The Science Journal of the American Association for Respiratory Care

2006 OPEN FORUM Abstracts

Respiratory monitor employing a load vs. tolerance strategy recommends appropriate pressure support ventilation settings: clinical validation study

Michael A. Gentile RRT FAARC, Chun-Cheih Yang MD,
John D. Davies RRT FAARC, Neil R. MacIntyre MD, FAARC
Duke University Medical Center , Durham , NC

Background: Assessments of respiratory muscle loads, reflected by power of breathing (work of breathing / min), and tolerance of these loads, reflected by spontaneous breathing frequency ( f ) and tidal volume (VT), are fundamental for patient management. Pressure support ventilation (PSV) should be adjusted so that muscle loads are not too high or low, predisposing to fatigue and atrophy. To address these conditions, we evaluated a respiratory monitor employing a fuzzy logic inference system using an artificial neural network for the non-invasive calculation of power of breathing (POBN),1  combined with f and VT to make recommendations for setting appropriate PSV. To validate these recommendations, we performed a clinical trial.

Methods: 30 adult patients (age 59 ± 16 yrs, wt. 92 ± 32 kg) receiving PSV were enrolled in an IRB approved study. Data from a combined CO2/flow sensor, positioned between the endotracheal tube and Y-piece of the ventilator breathing circuit, were directed to a monitor (NICO2, Respironics, Wallingford , CT ) and computer (Convergent Engineering, Gainesville , FL ) for measurements of POBN, f and VT. Recommendations from the monitor (to increase, maintain, or decrease PSV) for setting PSV were examined for validity (accuracy) by a clinical team (MD and RRT).

Results: The range of PSV for all subjects enrolled in the study was 5 - 25 cm H2O. There were a total of 94.5% agreements (p < 0.05); (79 agreements out of 84 recommendations) between all recommendations from the monitor when compared with those from the clinical team.

Conclusion: Valid recommendations for setting PSV to appropriately unload the respiratory muscles were provided by the monitor. A respiratory monitor employing a complimentary load (POBN) and tolerance (f and VT) strategy for assessing patients with respiratory failure provides clinically valid recommendations for setting PSV.

1. Banner et al, Crit Care Med 2006; 34: 1052 - 1059.

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