2005 OPEN FORUM Abstracts
VENTILATION VARIABILITY USING FLOW-INFLATING VERSUS SELF-INFLATING MANUAL RESUSCITATORS IN A NEONATAL LUNG MODEL:
John Salyer RRT, Don Foubare RRT. Respiratory Care Department. Children's Hospital and Regional Medical Center, Seattle WA.
Introduction: Our growing understanding of the role of over-distention in the development of lung injury has led to changes in the way patients are ventilated, including close attention to limitation of tidal volumes (VT). Yet little attention seems to be paid to tidal volumes during manual ventilation, particularly in pediatrics. Investigators have shown more consistent ventilation is achieved with self-inflating versus flow-inflating bags (Pediatr Res 1997;13:312-316 & AJDC 1987;141:761-763). Yet, in our experience many hospitals continue to employ flow-inflating resuscitators, and many clinicians continue to favor them. We sought to compare variability of ventilation during use of different types of manual resuscitators on a pediatric test lung in a group of respiratory therapists from a pediatric hospital.
Methods: A pediatric test lung (Ingmar Adult-Pediatric) was used which had compliance adjusted to @ 1.5 mL/cmH2O and displayed both airway pressure and a visual analog for chest wall motion. Test subjects were 5 neonatal-pediatric respiratory therapists. Years experience, mean = 13.1 years, SD = 11.2, median = 12.7, range 1.1 to 26.8 years. Each subject was asked to manually ventilate the test lung to PIP = 30 cmH2O, PEEP = 5 cm H2O, f = 30/min for 2 minutes. This process was repeated for 3 different resuscitators, Mercury disposable self-inflating (M), Vent Labs disposable self-inflating (V), Rusch non-disposable flow-inflating (R). The M & V bags were equipped with disposable spring-loaded PEEP valves. VT, PIP, and PEEP were measured at the proximal airway with a computerized pneumotachometer (Cosmo, Novametrix Inc), which was calibrated in accordance with manufacturer's recommendations. Data were acquired with a PC using software designed for use with the Cosmo (Analysis Plus, Novametrix). Mean differences were tested using ANOVA with significance established as P < 0.05. Results: Mean values + SD are shown in the table at left. Differences in delivered PIP between bag types were neither clinically important nor statistically significant (P = 0.08). Differences in delivered VT and PEEP were statistically significant (P < 0.001 for VT and PEEP). Both self-inflating bags produced better (tighter) distributions of VT than the flow-inflating bag tested (see figure at above). The percent of delivered breaths that were > 50 mL were M = 2.8%, V = 8.6% and R = 25.3%. The percent of breaths where PEEP > 2 < 7 cm H20 was M = 85.0%, V = 67.9% and R = 77.1%.
|M||31.3 + 5.5||38.0 + 8.6||5.9 + 1.4|
|R||31.4 + 3.5||38.6 + 12.1||5.6 + 2.0|
|V||30.2 + 6.7||35.3 + 11.6||4.9 + 2.3|
Discussion: There are clearly differences in ventilation variability using self-inflating versus flow-inflating bags. We have also shown that different brands of self-inflating bags produce considerably different ventilation variability. The bag with the least ventilation variability seems to be the Mercury disposable self-inflating bag. In terms of volume variation, both self-inflating bags performed better than the flow-inflating bag.