2012 OPEN FORUM Abstracts
A COMPARISON OF NON-INVASIVE PROPORTIONAL PRESSURE VENTILATION AND SPONTANEOUS/TIMED MODES ON TOTAL PATIENT INSPIRATORY WORK OF BREATHING IN A LUNG MODEL.
Michael V. Sajor, David L. Vines; Respiratory Care, Rush University, Chicago, IL
BACKGROUND: Proportional pressure ventilation (PPV) automatically adjusts support as patient effort varies. Spontaneous/Timed mode (BiPAP) delivers pressure at a set level without adjustment based on patient effort. To better understand the effect non-invasive PPV has on total patient inspiratory work of breathing (TPiWOB) versus the standard BiPAP mode, we compared TPiWOB, tidal volume (VT), peak inspiratory pressure (PIP), and mean airway pressure (MAP) between these modes using a two-compartment mechanical lung model (Michigan Instruments Inc., Grand Rapids, MI) to simulate spontaneous breathing. METHODS: TPiWOB was estimated using a CO2SMO plus monitor (Respironics California, Inc., Carlsbad, CA) as follows: TPiWOB= WOB(B+A) WOBB, where WOBB was first measured on lung B using tidal volumes of 300, 400, 500, 600 mL with peak flows of 40, 60, 80 L/min via a sine wave. WOB(B+A) was then measured at these settings using lung B to drive lung A with a compliance of 40 mL/cm H2O and a resistance of 2.7 cm H2O/L/sec, decreased compliance of 20 mL/cm H20), and increased resistance of 20 cm H2O/L/sec. Lung A received assistance from either CPAP of 5 cm H2O, BiPAP of 10/5 or 15/5 cm H2O, PPV at 50% or 80% using a Philips Respironics V60 Ventilator (Respironics California, Inc., Carlsbad, CA). Elastance and resistance were manually set on PPV at a level below which run away occurred. WOB, VT, PIP, and MAP were collected on the CO2SMO plus monitor as a 10 breath average. TPiWOB was converted from joules to joules per liter (J/L) based on the delivered tidal volume to lung A. An ANOVA with a post hoc test (Newman-Keuls) was used to determine significant differences (p < 0.05). RESULTS: See Table 1. CONCLUSIONS: PPV 80% significantly lowered TPiWOB and provided a higher VT and PIP compared to other modes tested under all conditions. The lowest driver volume used was 300 mL and results may differ in some of the individual conditions tested. The method used to set elastance and resistance needs further clinical investigation. Sponsored Research - None Table 1. Mean data for all conditions tested. a = Significantly less than CPAP b = Significantly less than BiPAP 10/5 c = Significantly less than BiPAP 15/5 and PPV 50% d = Significantly greater than CPAP e = Significantly greater than BiPAP 10/5 f = Significantly greater than BiPAP 15/5 g= Significantly greater than PPV 50%