The Science Journal of the American Association for Respiratory Care

2005 OPEN FORUM Abstracts

POWER OF BREATHING AS A PREDICTOR FOR EXTUBATION FROM VENTILATORY SUPPORT

Steve Bonett RRT, Michael J. Banner PhD, Neil R. Euliano PhD, A. Joseph Layon MD, Luigi Viola MD, Andrea Gabrielli MD University of Florida, College of Medicine, Anesthesiology and Convergent Engineering, Gainesville, FL, USA

Introduction Power of breathing (POB), the rate at which work is done per minute, is a better assessment of respiratory muscle workloads than work of breathing per breath because it is a measure over time, not for an individual breath (normal adult POB range 4 - 8 Joule / min). Spontaneous breathing frequency (f), tidal volume (VT), f / VT ratio, minute ventilation (MV), PaO2 / FIO2 ratio, PaCO2, and sternocleidomastoid use (SCM) are used typically when evaluating a patient's readiness for extubation. We hypothesized that POB may be another parameter for predicting successful extubation. To test this hypothesis, we studied adults with respiratory failure who were candidates for extubation.

Methods Twenty-five adults (15 males, 10 females, age 56 ± 19 years, weight 80 ± 25 kg) were evaluated in an IRB approved study where POB was measured in real time and noninvasively (POBN), without the need of an esophageal balloon, using a monitor (NICO, Respironics, Convergent Engineering).1 Data from a combined pressure / flow sensor, positioned between the endotracheal tube (sizes ranged from 6 - 8 mm ID) and ventilator circuit, were directed to the monitor. All patients were studied immediately prior to extubation using minimal ventilator settings (intermittent mandatory ventilation 0 per min, pressure support ventilation 10 cm H20, continuous positive airway pressure 5 cm H2O, and FIO2 0.4). Data were analyzed using a Mann-Whitney U-test; alpha was set at 0.05 for statistical significance.

Results POBN ranged from 2 to 10 Joules / min for patients successfully extubated (n = 20) and 10 to 23 Joules / min for those failing extubation (n = 5), requiring re-intubation and ventilatory support. POBN was significantly lower and related breathing parameters where significantly different for patients successfully extubated (Table).

Data are mean ± SD. POBN (Joules / min), f (per min), VT (L), f / VT (breaths / min /L), MV (L/min), * < 0.05

Discussion POBN values > 10 Joules / min were associated with failed extubation. A critical value for POBN to predict successful extubation may be about 10 Joule / minute. A larger sample size is needed to thoroughly evaluate these pilot data findings for determining a critical value. POBN data coincided with typically used breathing parameters for assessing readiness for extubation, i. e., when f, VT, f / VT ratio, PaO2 / FIO2 ratio, and PaCO2 data were clinically acceptable and in the absence of SCM activity, patients were successfully extubated. It appears that POBN may be a parameter to consider for predicting extubation from ventilatory support.

1. Crit Care Med 2005; 32: A 107

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