The Science Journal of the American Association for Respiratory Care

1999 OPEN FORUM Abstracts

PERFORMANCE CHARACTERISTICS DURING CPAP IN NEW GENERATION MECHANICAL VENTILATORS

Takeuchi M, Williams P, Muelver, M, Fujino Y, Goddon S, Kratohvil J, Ritz R, Hess D, Kacmarek RM. Anaesthesia and Respiratory Care, Massachusetts General Hospital and Harvard Medical School, Boston, MA

Many studies have evaluated the performance characteristics of ventilators during assisted ventilation. However, little information on performance during CPAP is available. We questioned if the currently available ventilators were responsive to inspiratory efforts and capable of meeting peak inspiratory flow demands without imposing an expiratory load. We evaluated the performance of seven new generation ventilators during CPAP.

Methods: The Bear 1000, Drager Evita 4, Hamilton Galileo, Nellcor Puritan-Bennett 740 and 840, Siemens 300A and Intermed T-Bird were evaluated, using a lung model with three peak inspiratory flows (40, 60 and 80 L/min) during CPAP of 10 cmH2O. The effects of flow trigger (F) and pressure trigger (P) were compared in 4 of these ventilators that have both triggering systems. Triggering was set as sensitive as possible without causing autocycling. Time (trigger delay, sec) and pressure (trigger pressure, cmH2O) to trigger the ventilator, airway pressure time product during inspiration (insp. area, cmH2O* sec), pressure difference between minimum airway pressure and maximum pressure (press. swing, cmH2O) and airway pressure time product during expiration (exp. area, cmH2O*sec) were calculated.

Results:

Bear Drager Galileo PB740 PB840 S300 T-Bird
trigger F 0.11±0.01* 0.10±0.01* 0.11±0.01* 0.07±0.00 0.06±0.01 0.08±0.02 0.09±0.01
delay P 0.09±0.01 - 0.12±0.01* - 0.08±0.00 0.07±0.00 -
trigger F 4.6±1.2* 4.5±1.4 5.8±1.7* 3.9±0.7 2.3±0.8 2.3±0.7 3.2±0.7
pressure P 5.5±1.4* - 5.9±1.7* - 3.1±0.6 3.4±0.4 -
insp. F -1.0±0.1* -0.8±0.6* 1.7±0.7 1.2±0.6 1.1±0.3 0.8±0.6 0.4±0.3
area P -0.3±0.3* - 1.6±0.8 - 1.2±0.2 0.8±0.6 -
press. F 11.0±3.9 9.8±2.5 19.2±4.3* 11.6±1.9 8.0±1.6 12.5±2.6 12.3±3.0
swing P 15.0±5.9* - 19.2±4.3* - 9.0±1.5 13.6±2.4 -
exp. F 1.6±0.6 1.8±0.7 8.0±0.7* 1.9±0.6 3.3±0.8 2.5±1.7 6.8±1.7*
area P 3.6±1.0# - 8.1±1.0* - 3.3±1.1 2.4±1.9 -
mean ± SD
*p < 0.05 vs PB840 flow trigger, #p < 0.05 pressure vs. flow trigger. (ANOVA followed by Scheffe test)

CONCLUSION: There was a large range of variability in performance characteristics during CPAP among new generation mechanical ventilators. In addition, in the Bear ventilator there were large differences between flow and pressure triggers.

OF-99-218

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