The Science Journal of the American Association for Respiratory Care

1995 OPEN FORUM Abstracts

Comparison Of The Imposed Wob During Imv In Five Ventilators For Sub-Acute Care

Richard D. Branson, R.R.T. Kenneth Davis, Jr., M.D., and Jay A. Johannigman, M.D., Division of Trauma and Critical Care, Department of Surgery, University of Cincinnati Medical Center, Cincinnati, Ohio

INTRODUCTION: Sub-acute care for patients requiring long term weaning is a major growth industry. We studied the imposed work of breathing (WOB,) in 5 ventilators used for subacute care.

Methods: We simulated spontaneous breathing (SSB) using a two-chambered test lung at three tidal volume and flow combinations (200 mL at 30 L/min, 400 mL at 60 L/min, and 600 mL at 90 L/min) and at 0 and 5 cm PEEP. During SSB we connected the 5 ventilators (Aequitron LP-6 and LP-10, Bird TBird VS, LifeCare PLV-102, Puritan-Bennett 7200ae) to the experimental chamber in the IMV mode. A pneumotachograph and pressure tap were placed at the proximal airway and measurements of pressure, volume, and flow were recorded to a personal computer using a data acquisition system (Keithley DAS 16). From these signals the WOB, maximum negative pressure (Pmax), delay time (DT), and pressure time product (PTP) were calculated.

Results: All variables were significantly lower with the TBird VS and 7200ae. The WOB, through the three home care ventilators (LP-6, LP-10, PLV-100) was excessive. Table 1 shows data when V_T=400 mL, flow=60 L/min, and PEEP=0.

Delay Time Pmax WOBPTP

Ventilator(s) (cmH_2O)(J/L)(cmH_2O/s)

LP-60.63 (0.01)-5.9 (0.01) 0.30 (0.001) 2.3 (0.01)

LP-10 0.57 (0.01)-3.8 (0.06) 0.19 (0.002) 1.5 (0.02)

TBirdVS* 0.23 (0.02)# -1.6 (0.4)# 0.012 (0.002)# 0.13 (0.02)#

PLV-102 0.63 (0.01)-6.7 (0.04) 0.35 (0.003) 2.6 (0.02)

7200ae* 0.46 (0.06)-3.6 (1.3)0.07 (0.02) 0.60 (0.06)

Pmax = maximum negative pressure; WOB = work of breathing; and PTP =

pressure time product.

*All values statistically significant compared to LP-6, LP-10, PLV-102 (p < 0.001)

#Statistically significant vs 7200ae (p < 0.01)

CONCLUSION: The growing sub-acute care arena requires a ventilator capable of weaning long term ventilatory support patients. Our data confirm previous work demonstrating excessive WOBI with current home care ventilators. We also present a new ventilator with capabilities similar to an ICU ventilator (7200ae) in a package similar in size and weight to a home care ventilator.


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