A comparison of methods to identify open-lung PEEP.
OBJECTIVE
Many methods exist in the literature for identifying PEEP to set in ARDS patients following a lung recruitment maneuver (RM). We compared ten published parameters for setting PEEP following a RM.


METHODS
Lung injury was induced by bilateral lung lavage in 14 female Dorset sheep, yielding a PaO(2) 100-150 mmHg at F(I)O(2) 1.0 and PEEP 5 cmH(2)O. A quasi-static P-V curve was then performed using the supersyringe method; PEEP was set to 20 cmH(2)O and a RM performed with pressure control ventilation (inspiratory pressure set to 40-50 cmH(2)O), until PaO(2) + PaCO(2) > 400 mmHg. Following the RM, a decremental PEEP trial was performed. The PEEP was decreased in 1 cmH(2)O steps every 5 min until 15 cmH(2)O was reached. Parameters measured during the decremental PEEP trial were compared with parameters obtained from the P-V curve.


RESULTS
For setting PEEP, maximum dynamic tidal respiratory compliance, maximum PaO(2), maximum PaO(2) + PaCO(2), and minimum shunt calculated during the decremental PEEP trial, and the lower Pflex and point of maximal compliance increase on the inflation limb of the P-V curve (Pmci,i) were statistically indistinguishable. The PEEP value obtained using the deflation upper Pflex and the point of maximal compliance decrease on the deflation limb were significantly higher, and the true inflection point on the inflation limb and minimum PaCO(2) were significantly lower than the other variables.


CONCLUSIONS
In this animal model of ARDS, dynamic tidal respiratory compliance, maximum PaO(2), maximum PaO(2) + PaCO(2), minimum shunt, inflation lower Pflex and Pmci,i yield similar values for PEEP following a recruitment maneuver.
Caramez
Maria Paula
MP
Department of Anesthesia and Critical Care, and Respiratory Care, Massachusetts General Hospital, Boston, MA, USA.
Kacmarek
Robert M
RM
Helmy
Mohamed
M
Miyoshi
Eriko
E
Malhotra
Atul
A
Amato
Marcelo B P
MB
Harris
R Scott
RS
D000818:Animals; D001696:Biomechanical Phenomena; D001784:Blood Gas Analysis; D045853:Exhalation; D005260:Female; D055370:Lung Injury / Q000628:therapy*; D011175:Positive-Pressure Respiration; D012756:Sheep; D007507:Therapeutic Irrigation / Q000379:methods; D013990:Tidal Volume