title: Impact of obstructive sleep apnea on lung volumes and mechanical properties of the respiratory system in overweight and obese individuals.
abstract: BACKGROUND
  Even 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.
  
  
  METHODS
  A 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.
  
  
  RESULTS
  Functional 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/m(2) vs. 28.0 ± 3.0 kg/m(2), 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.
  
  
  CONCLUSIONS
  Total 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.
authors.affiliation: Postgraduate college of Xinjiang Medical University, Urumqi, China. arikiny@sina.com.|The People's Hospital of Xinjiang Uygur Autonomous Region, Urumqi, 830001, China. arikiny@sina.com.
authors.forename: Arikin
authors.initials: A
authors.lastname: Abdeyrim
authors.affiliation: Postgraduate college of Xinjiang Medical University, Urumqi, China. 13999233386@126.com.|The People's Hospital of Xinjiang Uygur Autonomous Region, Urumqi, 830001, China. 13999233386@126.com.
authors.forename: Yongping
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Postgraduate college of Xinjiang Medical University, Urumqi, China. nanfanglisci@126.com.|The People's Hospital of Xinjiang Uygur Autonomous Region, Urumqi, 830001, China. nanfanglisci@126.com.
authors.forename: Nanfang
authors.initials: N
authors.lastname: Li
authors.affiliation: Department of Pulmonary function test, The People's Hospital of Xinjiang Uygur Autonomous Region, Urumqi, China. xjfGN@126.com.
authors.forename: Minghua
authors.initials: M
authors.lastname: Zhao
authors.affiliation: Laboratory of sleep study, The People's Hospital of Xinjiang Uygur Autonomous Region, Urumqi, China. sleep_wyc@163.com.
authors.forename: Yinchun
authors.initials: Y
authors.lastname: Wang
authors.affiliation: The Center of Hypertension of the People's Hospital of Xinjiang Uygur Autonomous Region, Urumqi, China. linanfang0724@sina.com.
authors.forename: Xiaoguang
authors.initials: X
authors.lastname: Yao
authors.affiliation: Department of Otorhinolaryngology Head and Neck Surgery, The People's Hospital of Xinjiang Uygur Autonomous Region, Urumqi, China. youledusi@sina.cn.
authors.forename: Youledusi
authors.initials: Y
authors.lastname: Keyoumu
authors.affiliation: Laboratory of sleep study, The People's Hospital of Xinjiang Uygur Autonomous Region, Urumqi, China. amelieyinting@gmail.com.
authors.forename: Ting
authors.initials: T
authors.lastname: Yin
mesh_terms: D000403:Airway Resistance / Q000502:physiology*; D001696:Biomechanical Phenomena; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D005260:Female; D005652:Functional Residual Capacity / Q000502:physiology*; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications / Q000503:physiopathology*; D050177:Overweight / Q000150:complications / Q000503:physiopathology*; D017286:Polysomnography; D012129:Respiratory Function Tests; D012189:Retrospective Studies; D020181:Sleep Apnea, Obstructive / Q000150:complications / Q000503:physiopathology*; D013990:Tidal Volume / Q000502:physiology*