title: Accuracy of tidal volume, compliance, and resistance measurements on neonatal ventilator displays: an in vitro assessment.
abstract: OBJECTIVE
  To determine the accuracy of measures of respiratory mechanics derived from neonatal ventilators using an in vitro passive physical lung model to simulate newborn pulmonary conditions.
  
  
  METHODS
  Test lung models.
  
  
  METHODS
  Laboratory-based measurements.
  
  
  METHODS
  Three test lungs were constructed to simulate three severities of neonatal lung disease, with ranges of compliance from 0.5 to 2.0 mL/cm H2O and resistance from 25 to 150 cm H2O/(L/sec). Each ventilator was tested using 27 combinations of peak inspiratory pressure (15-25 cm H2O), positive end-expiratory pressure (5-7 cm H2O), and rate settings (20-60 B/min). Data were compared for five different ventilators across simulated lung severity as the ratio of ventilator readout to test lung reference value. A ratio of 1.0 indicated a completely unbiased result.
  
  
  RESULTS
  Overall, four of the five ventilators under-read expired tidal volume by about 1%-12% across all lung conditions, whereas the VIP Bird readout ranged from -4% to +4% bias. Changes in ventilator settings had only a modest effect on mechanics readout. As peak inspiratory pressure progressed from 15 to 25 cm H2O, bias in tidal volume readout changed from +5.0% to -2.5% (p < .001) in the VIP Bird, and from -11% to -9% (p < .001) in the Draeger Babylog VN500. Between positive end-expiratory pressure levels of 5 and 7 cm H2O, tidal volume bias in the Babylog varied between -13% and -7% (p < .001). In progressing from simulated normal to severely ill lung condition, bias in compliance measurements by the Avea and SLE5000 increased from -18% to -40% whereas in the VIP Bird it remained between -17% to -13%, and in the Draeger Evita XL-neo it changed from +17% to -13% and from -8% to -16% in the Babylog. Ratio of ventilator resistance readout to reference value with progressing simulated lung condition changed from 2.0 to 1.0 for the Draeger Evita, 1.6 to 1.1 for the Babylog, 4.2 to 2.0 for the SLE, and from 11.7 to 5.6 for the VIP Bird. The Avea, by design, did not display resistances >100 cm H2O/(L/sec), but overestimated the simulated normal lung resistance of 25 cm H2O/(L/sec) by a factor of 2.5.
  
  
  CONCLUSIONS
  Neonatal ventilator respiratory mechanics measurements and computation methods need further standardization to be useful in clinical settings.
authors.affiliation: Division of Neonatology, Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, PA, USA. abbasis@uphs.upenn.edu
authors.forename: Soraya
authors.initials: S
authors.lastname: Abbasi
authors.forename: Emidio
authors.initials: E
authors.lastname: Sivieri
authors.forename: Robin
authors.initials: R
authors.lastname: Roberts
authors.forename: Haresh
authors.initials: H
authors.lastname: Kirpalani
mesh_terms: D003187:Compliance; D006801:Humans; D007231:Infant, Newborn; D008168:Lung / Q000502:physiology*; D008953:Models, Anatomic; D012121:Respiration, Artificial / Q000295:instrumentation*; D015656:Respiratory Mechanics; D013990:Tidal Volume