title: Pay attention to treating a subgroup of positional obstructive sleep apnea patients.
abstract: OBJECTIVE
  Positional obstructive sleep apnea (OSA) is defined as an apnea hypopnea index at least twice as high in the supine position as in the lateral position. Whether a positional OSA patient persistently has positional OSA in the follow-up period is unknown. This study was conducted to investigate the maintenance of the positional effect on OSA patients and the predictors of changing from positional OSA to nonpositional OSA.
  
  
  METHODS
  Patients who were diagnosed to have positional OSA were screened for a follow-up polysomnography (PSG), which evaluated the effect of the same lateral position as baseline PSG on the severity of OSA. Those who met the criteria of positional OSA in both PSGs were classified as the unchanged group, the others were classified as the changed group.
  
  
  RESULTS
  Seventy-eight positional OSA patients were enrolled in the final analyses. Twenty-seven of the enrolled patients (35%) were changed to nonpositional OSA patients in the second PSG. A higher apnea index in the lateral position was found in the changed group compared with that in the unchanged group (p = 0.02). Logistic regression also showed that the apnea index in the lateral position was the only independent predictor of changing from positional OSA to nonpositional OSA in the follow-up PSG (odds ratio = 1.13, p = 0.004).
  
  
  CONCLUSIONS
  One-third of positional OSA patients who had a high apnea index in the lateral position tends to become nonpositional OSA patients in the follow-up PSG and must be closely monitored if receiving positional therapy only.
authors.affiliation: Sleep Center, Chang Gung Memorial Hospital, Chiayi, Taiwan; Division of Pulmonary and Critical Care Medicine, Chang Gung Memorial Hospital, Chiayi, Taiwan; Department of Nursing, Chang Gung Institute of Technology, Chiayi Campus, Taiwan; College of Medicine, Chang Gung University, Taoyuan, Taiwan.
authors.forename: Yu-Ting
authors.initials: YT
authors.lastname: Chou
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Chang Gung Memorial Hospital, Chiayi, Taiwan; Graduate Institute of Clinical Medical Sciences, Chang Gung University, Taoyuan, Taiwan; College of Medicine, Chang Gung University, Taoyuan, Taiwan; Department of Respiratory Care, Chang Gung Institute of Technology, Chiayi Campus, Taiwan.
authors.forename: Tsung-Ming
authors.initials: TM
authors.lastname: Yang
authors.affiliation: Sleep Center, Chang Gung Memorial Hospital, Chiayi, Taiwan; Division of Pulmonary and Critical Care Medicine, Chang Gung Memorial Hospital, Chiayi, Taiwan; Graduate Institute of Clinical Medical Sciences, Chang Gung University, Taoyuan, Taiwan; College of Medicine, Chang Gung University, Taoyuan, Taiwan.
authors.forename: Chin-Kuo
authors.initials: CK
authors.lastname: Lin
authors.affiliation: Sleep Center, Chang Gung Memorial Hospital, Chiayi, Taiwan; Division of Pulmonary and Critical Care Medicine, Chang Gung Memorial Hospital, Chiayi, Taiwan; Department of Nursing, Chang Gung Institute of Technology, Chiayi Campus, Taiwan; College of Medicine, Chang Gung University, Taoyuan, Taiwan.
authors.forename: Shu-Yi
authors.initials: SY
authors.lastname: Huang
authors.affiliation: Sleep Center, Chang Gung Memorial Hospital, Chiayi, Taiwan; Division of Pulmonary and Critical Care Medicine, Chang Gung Memorial Hospital, Chiayi, Taiwan; College of Medicine, Chang Gung University, Taoyuan, Taiwan; Department of Respiratory Care, Chang Gung Institute of Technology, Chiayi Campus, Taiwan.
authors.forename: Ying-Huang
authors.initials: YH
authors.lastname: Tsai
authors.affiliation: Sleep Center, Chang Gung Memorial Hospital, Chiayi, Taiwan; Division of Pulmonary and Critical Care Medicine, Chang Gung Memorial Hospital, Chiayi, Taiwan.
authors.forename: Ju-Fang
authors.initials: JF
authors.lastname: Chang
authors.affiliation: Sleep Center, Chang Gung Memorial Hospital, Chiayi, Taiwan; Division of Pulmonary and Critical Care Medicine, Chang Gung Memorial Hospital, Chiayi, Taiwan.
authors.forename: Yu-Jung
authors.initials: YJ
authors.lastname: Hou
authors.affiliation: Sleep Center, Chang Gung Memorial Hospital, Chiayi, Taiwan; Division of Pulmonary and Critical Care Medicine, Chang Gung Memorial Hospital, Chiayi, Taiwan; College of Medicine, Chang Gung University, Taoyuan, Taiwan; Department of Respiratory Care, Chang Gung Institute of Technology, Chiayi Campus, Taiwan. Electronic address: lin0927@gmail.com.
authors.forename: Yu-Ching
authors.initials: YC
authors.lastname: Lin
mesh_terms: D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D006305:Health Status Indicators; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D011187:Posture / Q000502:physiology*; D012189:Retrospective Studies; D012890:Sleep / Q000502:physiology*; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology* / Q000628:therapy; D016683:Supine Position / Q000502:physiology
keywords: obstructive; polysomnography; position; sleep apnea