title: Carbon dioxide rebreathing in non-invasive ventilation. Analysis of masks, expiratory ports and ventilatory modes.
abstract: OBJECTIVE
  Carbon dioxide (CO2) rebreathing is a complication of non-invasive ventilation (NIV). Our objectives were to evaluate the ability of masks with exhaust vents (EV) to avoid rebreathing while using positive pressure (PP) NIV with different levels of expiratory pressure (EPAP). Concerning volume-cycled NIV, we aimed to determine whether cylindrical spacers located in the circuit generate rebreathing.
  
  
  METHODS
  5 healthy volunteers were evaluated. Bi-level PP was used with 3 nasal and 2 facial masks with and without EV. Spacers of increasing volume attached to nasal hermetic masks were evaluated with volume NIV. Inspired CO2 fraction was analyzed.
  
  
  RESULTS
  Rebreathing was zero with all nasal masks and EPAP levels. Using facial masks 1 volunteer showed rebreathing. There was no rebreathing while using all the spacers.
  
  
  CONCLUSIONS
  In healthy volunteers, nasal and facial masks with EV prevent rebreathing. In addition, the use of spacers did not generate this undesirable phenomenon.
authors.affiliation: Respiratory Dept. Hospital de la Santa Creu i Sant Pau, Barcelona, Spain. dsamolski@gmail.com
authors.forename: D
authors.initials: D
authors.lastname: Samolski
authors.forename: N
authors.initials: N
authors.lastname: Calaf
authors.forename: R
authors.initials: R
authors.lastname: Güell
authors.forename: P
authors.initials: P
authors.lastname: Casan
authors.forename: A
authors.initials: A
authors.lastname: Antón
mesh_terms: D001944:Breath Tests; D002245:Carbon Dioxide; D006801:Humans; D001239:Inhalation; D036503:Inhalation Spacers / Q000009:adverse effects; D007320:Inspiratory Capacity; D008397:Masks / Q000009:adverse effects; D011175:Positive-Pressure Respiration / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods*
chemical_list: D002245:Carbon Dioxide