title: Feasibility of noninvasive single-channel automated differentiation of obstructive and central hypopneas with nasal airflow.
abstract: BACKGROUND
  The identification of obstructive and central hypopneas is considered challenging in clinical practice. Presently, obstructive and central hypopneas are usually not differentiated or scores lack reliability due to the technical limitations of standard polysomnography. Esophageal pressure measurement is the gold-standard for identifying these events but its invasiveness deters its usage in daily practice.
  
  
  OBJECTIVE
  To determine the feasibility and efficacy of an automatic noninvasive analysis method for the differentiation of obstructive and central hypopneas based solely on a single-channel nasal airflow signal. The obtained results are compared with gold-standard esophageal pressure scores.
  
  
  METHODS
  A total of 41 patients underwent full night polysomnography with systematic esophageal pressure recording. Two experts in sleep medicine independently differentiated hypopneas with the gold-standard esophageal pressure signal. Features were automatically extracted from the nasal airflow signal of each annotated hypopnea to train and test the automatic analysis method. Interscorer agreement between automatic and visual scorers was measured with Cohen's kappa statistic (ĸ).
  
  
  RESULTS
  A total of 1,237 hypopneas were visually differentiated. The automatic analysis achieved an interscorer agreement of ĸ = 0.37 and an accuracy of 69% for scorer A, ĸ = 0.40 and 70% for scorer B and ĸ = 0.41 and 71% for the agreed scores of scorers A and B.
  
  
  CONCLUSIONS
  The promising results obtained in this pilot study demonstrate the feasibility of noninvasive single-channel hypopnea differentiation. Further development of this method may help improving initial diagnosis with home screening devices and offering a means of therapy selection and/or control.
authors.affiliation: CIBER de Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Institute for Bioengineering of Catalonia and Deptartment ESAII, Universitat Politècnica de Catalunya (UPC), Barcelona, Spain. cmorgenstern@ibec.pcb.ub.es
authors.forename: C
authors.initials: C
authors.lastname: Morgenstern
authors.forename: W J
authors.initials: WJ
authors.lastname: Randerath
authors.forename: M
authors.initials: M
authors.lastname: Schwaibold
authors.forename: A
authors.initials: A
authors.lastname: Bolz
authors.forename: R
authors.initials: R
authors.lastname: Jané
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D003936:Diagnosis, Computer-Assisted; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009296:Nasal Cavity; D010865:Pilot Projects; D017286:Polysomnography; D012123:Pulmonary Ventilation / Q000502:physiology*; D015203:Reproducibility of Results; D020182:Sleep Apnea, Central / Q000175:diagnosis* / Q000503:physiopathology*; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis* / Q000503:physiopathology*