1999 OPEN FORUM Abstracts

EVALUATION OF THE EFFECT OF ENDOTRACHEAL TUBE LEAK ON THE PERFORMANCE OF THE HAMILTON GALILEO VENTILATOR IN THE ADAPTIVE SUPPORT VENTILATION MODE IN THE PEDIATRIC SETTING

Kenneth F. Watson MS RRT, Eman S. Al-Khadra MBBS, John E. Thompson RRT, John Arnold MD. Children's Hospital, Boston, MA

Background: We evaluated the response of the Hamilton Galileo ventilator in the adaptive support ventilation (ASV) mode at four patient weight settings to increasing percentages of endotracheal tube leak.

Methods: A Hamilton Galileo ventilator operating in the ASV mode was attached to a DB&M Products Infant Lung Simulator. Ideal body weights (IBW) from 5 to 20 Kg in increments of 5 Kg were set. An appropriate size endotracheal tube was selected for each weight. A V% setting of 100 per cent, PEEP of 5 cm H₂O, and lung/thorax compliance of 3 mL/cm H2O were maintained. An adjustable valve was placed distal to the ventilator/endotracheal tube connection to simulate leaks. A heated wire pneumotach was placed between the ventilator and the endotracheal tube connections to measure leak percentage. Leaks from 10 to 50 per cent were evaluated in 5 per cent increments. Delivered and exhaled tidal volumes were measured distal to the leak using a pressure differential pneumotach. We evaluated the actual value and percentage change from baseline value of expired tidal volume and minute volume distal to the leak for each IBW setting, endotracheal tube size, and leak percentage. P value was calculated at each leak increment for the decrease in expired minute volume from the baseline value.

Results: At an IBW setting of 5 Kg, minute volume did not decrease significantly from the baseline value (P ³ 0.05) at leaks as high as 50 per cent. At IBW settings of 10, 15, and 20 Kg, minute volume began to show significant decrease (P £ 0.05) at 35, 25, and 20 per cent leaks respectively. Therefore, proportionally larger decreases in expired minute ventilation were noted at larger IBW settings for a given percentage of leak.

Conclusions: For a patient weight range up to 15 Kg and an endotracheal tube leak less than or equal to 25 per cent, minute ventilation decrease in the ASV mode was not statistically significant. In patients whose IBW is 5 Kg, minute volume was statistically unaffected by leaks as high as 50 per cent. Although clinical investigation is warranted, ASV may be a desirable mode in small pediatric patients with a sizeable endotracheal tube leak.

OF-99-107