Impact of obstructive sleep apnea on lung volumes and mechanical properties of the respiratory system in overweight and obese individuals

Abstract

BackgroundEven through narrowing of the upper-airway plays an important role in the generation of obstructive sleep apnea (OSA), the peripheral airways is implicated in pre-obese and obese OSA patients, as a result of decreased lung volume and increased lung elastic recoil pressure, which, in turn, may aggravate upper-airway collapsibility.MethodsA total of 263 male (n = 193) and female (n = 70) subjects who were obese to various degrees without a history of lung diseases and an expiratory flow limitation, but troubled with snoring or suspicion of OSA were included in this cross-sectional study. According to nocturnal-polysomnography the subjects were distributed into OSA and non-OSA groups, and were further sub-grouped by gender because of differences between males and females, in term of, lung volume size, airway resistance, and the prevalence of OSA among genders. Lung volume and respiratory mechanical properties at different-frequencies were evaluated by plethysmograph and an impulse oscillation system, respectively.ResultsFunctional residual capacity (FRC) and expiratory reserve volume were significantly decreased in the OSA group compared to the non-OSA group among males and females. As weight and BMI in males in the OSA group were greater than in the non-OSA group (90 ± 14.8 kg vs. 82 ± 10.4 kg, p < 0.001; 30.5 ± 4.2 kg/m2 vs. 28.0 ± 3.0 kg/m2, p < 0.001), multiple regression analysis was required to adjust for BMI or weight and demonstrated that these lung volumes decreases were independent from BMI and associated with the severity of OSA. This result was further confirmed by the female cohort. Significant increases in total respiratory resistance and decreases in respiratory conductance (Grs) were observed with increasing severity of OSA, as defined by the apnea-hypopnea index (AHI) in both genders. The specific Grs (sGrs) stayed relatively constant between the two groups in woman, and there was only a weak association between AHI and sGrs among man. Multiple-stepwise-regression showed that reactance at 5 Hz was highly correlated with AHI in males and females or hypopnea index in females, independently-highly correlated with peripheral-airway resistance and significantly associated with decreasing FRC.ConclusionsTotal respiratory resistance and peripheral airway resistance significantly increase, and its inverse Grs decrease, in obese patients with OSA in comparison with those without OSA, and are independently associated with OSA severity. These results might be attributed to the abnormally increased lung elasticity recoil pressure on exhalation, due to increase in lung elasticity and decreased lung volume in obese OSA.Electronic supplementary materialThe online version of this article (doi:10.1186/s12890-015-0063-6) contains supplementary material, which is available to authorized users.

Sixteen weeks of aerobic training influence spirometry, s-klotho, and hemodynamic responses to sub-maximal exercise testing in obese men with severe obstructive sleep apnea

“…A possible conclusion could be that obesity within itself is a strong enough reducer of the ratio, regardless of the existence of OSA. 111,123 Based on this discovery alone and the fact that the OSA subjects of this study were obese, one could anticipate a reduced ratio, actually seen. 111,123…”

“…The fact that FVC predicted (%) was higher in the control group at rest compared to that of the experimental group for all sessions is well in accordance with the literature. 110,111 This variable has also been associated with the distance achieved during the 6MWT whereas shorter distances achieved were highly correlated with lower FVC predicted (%). 88 The same dynamic was observed in the current study.…”

Overnight Changes in Lung Function of Obese Patients with Obstructive Sleep Apnoea

“…There was a tendency for a direct relationship between respiratory disturbance index (RDI) and overnight changes in forced expiratory volume in 1 s in OSA (p = 0.05, r = 0.30) Lung A reduction in end-tidal lung volumes may lead to a heightened potential for collapse of the upper airways [5]. Indeed, the relationship between reduced lung volume, increased respiratory resistance and increased severity of OSA is already described [2][3][4]. In keeping with these studies, we also found a significant, albeit weak association between spirometric indices and OSA severity.…”

“…OSA is a disorder which not only affects the upper airways but can also impact on the intra-thoracic airways. Indeed, reduced lung volumes, decreased elasticity and increased resistance of the lower airways are associated with more severe disease [2][3][4][5]. In addition, chronic airway diseases, including asthma and chronic obstructive pulmonary disease (COPD), influence the course of OSA [6,7].…”

Morbidity and mortality associated with obesity

“…BMI showed a strong, independent and positive relation with asthma possibly because of the impact of adipose tissue on the chest wall causing a restrictive lung disease, but also as obesity is associated with a chronic inflammatory state (43,44). The pulmonary function tests (PFTs) of obese patients often show impaired expiratory reserve volume (ERV), functional residual capacity (FRC) and total lung capacity (TLC), secondary to increased abdominal load and disturbed chest wall mechanics (45,46).…”