title: Comparison of Tidal Volumes at the Endotracheal Tube and at the Ventilator.
abstract: OBJECTIVE
  Lung protective ventilation for children with acute respiratory distress syndrome requires accurate assessment of tidal volume. Although modern ventilators compensate for ventilator tubing compliance, tidal volume measured at the ventilator may not be accurate, particularly in small children. Although ventilator-specific proximal flow sensors that measure tidal volume at the endotracheal tube have been developed, there is little information regarding their accuracy. We sought to test the accuracy of ventilator measured tidal volume with and without proximal flow sensors against a calibrated pneumotachometer in children.
  
  
  METHODS
  Prospective, observational.
  
  
  METHODS
  Tertiary care PICU.
  
  
  METHODS
  Fifty-one endotracheally intubated and mechanically ventilated children younger than 18 years.
  
  
  METHODS
  Tidal volumes were measured at the ventilator, using a ventilator-specific flow sensor, and a calibrated pneumotachometer connected to the SensorMedics 2600A Pediatric Pulmonary Function Cart.
  
  
  RESULTS
  In a pressure control mode of ventilation: median tidal volume measured with the pneumotachometer (9.5 mL/kg [interquartile range, 8.2-11.7 mL/kg]) was significantly higher than tidal volume measured either at the ventilator (8.2 mL/kg [7.1-9.6 mL/kg]) or at the proximal flow sensor (8.1 mL/kg [7.2-10.0 mL/kg]) (p < 0.001). In pressure regulated volume control mode of ventilation: median tidal volume measured with the pneumotachometer (10.2 mL/kg [8.8-12.4 mL/kg]) was significantly higher than tidal volume measured either at the ventilator (8.0 mL/kg [7.1-9.7 mL/kg]) or at the proximal flow sensor (8.5 mL/kg [7.3-10.4 mL/kg]) (p < 0.001). These findings were consistent when subgrouped by ventilator type and circuit size.
  
  
  CONCLUSIONS
  Tidal volume measured either at the endotracheal tube with a proximal flow sensor or at the ventilator with compensation for tubing compliance are both significantly lower than tidal volume measured with a calibrated pneumotachometer. This underestimation of delivered tidal volume may be particularly important when managing children with acute respiratory distress syndrome.
authors.affiliation: 1Department of Pediatrics, New York University Langone Medical Center, New York, NY. 2Department of Pediatrics, Los Angeles County/University of Southern California Medical Center, Los Angeles, CA. 3Department of Anesthesiology Critical Care Medicine, Children's Hospital Los Angeles, Los Angeles, CA. 4Keck School of Medicine of USC, University of Southern California, Los Angeles, CA.
authors.forename: Paul
authors.initials: P
authors.lastname: Kim
authors.forename: Adler
authors.initials: A
authors.lastname: Salazar
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Ross
authors.forename: Christopher J L
authors.initials: CJ
authors.lastname: Newth
authors.forename: Robinder G
authors.initials: RG
authors.lastname: Khemani
mesh_terms: D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007442:Intubation, Intratracheal; D008297:Male; D008991:Monitoring, Physiologic / Q000295:instrumentation; D011446:Prospective Studies; D015203:Reproducibility of Results; D012121:Respiration, Artificial / Q000295:instrumentation; D013990:Tidal Volume; D014159:Transducers; D012122:Ventilators, Mechanical