The Science Journal of the American Association for Respiratory Care

2001 OPEN FORUM Abstracts

COMPARISONOF TIDAL VOLUME (VT) STABILITY BETWEEN VOLUME CONTROL AND PRESSURECONTROL VENTILATION (VCV, PCV) USING THE NIH ARDS NETWORK?S LOW VTPROTOCOL

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RH Kallet MS RRT, JM LuceMD, Departments of Anesthesia, and Pulmonary Critical Care Medicine, San FranciscoGeneral Hospital (SFGH)

Background: SFGHhas commenced voluntary utilization of NIH ARDS Network low VT protocolfor clinical management of ALI/ARDS patients. The NIH ARDS Network low VTprotocol requires use of VCV to insure that VT does not exceed theclinical-set target range. However, our institution routinely uses pressure-targetedmodes of ventilation when managing ALI/ARDS patients. PCV allows VTaugmentation during either patient-triggered breaths, or conditions of improvedlung compliance. Therefore, we inquired whether VT could be adequatelycontrolled utilizing PCV during clinical management with the NIH ARDS Networkprotocol.

Methods: We revieweddata on 14 ALI/ARDS patients managed clinically with the NIH ARDS Network protocol.Four of 14 patients were managed with both ventilator modes on separate days.The corrected VT (minus compression volume loss) and VTin mL/kg was recorded for all status reports. In addition, the VTon the first ventilator status report of the day was used as the reference fordetermining average VT variability for that day. An average of 6ventilator status reports/day were generated and 2 days of data collection oneach mode was used for each patient. If adjustments in VT or pressurecontrol had been made, only data prior to the change was used on that day. Averagerelative VT variability/day (± D mL) was recorded. Data was analyzedusing unpaired Mann-Whitney tests. Alpha was set at 0.05.

Results: A totalof 166 ventilator status reports generated over 17 days of protocol managementwere reviewed. There were 104 reports over 15 days for VCV and 76 reports over12 days for PCV. Only 17% of the VCV reports and 5% of PCV reports occurredduring patient-triggered conditions.

VCVPCVp
VT(mL) 372 ± 64409 ± 950.0007
VT(mL/kg)5.67 ± 0.686.72 ± 1.02<0.0001
D VT(mL)15.3 ± 12.038.8 ± 19.40.0007
D VT(mL/kg) 0.24 ± 0.210.62 ± 0.320.0011

Conclusion: VTwas higher and more variable during PCV. However the VT variabilityduring PCV was similar to the average VT variability allowed by theARDS Network protocol (± 0.5 mL/kg). However, as the majority of measurementswere made during controlled ventilation conditions, these data may not reflectpatient-triggered ventilation conditions (i.e.: augmented VT deliveryduring PCV or double-triggering during VCV).

OF-01-132

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