Obstructive sleep apnoea–hypoapnoea syndrome reversibly depresses cardiac response to exercise

Effects of Positive Airway Pressure on Cardiorespiratory Fitness in Patients with Concomitant Obstructive Sleep Apnea and Cardiovascular Disease

Background and Objectives: Obstructive sleep apnea (OSA) is common in cardiovascular disease (CVD), although positive airway pressure (PAP) treatment has not been demonstrated to improve the cardiovascular outcome. The objective of this study is to investigate the impact of adherence to PAP therapy on cardiopulmonary exercise testing (CPET) performance in patients with concomitant OSA and CVD. Materials and Methods: This preliminary study involved symptomatic OSA patients requiring PAP treatment who had CVD. All subjects underwent polysomnography, echocardiography, and CPET at baseline. After 6 to 12 months of PAP treatment, CPET performance was re-assessed. The changes in CPET parameters before and after PAP treatment were compared between patients who were adherent to PAP and patients who were not adherent to PAP. Results: A total of 16 OSA patients with an apnea-hypopnea index of 32.0 ± 23.4 were enrolled. Patients were classified into the adherent (n = 9) and non-adherent (n = 7) groups with regard to PAP adherence. After 6 to 12 months of PAP treatment, the PAP-adherent group showed a greater increase in peak VO2 than the PAP-non-adherent group, but the difference between the two groups was not significant (p = 0.581). The decrease in ventilatory equivalent for the carbon dioxide slope (VE/VCO2) was significantly greater in the PAP-adherent group compared to the PAP-non-adherent group (p = 0.030). Conclusions: Adherence to PAP therapy for OSA is associated with an improvement in the VE/VCO2 slope, as an index of the ventilatory response to exercise, in patients with CVD. Screening for sleep apnea in CVD patients may be warranted, and strategies to optimize adherence to PAP in these patients are beneficial. Further evidence is needed to elucidate whether CPET could be routinely used to monitor treatment responses of OSA to PAP therapy in patients with CVD.

Weight loss and lifestyle intervention for cardiorespiratory fitness in obstructive sleep apnea: The INTERAPNEA trial

INTRODUCTION

Although recent trials have shown benefits of weight loss and lifestyle interventions on obstructive sleep apnea (OSA) severity and comorbidities, the effect of these interventions on cardiorespiratory fitness (CRF) remains unknown. This study aimed to investigate the effects of an interdisciplinary weight loss and lifestyle intervention on CRF and self-reported physical fitness in adults with OSA.

METHODS

Eighty-nine men aged 18-65 years with moderate-to-severe OSA and a body mass index ≥25 kg/m2 were randomly assigned to a usual-care group or an 8-week interdisciplinary weight loss and lifestyle intervention. CRF was assessed through the 2-km walking test, and the International Fitness Scale (IFIS) was used to assess self-reported physical fitness.

RESULTS

As compared with usual-care, the intervention group had greater improvements at intervention endpoint in objective CRF (6% reduction in 2-km walking test total time, mean between-group difference, -1.7 min; 95% confidence interval, -2.3 to -1.1), and self-reported overall physical fitness (18% increase in IFIS total score, mean between-group difference, 2.3; 95% CI 1.2 to 3.3). At 6 months after intervention, the intervention group also had greater improvements in both 2-km walking test total time (10% reduction) and IFIS total score (22% increase), with mean between-group differences of -2.5 (CI 95%, -3.1 to -1.8) and 3.0 (CI 95%, 1.8 to 4.1), respectively.

CONCLUSIONS

An 8-week interdisciplinary weight loss and lifestyle intervention resulted in significant and sustainable improvements in CRF and self-reported physical fitness in men with overweight/obesity and moderate-to-severe OSA.

STUDY REGISTRATION

ClinicalTrials.gov registration (NCT03851653).

Exercise capacity remains supernormal, though mildly reduced in middle-aged military personnel with Moderate to Severe Obstructive Sleep Apnea

INTRODUCTION

The relationship between moderate to severe OSA and exercise capacity remains unclear. Prior studies showing a reduction in VO₂ max in this population have mostly involved middle-aged, overweight patients. We aimed to study this relationship in a similarly aged population of military personnel with previously undiagnosed moderate to severe OSA.

METHODS

We studied late-career male military personnel who underwent CPET and polysomnography (PSG). Patients were categorized either into an OSA group (apnea-hypopnea index (AHI) ≥ 15 events/h) or a control group (AHI < 15 events/h). VO₂ max was compared between groups.

RESULTS

170 male military personnel met criteria for the study. Mean AHI was 29.0/h in the OSA group (n = 58) versus 7.4/h in the controls (n = 112) while SpO₂ nadir was slightly lower (86.0% vs. 89.0%). Patients were of similar age (53.1 vs. 53.7 years), and BMI was slightly higher in the OSA group (27.5 kg/m² vs. 26.3 kg/m²). Percent-predicted VO₂ max was supernormal in both groups, though it was comparatively lower in the OSA group (117% vs. 125%; p < 0.001).

CONCLUSIONS

Military personnel with moderate to severe OSA were able to achieve supernormal VO₂ max values, yet had an 8% decrement in exercise capacity compared to controls. These findings suggest that OSA without significant hypoxemia may not significantly influence exercise capacity. It remains likely that the effects of untreated OSA on exercise capacity are complex and are affected by several variables including BMI, degree of associated hypoxemia, and regularity of exercise. Statistically lower VO₂ max noted in this study may suggest that untreated OSA in less fit populations may lead to significant decrements in exercise capacity.

Effect of Short-Term Treatment with Continuous Positive Airway Pressure on Cardiopulmonary Exercise Tolerance, Pulmonary and Cardiac Function in Patients with Obstructive Sleep Apnea

Background: Obstructive sleep apnea (OSA) is a condition with a high prevalence, linked to an increased risk of cardiovascular disease as well as increased morbidity and death. CPAP is currently considered the "gold standard" treatment for OSA, but more thorough research and testing are required to assess its efficacy on cardiopulmonary function. Objectives: To evaluate pulmonary function of OSA patients, cardiopulmonary exercise tolerance test (CPET) performance, cardiac magnetic resonance imaging (MRI) parameters, and polysomnographic changes before and after 3 months of CPAP therapy. Materials and methods: A total of 34 patients diagnosed with moderate or severe OSA, as well as 17 patients as a control group for the evaluation of the cardiac MRI, were included in this study. All the subjects were obese (body mass index (BMI) > 30 kg/m²). Lung function tests, CPETs, cardiac MRIs, and polysomnography were performed at the time of the study's enrolment before the initiation of the CPAP therapy and after 3 months of the CPAP treatment. Results: The patients' VO_2max during the CPAP treatment tended to increase, but no statistical significance was found (before treatment it was 17.52 ± 3.79 mL/kg/min and after 3 months of treatment, it was 18.6 ± 3,4 mL/kg/min; p = 0.255). The CPAP treatment had positive effects on pulmonary ventilation at the anaerobic threshold (VE_AT): 44.51 L/min (43.21%) during the baseline visit and 38.60 L/min (37.86%) after the 3-month treatment period (p = 0.028). The ventilator equivalent for the carbon dioxide slope (VE/VCO₂) at peak exercise decreased from 23.47 to 20.63 (p = 0.042). The patients' pulmonary function tests were without abnormalities and did not change after treatment. When assessing cardiac the MRIs, the RV ejection fraction was lower in the OSA group compared to that of the control subjects (53.69 ± 8.91 and 61.35 ± 9.08, p = 0.016). Both LA and RA global longitudinal strains (GLS) improved after 3 months of treatment with CPAP (20.45 ± 7.25 and 26.05 ± 14.00, p = 0.043; 21.04 ± 7.14 and 26.18 ± 7.17, p = 0.049, respectively). Additionally, it was found that CPAP therapy led to statistical improvements in RV end-diastolic volume (164.82 ± 32.57 and 180.16 ± 39.09, p = 0.042). The AHI and oxygen desaturation index (ODI) significantly changed after 3 months of the initiation of the CPAP treatment (p = 0.049 and p = 0.001, respectively). The REM sleep duration decreased, while the duration of non-REM sleep increased after treatment initiation with CPAP (p = 0.016 and p = 0.017, respectively). Conclusions: Short-term CPAP treatment improves pulmonary ventilation, sleep efficiency, and sleep architecture. Significant alterations in both atrias' GLS and RV end-diastolic volume were observed after 3 months of treatment. Longer-term follow-up and a larger patient sample are needed to confirm the reproducibility of our results.

OSA and cardiorespiratory fitness: a review

The effects of untreated obstructive sleep apnea (OSA) on cardiopulmonary function remain unclear. Cardiorespiratory fitness (CRF), commonly reflected by VO₂ max measured during cardiopulmonary exercise testing, has gained popularity in evaluating numerous cardiopulmonary conditions and may provide a novel means of identifying OSA patients with the most clinically significant disease. This emerging testing modality provides simultaneous assessment of respiratory and cardiovascular function with results helping uncover evidence of evolving pathology in either organ system. In this review, we highlight the current state of the literature in regard to OSA and CRF with a specific focus on changes in cardiovascular function that have been previously noted. While OSA does not appear to limit respiratory function during exercise, studies seem to suggest an abnormal cardiovascular exercise response in this population including decreased cardiac output, a blunted heart rate response (ie, chronotropic incompetence), and exaggerated blood pressure response. Surprisingly, despite these observed changes in the cardiovascular response to exercise, results involving VO₂ max in OSA remain inconclusive. This is reflected by VO₂ max studies involving middle-aged OSA patients showing both normal and reduced CRF. As prior studies have not extensively characterized oxygen desaturation burden, we propose that reductions in VO₂ max may exist in OSA patients with only the most significant disease (as reflected by nocturnal hypoxia). Further characterizing this relationship remains important as some research suggests that positive airway pressure therapy or aerobic exercise may improve CRF in patients with OSA. In conclusion, while it likely that severe OSA, via an abnormal cardiovascular response to exercise, is associated with decreased CRF, further study is clearly warranted to include determining if OSA with decreased CRF is associated with increased morbidity or mortality.

CITATION

Powell TA, Mysliwiec V, Brock MS, Morris MJ. OSA and cardiorespiratory fitness: a review. J Clin Sleep Med. 2022;18(1):279-288.

Is Sleep Disordered Breathing Confounding Rehabilitation Outcomes in Spinal Cord Injury Research?

The purpose of this article is to highlight the importance of considering sleep-disordered breathing (SDB) as a potential confounder to rehabilitation research interventions in spinal cord injury (SCI). SDB is highly prevalent in SCI, with increased prevalence in individuals with higher and more severe lesions, and the criterion standard treatment with continuous positive airway pressure remains problematic. Despite its high prevalence, SDB is often untested and untreated in individuals with SCI. In individuals without SCI, SDB is known to negatively affect physical function and many of the physiological systems that negatively affect physical rehabilitation in SCI. Thus, owing to the high prevalence, under testing, low treatment adherence, and known negative effect on the physical function, it is contended that underdiagnosed SDB in SCI may be confounding physical rehabilitation research studies in individuals with SCI. Studies investigating the effect of treating SDB and its effect on physical rehabilitation in SCI were unable to be located. Thus, studies investigating the likely integrated relationship among physical rehabilitation, SDB, and proper treatment of SDB in SCI are needed. Owing to rapid growth in both sleep medicine and physical rehabilitation intervention research in SCI, the authors contend it is the appropriate time to begin the conversations and collaborations between these fields. We discuss a general overview of SDB and physical training modalities, as well as how SDB could be affecting these studies.

Exercise capacity and comorbidities in patients with obstructive sleep apnea

STUDY OBJECTIVES

There are few studies evaluating (1) exercise capacity as assessed by the 6-minute walking distance (6MWD) test in large populations with obstructive sleep apnea (OSA); and (2) correlations with patients' comorbidities.

METHODS

This study presents a cluster analysis performed on the data of 1,228 patients. Severity of exercise limitation was defined on the basis of 6MWD.

RESULTS

Sixty-one percent showed exercise limitation (29.2% and 31.9% mild and severe exercise limitation, respectively). About 60% and 40% of patients were included in cluster 1 (CL1) and 2 (CL2), respectively. CL1 included younger patients with high prevalence of apneas, desaturations, and hypertension with better exercise tolerance. CL2 included older patients, all with chronic obstructive pulmonary disease (COPD), high prevalence of chronic respiratory failure (CRF), fewer apneas but severe mean desaturation, daytime hypoxemia, more severe exercise limitation, and exercise-induced desaturations. Only CRF and COPD significantly (P < .001) correlated with 6MWD < 85% of predicted value. 6MWD correlated positively with apnea-hypopnea index, oxygen desaturation index, nocturnal pulse oxygen saturation (SpO₂), resting arterial oxygen tension, mean SpO₂ on exercise, and negatively with age, body mass index, time spent during night with SpO₂ < 90%, mean nocturnal desaturation, arterial carbon dioxide tension, and number of comorbidities. Patients without severe comorbidities had higher exercise capacity than those with severe comorbidities, (P < .001). Exercise limitation was significantly worse in OSA severity class I when compared to other classes (P < .001).

CONCLUSIONS

A large number of patients with OSA experience exercise limitation. Older age, comorbidities such as COPD and CRF, OSA severity class I, severe mean nocturnal desaturation, and daytime hypoxemia are associated with worse exercise tolerance.

Ventilatory response to exercise is preserved in patients with obesity hypoventilation syndrome

STUDY OBJECTIVES

Blunted ventilatory responses to hypoxia and hypercapnia during resting conditions are common findings in patients with obesity hypoventilation syndrome (OHS). Exercise increases the work and oxygen cost of breathing and produces excessive carbon dioxide (CO₂). The aim of this investigation was to study ventilatory responses to incremental exercise in patients with OHS.

METHODS

Sixty-eight obese adults with OHS (n = 15), eucapnic obstructive sleep apnea (n = 26), or simple obesity (n = 27) participated in an incremental exercise test on a cycle ergometer and an in-laboratory sleep study.

RESULTS

The peak oxygen uptake (peak VO₂) and peak pulse oxygen was decreased in patients with OHS compared with patients with either obstructive sleep apnea or simple obesity. The ventilatory response to exertional metabolic demand (nadir VE/VCO₂, ∆VE/∆VCO₂ slope, and VE/VCO₂ at peak exercise) did not significantly differ among the 3 groups. Minute ventilation, tidal volume, respiratory frequency, tidal volume/respiratory frequency, and inspiratory time/total time ratio at a given work rate were comparable among the 3 groups. Among the whole cohort, apnea-hypopnea index was not independently associated with peak VO₂, and no association was found between the ∆VE/∆VCO₂ slope and resting arterial partial pressure of CO₂.

CONCLUSIONS

The ventilatory response to incremental exercise is preserved in patients with OHS compared with patients with obstructive sleep apnea and simple obesity who were matched for age and body mass index. This result highlights the complexity of the respiratory control system during exercise for patients with OHS, which may be uncoupled with the ventilatory response during sleep and resting conditions.

Effect of continuous positive airway pressure on maximal exercise capacity in patients with obstructive sleep apnea: a systematic review and meta-analysis

STUDY OBJECTIVES

Exercise capacity is impaired in obstructive sleep apnea (OSA). There are conflicting reports on the effect of continuous positive airway pressure (CPAP) on maximal exercise capacity. The objective of this review was to determine if there is a change in exercise capacity and anaerobic threshold following CPAP treatment in OSA patients.

METHODS

We conducted a systematic review and meta-analyses to summarize the changes in peak rate of oxygen uptake (V̇O₂ peak) or maximum rate of oxygen uptake (V̇O2 max) and anaerobic threshold (AT) during cardiopulmonary exercise testing following CPAP intervention in patients with OSA. A systematic literature review was conducted to identify published literature on markers of V̇O₂ peak, V̇O₂ max, and AT pre- vs post-CPAP using a web-based literature search of PubMed/MEDLINE, Embase, CINAHL, and Cochrane review (CENTRAL) databases. Two independent reviewers screened the articles for data extraction and analysis.

RESULTS

The total search of all the databases returned 470 relevant citations. Following application of eligibility criteria, 6 studies were included in the final meta-analysis for V̇O₂ peak, 2 studies for V̇O₂ max, and five studies for AT. The meta-analysis showed a mean net difference in V̇O₂ peak between pre- and post-CPAP of 2.69 mL·kg^-1·min^-1, P = .02, favoring treatment with CPAP. There was no difference in V̇O₂ max or AT with CPAP treatment (mean net difference 0.66 mL·kg^-1·min^-1 [P = .78] and -144.98 mL·min^-1 [P = .20] respectively).

CONCLUSIONS

There is a paucity of high-quality studies investigating the effect of CPAP on exercise capacity. Our meta-analysis shows that V̇O₂ peak increases following CPAP treatment in patients with OSA, but we did not observe any change in V̇O₂ max or AT. Our findings should be considered preliminary and we recommend further randomized controlled trials to confirm our findings and to clarify the peak and maximum rates of oxygen uptake adaptations with CPAP therapy.

Prevalence and Patterns of Obstructive Sleep Apnea in Asian Indians With Congestive Heart Failure

Background Sleep-disordered breathing (SDB) has a potential association with the pathogenesis of congestive heart failure (CHF). We assessed the prevalence and patterns of obstructive sleep apnea (OSA) in patients presenting with CHF. Method This was a prospective, observational, all-comers study of consecutive 77 confirmed cases of CHF. All these patients were clinically assessed and evaluated for OSA with sleep study after routine blood testing, electrocardiogram (ECG), chest X-ray, and echocardiography. Results Of 77 patients with CHF 38 (49.4%) had apnea-hypopnea index (AHI) <5 while 39 (50.6%) had AHI >5. Of these 39, 37 (94.8%) patients showed the clinical features of OSA. The majority (64.9%) of them were males. The majority of OSA (64.9%) had coronary artery disease (CAD) (p<0.05) as the etiology of CHF, followed by dilated cardiomyopathy (32.4%) and valvular heart disease (2.7%). The prevalence of OSA was higher amongst New York Heart Association (NYHA) class 2 (51.4%) as compared to NYHA class 3 (37.8%) and NYHA class 4 (10.8%). There were 12 (32.8%) patients, each having OSA with a heart rate between 71 and 80 bpm and 81 and 90 bpm. Twenty-two (59.5%) had systolic blood pressure (BP) more than 120 mmHg and 20 (54.1%) had diastolic BP more than 80 mmHg. The majority (64.9%) patients had the lowest O2 saturation between 80% and 90%. A significantly large number of patients (62.2%) had ejection fraction 21%-30% (p<0.05). The majority (62.16%) of patients with OSA had AHI between 5 and 15. With 5-15 AHI, 20 (87%) patients with OSA had a snoring, tiredness, observed apnea, high BP, BMI, age, neck circumference, and male gender (STOP-Bang) score between 3 and 7 with AHI 5-15 (p<0.05). Conclusions In our cohort, the prevalence of OSA in CHF was 50.6%. Predictors of OSA in CHF were left ventricular ejection fraction (LVEF) 20%-30% and NYHA class 2. The majority had AHI between 5 and 15. Sleep apnea screening should be routinely implemented in the evaluation and follow-up of heart failure patients.

Does obstructive sleep apnea affect exercise capacity and the hemodynamic response to exercise? An individual patient data and aggregate meta-analysis

Obstructive sleep apnea (OSA) has been linked to altered cardiovascular response to exercise. A systematic review and individual patient data (IPD) meta-analysis were conducted to assess whether OSA patients present reduced exercise capacity. PubMed, Embase and Web of Science were searched until September 2018. Studies which performed sleep recording in both OSA patients and controls and measured maximal oxygen consumption (VO_2peak) via a maximal exercise test were included. IPD were provided for five trials upon the 18 eligible (N = 289) and a two-stage IPD meta-analysis model was used, allowing to standardize the apnea cutoff and adjust for confounders. IPD meta-analysis demonstrated that moderate to severe OSA patients had similar VO_2peak (mean difference: -1.03 mL·kg^-1 min^-1; 95% CI: -3.82 to 1.76; p = 0.47) and cardiovascular response to exercise compared to mild or non-OSA patients. By contrast, aggregate data (AD) meta-analysis including the 13 trials for which IPD were unavailable (N = 605) revealed that VO_2peak was reduced in OSA patients compared to controls (mean difference: -2.30 mL·kg^-1 min^-1; 95% CI: -3.96 to -0.63; p < 0.001) with high heterogeneity. In conclusion, IPD meta-analysis suggests that VO_2peak and the cardiovascular response to exercise are preserved in moderate to severe OSA patients while AD meta-analysis suggests lower VO_2peak in severe OSA.

Maximal exercise capacity in patients with obstructive sleep apnoea syndrome: a systematic review and meta-analysis

Maximal aerobic capacity is a strong health predictor and peak oxygen consumption (V'_O2peak) is considered a reflection of total body health. No systematic reviews or meta-analyses to date have synthesised the existing data regarding V'_O2peak in patients with obstructive sleep apnoea (OSA).A systematic review of English and French articles using PubMed/MEDLINE and Embase included studies assessing V'_O2peak in OSA patients either in mL·kg^-1·min^-1 compared with controls or in % predicted. Two independent reviewers analysed the studies, extracted the data and assessed the quality of evidence.Mean V'_O2peak expressed in mL·kg^-1·min^-1 was significantly lower in patients with OSA than in controls (mean difference -2.7 mL·kg^-1·min^-1; p<0.001; n=850). This reduction in V'_O2peak was found to be larger in non-obese patients (body mass index <30 kg·m^-2). Mean V'_O2peak % pred was 89.9% in OSA patients (n=643).OSA patients have reduced maximal aerobic capacity, which can be associated with increased cardiovascular risks and reduced survival in certain patient subgroups. Maximal exercise testing can be useful to characterise functional limitation and to evaluate health status in OSA patients.

Obstructive Sleep Apnea Syndrome, Objectively Measured Physical Activity and Exercise Training Interventions: A Systematic Review and Meta-Analysis

A systematic review of English and French articles using Pubmed/Medline and Embase included studies assessing objective physical activity levels of obstructive sleep apnea (OSA) patients and exploring the effects of exercise training on OSA severity, body mass index (BMI), sleepiness, and cardiorespiratory fitness [peak oxygen consumption (VO2peak)]. Two independent reviewers analyzed the studies, extracted the data, and assessed the quality of evidence. For objective physical activity levels, eight studies were included. The mean number of steps per day across studies was 5,388 (95% CI: 3,831–6,945; p < 0.001), which was by far lower than the recommended threshold of 10,000 steps per day. For exercise training, six randomized trials were included. There was a significant decrease in apnea–hypopnea-index following exercise training (mean decrease of 8.9 events/h; 95% CI: −13.4 to −4.3; p < 0.01), which was accompanied by a reduction in subjective sleepiness, an increase in VO2peak and no change in BMI. OSA patients present low levels of physical activity and exercise training is associated with improved outcomes. Future interventions (including exercise training) focusing on increasing physical activity levels may have important clinical impacts on both OSA severity and the burden of associated co-morbidities. Objective measurement of physical activity in routine OSA management and well-designed clinical trials are recommended.

Registration # CRD42017057319 (Prospero).

The Effect of Changes in Cardiorespiratory Fitness and Weight on Obstructive Sleep Apnea Severity in Overweight Adults with Type 2 Diabetes

STUDY OBJECTIVES

To examine the effect of changes in cardiorespiratory fitness on obstructive sleep apnea (OSA) severity prior to and following adjustment for changes in weight over the course of a 4-y weight loss intervention.

METHODS

As secondary analyses of a randomized controlled trial, 263 overweight/obese adults with type 2 diabetes and OSA participated in an intensive lifestyle intervention or education control condition. Measures of OSA severity, cardiorespiratory fitness, and body weight were obtained at baseline, year 1, and year 4. Change in the apnea-hypopnea index (AHI) served as the primary outcome. The percentage change in fitness (submaximal metabolic equivalents [METs]) and change in weight (kg) were the primary independent variables. Primary analyses collapsed intervention conditions with statistical adjustment for treatment group and baseline METs, weight, and AHI among other relevant covariates.

RESULTS

At baseline, greater METs were associated with lower AHI (B [SE] = -1.48 [0.71], P = 0.038), but this relationship no longer existed (B [SE] = -0.24 [0.73], P = 0.75) after adjustment for weight (B [SE] = 0.31 [0.07], P < 0.0001). Fitness significantly increased at year 1 (+16.53 ± 28.71% relative to baseline), but returned to near-baseline levels by year 4 (+1.81 ± 24.48%). In mixed-model analyses of AHI change over time without consideration of weight change, increased fitness at year 1 (B [SE] = -0.15 [0.04], P < 0.0001), but not at year 4 (B [SE] = 0.04 [0.05], P = 0.48), was associated with AHI reduction. However, with weight change in the model, greater weight loss was associated with AHI reduction at years 1 and 4 (B [SE] = 0.81 [0.16] and 0.60 [0.16], both P < 0.0001), rendering the association between fitness and AHI change at year 1 nonsignificant (B [SE] = -0.04 [0.04], P = 0.31).

CONCLUSIONS

Among overweight/obese adults with type 2 diabetes, fitness change did not influence OSA severity change when weight change was taken into account.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov identification number NCT00194259.

Obstructive sleep apnea is associated with impaired exercise capacity: a cross-sectional study

OBJECTIVE

Obstructive sleep apnea (OSA) is associated with increased risk of adverse cardiovascular events. Because cardiopulmonary exercise testing (CPET) aids in prognostic assessment of heart disease, there is rising interest in its utility for cardiovascular risk stratification of patients with OSA. However, the relationship between OSA and exercise capacity is unclear. This study was conducted to test the hypothesis that OSA is associated with impaired exercise capacity.

METHODS

Fifteen subjects with moderate-to-severe OSA (apnea-hypopnea index [AHI] ≥15 events/h) and 19 controls with mild or no OSA (AHI <15 events/h) were enrolled. Subjects underwent standard polysomnography to determine AHI and exclude other sleep disorders. Resting metabolic rate was measured via indirect calorimetry, followed by maximum, symptom-limited CPET. Subjects completed a sleep diary and physical activity questionnaire characterizing behaviors in the week prior to testing.

RESULTS

Percent predicted peak oxygen uptake (V˙O2) was significantly lower in OSA subjects than controls (70.1%±17.5% vs 83.8%±13.9%; p = 0.02). Each 1-unit increase in log-transformed AHI was associated with a decrease in percent predicted peak V˙O2 of 3.20 (95% CI 0.53-5.88; p = 0.02). After adjusting for baseline differences, this association remained significant (p < 0.01). AHI alone explained 16.1% of the variability observed in percent predicted peak V˙O2 (p = 0.02).

CONCLUSIONS

OSA is associated with impaired exercise capacity. Further study is needed to evaluate the utility of CPET for prognostic assessment of patients with OSA.

Sleep apnea-hypopnea syndrome and type 2 diabetes. A reciprocal relationship?

Epidemiological data suggest that sleep apnea-hypopnea syndrome (SAHS) is independently associated with the development of insulin resistance and glucose intolerance. Moreover, despite significant methodological limitations, some studies report a high prevalence of SAHS in patients with type 2 diabetes mellitus (DM2). A recent meta-analysis shows that moderate-severe SAHS is associated with an increased risk of DM2 (relative risk=1.63 [1.09 to 2.45]), compared to the absence of apneas and hypopneas. Common alterations in various pathogenic pathways add biological plausibility to this relationship. Intermittent hypoxia and sleep fragmentation, caused by successive apnea-hypopnea episodes, induce several intermediate disorders, such as activation of the sympathetic nervous system, oxidative stress, systemic inflammation, alterations in appetite-regulating hormones and activation of the hypothalamic-pituitary-adrenal axis which, in turn, favor the development of insulin resistance, its progression to glucose intolerance and, ultimately, to DM2. Concomitant SAHS seems to increase DM2 severity, since it worsens glycemic control and enhances the effects of atherosclerosis on the development of macrovascular complications. Furthermore, SAHS may be associated with the development of microvascular complications: retinopathy, nephropathy or diabetic neuropathy in particular. Data are still scant, but it seems that DM2 may also worsen SAHS progression, by increasing the collapsibility of the upper airway and the development of central apneas and hypopneas.

Effects of positive airway pressure therapy on exercise parameters in obstructive sleep apnea

BACKGROUND AND OBJECTIVES

Obstructive sleep apnea (OSA) is common in adult population and may cause many adverse clinical results. We aimed to investigate possible changes in cardiopulmonary exercise capacity in OSA patients after positive airway pressure treatment.

DESIGN AND SETTINGS

Patients who were admitted to Gaziantep University Pulmonary Diseases Sleep Center and diagnosed OSA were included. Studies carried out between May 2010 and July 2011. Sixty-five consecutive patients were included in this prospective study.

PATIENTS AND METHODS

Sixty-five adult sleep clinic patients diagnosed with OSA by polysomnography and in whom continuous positive airway pressure (CPAP) ventilation therapy was indicated were included. Cardiopulmonary exercise capacity was assessed by bicycle ergometry during diagnostic workup and at least 4 weeks later.

RESULTS

There were 57 (87.7%) males. The mean age was 45.29 (10.57) years, apnea-hypopnea index 38.02 (23.19 events/h, body mass index 31.72 (4.87) kg/m2. Patients were grouped with respect to compliance with CPAP. The peak oxygen consumption (VO2) did not change in the CPAP compliant group (n=33) (22.52 [6.62] mL/[min.kg] to 21.32 [5.26] mL/[min.kg]; P=.111), and decreased from 21.31 (5.66) mL/(min.kg) to 19.92 (5.40) mL/(min.kg) (P=.05) in the CPAP noncompliant group. Work rate increased from 84.0% to 85.0% in the CPAP compliant group and decreased from 79.6% to 77.1% in the noncompliant group (P=.041). In the group that used the device, ventilation (VE)/VCO2 at anaerobic threshold (AT) declined from 28.42 to 27.36; however, it increased from 27.41 to 27.81 in the group that did not use the device (P=.033).

CONCLUSIONS

Decline in the exercise capacity was prevented in patients with OSA after 4 weeks of CPAP therapy. The changes in VE/VCO2 at AT suggest the reversal of pathophysiologic changes in OSA with the CPAP therapy that may improve cardiac function and cause more efficient ventilation.

Sleep and exercise: a reciprocal issue?

Sleep and exercise influence each other through complex, bilateral interactions that involve multiple physiological and psychological pathways. Physical activity is usually considered as beneficial in aiding sleep although this link may be subject to multiple moderating factors such as sex, age, fitness level, sleep quality and the characteristics of the exercise (intensity, duration, time of day, environment). It is therefore vital to improve knowledge in fundamental physiology in order to understand the benefits of exercise on the quantity and quality of sleep in healthy subjects and patients. Conversely, sleep disturbances could also impair a person's cognitive performance or their capacity for exercise and increase the risk of exercise-induced injuries either during extreme and/or prolonged exercise or during team sports. This review aims to describe the reciprocal fundamental physiological effects linking sleep and exercise in order to improve the pertinent use of exercise in sleep medicine and prevent sleep disorders in sportsmen.

Effects of obstructive sleep apnea and obesity on exercise function in children

STUDY OBJECTIVES

Evaluate the relative contributions of weight status and obstructive sleep apnea (OSA) to cardiopulmonary exercise responses in children.

DESIGN

Prospective, cross-sectional study. Participants underwent anthropometric measurements, overnight polysomnography, spirometry, cardiopulmonary exercise function testing on a cycle ergometer, and cardiac doppler imaging. OSA was defined as ≥ 1 obstructive apnea or hypopnea per hour of sleep (OAHI). The effect of OSA on exercise function was evaluated after the parameters were corrected for body mass index (BMI) z-scores. Similarly, the effect of obesity on exercise function was examined when the variables were adjusted for OAHI.

SETTING

Tertiary pediatric hospital.

PARTICIPANTS

Healthy weight and obese children, aged 7-12 y.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Seventy-one children were studied. In comparison with weight-matched children without OSA, children with OSA had a lower cardiac output, stroke volume index, heart rate, and oxygen consumption (VO2 peak) at peak exercise capacity. After adjusting for BMI z-score, children with OSA had 1.5 L/min (95% confidence interval -2.3 to -0.6 L/min; P = 0.001) lower cardiac output at peak exercise capacity, but minute ventilation and ventilatory responses to exercise were not affected. Obesity was only associated with physical deconditioning. Cardiac dysfunction was associated with the frequency of respiratory-related arousals, the severity of hypoxia, and heart rate during sleep.

CONCLUSIONS

Children with OSA are exercise limited due to a reduced cardiac output and VO2 peak at peak exercise capacity, independent of their weight status. Comorbid OSA can further decrease exercise performance in obese children.

Blood pressure improvement with continuous positive airway pressure is independent of obstructive sleep apnea severity

STUDY OBJECTIVES

We sought to perform a patient-level meta-analysis using the individual patient data of the trials identified in our previous study-level meta-analysis investigating the effect of positive airway pressure (PAP) treatment for obstructive sleep apnea (OSA) on blood pressure (BP).

DESIGN

Patient-level meta-analysis.

SETTING

N/A.

PARTICIPANTS

968 adult OSA subjects without major comorbidities drawn from eight randomized controlled trials.

INTERVENTIONS

Therapeutic PAP versus non-therapeutic control conditions (sham-PAP, pill placebo or standard care) over at least one week.

MEASUREMENTS AND RESULTS

The mean reductions in BP between PAP and non-therapeutic control arms were -2.27 mm Hg (95% CI -4.01 to -0.54) for systolic BP and -1.78 mm Hg (95% CI -2.99 to -0.58) for diastolic BP. The presence of uncontrolled hypertension at baseline was significantly associated with a reduction in systolic BP of 7.1 mm Hg and diastolic BP of 4.3 mm Hg after controlling for OSA severity (apnea-hypopnea index, Epworth Sleepiness Scale score, PAP level), patient demographics (age, gender, body mass index, use of antihypertensive medication/s), and measures of PAP efficacy (PAP adherence and treatment duration).

CONCLUSIONS

OSA patients with uncontrolled hypertension are likely to gain the largest benefit from PAP in terms of a substantial reduction in BP, even after controlling for disease severity.

Reduced exercise capacity in Greek children with mild to moderate obstructive sleep apnea syndrome

INTRODUCTION

Obstructive sleep apnea syndrome (OSAS) is a common disease that is increasingly recognized among pediatric population. The exercise capacity of adults with OSAS has been demonstrated to be impaired, but there are no data about pediatric exercise response.

AIM

The aim of this study was to evaluate cardiopulmonary response to exercise in children with OSAS and to correlate exercise capacity and severity of OSAS.

METHODS

Twenty-seven children with habitual snoring (Group A) (mean age 10.5 ± 1.8 years) referred for overnight polysomnography and 13 apparently healthy controls (mean age 11 ± 1.5 years) were recruited. According to the apnea hypopnea index (AHI) group A consisted of 15 (55.6%) children with mild OSAS and 12 (44.4%) with moderate-severe OSAS. All children completed a maximal ramping cardiopulmonary exercise test (CPET) on cycle ergometer.

RESULTS

According to CPET children with OSAS had significantly lower VO2max (40.3 ± 8.4 ml/kg/min vs. 47.6 ± 7.9 ml/kg/min, P = 0.013) significantly lower VO2max (%) (77.7 ± 15 vs. 92.9 ± 10.5, P = 0.002), lower maximum heart-rate at peak exercise (86.6 ± 8.8 beat/min vs. 90.6 ± 7.2 beat/min) and higher systolic blood pressure level at peak exercise (145 ± 27.4 mmHg vs. 143.92 ± 20 mmHg) compared to control group.

CONCLUSION

The present study demonstrates that young patients with OSAS, even with mild OSAS, had reduced exercise capacity as compared to control group.

Functional aerobic capacity in patients with sleep-disordered breathing

Few studies have examined exercise capacity or cardiovascular responses to maximal exercise testing and recovery in patients with sleep-disordered breathing (SDB), and results from these studies are conflicting. The objective of this cross-sectional study conducted at a tertiary referral center was to examine the association between SDB and exercise testing outcomes independent of body mass index (BMI) and other cardiopulmonary risk factors. Between January 1, 2005 and January 1, 2010, 1,424 adults underwent exercise testing and within 6 months before first-time diagnostic polysomnography. Subjects were categorized by apnea-hypopnea index (AHI) into 4 groups: <5, 5 to 14, 15 to 29, and ≥30. A logistic regression model incorporated age, gender, BMI, smoking, hypertension, diabetes, beta-blocker use, and cardiac and pulmonary disease as covariates. The primary variable of interest was functional aerobic capacity (FAC). Mean age was 56.4 ± 12.4 years; 75% were men. Mean BMI was 32.4 ± 7.1 kg/m², and mean AHI 19.5 ± 22.1 per hour. On multivariate analysis, AHI as a continuous variable showed a negative correlation with FAC (R²adj = 0.30, p <0.001) and postexercise SBP (R²adj = 0.23, p = 0.03), and positively correlated with resting and peak DBP (R²adj = 0.09, p = 0.01 and R²adj = 0.09, p = 0.04 respectively). When comparing patients with severe SDB (AHI ≥30) with those without SDB (AHI <5), FAC and heart rate recovery were significantly lower, and resting, peak, and postexercise DBP were higher in those with severe apnea (all p <0.05), after accounting for confounders. In conclusion, SDB severity was associated with reduced FAC and increased resting and peak DBP. Even after accounting for confounders, severe SDB was associated with attenuated FAC, impaired heart rate recovery, and higher resting, peak, and postexercise DBP.

Does obstructive sleep apnea impair the cardiopulmonary response to exercise?

STUDY OBJECTIVES

The aim of this study was to evaluate cardiopulmonary exercise performance in lean and obese patients with obstructive sleep apnea (OSA) compared with controls.

DESIGN

Case-control study.

SETTING

The study was carried out in Sao Paulo Sleep Institute, Sao Paulo, Brazil.

PATIENTS AND PARTICIPANTS

INDIVIDUALS WITH SIMILAR AGES WERE ALLOCATED INTO GROUPS: 22 to the lean OSA group, 36 to the lean control group, 31 to the obese OSA group, and 26 to the obese control group.

INTERVENTIONS

The participants underwent a clinical evaluation, polysomnography, a maximum limited symptom cardiopulmonary exercise test, two-dimensional transthoracic echocardiography, and spirometry.

MEASUREMENTS AND RESULTS

The apnea-hypopnea index, arousal index, lowest arterial oxygen saturation (SaO2) and time of SaO2 < 90% were different among the groups. There were differences in functional capacity based on the following variables: maximal oxygen uptake (VO2max), P < 0.01 and maximal carbon dioxide production (VCO2max), P < 0.01. The obese patients with OSA and obese controls presented significantly lower VO2max and VCO2max values. However, the respiratory exchange ratio (RER) and anaerobic threshold (AT) did not differ between groups. Peak diastolic blood pressure (BP) was higher among the obese patients with OSA but was not accompanied by changes in peak systolic BP and heart rate (HR). When multiple regression was performed, body mass index (P < 0.001) and male sex in conjunction with diabetes (P < 0.001) independently predicted VO2max (mL/kg/min).

CONCLUSIONS

The results of this study suggest that obesity alone and sex, when associated with diabetes but not OSA, influenced exercise cardiorespiratory function.

Association between sleep disorders, obesity, and exercise: a review

Decreased sleep duration and quality is associated with an increase in body weight and adiposity. Insomnia, obstructive sleep apnea, and restless legs syndrome are three of the most prevalent types of sleep disorder that lead to an increased risk for numerous chronic health conditions. Various studies have examined the impact of these sleep disorders on obesity, and are an important link in understanding the relationship between sleep disorders and chronic disease. Physical activity and exercise are important prognostic tools in obesity and chronic disease, and numerous studies have explored the relationship between obesity, sleep disorders, and exercise. As such, this review will examine the relationship between sleep disorders and obesity. In addition, how sleep disorders may impact the exercise response and how exercise may impact patient outcomes with regard to sleep disorders will also be reviewed.

The effect of continuous positive airway pressure treatment on blood pressure: a systematic review and meta-analysis of randomized controlled trials

STUDY OBJECTIVES

We sought to provide an updated systematic review and meta-analysis of studies investigating the effect of positive airway pressure (PAP) treatment for obstructive sleep apnea (OSA) on systolic and diastolic blood pressure (SBP, DBP).

METHODS

Two independent investigators undertook a systematic search of the PubMed database (1980-2012) to identify randomized controlled trials comparing therapeutic PAP to sham-PAP, pill placebo, or standard care over at least one week in adult OSA patients without major comorbidities. The mean, variance, and sample size for diurnal and nocturnal SBP and DBP data were also extracted independently from each study. Random effects meta-analyses were conducted, followed by pre-specified subgroup and meta-regression analyses.

RESULTS

32 studies were identified, with data available from 28 studies representing n = 1,948 patients. The weighted mean difference in diurnal SBP (-2.58 mm Hg, 95% CI -3.57 to -1.59 mm Hg) and DBP (-2.01 mm Hg, 95% CI -2.84 to -1.18 mm Hg) both significantly favored PAP treatment over control arms, with similar results seen in nocturnal readings. Statistically significant reductions in BP were seen in studies whose patients were younger, sleepier, had more severe OSA, and exhibited greater PAP adherence. Meta-regression indicated that the reductions in DBP with PAP were predicted by mean baseline BP (β = -0.22, p = 0.02) and Epworth Sleepiness Scale scores (β = -0.27, p = 0.04).

CONCLUSIONS

PAP treatment for OSA is associated with modest but significant reductions in diurnal and nocturnal SBP and DBP. Future research should be directed towards identifying subgroups likely to reap greater treatment benefits as well as other therapeutic benefits provided by PAP therapy.

Blunted heart rate recovery is improved following exercise training in overweight adults with obstructive sleep apnea

BACKGROUND

Obstructive sleep apnea (OSA) predisposes individuals to cardiovascular morbidity, and cardiopulmonary exercise test (CPET) markers prognostic for cardiovascular disease have been found to be abnormal in adults with OSA. Due to the persistence of OSA and its cardiovascular consequences, whether the cardiovascular adaptations normally conferred by exercise are blunted in adults not utilizing established OSA treatment is unknown. The aims of this study were to document whether OSA participants have abnormal CPET responses and determine whether exercise modifies these CPET markers in individuals with OSA.

METHODS

The CPET responses of 43 sedentary, overweight adults (body mass index [BMI]>25) with untreated OSA (apnea-hypopnea index [AHI]≥ 15) were compared against matched non-OSA controls (n=9). OSA participants were then randomized to a 12-week exercise training (n=27) or stretching control treatment (n=16), followed by a post-intervention CPET. Measures of resting, exercise, and post-exercise recovery heart rate (HRR), blood pressure, and ventilation, as well as peak oxygen consumption (VO(2peak)), were obtained.

RESULTS

OSA participants had blunted HRR compared to non-OSA controls at 1 (P=.03), 3 (P=.02), and 5-min post-exercise (P=.03). For OSA participants, exercise training improved VO2 peak (P=.04) and HRR at 1 (P=.03), 3 (P<.01), and 5-min post-exercise (P<.001) compared to control. AHI change was associated with change in HRR at 5-min post-exercise (r=-.30, P<.05), but no other CPET markers.

CONCLUSIONS

These results suggest that individuals with OSA have autonomic dysfunction, and that exercise training, by increasing HRR and VO2 peak, may attenuate autonomic imbalance and improve functional capacity independent of OSA severity reduction.

Effect of chronic intermittent hypoxia on exercise adaptations in healthy subjects

Reduced exercise tolerance has been reported in obstructive sleep apnea syndrome (OSAS) patients, although the associated hypertension, obesity and/or metabolic disorder may underlie this reduction. Therefore, we evaluated the effects of chronic intermittent hypoxia (CIH) in 12 healthy subjects on exercise capacity, cardio-respiratory responses, and substrate oxidation during maximal and sub-maximal exercise. Subjects were exposed to 30 cycles of hypoxia-reoxygenation per hour for 14 nights. Although exercise capacity was unaltered PETCO(2) was reduced and V˙E/V˙CO(2) increased during both maximal and submaximal exercise tests, indicating a hyperventilatory response. Maximal heart rate was lower and diastolic arterial blood pressure (DBP) was higher in the 1st min of recovery after submaximal exercise. Subjects reached maximal lipid oxidation at a higher power output and had decreased blood lactate for a given power output. This suggests that although the metabolic adaptations to CIH in healthy subjects may improve exercise performance, the cardio-pulmonary modifications are similar to those observed in OSAS patients and could limit exercise capacity.

Effects of exercise training associated with continuous positive airway pressure treatment in patients with obstructive sleep apnea syndrome

PURPOSE

The aim of this study was to evaluate the effects of a 2-month exercise training associated with continuous positive airway pressure (CPAP) treatment on the subjective and objective sleep measurements, quality of life, and mood in moderate to severe obstructive sleep apnea syndrome (OSAS) patients.

METHODS

Male patients were randomized into two treatment groups: CPAP (n = 19) and CPAP + exercise (n = 13). All patients completed 1 month of sleep hygiene, 2 months of treatment (CPAP or CPAP + exercise), and 1 week of washout (no treatment). Fletcher and Luckett sleep questionnaire, Epworth sleepiness scale, sleep diaries, polysomnography, SF-36 inventory of quality of life, Profile of Mood States (POMS) questionnaire, neck circumference, and body composition were evaluated. CPAP + exercise group also underwent cardiopulmonary exercise test before and after treatment.

RESULTS

Both treatments were effective in improving subjective sleepiness but CPAP + exercise treatment was more effective in maintaining this improvement after washout. No significant differences were found in most of the sleep parameters studied in both groups. CPAP + exercise group showed lower values of tension and fatigue on POMS and higher values of physical functioning, general health perception, and vitality on SF-36 after treatment.

CONCLUSIONS

A 2-month exercise training associated with CPAP treatment for OSAS patients has a positive impact on subjective daytime sleepiness, quality of life (physical functioning and general health perception), and mood state (tension and fatigue).

C-reactive protein and heart rate recovery in middle-aged men with severe obstructive sleep apnea

OBJECTIVE

The study aimed to evaluate whether the inflammatory marker "high-sensitivity C-reactive protein (hsCRP)" level was associated with impaired heart rate recovery at 1 min after exercise termination (HRR-1) in middle-aged patients with severe obstructive sleep apnea (OSA).

METHODS

Thirty middle-aged male patients (40-64 years old) with severe OSA (apnea-hypopnea index [AHI] ≥ 30 h(-1)) and 30 subjects without OSA (AHI < 5 h(-1)), matched with age and body mass index (BMI), were recruited. All subjects underwent an overnight polysomnography and completed a symptom-limited maximal exercise test. Cardiopulmonary parameters included peak oxygen consumption (VO(2peak)) and heart rate response during and immediately after exercise. Fasting blood samples were drawn for hsCRP analysis.

RESULT

Patients with severe OSA had significantly higher hsCRP levels (0.18 vs. 0.07 mg/dl, P < 0.01), lower reduced HRR-1, peak heart rate, and VO(2peak) values than those in the controls. The hsCRP levels significantly correlated with HRR-1 in the OSA group (r = -0.69, P < 0.01) after adjustment for VO(2peak) (r = -0.66, P < 0.01). Furthermore, stepwise multiple regression analysis showed that HRR-1 and AHI were significant predictors of hsCRP levels in all participants (adjusted R(2) = 0.53, P < 0.01).

CONCLUSIONS

Blunted HRR was shown in middle-aged men with severe OSA, and it was associated with high hsCRP levels significantly.

Submaximal exercise in patients with severe obstructive sleep apnea

PURPOSE

Several studies have used the cardiopulmonary exercise test to assess patients with obstructive sleep apnea (OSA). However, no report has investigated the use of the 6-min walk test (6MWT) in this group of patients.

METHODS

We studied consecutive, newly diagnosed, OSA patients (aged >18 years). The control group was composed of matched healthy subjects with no clinical history indicative of sleep breathing disorders. The study population was divided into three groups: an OSA group, a control obese group, and a control lean group. The obese controls were gender-, age- (+/-2 years), height- (+/-5 cm), and weight- (+/-2 kg) matched to the OSA patients, while the lean controls were matched in gender, age, and height, but not weight. All patients underwent sleep study at our Sleep Disorders Center. Each subject underwent a single 6MWT within 1 week of the sleep study.

RESULTS

A total of 55 patients were recruited to the OSA group (age 36.7 +/- 7.9 years, body mass index 38.7 +/- 8.6 kg/m(2), and apnea hypopnea index 66.6 +/- 34.8/h), 32 subjects to the control obese group, and 30 to the control lean group. There was no difference in distance walked (6-min walk distance (6MWD)) between the OSA group (389 +/- 70 m) and the obese group (408 +/- 66 m). In the OSA group, the 6MWD results did not correlate with patient age, apnea hypopnea index, or other polysomnographic variables. At the end of the test, heart rate, systolic and diastolic blood pressure, and dyspnea perception were significantly increased in the OSA group compared with healthy subjects.

CONCLUSIONS

The 6MWT is easy to perform and well tolerated by patients with OSA. There were no correlations between the 6MWD and the severity of OSA or other polysomnographic parameters. However, patients with OSA exhibited abnormal hemodynamic responses to submaximal exercise.

[Smoking and sleep disorders]

Snoring and sleep apnea-hypopnea syndrome (SAHS) are two disorders of considerable relevance due to their high prevalence in the general population and their notable morbidity and mortality, particularly in association with their harmful effects on the cardiovascular system. As well as sex, age, weight, craniofacial malformations, alcohol consumption, and use of hypnotic drugs, it has been suggested that smoking may be a risk factor for developing sleep-disordered breathing. While there is solid evidence for the independent association between snoring and smoking in both children and adults, it is still unclear whether smoking constitutes an independent risk factor for developing SAHS, despite the many studies carried out to assess this link. This is probably because the association, if it exists, is very weak.

Potential clinical use of cardiopulmonary exercise testing in obstructive sleep apnea hypopnea syndrome

There is growing evidence linking obstructive sleep apnea hypopnea syndrome (OSAHS) with multiple cardiovascular and metabolic diseases. Exercise testing is generally available and routinely used to provide valuable information on cardiopulmonary function in healthy and diseased populations. This review summarizes and integrates recent findings on exercise testing in OSAHS and discusses the potential mechanisms that may contribute to the responses that seem to differentiate these patients from apparently healthy subjects and patients with other cardiopulmonary diseases. Although exercise testing is widely used in the evaluation and diagnosis of coronary artery disease patients, recent studies showed distinctive cardiopulmonary responses in OSAHS that raise the possibility of similar applications in this disorder, as well. Several studies illustrated in this review found that OSAHS patients have a reduced exercise capacity, as shown by low peak oxygen uptake achieved. Also, their exercise HR response was reported as significantly lower than in healthy peers, suggesting chronotropic incompetence. Exercise blood pressure response were atypical as well. OSAHS patients had increased systolic and diastolic BP during exercise and a persistently elevated systolic BP during the early post-exercise recovery period. Possible explanations for these responses include cardiac dysfunction, impaired muscle metabolism, chronic sympathetic over-activation, and endothelial dysfunction. Early identification of OSAHS using cardiopulmonary exercise testing (CPXT) shows promise for selecting patients at risk for this disorder in the clinical setting. A uniform definition and measurement of OSAHS together with more rigorous trials are necessary to establish the utility of exercise responses in clinical settings.

Cardiorespiratory response to exercise in men and women with obstructive sleep apnea

BACKGROUND

OSA severity has been associated with self-reported lack of exercise. Most of the research has been done with men recruited from sleep clinics. There is limited data on the exercise performance of women with OSA. Therefore, the aim of this study was to assess exercise performance in a prospective, consecutive sample of men and women with OSA to compare their cardio respiratory parameters, arterial blood pressure and heart rate responses during and after exercise.

METHODS

Sixty-two subjects (32 men) completed the protocol. Men had a higher peak VO2, percent predicted peak VO2, VCO2, heart rate, systolic BP, and oxygen pulse than women.

RESULTS

There were no differences between men and women for peak oxygen saturation, peak Borg scales for dyspnea and leg fatigue and diastolic BP. A significant negative correlation was found between severity of OSA as measured by AHI, and peak VO2 (r=-0.4) in women, but not in men.

CONCLUSION

Men with OSA have higher peak VO2 and higher peak exercise heart rate than women with OSA; they also have higher end-exercise systolic BP than women and higher SBP during recovery from exercise; although this difference is not significant when adjusted for peak systolic BP. In men with OSA, there is no correlation between peak VO2 and AHI, but there is a significant correlation between these variables in women. Heart rate and blood pressure behaved similarly during exercise in both groups.

Continuous positive airway pressure improves exercise capacity and heart rate recovery in obstructive sleep apnea

BACKGROUND

There is a relationship between obstructive sleep apnea (OSA) and heart failure (HF). Peak oxygen consumption (peak VO(2)), heart rate recovery, and N-terminal-pro-BNP (NT-proBNP) are strong prognostic predictors in HF. The effects of nasal continuous positive airway pressure (nCPAP) on these parameters in OSA patients are not well defined.

METHODS

Forty patients with newly diagnosed OSA [apnea-hypopnea index (AHI) 37 (20-65) h(-1)] underwent cardiopulmonary exercise testing for assessment of peak VO(2) and heart rate recovery at one (HRR-1) and two (HRR-2) minutes after exercise termination as well as NT-proBNP measurement at baseline and after 7.9+/-1.4 months of effective nCPAP (nightly usage>3.5 h). The effects of nCPAP were compared in patients with mild-to-moderate (AHI<30 h(-1); n=16) vs. severe (AHI>or=30 h(-1); n=24) OSA.

RESULTS

In the group as a whole, peak VO(2) (baseline: 31.9+/-9.3 vs. follow-up: 33.7+/-9.0 ml/kg/min; p=0.02) and HRR-2 [38 (32-43) vs. 42 (32-47) bpm; p=0.01] but not HRR-1 [22 (15-26) vs. 22 (16-27) bpm; p=0.16] improved from baseline to follow-up. The effect on peak VO(2) was mainly driven by a trend towards an increase in patients with mild-to-moderate OSA (31.8+/-10.7 vs. 33.9+/-10.2 ml/kg/min; p=0.08), whereas an effect on HRR-1 [20 (15-23) vs. 21 (16-26) bpm; p=0.03] and HRR-2 [38 (29-42) vs. 42 (33-47) bpm; p=0.004] was observed only in those with severe OSA. NT-proBNP levels remained unchanged [21 (11-45) vs. 26 (5-52) pg/ml; p=0.6].

CONCLUSIONS

Treatment with nCPAP is associated with an improvement in peak VO(2) and heart rate recovery in patients with OSA.

Attenuated heart rate recovery following exercise testing in overweight young men with untreated obstructive sleep apnea

STUDY OBJECTIVE

To evaluate whether cardiovascular responses to maximal exercise testing and recovery are altered with obstructive sleep apnea (OSA) in overweight young adult men.

DESIGN

Three sedentary subject groups were recruited: Overweight with OSA (OSA), overweight without OSA (No-OSA), and normal weight without OSA (Control). Presence of OSA was screened via portable diagnostic device. Body composition was measured with dual-energy X-ray absorptiometry. Subjects performed maximal ramping exercise testing (RXT) on a cycle ergometer with 5 minutes of active recovery. Exercise measurements included heart rate (HR), blood pressure (BP), respiratory exchange ratio (RER), and oxygen consumption (VO2). Recovery HR was converted to a HR difference (HR(diff)) calculation (HR(peak) - HR(each minute recovery)), and BP was converted to a recovery ratio for each minute.

SETTING

The study was carried out on the campus of Virginia Tech, Department of Human Nutrition, Foods, and Exercise, Blacksburg, Virginia.

PARTICIPANTS

14 OSA, 16 No-OSA, and 14 Control volunteers.

INTERVENTION

N/A.

MEASUREMENTS AND RESULTS

In OSA subjects, HR recovery was significantly attenuated compared to the No-OSA and Control groups throughout recovery (P = 0.009). No differences were noted in the HR or BP response to exercise in any group. The VO2, adjusted for fat-free soft tissue mass, did not differ between groups.

CONCLUSIONS

We found that OSA elicits alterations in the cardiovascular response post exercise, reflected by an attenuated HR recovery. This may indicate an imbalance in the autonomic regulation of HR. Exercise tests may provide utility in risk stratification for those at risk for OSA.

Influence of cardiac resynchronisation therapy on different types of sleep disordered breathing

AIMS

This study investigates the influence of cardiac resynchronisation therapy (CRT) on sleep disordered breathing (SDB) in patients with severe heart failure (HF).

METHODS AND RESULTS

Seventy-seven patients with HF (19 females; 62.6+/-10 years) eligible for CRT were screened for presence, type, and severity of SDB before and after CRT initiation (5.3+/-3 months) using cardiorespiratory polygraphy. NYHA class, frequency of nycturia, cardiopulmonary exercise, 6-minute walking test results, and echocardiography parameters were obtained at baseline and follow-up. Central sleep apnoea (CSA) was documented in 36 (47%), obstructive sleep apnoea (OSA) in 26 (34%), and no SDB in 15 (19%) patients. CRT improved clinical and haemodynamic parameters. SDB parameters improved in CSA patients only (apnoea hypopnoea index: 31.2+/-15.5 to 17.3+/-13.7/h, p<0.001; SaO2min: 81.8+/-6.6 to 84.8+/-3.3%, p=0.02, desaturation: 6.5+/-2.3 to 5.5+/-0.8%, p=0.004). Daytime capillary pCO2 was significantly lower in CSA patients compared to those without SDB with a trend towards increase with CRT (35.5+/-4.2 to 37.9+/-5.7 mm Hg, ns). After classifying short term clinical and haemodynamic CRT effects, improved SDB parameters in CSA occurred in responders only.

CONCLUSIONS

In patients with severe HF eligible for CRT, CSA is common and can be influenced by CRT, this improvement depends on good clinical and haemodynamic response to CRT.

Unique cardiopulmonary exercise test responses in overweight middle-aged adults with obstructive sleep apnea

BACKGROUND

Obstructive sleep apnea (OSA) is characterized by repetitive nighttime obstructions of the upper airway that induce hypoxemia, hypercapnia, sympathetic activation, and arousals. This disorder induces cardiovascular autonomic imbalance and contributes to the development of hypertension. While the diagnostic and prognostic utility of exercise testing is well established in cardiology, the clinical utility of the exercise test in screening for OSA has not been carefully explored. To explore this potential application, we contrasted cardiopulmonary responses to exercise testing in patients recently diagnosed with OSA with apparently healthy counterparts of similar physical inactivity history, age, and body habitus.

METHODS

Twenty-three normotensive overweight adults with OSA [apnea-hypopnea index (AHI)=24.7+/-13.5 events h(-1); body mass index (BMI)=33.1+/-5.5 kg m(-2); age=45.6+/-10.7 years] and nine apparently healthy controls of similar age and morphology (BMI=29.5+/-5.5 kg m(-2); age=40.2+/-8.1 years; AHI=4.9+/-0.1) completed a maximal ramping cardiopulmonary exercise tolerance test on a cycle ergometer. Measures included oxygen consumption (VO(2)pk), ventilation (V(E)), heart rate (HR), blood pressure (BP), cardiac output (Qc), and stroke volume (SV).

RESULTS

Age, BMI, rest HR, rest BP, rest and exercise cardiac index (QI), rest and exercise stroke volume index (SVI), and V O(2)pk were not different between OSA patients and controls (p>0.05). Exercise heart rate was significantly lower and diastolic BP higher in the OSA group (p<0.05). In the physically active recovery (low-load pedaling), systolic BP recovery was delayed (p<0.05) in the OSA group while diastolic BP tended to remain higher (p=0.056).

CONCLUSION

Patients with OSA have a distinctive response to graded exercise, characterized by a blunted HR response, markedly delayed systolic BP response in early recovery, and elevated diastolic BP in both exercise and early recovery. Clinical trials are justified to determine the clinical utility of graded exercise testing to independently inform clinical decision-making for triaging patients to diagnostic polysomnography.

[Role of oxidative stress in respiratory diseases and its monitoring]

Together with inflammation and subsequent remodeling of airways, an imbalance between oxidative and anti-oxidative agents is generated during the development of numerous pulmonary diseases. This process seems to be involved in both the pathogenesis and chronification of asthma, chronic obstructive pulmonary disease (COPD), SOAS, interstitial lung diseases and cystic fibrosis. Reactive oxygen species including superoxide anion, hidroxyl radicals and hydrogen peroxide (H2O2) are synthetised as a response of inflammatory cells and are responsible of the oxidation of nucleic acids, proteins and membrane lipids, leading to cell damage and enhanced inflammation. Until recently, it was difficult to quantify the airway production of reactive oxidative species (ROS). In fact, it has been only in the last few years when it has been possible to determine indirectly the levels of ROS in expired air and in tissue of asthmatic patients. The analysis of exhaled air is a single, reproducible and non-invasive technique which is useful in the study of volatile and non-volatile gases generated in different conditions. The determination of exhaled nitric oxide and carbon monoxide (CO) has a great usefulness in the assessment of asthma. Nitric oxide seems to be closely related to the physiopathology of asthma and COPD. In fact, it is correlated with the levels of sputum eosinophils and with the response to the treatment with steroids. Yet a correlation with the degree of airflow obstruction and the seriousness of the process has not been found. Exhaled CO is another indirect marker of inflammation and it is increased in asthma, COPD, cystic fibrosis and bronchectases. Even though numerous studies have shown its usefulness as a marker of inflammation and in the response to corticosteroids, its clinical application has limitations. In particular, it is not a specific and exclusive marker of oxidative stress and its levels are highly influenced by tobacco smoke. On the other hand, the association between exhaled CO and FEV1 is not clear and no relationship has been proved so far with the improvement of pulmonary function after steroid therapy and with the decrease of maximum expiratory flow at relapses. In this Review, we describe the advances in the knowledge of oxidative stress as a decisive factor in the pathogenesis of prevalent pulmonary diseases, as well as the methods allowing its analysis and monitoring.