title: What can impulse oscillometry and pulmonary function testing tell us about obstructive sleep apnea: a case-control observational study?
abstract: OBJECTIVE
  This study aims to determine whether functional residual capacity (FRC) in obese patients with obstructive sleep apnea (OSA) decreases more than in patients without OSA because of decreased outward recoil from chest wall mass loading as well as increased lung inward recoil.
  
  
  METHODS
  Subjects who were overweight and obese to various degrees with normal spirometric values underwent overnight polysomnography to determine the presence or absence of OSA and were labeled as cases or controls. Lung volume and respiratory mechanical properties were measured by plethysmograph and impulse oscillometry, respectively.
  
  
  RESULTS
  A total of 76 men and 31 women were diagnosed with OSA (cases); 64 men and 33 women without OSA were confirmed as controls. Expiratory reserve volume and FRC were significantly decreased in cases compared with controls. Respiratory impedance and resistance at 5 Hz were significantly higher in cases than in controls, although reactance at low frequencies was significantly lower in cases than in controls. Reactance at 5 Hz (Xrs5) was found to be independently highly correlated with the severity of OSA as defined by the Apnea-Hypopnea Index and was significantly correlated with FRC.
  
  
  CONCLUSIONS
  FRC is significantly decreased in overweight or obese patients with OSA compared with those without OSA, which may be attributed to an increase in lung elastic recoil. The stronger correlation between Xrs5 and OSA severity might indicate upper airway stenosis, and abnormally increased lung elastic recoil may contribute to OSA.
authors.affiliation: The Center of Diagnosis, Treatment, and Research of Hypertension in Xinjiang, The People's Hospital of Xinjiang Uygur Autonomous Region, Tianchi Road No. 91, Tianshan District, Urumqi, Xinjiang, China, 830001.|Postgraduate College of Xinjiang Medical University, Urumqi, China.
authors.forename: Arikiny
authors.initials: A
authors.lastname: Abdeyrim
authors.affiliation: The Center of Diagnosis, Treatment, and Research of Hypertension in Xinjiang, The People's Hospital of Xinjiang Uygur Autonomous Region, Tianchi Road No. 91, Tianshan District, Urumqi, Xinjiang, China, 830001. lnanfang2010@sina.com.|Postgraduate College of Xinjiang Medical University, Urumqi, China. lnanfang2010@sina.com.
authors.forename: NanFang
authors.initials: N
authors.lastname: Li
authors.affiliation: The Center of Diagnosis, Treatment, and Research of Hypertension in Xinjiang, The People's Hospital of Xinjiang Uygur Autonomous Region, Tianchi Road No. 91, Tianshan District, Urumqi, Xinjiang, China, 830001.
authors.forename: Liang
authors.initials: L
authors.lastname: Shao
authors.affiliation: Laboratory of Sleep Study, The People's Hospital of Xinjiang Uygur Autonomous Region, Urumqi, China.
authors.forename: Mulalibieke
authors.initials: M
authors.lastname: Heizhati
authors.affiliation: Laboratory of Sleep Study, The People's Hospital of Xinjiang Uygur Autonomous Region, Urumqi, China.
authors.forename: Yingchun
authors.initials: Y
authors.lastname: Wang
authors.affiliation: The Center of Diagnosis, Treatment, and Research of Hypertension in Xinjiang, The People's Hospital of Xinjiang Uygur Autonomous Region, Tianchi Road No. 91, Tianshan District, Urumqi, Xinjiang, China, 830001.
authors.forename: Xiaoguang
authors.initials: X
authors.lastname: Yao
authors.affiliation: The Center of Diagnosis, Treatment, and Research of Hypertension in Xinjiang, The People's Hospital of Xinjiang Uygur Autonomous Region, Tianchi Road No. 91, Tianshan District, Urumqi, Xinjiang, China, 830001.
authors.forename: Suofeiya
authors.initials: S
authors.lastname: Abulikemu
authors.affiliation: The Center of Diagnosis, Treatment, and Research of Hypertension in Xinjiang, The People's Hospital of Xinjiang Uygur Autonomous Region, Tianchi Road No. 91, Tianshan District, Urumqi, Xinjiang, China, 830001.
authors.forename: Delian
authors.initials: D
authors.lastname: Zhang
authors.affiliation: The Center of Diagnosis, Treatment, and Research of Hypertension in Xinjiang, The People's Hospital of Xinjiang Uygur Autonomous Region, Tianchi Road No. 91, Tianshan District, Urumqi, Xinjiang, China, 830001.
authors.forename: Guijuan
authors.initials: G
authors.lastname: Chang
authors.affiliation: Laboratory of Sleep Study, The People's Hospital of Xinjiang Uygur Autonomous Region, Urumqi, China.
authors.forename: Ting
authors.initials: T
authors.lastname: Yin
authors.affiliation: The Center of Diagnosis, Treatment, and Research of Hypertension in Xinjiang, The People's Hospital of Xinjiang Uygur Autonomous Region, Tianchi Road No. 91, Tianshan District, Urumqi, Xinjiang, China, 830001.
authors.forename: Cai
authors.initials: C
authors.lastname: Li
authors.affiliation: The Center of Diagnosis, Treatment, and Research of Hypertension in Xinjiang, The People's Hospital of Xinjiang Uygur Autonomous Region, Tianchi Road No. 91, Tianshan District, Urumqi, Xinjiang, China, 830001.
authors.forename: Jing
authors.initials: J
authors.lastname: Meng
authors.affiliation: Department of Pulmonary Function Testing, The People's Hospital of Xinjiang Uygur Autonomous Region, Urumqi, China.
authors.forename: MingHua
authors.initials: M
authors.lastname: Zhao
authors.affiliation: The Center of Diagnosis, Treatment, and Research of Hypertension in Xinjiang, The People's Hospital of Xinjiang Uygur Autonomous Region, Tianchi Road No. 91, Tianshan District, Urumqi, Xinjiang, China, 830001.
authors.forename: Ling
authors.initials: L
authors.lastname: Zhou
authors.affiliation: The Center of Diagnosis, Treatment, and Research of Hypertension in Xinjiang, The People's Hospital of Xinjiang Uygur Autonomous Region, Tianchi Road No. 91, Tianshan District, Urumqi, Xinjiang, China, 830001.
authors.forename: Jing
authors.initials: J
authors.lastname: Hong
authors.affiliation: The Center of Diagnosis, Treatment, and Research of Hypertension in Xinjiang, The People's Hospital of Xinjiang Uygur Autonomous Region, Tianchi Road No. 91, Tianshan District, Urumqi, Xinjiang, China, 830001.
authors.forename: Yongping
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D005105:Expiratory Reserve Volume / Q000502:physiology; 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; D009991:Oscillometry / Q000379:methods*; D050177:Overweight / Q000150:complications / Q000503:physiopathology; D010991:Plethysmography; D010992:Plethysmography, Impedance; D017286:Polysomnography; D012016:Reference Values; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics / Q000502:physiology; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis* / Q000503:physiopathology; D035441:Thoracic Wall / Q000503:physiopathology
keywords: Functional residual capacity; Lung volume; Obstructive sleep apnea; Respiratory function tests