The Science Journal of the American Association for Respiratory Care

2001 OPEN FORUM Abstracts

COMPARISON OF PERFORMANCECHARACTERISTICS FOR PROPORTIONAL ASSIST VENTILATION (PAV) IN TWO DIFFERENT VENTILATORS.A LUNG MODEL STUDY.

K. Suchodolski, G. Schettino,K.A. Sedeek, D. Hess and RM. Kacmarek. Harvard Medical School and MassachusettsGeneral Hospital, Boston, MA.

Proportionalassist ventilation (PAV) is a new mode of mechanical ventilation, devised toincrease airway pressure in proportion to patient effort. . This is accomplishedby a positive feedback control that amplifiers airway pressure proportionallyto instantaneous inspiratory flow rate and volume. Since PAV may soon becomean available option to treat patients with respiratory failure, the presentlung model study was designed to compare the function of PAV under a varietyof loading conditions in two ventilators: Evita-4 (Dräger) and Vision (Respironics).

Methods: A two-compartmentspontaneously breathing LM (Michigan, TTL model 1600) was used. One chamberof the LM (resistance of 5 H2O/l/sec, compliance of 80 ml/cm H2O)was connected to the tested ventilator, the second was driven by a Puritan Bennett7200 ventilator to simulate the following spontaneous breathing pattern: TI=0.8 sec, RR of 12 breath/min, and peak inspiratory flow of 60 l/min. We comparedthree different levels of PAV 80%, 50% and 30% on each tested ventilator.

Results: Data (mean± SD) are listed in following table.

Volume (ml)Peak Press (cm H2O)Peak Flow. (l/min)Flow after 0.1 sec (l/min)PTP (cm H20á sec/min)
Vision PAV 80%620 ± 014.3 ± 0.2105 ± 164.9 ± 1.14.6 ± 0.3
Evita-4 PAV 80%650 ± 019.0 ± 0.1108 ± 121.2 ± 0.418.0 ± 0.4
Vision PAV 50% 600 ± 09.8 ± 088 ± 1 62.2 ± 3.1 5.7 ± 0.1
Evita-4 PAV 50% 610 ± 012.6 ± 095 ± 1 25.4 ± 0.619.2 ± 0.3
Vision PAV 30% 580 ± 0 7.6 ± 079 ± 064.6 ± 1.88.3 ± 0.2
Evita-4 PAV 30% 580 ± 09.0 ± 0 87 ± 025.8 ± 0.221.2 ± 0.3

Fig.1: Pressure and flow waveforms for Vision and Evita-4 at PAV of 80%

Conclusions: During all settings of ventilatory support (PAV 80-30%) PTP was lower with the Vision ventilator as a result of higher flow acceleration and better trigger performance.

OF-01-221

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