The Science Journal of the American Association for Respiratory Care

1998 OPEN FORUM Abstracts

RESPONSIVENESS OF THE T-BIRD VS VENTILATOR COMPARED TO THE BIPAP ST/D 30: A BENCH TEST STUDY.

Michael D. Coutts, RRT,. Vancouver Hospital & Health Science Centre, Vancouver, British Columbia, Canada

Introduction: As the use of noninvasive pressure targeted ventilators (PTV) continues to increase, different studies will be conducted to ensure that use of these machines is appropriate. There have been studies that indicated that there is potential for CO_{2} built up in the single limb circuit of a PTV. Also, all of the PTV's available do not have a built in battery system which make them difficult to be used for patient transports. The T-Bird VS Ventilatory System incorporates an internal battery and uses a dual limb circuit. The purpose of this study is to determine and compare the responsiveness of the T-Bird VS, for the use of noninvasive ventilation, to the Respironics Bipap ST/D 30. Methods: A two chambered lung model was used with one side of the chamber connected to the testing machines and the other chamber connected to a ventilator to be used to simulate patient effort. The T-Bird VS was set in the Cpap mode with PEEP of 4 cmH_{2}O and Pressure Support of 6 cmH_{2}O. The ST/D 30 was set at Epap of 4 cmH_{2}O and Ipap of 10 cmH_{2}O. Responsiveness was tested at 30, 60, and 90 L/min. Responsiveness was also test during oxygen titration at 30 L/min with 5 L/min oxygen, 60 L/min with 10 L/min oxygen and 90 L/min and 15 L/min oxygen. Response time (Tr), rise time and maximum negative deflection below baseline (Pneg) were determined. Statistical analysis was done by ANOVA with differences considered significant when p < 0.05. Results: During the oxygen titration testing the T-Bird had a significantly shorter Tr, rise time and higher Pneg (p < 0.05). However, during the inspiratory demand tests with no oxygen titration the T-Bird VS had a significantly longer Tr and higher Pneg at 60 L/min (p < 0.05). At 90 L/min the T-Bird VS had a significantly longer Tr (p < 0.05). Mean values at ventilator flowrates of 60 L/min and 90 L/min are listed below.

ST/D 30 T-Bird VS ST/D 30 T-Bird VS

60 L/min 60 L/min 90 L/min 90 L/min

Rise Time 183±12* 338±13 262±12 238±23

(msec)

Tr (msec) 153±15 133±22 148±29 # 187±14

Pneg -.69±0.04$ -1.14±0.05 -1.27±0.02 -1.45±0.14

(cmH_{2}O)

*p < 0.05 ST/D 30 significantly shorter rise time vs T-Bird VS

#p < 0.05 ST/D 30 significantly shorter Tr vs T-Bird VS

$p < 0.05 ST/D 30 significantly lower Pneg vs T-Bird VS

Conclusions: As the data indicates there are significant responsiveness differences between the machines tested. From a bench test perspective it appears that the T-Bird VS can be used as a noninvasive PTV. However, the T-Bird VS was not tested with a leak in the system. In the clinical setting it is sometimes difficult to maintain a leak free environment when using noninvasive ventilation. Further studies need to be done on the T-Bird VS to determine whether it can be used in the clinical setting when there are leaks in the circuit due to mask interface.

The 44th International Respiratory Congress Abstracts-On-Disk®, November 7 - 10, 1998, Atlanta, Georgia.

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