The Science Journal of the American Association for Respiratory Care

2000 OPEN FORUM Abstracts

VOLUME MONITORING ACCURACY OF CRADLE TO THE GRAVE VENTILATORS IN THE NEONATAL RANGE

Richard D. Branson BA, RRT, Robert S. Campbell RRT, FAARC. University of Cincinnati, Department of Surgery, 231 Bethesda Avenue, Cincinnati, OH

Background: In recent years, ventilators capable of operating in the neonatal to adult range (cradle to the grave) have been introduced. We evaluated the accuracy of tidal volume (VT) measurement of three of these ventilators during pressure control ventilation (PCV) compared to a traditional neonatal ventilator. Method: Four ventilators were studied: 1) Drager Babylog, 2) Drager E-4 with NeoFlow, 3) Siemens 300, and 4) Hamilton Galileo. All were set to deliver VTs of 4, 16, and 32 mL in the PCV mode. Changes in VTs were accomplished by increasing pressure or flow (Babylog). FIO2 was set at 0.60, PEEP at 4 cm H2O, and frequency at 28 breaths/min. Ventilators were connected to a neonatal test lung (Bio-Tek VT-1) set at compliance and resistance combinations of 1 mL/cm H2O, 3 mL/cm H2O, 20 cm H2O/L/s, and 50 cm H2O/L/s. VTs were measured with a calibrated, pneumotachograph (Hans Rudolph #001) and signals recorded to a PC for analysis using Excel. At each condition (3 VTs, 4 compliance & resistance combinations) the VT of 5 breaths were recorded from the calibrated system and the VT display of each ventilator. With the Siemens 300, tests were repeated with and without correction for circuit compliance of 0.25 mL/cm H2O. PIP was also recorded. Data were analyzed using a students T-test and bias and precision determined using the method of Bland and Altman. Percent error was calculated as actual VT -- measured VT/actual VT.

Results:
Table 1 shows results from a set VT of 4 mL, compliance of 1 mL/cm H2O, and resistance of 50 mL/cmH2O/L/s.

Actual VT VT ventilator PIP(cm H2O) % error
Babylog 4.0 ± 0.02 3.48 ± 0.08 9.1 ± 0.2 0.13
E-4 4.0 ± 0.01 4.04 ± 0.03 8.4± 0.3 0.01
Siemens 4.0 ± 0.08 4.46 ± 0.09 5.7 ± 0.6 0.11
Galileo 4.0 ± 0.03 5.40 ± 0.54 9.2 ± 0.04 0.35

Conclusions: Accuracy of VT measurement with each of the ventilators tested was good. There were differences in accuracy between instruments, but the clinical relevance of these differences would appear minor.

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