2002 OPEN FORUM Abstracts
IS VALI CAUSED BY PPLAT=35 CMH2O OR HIGH LUNG VOLUME EXCURSION?
Dana A Simonson BA, John R Hotchkiss MD, Alexander B Adams RRT, Sung Chul Lim MD, John J Marini MD, David J Dries MD. Regions HospitalÑHealthPartners, University of MN, St. Paul, MN.
Background: To avoid ventilator associated lung injury (VALI), plateau pressure should be maintained ² 32 cmH2O. Other workers report that lung volume excursion, or the opening and closing of lungs during ventilation, may contribute to or cause VALI. As the difference between plateau pressure and PEEP defines volume excursion, elevating PEEP reduces excursion and may protect against VALI.
Methods: Anesthetized pigs were placed on PCV, f=20/min, I:E=1:2 for six hours at Pset/PEEP settings of 20/3 (control), 35/15 (high pressure, low excursion), or 35/3 (high pressure, high excursion). ABGs, and pulmonary mechanics were continuously monitored. At study completion, wet weight/dry weight ratios (WW/DW) were determined.
Results: PaO2 and VT decreased with PCV = 35/3 but remained relatively unchanged for both 20/3 and 35/15. Edema, as measured by WW/DW, was increased with PCV of 35/3. Lung volume excursion or mean VT was greater for the PCV=35/3 group. The indicators of lung injury (WW/DW, DPaO2, DVT) were associated with a difference in VT, not a difference in Ppeak.
Conclusions: This report of preliminary data from a study of VALI finds the effect of increased excursions of pressure or volume to be important. Along with the elevated plateau pressure in the induction of lung injury, increased PEEP may decrease lung volume (and pressure) excursion and protect the lungs from VALI. AHA SDG 9930184N; NIH SCOR 50152