title: Precision and accuracy of oxygen flow meters used at hospital settings.
abstract: BACKGROUND
  Oxygen therapy is an important therapeutic resource for patients with hypoxemia. When changing oxygen flow meters, we have observed that sometimes, even with the same oxygen flow setting as before, a different S(pO(2)) is obtained.
  
  
  OBJECTIVE
  To analyze  the precision and accuracy of flow meters used in hospital settings.
  
  
  METHODS
  An experimental study was performed to test oxygen flow meters from a tertiary hospital, by using a calibrated flow analyzer. Used and new flow meter accuracy was tested by reading in the gas analyzer a single measurement  at flow rates of 1, 3, 5, and 10 L/min in 91 flow meters, and they were compared using the Student t test or Mann-Whitney U test. Flow meter precision was tested by reading in the flow analyzer 3 repetitive measurements set at flow rates of 1, 3, 5, and 10 L/min in 11 flow meters, and  the reproducibility of these measurements was conducted by using the intraclass correlation coefficient and the Friedman test.
  
  
  RESULTS
  The mean measured flow rates were slightly lower than the stipulated flow rate at 1 L/min, very close for 3 L/min, and higher for the 5 and 10 L/min flow  rates. There was a large variability among the measurements from different flow meters, mainly at low flow rates (1 and 3 L/min). There was no difference between new and used flow meters at the flow rates measured, except at 10 L/min. Flow meters precision analysis showed a good reproducibility  in 3 repetitive measurements for each flow rate (minimum 0.95, maximum 0.99 intraclass correlations).
  
  
  CONCLUSIONS
  The flow meters tested showed good precision and poor accuracy.
authors.affiliation: Department of Medicine, Universidade Federal de São Paulo, São Paulo, Brazil.
authors.forename: Josy
authors.initials: J
authors.lastname: Davidson
authors.forename: Claudia
authors.initials: C
authors.lastname: Gazzeta
authors.forename: Luciano C
authors.initials: LC
authors.lastname: Torres
authors.forename: José R
authors.initials: JR
authors.lastname: Jardim
authors.forename: Oliver A
authors.initials: OA
authors.lastname: Nascimento
mesh_terms: D002138:Calibration; D045268:Flowmeters / Q000592:standards*; D006761:Hospitals; D006801:Humans; D008422:Materials Testing; D010101:Oxygen Consumption; D010102:Oxygen Inhalation Therapy / Q000295:instrumentation*; D015203:Reproducibility of Results