CPAP usage, objective sleepiness by modified Osler test, vigilance and health related quality of life. A total of 181 of 200 patients completed the study. At the end of the study, patients expressed no significant difference in the primary outcome, patient preference, 72 patients preferring fixed and 69 preferring variable-pressure CPAP. Epworth score was lower on variable (9.5, SEM 0.4) than fixed-pressure CPAP (10.0, SEM 0.3; P = 0.031). Mean CPAP use was higher on variable (4.2, SEM 0.2 h/night) than fixed-pressure CPAP (4.0, SEM 0.2 h/night; P = 0.047). There were no other significant differences between treatments. CONCLUSIONS This study shows no difference in patient preference and only a marginal benefit of variable over fixed-pressure CPAP in OSAHS in terms of subjective sleepiness and CPAP use. The clinical value of this difference remains to be determined.

CLINICAL TRIAL INFORMATION

Variable-pressure versus fixed-pressure continuous positive airway pressure (CPAP) treatment for patients with obstructive sleep apnoea/hypopnoea syndrome (OSAHS); Registration # ISRCTN43085025.http://www.controlled-trials.com//SRCTN43085025.

Lipid peroxides, superoxide dismutase and circulating IL-8 and GCP-2 in patients with severe obstructive sleep apnea: a pilot study

Obstructive sleep apnea (OSA) is associated with cardiovascular morbidity and mortality and many other physiological and immunological disorders. An increase in hypoxia due to OSA may cause generation of reactive oxygen species (ROS). ROS are toxic to biomembranes and may lead to peroxidation of lipids. An increase in systemic biomarkers of inflammation and oxidative stress has been found in patients with OSA. The first aim of this study was to test the hypothesis that OSA is linked to increased oxidative stress (lipid peroxidation) and decreased antioxidant defense [superoxide dismutase (SOD)]. The second aim was to measure the serum levels of neutrophil chemokines [interleukin-8 (IL-8)], and granulocyte chemotactic protein-2 (GCP-2) in OSA patients. Twenty five patients with severe OSA and 17 healthy subjects were recruited. IL-8 and GCP-2 were measured in the serum by a specific enzyme immunoassay kit. Oxidative stress level was quantitated by measurement of thiobarbituric acid reactive substances. SOD enzymatic activity was measured by purely chemical system based on NAD(P)H oxidation. Mean SOD and lipid peroxidation concentrations of patients were not significantly different from those of control subjects (0.29+/-0.015 vs 0.31+/-0.01 U/ml and 4.64+/-0.57 vs 4.62+/-0.54 mmol/ml, respectively). Higher concentrations of IL-8 and GCP-2 were found in OSA patients (198.8+/-4.76 vs 180.83+/-3.38 and 383.34+/-46.19 vs 218+/-13.16 pg/ml, respectively, p<0.005). The present study does not support the hypothesis that OSA is linked to increased oxidative stress and decreased antioxidant defense. On the other hand, it suggests that systemic inflammation characterizes OSA patients.

Determinants of daytime blood pressure in relation to obstructive sleep apnea in men

This study investigated the roles of different potential pathophysiological mechanisms in the determination of blood pressure in relation to obstructive sleep apnea. The study was designed as a cross-sectional study. Consecutive healthy male subjects who were to undergo polysomnography were recruited. Demographic and anthropometric data were collected. Blood pressure measurements were taken in the evening before sleep and the next morning on waking. Overnight urinary samples for catecholamines and fasting blood for cortisol, insulin, glucose, and lipids were taken. Ninety-four men were analyzed, with a mean age of 43.7 +/- 9.3 years and mean apnea-hypopnea index (AHI) of 27.5 +/- 26.2 events/h. Sixty-nine patients (73%) had obstructive sleep apnea (AHI >or= 5). Urinary catecholamines were positively correlated with severity of sleep apnea, independent of obesity. Blood pressure measurements correlated with age, obesity, severity of sleep apnea, and urinary catecholamines. Regression analysis showed that sleep indices and urinary catecholamines were independent determinants of morning systolic and diastolic blood pressure, respectively, while total cholesterol and waist circumference were respective additional factors. Urinary catecholamines and waist circumference were determinants of evening blood pressure, with morning cortisol being an additional determinant for diastolic blood pressure. Obstructive sleep apnea and related sympathetic activity contributed significantly to the determination of daytime blood pressure in overweight middle-aged men without overt cardiometabolic diseases, and other contributing factors include abdominal obesity, total cholesterol, and cortisol levels.

Perceived informational needs, side-effects and their consequences on adherence - a comparison between CPAP treated patients with OSAS and healthcare personnel

OBJECTIVE

To compare perceptions among continuous positive airway pressure (CPAP) treated patients with obstructive sleep apnoea syndrome (OSAS) and healthcare personnel with regard to informational needs, side-effects and their consequences on adherence.

METHODS

A cross-sectional descriptive design was used including 350 CPAP treated OSAS patients from three Swedish hospitals and 105 healthcare personnel from 26 Swedish hospitals. Data collection was performed using two questionnaires covering informational needs, side-effects and adherence to CPAP.

RESULTS

Both groups perceived all surveyed informational areas as very important. Patients perceived the possibilities to learn as significantly greater in all areas (p<0.001) compared to healthcare personnel, and scored significantly higher regarding positive effects on adherence of information about pathophysiology (p<0.05), self-care (p<0.001) and troubleshooting (p<0.01). A total of 11 out of 15 surveyed side-effects were perceived to be more frequent by healthcare personnel (p<0.01-p<0.001). They also scored all side-effects to cause greater problems and decrease the CPAP use to a greater extent (p<0.001).

CONCLUSION

Knowledge about these differences between patients and healthcare personnel regarding educational needs, side-effects and their effects on adherence can be important when designing educational programmes to increase CPAP adherence.

PRACTICE IMPLICATIONS

Measurement of these parameters before, during and after educational programs are suggested.

Alterations in Glucose Disposal in Sleep-disordered Breathing

RATIONALE

It is well established that sleep-disordered breathing (SDB) is independently associated with insulin resistance, glucose intolerance, and type 2 diabetes mellitus. However, data on whether SDB alters in vivo kinetics of glucose and insulin are lacking.

OBJECTIVES

The primary goal of this study was to use the frequently sampled intravenous glucose tolerance test (FSIVGTT) in subjects with and without SDB to model the in vivo kinetics of glucose and insulin. Minimal model analysis of the FSIVGTT data was used to derive parameters of insulin sensitivity, glucose effectiveness (a measure of the ability of glucose to mediate its own disposal), and pancreatic beta-cell function.

RESULTS

A total of 118 nondiabetic subjects underwent polysomnography, the FSIVGTT, and body composition measurements including determination of percent body fat. Compared with normal subjects (apnea-hypopnea index < 5 events/h), those with mild, moderate, and severe SDB displayed a 26.7, 36.5 and 43.7% reduction in insulin sensitivity, respectively, independent of age, sex, race, and percent body fat. The disposition index, an integrated measure of pancreatic beta-cell function, was also reduced in patients with moderate to severe SDB. The decrease in insulin sensitivity and the disposition index were correlated with the average degree of oxyhemoglobin desaturation. In contrast, glucose effectiveness was negatively correlated with the frequency of respiratory event-related arousals.

CONCLUSIONS

The results of this study suggest that, independent of adiposity, SDB is associated with impairments in insulin sensitivity, glucose effectiveness, and pancreatic beta-cell function. Collectively, these defects may increase the risk of glucose intolerance and type 2 diabetes mellitus in SDB.

Intermittent hypoxia: cause of or therapy for systemic hypertension?

During acute episodes of hypoxia, chemoreceptor-mediated sympathetic activity increases heart rate, cardiac output, peripheral resistance and systemic arterial pressure. However, different intermittent hypoxia paradigms produce remarkably divergent effects on systemic arterial pressure in the post-hypoxic steady state. The hypertensive effects of obstructive sleep apnea (OSA) vs. the depressor effects of therapeutic hypoxia exemplify this divergence. OSA, a condition afflicting 15-25% of American men and 5-10% of women, has been implicated in the pathogenesis of systemic hypertension and is a major risk factor for heart disease and stroke. OSA imposes a series of brief, intense episodes of hypoxia and hypercapnia, leading to persistent, maladaptive chemoreflex-mediated activation of the sympathetic nervous system which culminates in hypertension. Conversely, extensive evidence in animals and humans has shown controlled intermittent hypoxia conditioning programs to be safe, efficacious modalities for prevention and treatment of hypertension. This article reviews the pertinent literature in an attempt to reconcile the divergent effects of intermittent hypoxia therapy and obstructive sleep apnea on hypertension. Special emphasis is placed on research conducted in the nations of the former Soviet Union, where intermittent hypoxia conditioning programs are being applied therapeutically to treat hypertension in patients. Also reviewed is evidence regarding mechanisms of the pro- and anti-hypertensive effects of intermittent hypoxia.

An update on obstructive sleep apnea and the metabolic syndrome

PURPOSE OF REVIEW

Patients with obstructive sleep apnea are often overweight or obese, and they frequently exhibit metabolic aberrations, collectively known as the metabolic syndrome, an established cardiovascular risk factor. We review recent data on the relationship between obstructive sleep apnea and metabolic syndrome or its components, including abdominal obesity, insulin resistance, hypertension, and dyslipidemia.

RECENT FINDINGS

There is accumulating evidence for an independent association between obstructive sleep apnea and metabolic syndrome or its components. Recent epidemiologic and clinical data suggest a causal role of severe obstructive sleep apnea in development of hypertension, but findings for insulin resistance and dyslipidemia are controversial. Visceral obesity remains a confounding issue in analyses. Animal models and translational studies indicate that obstructive sleep apnea may promote metabolic dysfunction through cycles of intermittent hypoxia; proposed underlying pathophysiologic mechanisms include oxidative stress, sympathetic activation, and inflammation.

SUMMARY

There is suggestive evidence, but independent associations between obstructive sleep apnea and metabolic syndrome or its components are not fully established because of the confounding effect of obesity. Large randomized interventional trials are needed to identify any cause-effect relationship. Long-term follow-up studies would help to clarify the role of treatment of sleep apnea in reducing cardio-metabolic morbidity.

Parallel changes in resting muscle sympathetic nerve activity and blood pressure in a hypertensive OSAS patient demonstrate treatment efficacy

Studies comparing the efficacy of continuous positive airway pressure (CPAP) versus surgery in correcting cardiovascular abnormalities in OSAS are lacking. We describe an OSAS patient with hypertension who responded favorably to CPAP treatment, whereas subsequent uvulopalatopharyngoplasty (UPPP) was less successful. While CPAP markedly lowered daytime muscle sympathetic nerve activity (MSNA) and blood pressure (BP), findings after UPPP were comparable to pre-treatment baseline. Thus, parallel changes in MSNA and BP demonstrated treatment efficacy.

Continuous positive airways pressure for obstructive sleep apnoea in adults

BACKGROUND

Obstructive sleep apnoea is the periodic reduction (hypopnoea) or cessation (apnoea) of breathing due to narrowing or occlusion of the upper airway during sleep. The main symptom is daytime sleepiness and it has been suggested it is linked to premature death, hypertension, ischaemic heart disease, stroke and road traffic accidents.

OBJECTIVES

The main treatment for sleep apnoea is with the use of continuous positive airways pressure (CPAP), which requires a flow generator and mask. These are used at night to prevent apnoea, hypoxia and sleep disturbance. The objective was to assess the effects of CPAP in the treatment of obstructive sleep apnoea in adults.

SEARCH STRATEGY

We searched the Cochrane Airways Group Trials Register and reference lists of articles. We consulted experts in the field. Searches were current to July 2005.

SELECTION CRITERIA

We included randomised trials comparing nocturnal CPAP with an inactive control or oral appliances in adults with obstructive sleep apnoea (an apnoea and hypopnoea index greater than five per hour). Trials had a minimum intervention period of two weeks.

DATA COLLECTION AND ANALYSIS

Trial quality was assessed and two review authors extracted data independently. Study authors were contacted for missing information. Parallel and crossover group trials were analysed separately.

MAIN RESULTS

Thirty-six trials involving 1718 people met the inclusion criteria. Study quality was mixed. Compared with control, CPAP showed significant improvements in objective and subjective sleepiness and several quality of life, cognitive function and depression measures (parallel-group studies: Epworth sleepiness scale (ESS) -3.83 units, 95% CI -4.57 to -3.09; crossover studies: ESS -1.84 units, 95% CI -2.57 to -1.11). Twenty-four hour systolic and diastolic blood pressures were lower with CPAP compared with control (parallel-group trials). Compared with oral appliances, CPAP significantly reduced the apnoea and hypopnoea index (crossover studies: -7.97 events/hr, 95% CI -9.56 to -6.38) and improved sleep efficiency (crossover studies: 2.31%, 95% CI 0.02 to 4.6) and minimum oxygen saturation (4.14%, 95% CI 3.25 to 5.03). Responders to both treatments expressed a strong preference for the oral appliance. However, participants were more likely to withdraw on OA than on CPAP therapy.

AUTHORS' CONCLUSIONS

CPAP is effective in reducing symptoms of sleepiness and improving quality of life measures in people with moderate and severe obstructive sleep apnoea (OSA). It is more effective than oral appliances in reducing respiratory disturbances in these people but subjective outcomes are more equivocal. Certain people tend to prefer oral appliances to CPAP where both are effective. This could be because they offer a more convenient way of controlling OSA. Short-term data indicate that CPAP leads to lower blood pressure than in controls. Long-term data are required for all outcomes in order to determine whether the initial benefits seen in short-term clinical trials persist.

The interaction between respiratory and autonomic function during sleep-related changes in pharyngeal airway patency

Sleep-related changes in pharyngeal function result in an increased resistance to airflow and in some people complete pharyngeal occlusion. Clinically, pharyngeal occlusion causes obstructive sleep apnoea syndrome (OSA). This is a prevalent disorder, which is an independent risk factor for the development of systemic hypertension. Several mechanisms contribute to the sleep-related changes in pharyngeal function in both health and disease, including a reduction in respiratory-related muscle activation, and an increase in latency of the pharyngeal reflex to negative intralumenal pressure. Arousal from sleep causes increases in ventilation and autonomic cardiovascular function that far exceed physiological requirements--the so-called 'waking reflex'. In patients with OSA the waking reflex is augmented either by hypoxemia, hypercapnia, or large swings in intrathoracic pressure. How these factors interact to cause the acute surges in heart rate and systemic blood pressure that occur at the termination of an apnoea will be reviewed, together with the longer term consequences of pharyngeal occlusion during sleep.

Nonarteritic anterior ischemic optic neuropathy in patients with sleep apnea while being treated with continuous positive airway pressure

PURPOSE

To report three cases of nonarteritic anterior ischemic optic neuropathy (NAION) that occurred in patients with sleep apnea syndrome (SAS) while being treated with continuous positive airway pressure (CPAP).

DESIGN

A prospective, noncomparative case series.

METHODS

Prospective review of 108 patients with NAION diagnosed between 2002 and 2003 to identify any patients who developed NAION while being treated for SAS with CPAP.

RESULTS

One patient had bilateral sequential NAION and two patients had unilateral NAION despite treatment with CPAP for SAS. All the patients were being treated with CPAP for a period ranging from 4 months to 6 years before the onset of NAION.

CONCLUSIONS

In this series, CPAP did not prevent the development of NAION in SAS patients. Larger observational studies are needed to study the benefit of CPAP in preventing NAION in patients with SAS.