The Science Journal of the American Association for Respiratory Care

1996 OPEN FORUM Abstracts

INTERMITTENT AIRWAY GRAPHIC ANALYSIS (AGA) FAILS TO DETECT ADVERSE EFFECTS OF CONTINUOUS MECHANICAL VENTILATION (CMV)

Barbara G. Wilson, MEd. RRT. Pediatric Critical Care & Respiratory Care Services. Duke University Medical Center, Durham, NC.

Introduction: AGA displays patient-ventilator interactions in children by measuring tidal volume, pressure and flow at the endotracheal tube during CMV. AGA can be used to identify pulmonary overdistention (OD), intrinsic PEEP (PEEPi) and causes of patient-ventilator dys-synchrony (dys-sync). The purpose of this study was to determine the incidence of adverse ventilatory effects and examine the effects of continuous vs. intermittent AGA in mechanically ventilated children. Incidents of dys-synchrony were examined to identify the cause (e.g. trigger failure, inadequate inspiratory flow or excessive inspiratory time) Method: PICU RCPs had 3 years experience with AGA interpretation prior to this study. Practice standards were in place to examine AGA to identify adverse ventilatory effects and direct ventilatory strategies to correct effects. Twenty-eight CMV patients, 2 days to 15 years of age were studied. AGA was assessed daily by one investigator for the presence of OD, PEEPi and dys-sync. Thirteen patients received continuous AGA via a Bird VIP ventilator with Partner IIi and graphics monitor (Bird Products Corp., Palm Springs, CA). Fifteen patients received intermittent AGA monitoring via a "snapshot" study using a VenTrak Respiratory Mechanics Monitor (Novametrix Medical Systems, Inc., Wallingford, CT). The incidence of adverse events was compared in the two groups. Data was compared using chi square analysis, with p < .05 considered significant(^{*}). Results: Significant differences were found between groups for all adverse effects. 100% of dys-synchrony events were caused by trigger failure. The rate of pressure trigger failure was 92% (11/12)^{*} (p < .001) as compared to a flow trigger failure rate of 8% (1/12).

Int. AGA Cont. AGA p Value

Dys-Sync 9/36 (25%)* 3/32 (9%) .004

PEEPi 6/36 (17%)* 2/32 (6%) .004

OD 5/36 (14%)* 1/32 (3%) .005

Total 20/108 (19%)} 6/96 (6%) .001

Conclusions: Intermittent AGA fails to adequately identify adverse ventilatory effects. Failure of pressure triggers contributes greatly to patient-ventilator dys-synchrony in children. Continuous AGA monitoring is recommended to identify adverse ventilatory effects. PICU staff can then correct ventilatory strategies to minimize occurrence.

Reference: OF-96-114

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