The Science Journal of the American Association for Respiratory Care

2009 OPEN FORUM Abstracts

EFFECT OF PRESSURE RISE TIME ON VOLUME DELIVERY WITH CHANGING PULMONARY MECHANICS

Teresa A. Volsko1, Gina McMonagle3,1, Shannon Cook2, Robert L. Chatburn2; 1Health Professions, Youngstown State University, Youngstown, OH; 2Respiratory Institute, The Cleveland Clinic, Cleveland, OH; 3Anesthesia Institute, The Cleveland Clinic, Cleveland, OH

BACKGROUND: During pressure controlled ventilation, the inspiratory pressure rise time (PRT) - the time it takes to reach the set peak airway pressure - may be operator adjusted. Available PRT settings vary among manufacturers and there are few data describing PRT performance. The purpose of this study was to compare the effects of PRT setting and lung mechanics on tidal volume delivery with a lung simulator. METHODS: The Ingmar Medical ASL 5000 was used to simulate a passive respiratory system with normal compliance (NC = 75 mL/cm H2O) and low compliance (LC = 12 mL/cm H2O). Airway resistance was 6 cm H2O/L/second for all experiments. Ventilators evaluated: PB 840 (Covidien Healthcare), Servo i (Marquet), Evita XL (Draeger Medical), G5 (Hamilton Medical) and the Avea (Cardinal Health). Ventilator settings: mode = pressure controlled continuous mandatory ventilation, frequency = 30/min, inspiratory time = 0.7 seconds, inspiratory pressure = 15 cm H2O above PEEP of 5 cm H2O. Inspiratory PRT was set at lowest and highest settings. The change in tidal volume (?VT) and time to reach 90% of peak inspiratory pressure (?T90) were the difference between low and high rise times. Mean ?VT and ?T90 were compared with t-test and ANOVA, P < 0.05 considered significant. RESULTS: T90 varied greatly among ventilators. At LC, T90 range was 38 ms (PB 840) to 260 ms (G5) for the shortest PRT settings. At NC the range was 147 ms (PB 840) to 267 ms (Avea). The table shows summary means and standard deviations (SD). Increasing PRT increased T90 and decreased VT (average about 18%) for all ventilators but to different degrees (P < 0.001). The effect on VT was magnified with NC compared to LC. CONCLUSIONS: Differences in design of pressure rise time algorithms among ventilators and differences in lung mechanics, lead to statistically significant and potentially clinically important effects on volume delivery. Sponsored Research - None

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