title: C-Flex technology: effects on breathing parameters and inspiratory flow limitation.
abstract: BACKGROUND
  Expiratory pressure relief continuous positive airway pressure (pressure relief CPAP, C-Flex) is known to be as effective in the treatment of obstructive sleep apnea (OSA) as conventional CPAP while improving overall patients' adherence. However, the effects of C-Flex on ventilation during sleep have not been studied yet.
  
  
  OBJECTIVE
  This study investigates the effects of pressure relief CPAP on respiratory parameters and possible inspiratory flow limitation with increased difference between inspiratory and expiratory pressure compared with conventional CPAP.
  
  
  METHODS
  In total, 24 patients were investigated both during conventional CPAP and during three C-Flex pressure relief settings in randomized order during rapid-eye-movement (REM) and non-REM (NREM) sleep. Airflow was monitored with a pneumotachograph; inspiratory flow limitation was assessed by analyzing airflow and esophageal pressure swings.
  
  
  RESULTS
  Using higher C-Flex gains, expiratory time decreased in favor of the inspiratory duty cycle while there was no significant change in tidal volume. Analysis of inspiratory flow limitation showed no significant difference between conventional CPAP and the C-Flex gains studied.
  
  
  CONCLUSIONS
  The increase in the inspiratory duty cycle with C-Flex might either indicate an increase in the work of breathing or a decrease in the work of breathing due to a lower peak end-expiratory pressure and consecutive alleviation of passive expiration. Both treatments appeared equivalent regarding the occurrence of inspiratory flow limitation.
authors.affiliation: Faculty of Medicine, Sleep Disorders Center, Philipps University, DE-35043 Marburg, Germany. canisius@staff.uni-marburg.de
authors.forename: Sebastian
authors.initials: S
authors.lastname: Canisius
authors.forename: Karl
authors.initials: K
authors.lastname: Kesper
authors.forename: Lukas
authors.initials: L
authors.lastname: Jerrentrup
authors.forename: Thomas
authors.initials: T
authors.lastname: Ploch
authors.forename: Claus
authors.initials: C
authors.lastname: Vogelmeier
authors.forename: Thomas
authors.initials: T
authors.lastname: Penzel
authors.forename: Andreas
authors.initials: A
authors.lastname: Jerrentrup
mesh_terms: D000328:Adult; D000368:Aged; D045422:Continuous Positive Airway Pressure / Q000295:instrumentation* / Q000379:methods; D005260:Female; D006801:Humans; D001239:Inhalation; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D012890:Sleep; D020181:Sleep Apnea, Obstructive / Q000628:therapy*; D013990:Tidal Volume