title: Technical assessment of spirometers connected in series.
abstract: BACKGROUND
  Office spirometers are now widely used to detect obstructive lung diseases. To test the technical characteristics of these devices, simulation of different forced expiratory maneuvers is performed, using computer generated waveforms. However, the tests with human subjects are also useful to detect technical flaws. The procedure used by some authors to test the accuracy of office spirometers is to compare measurements made by 2 spirometers connected in series.
  
  
  OBJECTIVE
  The aim of this study was to evaluate the accuracy of this latter procedure.
  
  
  METHODS
  Two sets of 2 spirometers connected in series were used: the PocketSpiro with the MicroLoop, and the PocketSpiro with the SpiroScout. Different standard American Thoracic Society curves were selected for both ambient temperature and pressure (ATP) and body temperature and pressure saturated (BTPS) conditions and generated with a waveform simulator. We compared lung function indices (FVC, peak expiratory flow, and FEV(1)) recorded by the PocketSpiro when it was placed respectively upstream or downstream in the assembly.
  
  
  RESULTS
  In ATP conditions, lung function indices were generally higher when the spirometer was placed downstream rather than upstream. The observed deviations reached up to 10%. In BTPS conditions, lung function indices were underestimated when the spirometer was placed downstream, as compared to the ATP procedure. The modification of the flow characteristics and the temperature drop are the 2 mechanisms that could explain our results.
  
  
  CONCLUSIONS
  Connecting the spirometers in series gives variable results, depending on the position of the spirometer in the assembly. Individual tests are therefore essential, as results are not interchangeable.
authors.affiliation: Institute of Mechanics, Materials and Civil Engineering, Université Catholique de Louvain, Louvain-la-Neuve, Belgium.
authors.forename: Quentin
authors.initials: Q
authors.lastname: Lefebvre
authors.forename: Thomas
authors.initials: T
authors.lastname: Vandergoten
authors.forename: Eric
authors.initials: E
authors.lastname: Derom
authors.forename: Emilie
authors.initials: E
authors.lastname: Marchandise
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Liistro
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D004869:Equipment Safety; D006801:Humans; D008173:Lung Diseases, Obstructive / Q000175:diagnosis*; D011786:Quality Control; D012129:Respiratory Function Tests; D013147:Spirometry / Q000295:instrumentation*