title: Respiratory flow measurements and anesthetic drugs: some in vitro observations.
abstract: OBJECTIVE
  To illustrate the influence of anesthetic gases on respiratory flow measurements and to correct this influence.
  
  
  METHODS
  In vitro evaluation.
  
  
  METHODS
  Laboratory.
  
  
  RESULTS
  An in vitro method using a 120-L Tissot water-seal spirometer was used along with a Bicore CP-100, designed for use in intensive care units, and a Datex Ultima, designed for use in the operating room. The flow transducer of one of the instruments being tested was placed in the gas inlet of the Tissot so that simultaneous measurements could be made. Timed flows (2 to 60 L/min) of various gases (O2 and air) and gas mixtures (halothane-O2, isoflurane-O2, N2O-O2, and N2O-O2-isoflurane) were used and the measurements made by the Tissot and the test instrument compared. The Datex Ultima, which includes software corrections for anesthetics, was able to accurately measure gas flows (2 to 60 L/min) of air, 100% oxygen, and anesthetic gas mixtures to within +/- 10% of measurements made by the Tissot. The Bicore CP-100, intended for use with mechanically ventilated patients, accurately measured air and 100% oxygen flow rate to within +/- 8% of the measurements made by the Tissot, but there were large errors (up to 40%) when anesthetics were used.
  
  
  CONCLUSIONS
  This study illustrates the effects of anesthetic gases on measurements of ventilatory flow and the need to ascertain whether corrections are needed to improve the accuracy of flow transducers.
authors.affiliation: Department of Anesthesiology, College of Physicians & Surgeons, Columbia University, New York, NY, USA.
authors.forename: W G
authors.initials: WG
authors.lastname: Filmyer
authors.forename: A
authors.initials: A
authors.lastname: Sardar
authors.forename: C
authors.initials: C
authors.lastname: Weissman
mesh_terms: D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D006801:Humans; D012119:Respiration / Q000187:drug effects*; D012121:Respiration, Artificial; D013147:Spirometry
chemical_list: D018685:Anesthetics, Inhalation