(Chest. 1999;116:16S-17S.)
© 1999
American College of Chest Physicians
Optimal Positive End-Expiratory Pressure Fails to Preserve Nonrespiratory Lung Function in Acute Lung Injury*
K. Creamer, MD;
L. McCloud;
L. Fisher, MD and
I. Ehrhart
*
From the Medical College of Georgia, Vascular Biology Center, and Pediatric Critical Care, Augusta, GA.
Correspondence to: Kevin Creamer, MD, Pediatric Critical Care, Children's Medical Center, 1446 Harper St, Augusta, GA 30912
 |
Introduction
|
|---|
Our
objective
was to test the hypothesis that optimal positive end-expiratory
pressure (PEEP) would diminish the manifestations of lung injury.
|
Materials and Methods
|
|---|
Isolated dog lungs were perfused with blood and mechanically
ventilated with a ventilator (model 900C; Siemens-Elema AB; Solna,
Sweden). Ventilation was performed with PEEP (4.6 ± 1 cm
H2O) and tidal volume (10.7 ± 9 mL/kg) determined
individually for each lobe, to keep end-expiratory lung volume above
closing volume and to avoid overdistention. Three groups were followed
up with serial measures of lung injury, which included static
compliance (Csta), WBC counts with differentials, and pulmonary
vascular resistance. In addition, indexes of endothelial function were
performed using first-pass metabolism of tritiated benzoyl-Phe-Ala-Pro
([3H]-BPAP), a substrate of angiotensin-converting
enzyme. [3H]-BPAP was used to measure dynamically
perfused surface area and percent metabolism by pulmonary vascular
endothelium. After 1 h of stable perfusion and ventilation,
baseline measurements were obtained. The injury and intervention groups
were then injured with phorbol myristate acetate (0.1 µg/mL of
perfusate), a potent neutrophil and platelet activator. Ten minutes
after injury, the intervention group had the PEEP increased to optimal
PEEP (mean 10 ± 4 cm H2O), as determined by
pressure-volume curves of previously injured lobes. Forty minutes after
injury, follow-up measurements were taken. Results for each group were
compared vs baseline and vs control with t tests and
analysis of variance.
|
Results
|
|---|
The control group remained in stable condition throughout the
experiment. Although optimized PEEP allowed preservation of Csta in the
intervention group, it failed to blunt other manifestations of lung
injury (Table 1)
.
All measures of nonrespiratory function worsened in both injury and
intervention groups.
|
Conclusions
|
|---|
Optimal PEEP preserves respiratory function as measured by Csta
but does not blunt the effects of acute lung injury on the other
functions of the lung. This study highlights the distinction between
respiratory and nonrespiratory functions of the
lung.
TOP
Introduction
Materials and Methods
