The Science Journal of the American Association for Respiratory Care

1999 OPEN FORUM Abstracts

COMPARISON OF WEANING PARAMETERS VIA EXTERNAL SPIROMETRY VERSUS CPAP/FLOW-BY MODE OF A MECHANICAL VENTILATOR.

Daniel Ray, M.D., Kenneth Miller, RRT, Thomas Wasser, PhD., Kathy Baker, RN, Marsha Becker, RRT, Frederick Wieand, RRT, Uma Bhatt, RRT Lehigh Valley Hospital. Allentown, PA, USA, 18105.

Weaning Parameters (WP) to assess readiness for liberation from mechanical ventilation are typically measured with a hand-held spirometer/manometer. Flow-by triggering on newer ventilators has allowed WP to be measured through the ?internal? circuitry of the ventilator. Objective: Determine differences between WP as measured by the external spirometer/manometer (EXT) compared to the ?internal? tachometer/manometer (INT) of the Purittan-Bennett(PB)7200 ventilator.

Methods: This study was conducted in a 16 bed intensive care unit (ICU). 67 sets of WP were measured by each method in 49 patients who underwent WP measurement as part of their medical care. WP measures included respiratory rate (f), tidal volume (Vt), minute ventilation (VE), Vital Capacity (EVC), maximal inspiratory pressure (MIP) and respiratory rate to tidal volume ratio (f/Vt). EXT and INT were measured sequentially in each patient so that patients served as their own controls. Paired t-tests were used to determine differences between methods.

Results: No significant differences (p>0.4) were found between INT and EXT WP methods for f (26.2 vs 24.6), Vt (.551 vs .611), VE (8.91 vs 8.71), EVC (1.1 l vs 1.01 l), or the f/Vt ratio (104 vs 103). The maximal inspiratory pressure (MIP) was significantly lower with the EXT method compared to the INT method (-21 cm H2O vs -32 cm H2O, p<.001). No adverse events were recorded. Conclusion: With the exception of MIP, obtaining weaning parameters through the internal circuitry of the PB7200 ventilator is safe and reliable. Additionally, it has the potential to decrease costs through reduced equipment use and may also reduce the risk of nosocomial pneumonia by maintaining a closed ventilation system.

The Dexter F. and Dorothy H. Baker Fund

OF-99-014

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