The Science Journal of the American Association for Respiratory Care

2010 OPEN FORUM Abstracts


Olga Nazarenko, Robert L. Chatburn, Madhu Sasidhar; Respiratory Institute, Cleveland Clinic, Cleveland, OH

BACKGROUND: Leaks occur during ventilation and may cause a reduction in minute ventilation. Leaks may arise through a chest tube (CT) to treat a bronchopleural fistula. There are few data available to determine what affect mode of ventilation has on leaked volume. At least one study, of infant ventilation, suggests that pressure control ventilation (PC) is more efficient in maintaining minute ventilation than volume control ventilation (VC) in systems with endotracheal tube leaks (Respir Care 1996;41(8):728-735). The purpose of this study was to compare PC and VC using an adult model of ARDS in the presence of simulated CT leaks. We hypothesized that like the previous study, PC would be more favorable than VC. METHODS: We used an Ingmar ASL 5000 lung simulator (with Leak Module) set with a compliance = 35 mL/cm H2O, resistance = 3 cm H2O/L/s. A linear resistor (6 cm H2O/L/s) was attached to represent airway resistance above the leak. A 7.0 mm id endotracheal tube was connected between the resistor and the ventilator. The ventilator was a CareFusion Avea set to deliver conventional PC or VC at frequencies of 10, 20, and 30 breaths/min (bpm); baseline tidal volume ª 500 mL (with no leak). Flow (in VC) or inspiratory time (in PC) was adjusted with frequency to keep I:E ª 1:2. Mean and standard deviations (for 10 breaths) for expiratory tidal volumes (V) were calculated using the ASL Post Analysis feature. For each frequency, percent leak = 100% ¥ (Vno leak – Vleak) ÷ Vno leak. The study was conducted 3 times and mean values were compared one way ANOVA, with P < 0.05 considered significant. RESULTS: The data for percent leak are shown in the Figure. Percent leak for VC ranged from 2 to 7 times larger than PC. Leak decreased as frequency increased (P < 0.036) for VC (P = 0.017), but not PC. CONCLUSIONS: This bench study confirms the previous study of neonatal endotracheal tube leaks that pressure control preserves minute ventilation by decreasing percent leak better than volume control in the presence of simulated adult chest tube leaks. Furthermore, for volume control, increasing the frequency reduces the percent leak. Sponsored Research - None