2001 OPEN FORUM Abstracts
DETERMINATIONOF OPTIMAL SETTINGS FOR HIGH PRESSURE RECRUITMENT MANEUVERS (RM) IN AN ARDSSHEEP MODEL.
K. Suchodolski,K.A. Sedeek, G. Schettino, M. Takeuchi and RM. Kacmarek. Harvard Medical School and MassachusettsGeneral Hospital, Boston, MA.
Animal data and preliminarypatient data clearly suggest that the use of lung RM can markedly improve PaO2levels. However, controversy regarding the approach and the need to optimizelung RM still exists. Based on data from a previous study1 whichshows greatest recruitment at PIP of 60 in contrast to 40 cm H2Owe compared 3 high pressure RM (PIP of 60 cm H2O) with 3 differentPEEP levels.
Methods:This study was designed as a Cross-Over Study. Saline lung lavage injury wasperformed in 8 sheep (30.5±2.1 kg) until PaO2 decreased to 63±2.5mm Hg at an FiO2 of 1.0 and PEEP of 5 cm H2O(BL). Each RM consisted of a maximum of three successive high pressure ventilationperiods (HPVP) for 60 sec, RR of 10/min, I:E 1:1; RM-1): PEEPof 25 and PIP of 60 cm H2O RM-2): PEEP of 35 and PIPof 60 cm H2O, RM-3): PEEP of 45 and PIP of 60 cm H2O.Each HPVP was followed by protective ventilation (PV): RR of 30/min, I:E 1:1,PIP of 35 cm H2O, PEEP LIP + 2 or 22 if LIP was 21 cm H2O.A successful RM was defined as a PaO2 400 mm Hg after 5 min. Aftereach RM and 20 min of PV the lung was derecruited to the BL. The order of RMswas randomized in each animal.
Results:During RM-1 HPVP was performed 11x; during RM-2 9x; during RM-3 13x. Oneanimal developed a pneumothorax. There was no statistical difference betweenthe three RM regarding: PaO2, PaCO2, Vt, bloodpressure, heart rate and cardiac output.
Fig1:PaO2 levels after RM during PV (mean ±SD for all animals)
Conclusion:High pressure RM is not affected by PEEP, if the PEEP level is high enoughto avoid collapse of recruited lung (PEEP LIP). We considered RM-1 optimal becauseof the lower mean airway pressure.
Reference:1. Y. Fujino at al.: Repetitive high-pressure recruitment maneuvers requiredto maximally recruit lung in a sheep model of acute respiratory distress syndrome.Crit Care Med 2001 Vol.29 No. 8 (in press)