title: Regional distribution of ventilation in patients with obstructive sleep apnea: the role of thoracic electrical impedance tomography (EIT) monitoring.
abstract: OBJECTIVE
  The aim of our study was to apply the electrical impedance tomography (EIT) technique to the study of ventilation during wake and NREM and REM sleep in patients with obstructive sleep apneas (OSA).
  
  
  METHODS
  This is a prospective, observational, monocentric, pilot study in a neurology department with a sleep disorder center. Inclusion criteria were age ≥18 years, both gender, and diagnosis of OSA. Exclusion criteria were the contraindications to the thoracic EIT. All patients underwent laboratory-based polysomnography (PSG) alongside thoracic EIT. Primary endpoint was to compare the global impedance (GI) among the conditions: "Wake" vs "Sleep," "NREM" vs "REM," and "OSA" vs "Non-OSA." Secondary endpoint was to measure the regional distribution of impedance in the four regions of interest (ROIs), in each condition.
  
  
  RESULTS
  Of the 17 consecutive patients enrolled, two were excluded because of poor-quality EIT tracings. Fifteen were analyzed, 10 men and 5 women, mean age 51.6 ± 14.4 years. GI was higher in Wake vs Sleep (Wake 13.24 ± 11.23; Sleep 12.56 ± 13.36; p < 0.01), in NREM vs REM (NREM 13.48 ± 13.43; REM 0.59 ± 0.01; p < 0.01), and in Non-OSA vs OSA (Non-OSA 10.50 ± 12.99; OSA 18.98 ± 10.06; p < 0.01). No significant differences were observed in the regional distribution of impedance between Wake and Sleep (χ2= 3.66; p = 0.299) and between Non-OSA and OSA (χ2= 1.00; p = 0.799); conversely, a significant difference was observed between NREM and REM sleep (χ2= 62.94; p < 0.001).
  
  
  CONCLUSIONS
  To our knowledge, this is the first study that addresses the issue of regional ventilation in OSA patients during sleep. Thoracic electrical impedance changes through the sleep-wake cycle and during obstructive events. The application of thoracic EIT can prove a valuable additional strategy for the evaluation of OSA patients.
authors.affiliation: Institute of Anesthesiology and Intensive Care Medicine, Catholic University, Rome, Italy.
authors.forename: Filippo
authors.initials: F
authors.lastname: Bongiovanni
authors.affiliation: Institute of Anesthesiology and Intensive Care Medicine, Catholic University, Rome, Italy.
authors.forename: Benedetta
authors.initials: B
authors.lastname: Mura
authors.affiliation: Institute of Anesthesiology and Intensive Care Medicine, Catholic University, Rome, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Tagliaferri
authors.affiliation: Institute of Anesthesiology and Intensive Care Medicine, Catholic University, Rome, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Bisanti
authors.affiliation: Institute of Neurology, Catholic University, Rome, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Testani
authors.affiliation: Institute of Anesthesiology and Intensive Care Medicine, Catholic University, Rome, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Maviglia
authors.affiliation: Institute of Neurology, Catholic University, Rome, Italy. giacomodellamarca@gmail.com.
authors.forename: Giacomo
authors.initials: G
authors.lastname: Della Marca
mesh_terms: D000328:Adult; D000368:Aged; D017097:Electric Impedance; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D012123:Pulmonary Ventilation / Q000502:physiology*; D012016:Reference Values; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology*; D012894:Sleep Stages / Q000502:physiology*; D013909:Thorax / Q000503:physiopathology; D014054:Tomography / Q000295:instrumentation / Q000379:methods*
keywords: Electrical impedance tomography; Obstructive sleep apnea; Polysomnography; Regional ventilation; Sleep