title: Influence of bag volume on reproducibility of inert gas rebreathing pulmonary blood flow measurements in patients with pulmonary diseases.
abstract: OBJECTIVE
  Non-invasive inert gas rebreathing (IGR) has shown promising results in the determination of pulmonary blood flow. The volume of the rebreathing bag (V bag) is proposed by the system. However, elderly patients or those with severe pulmonary disease may be unable to rebreathe this volume entirely. We evaluated the effect of adapting V bag on the reproducibility of IGR.
  
  
  METHODS
  A total of 270 valid measurements were obtained from 45 patients with obstruction (group A), restriction (group B), and in healthy controls (group C). Two measurements for each of three different V bag of 1,200, 1,700, and 2,200 ml were conducted in the supine position.
  
  
  RESULTS
  We found no statistically significant difference of the repeated measurements neither between the different V bag in groups A to C nor between the three groups for identical V bag. There was a weak yet significantly worse coefficient of variation between a V bag of 2,200 ml in group A compared with group C with 2,200 and 1,200 ml, respectively. Intraclass correlation coefficient and repeatability coefficient yielded significantly worse values in group A for a V bag of 2,200 ml compared with healthy controls and lower bag volumes. No difference could be found intraclass nor interclass in groups B and C.
  
  
  CONCLUSIONS
  V bag can be altered between 1,200 and 2,200 ml in most situations without affecting the reproducibility. Attention has to be paid to extreme volumes in obstructive patients. Nevertheless, V bag should be chosen as large as possible and therefore has to be carefully adapted, particularly in patients with obstruction or restriction.
authors.affiliation: 1st Department of Medicine (Cardiology, Angiology, Pneumology, Intensive Care), Universitätsmedizin Mannheim, Theodor-Kutzer-Ufer 1-3, 68167, Mannheim, Germany, joachim.saur@umm.de.
authors.forename: Joachim
authors.initials: J
authors.lastname: Saur
authors.forename: Franziska
authors.initials: F
authors.lastname: Kraus
authors.forename: Joachim
authors.initials: J
authors.lastname: Brade
authors.forename: Dariusch
authors.initials: D
authors.lastname: Haghi
authors.forename: Michael
authors.initials: M
authors.lastname: Behnes
authors.forename: Ursula
authors.initials: U
authors.lastname: Hoffmann
authors.forename: Martin
authors.initials: M
authors.lastname: Borggrefe
authors.forename: Jens J
authors.initials: JJ
authors.lastname: Kaden
authors.forename: Frederik
authors.initials: F
authors.lastname: Trinkmann
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001827:Body Height / Q000502:physiology; D016022:Case-Control Studies; D005260:Female; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008168:Lung / Q000098:blood supply* / Q000503:physiopathology; D008171:Lung Diseases / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D005741:Noble Gases / Q000378:metabolism*; D012039:Regional Blood Flow / Q000502:physiology*; D015203:Reproducibility of Results; D012129:Respiratory Function Tests / Q000379:methods*; D012737:Sex Factors
chemical_list: D005741:Noble Gases