Heart rate recovery and oxygen kinetics after exercise in obstructive sleep apnea syndrome

Preterm birth and exercise capacity: what do we currently know?

Objectives

The long-term cardiopulmonary outcomes following preterm birth during the surfactant era remain unclear. Respiratory symptoms, particularly exertional symptoms, are common in preterm children. Therefore, cardiopulmonary exercise testing may provide insights into the pathophysiology driving exertional respiratory symptoms in those born preterm. This review aims to outline the current knowledge of cardiopulmonary exercise testing in the assessment of children born preterm in the surfactant era.

Design

This study is a narrative literature review.

Methods

Published manuscripts concerning the assessment of pulmonary outcomes using cardiopulmonary exercise testing in preterm children (aged <18 years) were reviewed. Search terms related to preterm birth, bronchopulmonary dysplasia, and exercise were entered into electronic databases, including Medline, PubMed, and Google Scholar. Reference lists from included studies were scanned for additional manuscripts.

Results

Preterm children have disrupted lung development with significant structural and functional lung disease and increased respiratory symptoms. The association between these (resting) assessments of respiratory health and exercise capacity is unclear; however, expiratory flow limitation and an altered ventilatory response (rapid, shallow breathing) are seen during exercise. Due to the heterogeneity of participants, treatments, and exercise protocols, the effect of the aforementioned limitations on exercise capacity in children born preterm is conflicting and poorly understood.

Conclusion

Risk factors for reduced exercise capacity in those born preterm remain poorly understood; however, utilizing cardiopulmonary exercise testing to its full potential, the pathophysiology of exercise limitation in survivors of preterm birth will enhance our understanding of the role exercise may play. The role of exercise interventions in mitigating the risk of chronic disease and premature death following preterm birth has yet to be fully realized and should be a focus of future robust randomized controlled trials.

Cardiovascular capacity in adults with obstructive sleep apnoea

BACKGROUND: Obstructive sleep apnoea (OSA) patients have a decreased exercise capacity. Potential cardiovascular capacity in patients with OSA with different severity without known cardiovascular disease has not been described.OBJECTIVE: To evaluate impaired potential exercise cardiovascular capacity during cardiopulmonary exercise testing (CPET) in OSA patients and to compare cardiovascular performance reaction with different severity during graded exercise stages.DESIGN: All participants were accompanied without cardiovascular disease, especially hypertension and arrhythmia. Parameters of different stages were compared between subjects with and without OSA, and among OSA patients with varied severity.RESULTS: Despite having significantly higher peak exercise diastolic blood pressure (DBP) and ventilatory equivalent for CO2 (EQCO₂), patients with OSA had a lower peak oxygen uptake (VO₂), heart rate (HR), heart rate recovery (HRR) and respiratory reserve (BR) than normal subjects. Furthermore, significant correlations were found between VO₂, DBP, EQCO₂, HRR, BR and the apnoea-hypopnea index. In severe OSA, there was a greater difference in HR and HRR during the anaerobic threshold stages.CONCLUSIONS: OSA patients demonstrate reduced potential cardiovascular capacity, even without documented cardiovascular disease. Patients with severe OSA develop impaired exercise capacity at early stage during exercise. These data point to exaggerated haemodynamic response to graded exercise and delayed post-exercise cardiovascular response recovery in OSA patients. CPET can be a supplement for assessment of OSA severity.

Cerebral oxygenation during cardiopulmonary exercise testing in cardiorespiratory diseases: A systematic review

BACKGROUND

Cardiopulmonary exercise testing (CPET) is the gold standard for analyzing cardiorespiratory fitness and integrating physiological responses. However, the presence of chronic diseases may compromise cerebral hemodynamic responses during CPET. In addition, the acute response of cerebral oxygenation during incremental CPET may identify abnormal behavior and ensure greater safety for patients with cardiovascular, respiratory, and metabolic diseases.

OBJECTIVE

To summarize the cerebral oxygenation acute response during CPET of patients with cardiovascular, metabolic, or respiratory diseases.

METHODS

From inception to 23rd September 2022, five databases (PubMed, SCOPUS, Web of Science, Embase and CINAHAL) were searched for cross-sectional studies performing incremental CPET and measuring the cerebral oxygenation acute response in cardiovascular, metabolic, or respiratory diseases compared with healthy individuals. The Downs and Black tool assessed the risk of bias of the studies.

RESULTS

We included seven studies with 428 participants (305 men and 123 women), aged 43 to 70 years. Of these, 101 had heart failure NYHA II and III; 77 idiopathic dilated cardiomyopathy; 33 valvular disease; 25 coronary heart disease; 22 pulmonary arterial hypertension; 15 had severe obstructive sleep apnea (OSA) and 166 were apparently healthy. There was no eligible article with metabolic disease. There was a lower magnitude increase in cerebral oxygenation of cardiovascular patients compared with the healthy individuals during the CPET. Furthermore, pulmonary arterial hypertension patients presented increased cerebral oxygen extraction, differently to those with severe OSA.

CONCLUSION

Considering the heterogeneity of the included studies, patients with cardiovascular disease may suffer from reduced cerebral oxygen supply, and individuals with OSA presented lower brain oxygen extraction during the CPET. Future studies should aim for strategies to improve cerebral oxygenation to ensure greater safety at CPET of cardiovascular and OSA patients. An acute response pattern for metabolic and other respiratory diseases was not established.

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

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

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.

Herrick J. Energy cost of walking and functional aerobic capacity during moderate intensity exercise in adults with obstructive sleep apnea: a cross-sectional study

Background

Autonomic dysregulation associated with obstructive sleep apnea (OSA) may limit cardiopulmonary responses to exercise, which, in turn, may impair functional aerobic capacity (FAC) and walking economy. We aimed to characterize walking economy and FAC in OSA patients compared with healthy adults (non-OSA) and examine their relationship with OSA severity (apnea-hypopnea index [AHI]).

Methods

A total of 26 adults (OSA, n = 13; non-OSA, n = 13) participated in this cross-sectional study. In this study, the participants with OSA were between the ages of 25 and 60 years, with a body mass index of 25 kg/m2 to 39 kg/m2, and who had undergone a recent third-party sleep study with an AHI of 5 or greater. Participants completed a maximal integrated cardiopulmonary exercise test, three separate exercise bouts of constant work rate (CWR) treadmill test at 85% of anaerobic threshold (AT), and a 10-min walk test (10MWT). Multiple linear regression analysis corrected for weight, age, and BMI were performed to examine the associations.

Results

There were significant differences between OSA and non-OSA participants in VO2peak (29.7 ± 5.6 mL/kg/min vs. 37.5 ± 6.5 mL/kg/min, p = 0.03) and Net VO2 during CWR (12.7 ± 5 vs.19 ± 6 mL/kg/min, p = 0.02). The 10MWT speed and distance were significantly lower in the OSA group (all p < 0.001). The energy cost of walking during submaximal exercise and 10-min walk test was higher among patients with OSA (all p < 0.001). The AHI scores were associated with 10MWT distance (R2 = 0.85, p < 0.001), energy cost of walking (R2 = 87, p < 0.001), and VO2 at anaerobic threshold (R2 = 0.92, p < 0.001).

Conclusions

The findings of this study show that patients with OSA have reduced FAC and a higher energy cost of walking. AHI explained 87% of variance in the energy cost of walking during the 10MWT. The results suggest that individuals with more severe obstructive sleep apnea experience greater impairment in functional performance.

Attenuated heart rate recovery in children and adolescents with obstructive sleep apnea syndrome

BACKGROUND

Autonomic dysfunction is a key trait in the development of obstructive sleep apnea syndrome (OSAS) in adults. However, few similar studies focused on children and adolescents. We investigated if there was any association between heart rate recovery (HRR) and the severity of OSAS in children and adolescents.

METHODS

A total of 161 subjects were included: 87 healthy controls, 35 mild OSAS patients (M-OSAS) and 39 moderate-severe OSAS (M-S-OSAS) patients. Clinical parameters, cardiopulmonary exercise test (CPET) indexes including HRR and polysomnographic records including apnea-hypopnea index (AHI) were compared among the three groups. Pearson correlation analysis and multivariable linear regression analysis were used to detect the relationship between HRR and polysomnographic parameters.

RESULTS

HRR values in either the OSAS group were lower than those of the control group, and the values in the M-S OSAS group were even lower than those of the M-OSAS group (P < 0.05). Correlation analysis showed that HRR was inversely correlated with AHI (r = -0.190, P < 0.01). Moreover, multivariable linear regression analyses showed the association between HRR and AHI was significant (β = 0.174, P < 0.01).

CONCLUSIONS

HRR was closely associated with OSAS severity, which suggested that HRR might be a promising index for risk stratification and clinical management in children and adolescents with OSAS.

IMPACT

Heart rate recovery (HRR), a noninvasive and reliable index of automatic nervous system, is closely associated with the severity of obstructive sleep apnea syndrome (OSAS) in children and adolescents. To our knowledge, our study was the first study in China focusing on evaluating the role of HRR in children with OSAS. We found HRR was closely associated with OSAS severity in children and adolescents, and it suggested that HRR might be a promising index for risk stratification and clinical management in children and adolescents with OSAS.

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.

Childhood Obesity and its Influence on Sleep Disorders: Kids-Play Study

Background: Sleep disorders are associated with overweight and obese children, and could decrease life quality with limitations to normal daily activities. The purpose of the study is to describe the prevalence of sleep disorders in a cohort of overweight/obese children using respiratory polygraphy. Methods: A descriptive cross-sectional study was conducted in Granada (Spain) on a sample of 98 children with overweight or obesity. The presence of sleep disorders was determined by respiratory polygraphy. Results: Regarding apnoea–hypopnea-index (AHI) results, 44% of affected children had severe sleep apnoea–hypopnea syndrome (SAHS), and the remaining 56% had a mild form of the disorder. With respect to oxygen-desaturation index, 56% of the same group had severe SAHS, 32% had mild SAHS, and the remaining 12% did not suffer from SAHS. Among participants, average scores of 13.8 obstructive apnoea, 7.7 central apnoea, and 13.6 hypopnoea were recorded. Conclusions: Respiratory polygraphy can provide conclusive results in the diagnosis of SAHS in overweight/obese children. Interventional programmes designed and implemented to reduce overweight and obesity can improve quality of sleep and life in children.

Cardiopulmonary exercise testing in patients with asthma: What is its clinical value?

Asthma is one of the most common respiratory disorders, characterized by fully or largely reversible airflow limitation. Asthma symptoms can be triggered or magnified during exertion, while physical activity limitation is often present among asthmatic patients. Cardiopulmonary exercise testing (CPET) is a dynamic, non-invasive technique which provides a thorough assessment of exercise physiology, involving the integrative assessment of cardiopulmonary, neuromuscular and metabolic responses during exercise. This review summarizes current evidence regarding the utility of CPET in the diagnostic work-up, functional evaluation and therapeutic intervention among patients with asthma, highlighting its potential role for thorough patient assessment and physician clinical desicion-making.

Moderate to Severe Obstructive Sleep Apnea in Military Personnel Is Not Associated With Decreased Exercise Capacity

STUDY OBJECTIVES

Studies of older and less active patients with obstructive sleep apnea (OSA) have reported decreased exercise capacity as measured by peak oxygen uptake (VO₂ max) during cardiopulmonary exercise testing (CPET). We looked to determine whether VO₂ max was decreased in younger patients with OSA who regularly exercise as would be encountered in the military.

METHODS

We evaluated military personnel who had undergone pulmonary function testing (PFT), CPET, and polysomnography (PSG) as part of the larger STAMPEDE III study for comprehensive evaluation of exertional dyspnea. For analysis, patients were classified into two groups, the OSA group with an apnea-hypopnea index (AHI) ≥ 15 events/h and a control group with an AHI < 15 events/h.

RESULTS

Mean AHI was 32.7 in the OSA group (n = 40) versus 5.8 in the control group (n = 58) with no significant difference in age (40.7 years versus 39.4 years) or body mass index (30.4 kg/m² versus 29.9 kg/m²). PFT was normal in both groups including diffusing capacity (100.7% versus 96.5%) and FEV₁ (89.2% versus 86.2%). VO₂ max was not significantly different in the OSA group compared to the control group (101.3% versus 102.8%; P = .60) with both groups having normal exercise capacity. Exercise blood pressure response was normal and peak heart rate trended toward a blunted response in the OSA group (166.0 bpm versus 171.6 bpm, P = .09).

CONCLUSIONS

Younger military personnel with moderate to severe OSA do not have decreased exercise capacity. The effect of OSA on exercise tolerance may be influenced by additional factors and is likely too small to be noted in this population.

COMMENTARY

A commentary on this article appears in this issue on page 819.

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.

Influence of obesity in pulmonary function and exercise tolerance in obese women with obstructive sleep apnea

OBJECTIVE

To evaluate the influence of obesity on pulmonary function and exercise tolerance in women with obstructive sleep apnea (OSA).

SUBJECTS AND METHODS

A descriptive analytic cross- sectional study was carried out. Thirty-nine (39) sedentary climacteric women, aged 45 to 60 years, were evaluated and submitted to polysomnography. The participants were divided into 4 groups: a) 'eutrophic non-OSA' (n = 13); b) 'eutrophic OSA' (n = 5); c) 'obese non-OSA' (n = 6); d) 'obese OSA' (n = 15). All subjects underwent clinical and anthropometric evaluation, followed by pulmonary function tests and 6-minute walk test (6MWT).

RESULTS

There was a significant difference in the predicted percentage values of FEV1/FVC when comparing 'eutrophic OSA' and 'obese OSA' (97.6% ± 6.1% vs. 105.7% ± 5.7%, respectively; p = 0.025). The other spirometric variables did not show any differences between the studied groups. There was no significant difference in the maximum distance walked when the 'eutrophic non-OSA', 'eutrophic OSA', 'obese non-OSA' and 'obese OSA' groups were compared.

CONCLUSION

Considering the results of this study, OSA itself did not influence pulmonary function or functional capacity parameters compared to eutrophic women. However, not only isolated obesity but also obesity associated with OSA can negatively impact sleep quality and lung function.

Brief Review: Ergospirometry in Patients with Obstructive Sleep Apnea Syndrome

This brief review summarizes the available literature on the intersection of obstructive sleep apnea syndrome (OSAS) and ergospirometry. Ergospirometry provides an assessment of integrative exercise responses involving pulmonary, cardiovascular, neuropsychological, and skeletal muscle systems, which are not adequately reflected through the measurement of individual organ system functions. Sleep disorders, including OSAS, often exacerbate problems in the operation of the autonomic nervous system, heart function, lung mechanics, anxiety, and muscle metabolism. Patients with OSAS have low aerobic capacity due to dysfunction of these systems, which often affect quality of sleep. Further research is necessary to elucidate the precise mechanisms through which ergospirometry can be useful in the assessment and early identification of patients with OSAS.

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.

Pulmonary consequences of hypothyroidism

BACKGROUND

Although hypothyroidism has an insidious onset and relatively asymptomatic, exertional dyspnea and fatigue can be the presenting complaints.

OBJECTIVES

The aim is to assess functional lung impairment in hypothyroid patients both at rest and during exercise.

METHODS

A case-control study was carried out on 42 patients with newly diagnosed hypothyroidism and 12 control subjects. Hypothyroidism was diagnosed based on high value of thyroid stimulating hormone (TSH) ≥6 μIU/ml, and low value of free thyroxin (FT4) ≤0.8 ng/dl, both groups had chest X-ray, spirometry, diffusing capacity of the lungs for carbon monoxide (DLCO), arterial blood gases (ABGs) and symptom-limited exercise testing using treadmill.

RESULTS

Both groups were comparable as regard age, sex, and body mass index. Although ABG and spirometry were within normal in both groups, forced vital capacity %, and forced expiratory flow (FEF_25-75) % were significantly reduced in the hypothyroid group (P = 0.014, 0.000, respectively), DLCO significantly reduced in hypothyroidism (P = 0.005). As regard exercise testing parameters, maximum oxygen consumption %, minute ventilation, tidal volume, and oxygen pulse were significantly reduced in hypothyroidism (0.005, 0.000, 0.000, and 0.02 respectively). TSH significantly negatively correlated with forced expiratory volume in 1 s %, FEF_25-75%, and DLCO while they significantly positively correlated with FT4.

CONCLUSION

Even with the presence of normal chest X-ray, arterial blood gases, and spirometry in patients with hypothyroidism DLCO and exercise testing parameters can be significantly reduced.

Apnea-hypopnea index prediction through an assessment of autonomic influence on heart rate in wakefulness

With the high prevalence of obstructive sleep apnea, the issue of developing a practical tool for obstructive sleep apnea screening has been raised. Conventional obstructive sleep apnea screening tools are limited in their ability to help clinicians make rational decisions due to their inability to predict the apnea-hypopnea index. Our study aimed to develop a new prediction model that can provide a reliable apnea-hypopnea index value during wakefulness. We hypothesized that patients with more severe obstructive sleep apnea would exhibit more attenuated waking vagal tone, which may result in lower effectiveness in decreasing heart rate as a response to deep inspiration breath-holding. Prior to conducting nocturnal in-laboratory polysomnography, 30 non-obstructive sleep apnea (apnea-hypopnea index<5events/h) subjects and 246 patients with obstructive sleep apnea participated in a 75-second experiment that consisted of a 60-second baseline measurement and consecutive 15-second deep inspiration breath-hold sessions. Two apnea-hypopnea index predictors were devised by considering the vagal activities reflected in the electrocardiographic recordings acquired during the experiment. Using the predictors obtained from 184 individuals, regression analyses and k-fold cross-validation tests were performed to develop an apnea-hypopnea index prediction model. For the remaining 92 individuals, the developed model provided an absolute error (mean±SD) of 3.53±2.67events/h and a Pearson's correlation coefficient of 0.99 (P<0.01) between the apnea-hypopnea index predictive values and the reference values reported by polysomnography. Our study is the first to achieve reliable and time-efficient prediction of the apnea-hypopnea index during wakefulness.

Comparison of the six-minute walk test with a cycle-based cardiopulmonary exercise test in people following curative intent treatment for non-small cell lung cancer

This study is aimed to (i) compare both the magnitude of impairment in exercise capacity and exercise responses measured during the six-minute walk test (6MWT) and the cardiopulmonary exercise test (CPET) and (ii) investigate the effect of test repetition on six-minute walk distance (6MWD) in people following curative intent treatment for non-small cell lung cancer (NSCLC). Twenty participants (67 ± 10 years; 14 females), 6-10 weeks following lobectomy, underwent a CPET and two 6MWTs. Peak exercise responses, dyspnoea and leg fatigue, as well as heart rate (HR) and oxygen saturation (SpO2) during the 6MWT, were compared to those during the CPET. Compared with exercise capacity when expressed as peak rate of oxygen consumption (%pred) measured during the CPET, exercise capacity when expressed as 6MWD (%pred) was less impaired (81 ± 10 vs. 63 ± 15 %pred; p < 0.001). Compared with the CPET, the 6MWT elicited lower peak HR (119 ± 15 vs. 128 ± 18 beats minute(-1); p = 0.02), lower SpO2 (93 ± 2 vs. 95 ± 3%; p < 0.05), less dyspnoea (3.1 ± 1.6 vs. 6.9 ± 2.6; p < 0.01) and less leg fatigue (2.0 ± 1.9 vs. 6.8 ± 2.4; p < 0.01). The 6MWD increased 19 ± 19 metre (4 ± 4%) with test repetition (p < 0.001). In people following curative intent treatment for NSCLC, the 6MWT appears to elicit sub-maximal exercise responses when compared with the CPET. There is a significant effect of test repetition on 6MWD.

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.

Pulmonary oxygen uptake kinetics during exercise in subclinical hypothyroidism

BACKGROUND

Patients with subclinical hypothyroidism (SCH) have lower exercise tolerance, but the impact on oxygen uptake (VO2) kinetics is unknown. This study evaluated VO2 kinetics during and after a constant load submaximal exercise in SCH.

METHODS

The study included 19 women with SCH (thyrotropin (TSH)=6.87±2.88 μIU/mL, free thyroxine (fT4)=0.97±0.15 ng/dL) and 19 controls (TSH=2.29±0.86 μIU/mL, T4=0.99±0.11 ng/dL) aged between 20 and 55 years. Ergospirometry exercise testing was performed for six minutes with a constant load of 50 W, followed by six minutes of passive recovery. The VO2 kinetics was quantified by the mean response time (MRT), which is the exponential time constant and approximates the time needed to reach 63% of change in VO2 (ΔVO2). The O2 deficit-energy supplied by anaerobic metabolism at the onset of exercise-and O2 debit-extra energy demand during the recovery period-were calculated by the formula MRT×ΔVO2. Values are mean±standard deviation.

RESULTS

In the rest-exercise transition, patients with SCH showed slower VO2 kinetics (MRT=47±8 sec vs. 40±6 sec, p=0.004) and a higher oxygen deficit (580±102 mL vs. 477±95 mL, p=0.003) than controls respectively. In the exercise-recovery transition, patients with SCH also showed slower VO2 kinetics (MRT=54±6 sec vs. 44±6 sec, p=0.001) and a higher oxygen debit (679±105 mL vs. 572±104 mL, p=0.003). The VO2 kinetics showed a significant correlation with TSH (p<0.05).

CONCLUSIONS

This study demonstrates that women with SCH have the slowest VO2 kinetics in the onset and recovery of a constant-load submaximal exercise and highlights that this impairment is already manifest in the early stage of the disease.

Heart rate recovery post 6-minute walking test in obstructive sleep apnea: cycle ergometry versus 6-minute walking test in OSA patients

PURPOSE

To examine the clinical usefulness of heart rate recovery (HRR) post 6-minute walking test (6MWT) as a simple marker of cardiovascular risk in obstructive sleep apnea (OSA) patients in comparison to HRR post cycle ergometry, the validated and more sophisticated protocol.

METHODS

Seventy-four participants underwent full overnight polysomnography, cycle ergometry and 6MWT. The HRR at 1, 2 and 3 min (HRR-1, HRR-2 and HRR-3) 6MWT was compared to HRR at 1, 2, and 3 min post cycle ergometry in normal subjects and in moderate and severe OSA patients before and after 6-month CPAP treatment.

RESULTS

The HRR-1, HRR-2 and HRR-3 in 6MWT were significantly different between normal, moderate and severe OSA patients with higher rates achieved in normal. The higher the severity of OSA the lower the HRR was. There were also no differences found between work rate and distance walked during cycle ergometry or 6MWT, respectively, concerning normal, moderate and severe OSA patients. Heart rate recovery was further associated with minimum saturation of oxygen during sleep independently of the duration of apnea episodes of BMI and ESS. The treatment with CPAP had a beneficial effect on HRR both post-6MWT and post cycle ergometry.

CONCLUSIONS

Autonomic nervous system dysfunction in OSA can be found even with submaximal exertion. Heart rate recovery post-6MWT, such as HRR post cycle ergometry, was significantly impaired in OSA patients in comparison to normals and was favorably influenced from CPAP treatment. Furthermore, it was found to be more sensitive compared with distance walked in 6MWT in discriminating severity of OSA. The HRR post-6MWT was found to be an easily measured and reliable marker of OSA severity both before and after CPAP treatment.

Qualidade do sono e tolerância ao esforço em portadores de apneia obstrutiva do sono

INTRODUÇÃO: O sono é um estado natural e recorrente, no qual acontecem processos neurobiológicos importantes. A má qualidade do sono está diretamente associada com piores indicadores de saúde. A qualidade do sono pode ser medida objetiva e subjetivamente por métodos como a polissonografia, que é o padrão de referência, ou por meio de testes e questionários, como o índice de qualidade de sono de Pittsburgh (IQSP).OBJETIVO: Correlacionar a qualidade do sono com a tolerância ao esforço em pacientes portadores da síndrome da apneia/hipopneia obstrutiva do sono (SAHOS).MÉTODOS: Participaram do estudo 63 indivíduos (57 mulheres e seis homens), média de idade de 51,7 ± 6,6 anos; índice de massa corpórea (IMC) média de 28,2 ± 5,0 kg/m2); índice de apneia/hipopneia (IAH) médio de 7,3 ± 10,50 eventos/hora, verificado através da polissonografia. Para a avaliação da qualidade do sono, os participantes responderam ao IQSP, e para a avaliação da tolerância ao esforço, realizaram o teste de caminhada de 6 minutos (TC6M).RESULTADOS: Não houve correlação entre o IQSP e o TC6M (Rs= -0,103620, p = 0,419), assim como entre o IAH e o TC6M (Rs= -0, 000984, p = 0,9939). Podemos sugerir que a qualidade do sono e a gravidade da SAHOS não afetam a tolerância ao esforço dos indivíduos com SAHOS.CONCLUSÃO: Estudos com uma amostra maior, levando-se em consideração a estratificação pela gravidade da SAHOS e utilizando métodos mais acurados de avaliação da capacidade funcional, devem ser realizados, a fim de que resultados mais abrangentes possam ser obtidos.

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.

Clinical usefulness of response profiles to rapidly incremental cardiopulmonary exercise testing

The advent of microprocessed "metabolic carts" and rapidly incremental protocols greatly expanded the clinical applications of cardiopulmonary exercise testing (CPET). The response normalcy to CPET is more commonly appreciated at discrete time points, for example, at the estimated lactate threshold and at peak exercise. Analysis of the response profiles of cardiopulmonary responses at submaximal exercise and recovery, however, might show abnormal physiologic functioning which would not be otherwise unraveled. Although this approach has long been advocated as a key element of the investigational strategy, it remains largely neglected in practice. The purpose of this paper, therefore, is to highlight the usefulness of selected submaximal metabolic, ventilatory, and cardiovascular variables in different clinical scenarios and patient populations. Special care is taken to physiologically justify their use to answer pertinent clinical questions and to the technical aspects that should be observed to improve responses' reproducibility and reliability. The most recent evidence in favor of (and against) these variables for diagnosis, impairment evaluation, and prognosis in systemic diseases is also critically discussed.

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.

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.

Heart rate recovery: a practical clinical indicator of abnormal cardiac autonomic function

The autonomic nervous system (ANS) and cardiovascular function are intricately and closely related. One of the most frequently used diagnostic and prognostic tools for evaluating cardiovascular function is the exercise stress test. Exercise is associated with increased sympathetic and decreased parasympathetic activity and the period of recovery after maximum exercise is characterized by a combination of sympathetic withdrawal and parasympathetic reactivation, which are the two main arms of the ANS. Heart rate recovery after graded exercise is one of the commonly used techniques that reflects autonomic activity and predicts cardiovascular events and mortality, not only in cardiovascular system disorders, but also in various systemic disorders. In this article, the definition, applications and protocols of heart rate recovery and its value in various diseases, in addition to exercise physiology, the ANS and their relationship, will be discussed.

Membrane level of omega-3 docosahexaenoic acid is associated with severity of obstructive sleep apnea

BACKGROUND

Patients with obstructive sleep apnea (OSA) are at increased risk of cardiovascular disease (CVD). The omega-3 fatty acid docosahexaenoic acid (DHA) is a major component of neural tissues, and supplementation with fish oils improves autonomic tone and reduces risk for CVD. A link between low DHA status and less mature sleep patterns was observed in newborns.

METHODS

We investigated the relations between red blood cell (RBC) levels of DHA and OSA severity in 350 sequential patients undergoing sleep studies. Severity categories were defined as none/mild, moderate, and severe, based on apnea hypopnea index (AHI) scores of 0 to 14, 15 to 34, and > 34, respectively.

RESULTS

After controlling for age, sex, race, smoking, BMI, alcohol intake, fish intake, and omega-3 supplementation, RBC DHA was inversely related with OSA severity. For each 1-SD increase in DHA levels, a patient was about 50% less likely to be classified with severe OSA. The odds ratios (95% CI) were 0.47 (0.28 to 0.80) and 0.55 (0.31 to 0.99) for being in the severe group versus the none/mild or moderate groups, respectively.

CONCLUSION

These findings suggest that disordered membrane fatty acid patterns may play a causal role in OSA and that the assessment of RBC DHA levels might help in the diagnosis of OSA. The effects of DHA supplementation on OSA should be explored.