2001 OPEN FORUM Abstracts
Doeshigh level minute ventilation yEdemand limit implementation of the acute respiratory distress syndrome (ARDS)Network low VT ventilation protocol?
RH Kallet MS RRT, W CorralBSN, D Hayden MA, H Silverman MD, JM Luce MD. NHLBI ARDS Clinical Trials Network,San Francisco General Hospital, University of Maryland Medical Center. (NIHR01-HL51856)
Background:Because the ARDS Network low VT protocol places an upper limit of35 on the set respiratory rate, there also is an upper limit of pre-set yEthat can be achieved when the VT is reduced to 6 mL kg. Thismay present a potential difficulty in implementing the protocol in patientswith high yE demand. We retrospectively assessed the potential forhigh yE demand to limit the achievement of protocol goals by analyzingdata from the ARDS Network low VT study.
Methods: Allpatients randomized to the low VT ventilation protocol were assignedto 3 groups based upon the level of yE demand prior to randomization:yE < 15 L/min, 15-18 L/min, and > 18 L/min. The pH, PaCO2,PPLAT, VT from the reference period on study day 1(approximately6-24 h after randomization) were compared between groups.
Pair-wise multiplecomparisons between the yE groups were made using Tukey-Kramer tests.Between-group differences in variables (in terms of being within or outsideprotocol target range) was analyzed by Chi Square Tests. Alpha was set at 0.05.
Results: No differenceswere found in VT, PPLAT , PaCO2 and arterialpH when the yE < 18 L/min. When yE was >18 L/min, pH was significantly lower than the other groups and VTwas significantly higher than the lowest yE group. The incidenceof PPLAT exceeding the upper protocol limit (30 cm H2O)was nearly doubled when yE exceeded 18 L/min 23.8% vs. 14.1%), butwas not statistically different. The incidence of VT exceeding theupper protocol limit (> 6.5 mL/kg) was significantly higher as yEexceeded 15 L/min (13.7% at < 15 L/m vs. 26 and 30.3% at 15-18 and > 18L/m respectively).
|yE Group||Variable||Pre-enrollment||Day 1|
< 15 L/m
|VT (mL)||10.1 ± 2.0||6.1 ± 0.8|
|PPLAT(cmH2O)||29.0 ± 7.4||24.5 ± 6.5|
|PaCO2(mmHg)||37.8 ± 7.6||40.2 ± 8.8|
|pH||7.40 ± 0.07||7.39 ± 0.08|
15-18 L/m )
|VT (mL||10.1 ± 1.9||6.3 ± 0.9|
|PPLAT(cmH2O)||30.8 ± 8.1||25.6 ± 5.7|
|PaCO2(mmHg)||36.1 ± 8.2||40.3 ± 11.1|
|pH||7.39 ± 0.08||7.38 ± 0.07|
> 18 L/m
|VT (mL)||10.4 ± 1.9||6.5 ± 1.3*|
|PPLAT(cmH2O)||31.8 ± 8.3||26.3 ± 7.7|
|PaCO2(mmHg)||30.8 ± 7.8||37.9 ± 14.0|
|pH||7.37 ± 0.08||7.33 ± 0.09?*|
p< 0.01; ? p < 0.001 compared to Day 1 yE < 15 L/mGroup
Conclusion: TheARDS Network study data suggest that despite very high levels of yE(> 18 L/min) demand, low VT ventilation could be maintained inthe majority of patients.