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

Revisiting the clinical utilization of cardiopulmonary exercise testing in Saudi Arabia after 2 decades: A cross-sectional study

OBJECTIVES

To assess the prevalence of cardiopulmonary exercise testing (CPET) usage and identify barriers among major hospitals and medical centers in Saudi Arabia. We also aim to compare these findings with data from nearly 2 decades ago.

METHODS

In this cross-sectional study, 70 major hospitals and medical centers were contacted, and 52 (74.2%) responded. The participants involved in this study were healthcare providers proficient in carrying out CPET from different specialties. The survey comprised 21 items covering CPET utilization, exercise mode characteristics, common protocols, types of patients or disorders, and barriers to not carrying out CPET.

RESULTS

The majority (n=37; 71.9%) of the centers reported a lack of CPET utilization. Of the 15 centers that used CPET, only 11 carried out regular CPET. Cardiac-related conditions were the most commonly referred clinical cases (n=7), followed by pulmonary conditions and cardiopulmonary fitness. The common barriers to carrying out CPET have remained unchanged compared to 2 decades ago - that is, the lack of equipment or trained technicians. However, there has been a 14.1% increase in the utilization of CPET and a 10.1% increase in the use of treadmill mode compared to a survey carried out 2 decades ago.

CONCLUSION

Although CPET utilization has increased over 2 decades, this still falls below the desired benchmark. This highlights the need for collaborative efforts among policymakers, and healthcare institutions to address barriers and improve CPET integration into clinical practice.

Effect of Sleep-Disordered Breathing on Exercise Capacity after Myocardial Infarction - A Cross-Sectional Study

Background

Exercise capacity reflects the cardiovascular risk after myocardial infarction (MI). The study aims to evaluate the impact of sleep-disordered breathing (SDB) on exercise capacity after MI.

Methods

Consecutive patients referring to outpatient cardiac rehabilitation up to 28 days after MI and participating in the Polish Managed Care after Acute Myocardial Infarction (MC-AMI) program were included. On admission, we assessed the presence and the severity of SDB using the home sleep apnea test (HSAT), patients' maximum exercise capacity on a treadmill exercise stress test (EST), and a 6-minute walk test (6MWT), as well as the effect of SDB on the results obtained. In the multivariate analysis, we verified the strength of the observed associations concerning age, anthropometric parameters, and left ventricular ejection fraction (LVEF).

Results

A total of 254 patients aged 60.00 (interquartile range 51.00-67.00), including 39 (15.4%) women, with technically adequate HSAT, constituted the study group. Mild SDB was found in 82 (32.3%), moderate in 54 (21.3%), and severe in 51 (20.1%) patients. Among those diagnosed with SDB, obstructive sleep apnea (OSA) was dominant in 167 (89.8%). With the worsening of SDB, the distance in 6MWT and the maximum physical exertion achieved in EST, expressed in metabolic equivalents (METs) and maximal heart rate (MHR), decreased. The linear regression analysis confirmed the following: (1) inversely proportional relationship between the respiratory event index and METs, MHR, and 6MWT distance (p = 0.005, p = 0.008, and p = 0.004), and the maximum apnea duration and MET and 6MWT distance (p = 0.042 and p = 0.002); and (2) directly proportional relationship between mean arterial oxygen saturation ( SpO 2 ) during sleep and MET, MHR, and 6MWT distance (p = 0.019, p = 0.006, and p = 0.013), and minimum SpO 2 and MET and MHR (p = 0.040 and p < 0.001). However, the independent risk factors for impaired exercise capacity, determined using multivariable regression analysis, were age, female sex, higher body mass index (BMI), and decreased LVEF, but not SDB parameters.

Conclusions

SDB negatively impacts exercise capacity after MI. However, the strength of this association may be less pronounced due to the interaction of risk factors common for SDB and impaired exercise capacity, e.g., sex, age, BMI, and LVEF.

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.

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.

Snoring was related to self-reported daytime sleepiness and tiredness in young adults performing compulsory conscript service

STUDY OBJECTIVES

In young adults performing compulsory military service, fatigue and somnolence are common and presumably associated with objective or self-reported sleep deprivation. We aimed to find out whether objective sleep parameters from ambulatory polysomnography could explain their self-reported tiredness and sleepiness and whether habits were associated with sleep parameters or tiredness.

METHODS

Seventy (67 male, age 18-24 years) participants had their sleep assessed with polysomnography. Their self-reported symptoms and demographic data were obtained from online survey including Epworth Sleepiness Scale, Beck's Depression Inventory, items from Basic Nordic Sleep Questionnaire, Internet Addiction Scale, and lifestyle questions.

RESULTS

Snoring (audio recording, percentage of total sleep time) was associated with self-reported sleepiness (P = .010) and tiredness (P = .030) and snoring seemed to, partially, explain sleepiness (P = .029). Twenty-six percent of the conscripts had self-reported sleep deprivation (mismatch between reported need for sleep and reported sleep). Self-reported sleep deprivation was significantly associated with somnolence (P = .016) and fatigue (P = .026). Smartphone usage, both average time (P = .022) and frequency of usage (P = .0093) before bedtime, was associated with shorter total sleep time. On average, objective sleep time was rather short (7 hours, 6 minutes), sleep efficiency high (94.9%), proportion of N3 sleep high (27.7%), and sleep latency brief (9 minutes)-suggesting that many of the conscripts might have chronic partial sleep deprivation.

CONCLUSIONS

Snoring might predispose to tiredness in presumably healthy young adults. Conscripts may have partial sleep deprivation.

CITATION

Orjatsalo M, Toppila J, Heimola M, et al. Snoring was related to self-reported daytime sleepiness and tiredness in young adults performing compulsory conscript service. J Clin Sleep Med. 2023;19(2):243-251.

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.

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.

Burn pit exposure in military personnel: is there an effect on sleep-disordered breathing?

PURPOSE

Exposure to elevated concentrations of respirable particulate matter (< 10 μm) may influence sleep-disordered breathing. Burn pits as utilized by the US military in the Middle East until 2011 produced elevated particle matter concentrations. We seek to determine if subjective exposure to burn pits during deployment affects prevalence or severity of obstructive sleep apnea (OSA) in military personnel.

METHODS

As part of a prospective observational study of previously deployed military personnel with exertional dyspnea (n = 145), all patients underwent pulmonary function testing, screening for burn pit exposure, and if warranted by questionnaires, overnight polysomnography. A total of 100 patients completed all testing. For analysis, patients were classified into a burn pit exposure group (45 patients) and a no exposure group (55 patients). Additional analyses were performed on those endorsing burn pit maintenance during deployment (25 patients) and those with > 12 h of daily exposure (17 patients).

RESULTS

The prevalence of OSA, defined by apnea-hypopnea index (AHI) > 5/h, was similarly high in both groups (69% vs. 71%, p = 0.83). Surprisingly, the mean AHI was lower in the exposed group (12.8/h vs. 19.7/h, p = 0.04) while nadir of oxygen saturation was similar (87% vs. 86%, p = 0.39). Subgroup analyses revealed similar findings in those who performed burn pit maintenance (prevalence = 80%, p = 0.58; AHI = 14.8, p = 0.16) and those with > 12 h of daily exposure (prevalence = 88%, p = 0.33; AHI = 18.0, p = 0.62).

CONCLUSIONS

Subjective burn pit exposure does not appear to influence OSA development in previously deployed military personnel. Given the high rate of OSA in this cohort, continued investigation of deployment exposures which may influence sleep-disordered breathing is recommended.

CPAP Effect on Cardiopulmonary Exercise Testing Performance in Patients with Moderate-Severe OSA and Cardiometabolic Comorbidities

Background and Objectives: Obstructive sleep apnea (OSA) is associated with daytime somnolence, cognitive impairment and high cardiovascular morbidity and mortality. Obesity, associated cardiovascular comorbidities, accelerated erythropoiesis and muscular mitochondrial energetic dysfunctions negatively influence exercise tolerance in moderate-severe OSA patients. The cardiopulmonary exercise testing (CPET) offers an integrated assessment of the individual's aerobic capacity and helps distinguish the main causes of exercise limitation. The purpose of this study is to evaluate the aerobic capacity of OSA patients, before and after short-term continuous positive airway pressure (CPAP). Materials and Methods: Our prospective study included 64 patients with newly diagnosed moderate-severe OSA (apnea hypopnea index (AHI) 39.96 ± 19.04 events/h) who underwent CPET before and after CPAP. Thirteen patients were unable to tolerate CPAP or were lost during follow-up. Results: 49.29% of our patients exhibited a moderate or severe decrease in functional capacity (Weber C or D). CPET performance was influenced by gender but not by apnea severity. Eight weeks of CPAP induced significant improvements in maximal exercise load (Δ = 14.23 W, p = 0.0004), maximum oxygen uptake (Δ = 203.87 mL/min, p = 0.004), anaerobic threshold (Δ = 316.4 mL/min, p = 0.001), minute ventilation (Δ = 5.1 L/min, p = 0.01) and peak oxygen pulse (Δ = 2.46, p = 0.007) as well as a decrease in basal metabolic rate (BMR) (Δ = -8.3 kCal/24 h, p = 0.04) and average Epworth score (Δ = -4.58 points, p < 0.000001). Conclusions: Patients with moderate-severe OSA have mediocre functional capacity. Apnea severity (AHI) was correlated with basal metabolic rate, resting heart rate and percent predicted maximum effort but not with anaerobic threshold or maximum oxygen uptake. Although CPET performance was similar in the two apnea severity subgroups, short-term CPAP therapy significantly improved most CPET parameters, suggesting that OSA per se has a negative influence on effort capacity.