The Science Journal of the American Association for Respiratory Care

2010 OPEN FORUM Abstracts

A COMPARISON OF PROPORTIONAL ASSIST VENTILATION AND VOLUME SUPPORT ON TOTAL PATIENT INSPIRATORY WORK OF BREATHING IN A LUNG MODEL.

David Vines1, Cherie Albertson2, Casey Reynolds-McCarty2; 1Respiratory Care, Rush University, Chicago, IL; 2Respiratory Care, UT Health Science Center San Antonio, San Antonio, TX

BBACKGROUND: In theory, proportional assist ventilation (PAV) will automatically adjust support as the total patient inspiratory work of breathing (TPiWOB) increases. Volume Support (VS) will adjust support to maintain an inspired tidal volume as lung mechanics vary. To gain a better understanding of the effect that PAV and VS has on TPiWOB, we compared TPiWOB between assisted-volume control (VC), pressure support ventilation (PSV), VS, and PAV using a two-compartment mechanical lung model (Michigan Instruments Inc., Grand Rapids, MI) to simulate spontaneous breathing. METHODS: TPiWOB was estimated using the Ventrak 1550 Respiratory Mechanics Monitoring System (Novametrix Medical Systems, Inc., Wallingford, CT) as follows: TPiWOB= WOB(B+A) – WOBB, where WOBB was first measured on lung B using tidal volumes of 200, 400, 600, and 800 mL with peak flows of 40, 60, 80, and 100 L/min via a sine wave. WOB(B+A) was then measured at these settings using lung B to drive lung A with normal compliance (0.05 L/cm H2O) and resistance (2.7 cm H2O/L/sec), decreased compliance (0.02 L/cm H20), and increased resistance (17.6 cm H2O/L/sec). Lung A received assistance from either VC with a fixed inspiratory flow 60 L/min and VT of 600 mL, PSV of 10, 15 or 20 cm H2O, VS at a target VT of 600 mL or PAV at 50% or 80% using a PB 840 (Covidien-Puritan Bennett, Boulder, CO) . 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 follow up test (Newman-Keuls) was used to determine significant differences. RESULTS: See Table. CONCLUSIONS: As expected TPiWOB decreased as PSV increased from 10 to 20 cm H2O. PSV at 20 cm H2O provided the lowest TPiWOB. Although the difference did not reach statisical significance, PAV 80% resulted in a lower TPiWOB compared to VS in this model. Sponsored Research - None a.significantly less than VC; b.significantly less than PSV+10; c.significantly less than VS; d.significantly less than PAV 50%; e.significantly less than PAV 80%; (p < 0.05)