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

The Science Journal of the American Association for Respiratory Care

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

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.

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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