title: Optimized temperature and deadspace correction improve analysis of multiple breath washout measurements by ultrasonic flowmeter in infants.
abstract: BACKGROUND
  Assessment of lung volume (FRC) and ventilation inhomogeneities with ultrasonic flowmeter and multiple breath washout (MBW) has been used to provide important information about lung disease in infants. Sub-optimal adjustment of the mainstream molar mass (MM) signal for temperature and external deadspace may lead to analysis errors in infants with critically small tidal volume changes during breathing.
  
  
  METHODS
  We measured expiratory temperature in human infants at 5 weeks of age and examined the influence of temperature and deadspace changes on FRC results with computer simulation modeling. A new analysis method with optimized temperature and deadspace settings was then derived, tested for robustness to analysis errors and compared with the previously used analysis methods.
  
  
  RESULTS
  Temperature in the facemask was higher and variations of deadspace volumes larger than previously assumed. Both showed considerable impact upon FRC and LCI results with high variability when obtained with the previously used analysis model. Using the measured temperature we optimized model parameters and tested a newly derived analysis method, which was found to be more robust to variations in deadspace. Comparison between both analysis methods showed systematic differences and a wide scatter.
  
  
  CONCLUSIONS
  Corrected deadspace and more realistic temperature assumptions improved the stability of the analysis of MM measurements obtained by ultrasonic flowmeter in infants. This new analysis method using the only currently available commercial ultrasonic flowmeter in infants may help to improve stability of the analysis and further facilitate assessment of lung volume and ventilation inhomogeneities in infants.
authors.affiliation: Division of Respiratory Medicine, Children's University Hospital of Berne, Bern, Switzerland. philipp.latzin@insel.ch
authors.forename: P
authors.initials: P
authors.lastname: Latzin
authors.forename: L
authors.initials: L
authors.lastname: Sauteur
authors.forename: C
authors.initials: C
authors.lastname: Thamrin
authors.forename: A
authors.initials: A
authors.lastname: Schibler
authors.forename: D
authors.initials: D
authors.lastname: Baldwin
authors.forename: G J
authors.initials: GJ
authors.lastname: Hutten
authors.forename: M
authors.initials: M
authors.lastname: Kyburz
authors.forename: R
authors.initials: R
authors.lastname: Kraemer
authors.forename: T
authors.initials: T
authors.lastname: Riedel
authors.forename: U
authors.initials: U
authors.lastname: Frey
mesh_terms: D003198:Computer Simulation; D005260:Female; D045268:Flowmeters / Q000592:standards; D005652:Functional Residual Capacity / Q000502:physiology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008954:Models, Biological; D012126:Respiratory Dead Space; D013696:Temperature; D014463:Ultrasonography / Q000379:methods*