The Science Journal of the American Association for Respiratory Care

2009 OPEN FORUM Abstracts

DIAPHRAGMATIC ELECTRICAL ACTIVITY MONITORING UNMASKS BREATH-CYCLE ASYNCHRONY DURING CONVENTIONAL MECHANICAL VENTILATION

Daniel D. Rowley1, Stuart M. Lowson2, Frank J. Caruso1; 1Pulmonary Diagnostics & Respiratory Therapy Services, University of Virginia Medical Center, Charlottesville, VA; 2Anesthesiology, University of Virginia Medical Center, Charlottesville, VA

BACKGROUND: It has been reported that up to 27% of spontaneously breathing adult patients experience pneumatically triggered breath-cycle asynchrony (BCA) while on conventional modes of mechanical ventilation (MV). Clinicians commonly use airway pressure and flow scalar graphics to identify BCA objectively. Varying clinician skill levels and patient monitoring limitations may contribute to unrecognized and under reported BCA prevalence. An advancement in mechanical ventilation technology permits detection of BCA by measuring and displaying cyclic diaphragmatic EMG (Edi) signals and corresponding airway pressure waveforms simultaneously. We evaluated this technology to determine if Edi monitoring can be used to identify pneumatically triggered BCA during conventional modes of mechanical ventilation. METHOD: 16 adult MV patients were identified prospectively for BCA assessments if they were spontaneously breathing with an Edi catheter inserted. Scalar graphics were recorded and 10 sequential breaths were randomly selected and examined for asynchrony. Asynchrony was determined visually by comparing and identifying differences in corresponding Edi and airway pressure waveform morphology. Differences in waveform morphology at the beginning or end of a breath-cycle was considered an asynchrony. RESULTS: All 16 patients experienced delayed breath-cycle trigger (64%) and delayed inspiratory cycle-off (84%) asynchrony. Asynchrony existed during volume A/C (n= 7) and PSV (n= 9) modes regardless of flow or pressure triggering. 5 patients experienced ineffective breath-cycle triggering despite detectable Edi activity; 3 patients triggered breaths with minimal or no Edi activity; 1 patient triggered breath assistance for 8 of 10 breaths before Edi activity was detected. Refer to table. CONCLUSION: In a study of ventilated patients examining pressure and flow graphics, Thielle et al reported that significant asynchrony (defined as asynchrony in > 10% of breaths) was present in 25% of patients. The authors stated that more sensitive forms of respiration monitoring, such as diaphragmatic EMG, would likely detect an even greater incidence of asynchrony. Our data confirms their hypothesis. Using NAVA preview as a monitoring tool, significant asynchrony was present in all ventilated patients we assessed. Future studies should evaluate Edi measurement trends to determine if proportional changes in Edi peak and Vt measurements are predicive of extubation readiness. Sponsored Research - - Edi catheters were provided by Maquet.

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