The Science Journal of the American Association for Respiratory Care

2003 OPEN FORUM Abstracts


Using a dual control mode of ventilation in the neonatal/pediatric age range: Validation studies in four ventilators

Giulia Mesiano, RRT, Krishna Mullahoo, RRT, Michael Davis, MD.
Montreal Children's Hospital, McGill University Health Centre, Montreal, Quebec, Canada

AIM: With the advent of fifth generation ventilators, dual control modes are becoming popular in the pediatric setting. A bench study to validate the accuracy of measured tidal volume (Vt) and peak inspiratory pressure (PIP) of four ventilators that offer this mode was performed.

Methods:
Four ventilators (Siemens Servo 300, Tyco Healthcare Puritan Bennett 840, Viasys Avea, Dräger Evita 4) were used to ventilate a neonatal test lung (Manley neonatal lung simulator, Online Medequip Ltd). The ventilator circuit used was a dual heated wire circuit (Allegiance Airlife-Infant) with a Fisher & Paykel MR290 humidifier chamber (dry and unheated). Circuit compliance (Ccirc) = 1.1 ml/cmH2O. Identical dual control parameters were used in the neonatal/pediatric range: PRVC (Servo300, Avea), VC+ (PB840), Vol SIMV autoflow in Neomode (Evita4). RR 30 bpm, Set Vt: 30 ml., PEEP 5 cmH2O, Ti: 0.50 sec., Flow cycle:0, Rise Time: 50%, FiO2: 0.21. The test lung was ventilated with Clung set at 1.0 and 0.5 ml/cmH2O. Displayed Vt was recorded. Delivered Vt was measured using a stand alone Infant PFT system (Raytech Instruments, Vancouver) placed proximal to the neonatal lung simulator.

RESULTS:
In all ventilators, there was a significant difference (p<0.01) in measured Vt and PiP when lung compliance was changed from 1.0 to 0.5 ml/cmH20. None of the ventilators tested were able to deliver the target tidal volume, even though all other set parameters were consistent.

CONCLUSION:
Simulation of a clinical change in lung compliance resulted in significant changes in delivered tidal volumes. There was great variability between ventilators in regards to their pressure-saving strategies. This may be due, in part, to fundamental operating differences in set tidal volumes between these ventilators.   

Test Recording Format:
C = 1 ml/cmH2O C = ml/1 cmH2O  C = 0.5 ml/cmH2O C = ml/1 cmH2O  C = 1 ml/cmH2O

 VC  PRVC  PRVC  PRVC VC

  Vte PIP Vte PIP Vte PIP Vte PIP Vte PIP
Servo300 14.2* 20.2 * 13.9 20.2 9.2 24.6 15.8 21.8 14.2 * 20.3 *
Avea     10.8 18 7.3 20.1 10.8 18.2 10.6 17
PB840 18.9 23.7 18.7 23.6 15.2 33.2 21.1 25.9    
Evita4     26.8 31.8 20.7 44.7 31.0 35.3    


* = square wave

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Using a dual control mode of ventilation in the neonatal/pediatric age range: Validation studies in four ventilators