title: Factors of tidal volume variation during augmented spontaneous ventilation in patients on extracorporeal carbon dioxide removal. A multivariate analysis.
abstract: BACKGROUND
  Extracorporeal carbon dioxide removal (ECCO2-R) allows lung protective ventilation using lower tidal volumes (VT) in patients with acute respiratory failure. The dynamics of spontaneous ventilation under ECCO2-R has not been described previously. This retrospective multivariable analysis examines VT patterns and investigates the factors that influence VT, in particular sweep gas flow and blood flow through the artificial membrane.
  
  
  METHODS
  We assessed VT, respiratory rate (RR), minute ventilation (MV), and levels of pressure support (0-24 cm H2O), sweep gas flow (0-14 L/min) and blood flow through the membrane (0.8-1.8 L/min) in 40 patients from the moment they were allowed to breathe spontaneously. Modest hypercapnia was accepted.
  
  
  RESULTS
  Patients tolerated moderate hypercapnia well. In a generalized linear model the increase in sweep gas flow (P<0.001), a low PaCO2 (P=0.029), and an increased breathing frequency (P<0.001) were associated with lower VT. Neither blood flow through the membrane (P=0.351) nor the level of pressure support (P=0.595) influenced VT size.
  
  
  CONCLUSIONS
  Higher sweep gas flow is associated with low VT in patients on extracorporeal lung assist and augmented spontaneous ventilation. Such a technique can be used for prolonged lung protective ventilation even in the patient's recovery period.
authors.affiliation: Department of Anesthesia and Operative Intensive Care, Regensburg University Hospital, Regensburg, Germany - thomas.bein@klinik.uni-regensburg.de.
authors.forename: T
authors.initials: T
authors.lastname: Bein
authors.forename: T
authors.initials: T
authors.lastname: Müller
authors.forename: B M
authors.initials: BM
authors.lastname: Graf
authors.forename: A
authors.initials: A
authors.lastname: Philipp
authors.forename: F
authors.initials: F
authors.lastname: Zeman
authors.forename: M J
authors.initials: MJ
authors.lastname: Schultz
authors.forename: A S
authors.initials: AS
authors.lastname: Slutsky
authors.forename: S
authors.initials: S
authors.lastname: Weber-Carstens
mesh_terms: D000328:Adult; D002245:Carbon Dioxide / Q000302:isolation & purification*; D005260:Female; D006801:Humans; D006935:Hypercapnia / Q000628:therapy; D008297:Male; D008875:Middle Aged; D011659:Pulmonary Gas Exchange; D012121:Respiration, Artificial / Q000379:methods*; D056152:Respiratory Rate; D012189:Retrospective Studies; D013990:Tidal Volume
chemical_list: D002245:Carbon Dioxide