title: Accuracy of automatic tube compensation in new-generation mechanical ventilators.
abstract: OBJECTIVE
  To compare performance of flow-adapted compensation of endotracheal tube resistance (automatic tube compensation, ATC) between the original ATC system and ATC systems incorporated in commercially available ventilators.
  
  
  METHODS
  Bench study.
  
  
  METHODS
  University research laboratory.
  
  
  METHODS
  The original ATC system, Dräger Evita 2 prototype, Dräger Evita 4, Puritan-Bennett 840.
  
  
  METHODS
  The four ventilators under investigation were alternatively connected via different sized endotracheal tubes and an artificial trachea to an active lung model. Test conditions consisted of two ventilatory modes (ATC vs. continuous positive airway pressure), three different sized endotracheal tubes (inner diameter 7.0, 8.0, and 9.0 mm), two ventilatory rates (15/min and 30/min), and four levels of positive end-expiratory pressure (0, 5, 10, and 15 cm H2O).
  
  
  RESULTS
  Performance of tube compensation was assessed by the amount of tube-related (additional) work of breathing (WOBadd), which was calculated on the basis of pressure gradient across the endotracheal tube. Compared with continuous positive airway pressure, ATC reduced inspiratory WOBadd by 58%, 68%, 50%, and 97% when using the Evita 4, the Evita 2 prototype, the Puritan-Bennett 840, and the original ATC system, respectively. Depending on endotracheal tube diameter and ventilatory pattern, inspiratory WOBadd was 0.12-5.2 J/L with the original ATC system, 1.5-28.9 J/L with the Puritan-Bennett 840, 10.4-21.0 J/L with the Evita 2 prototype, and 10.1-36.1 J/L with the Evita 4 (difference between each ventilator at identical test situations, p <.025). Expiratory WOBadd was reduced by 5%, 26%, 1%, and 70% with the Evita 4, the Evita 2 prototype, the Puritan-Bennett 840, and the original ATC system, respectively. The expiratory WOBadd caused by an endotracheal tube of 7.0 mm inner diameter was 5.5-42.2 J/L at a low ventilatory rate and 19.6-82.3 J/L at a high ventilatory rate. It was lowest with the original ATC system and highest with the Evita 4 ventilator (p <.025).
  
  
  CONCLUSIONS
  Flow-adapted tube compensation by the original ATC system significantly reduced tube-related inspiratory and expiratory work of breathing. The commercially available ATC modes investigated here may be adequate for inspiratory but probably not for expiratory tube compensation.
authors: Department of Internal Medicine, Hospital Langenthal, Switzerland.
authors: Serge
authors: S
authors: Elsasser
authors: Josef
authors: J
authors: Guttmann
authors: Reto
authors: R
authors: Stocker
authors: Georg
authors: G
authors: Mols
authors: Hans-Joachim
authors: HJ
authors: Priebe
authors: Christoph
authors: C
authors: Haberthür
mesh_terms: D004867:Equipment Design; D011175:Positive-Pressure Respiration / Q000379:methods*; D012122:Ventilators, Mechanical; D014939:Work of Breathing