2006 OPEN FORUM Abstracts
OPEN LUNG APPROACH (OLA) USING CONVENTIONAL MECHANICAL VENTILATION (CMV) OR HIGH FREQUENCY OSCILLATION (HFO) IMPROVES OXYGENATION AND COMPLIANCE IN ARDS BETTER THAN THE ARDSNET PROTOCOL
Maria Paula Caramez MD, Mohamed
Helmy MD, Eriko Miyoshi MD, R. Scott Harris MD, Atul Malhotra MD,
Robert M. Kacmarek PhD, RRT. Massachusetts General Hospital,
Brigham and Women’s Hospital, and Harvard Medical School. Boston, Massachusetts
Background: Approaches to
protective ventilation focus on different aspects of lung mechanics. We
questioned if an approach that maintains persistent atelectasis would
differ in outcome compared to the open lung approach with either CMV or
HFO.
Methods: Lung injury was produced by bilateral saline lung
lavage in
21 female Dorset sheep.
Following lung injury 7 animals were randomized into the following groups 1) OLA-CMV 2)
OLA-HFO and 3) ARDSnet. Groups 1 and 2 received a recruitment maneuver (PIP
50 cmH2O/PEEP 20 cmH2O) followed by a decremental
PEEP trial to determine optimal PEEP or mean airway pressure (MAP). Optimal
PEEP was defined as the PEEP level below which a 10 % fall from the maximum
PaO2+PaCO2 was observed. Once PEEP/MAP was set the
FIO2 was decreased until the PO2 was 60 to 100 mmHg.
VT in ARDSnet and OLA-CMV were 6 ml/kg. In all groups fluid was
administered to maintain cardiac output equivalent to baseline. The ARDSnet
group was ventilated according to protocol. All animals were ventilated for
5 hours.
Results: At the end
of the ventilation period we found differences in PEEP (p<0.05),
compliance (p=0.002), PaO2/FIO2 (p
<0.05), and cardiac output (p=0.06).
ARDSnet had the lowest PEEP (7 ± 4 cmH2O), highest FIO2 (0.51) and lowest compliance (7 ml/cmH2O), OLA-CMV the
highest PEEP (18 ± 2 cmH2O), lowest FIO2 (0.28) and highest compliance (17 ml/cmH2O).
HFO had the lowest CO 2.7 L/min vs. 3.7 l/min OLA-CMV vs. 4.8l/min ARDSnet.
Pathology and cytokine analysis are underway.
Conclusions: The use of
permissive atelectasis vs. an open lung approach results in markedly
different gas exchange, lung mechanics and cardiac output.
Funding
in part by Maquet.