Negative effects of increasing PEEP in injurious mechanical ventilation model?

Nike MML Stikkelbroeck   (2007-07-06 16:27)  University Medical Center Nijmegen

To the editor:

In their article about the effect of injurious mechanical ventilation in normal rat lung tissue, Pavone et al. (1) conclude that large change in lung volume (by high pressure/low PEEP ventilation) leads to unstable alveoli and pulmonary damage. They suggest that increasing PEEP is beneficial: it reduces tidal volumes, prevents alveolar instability and reduces tissue injury. We would like to argue that the results as presented in table 1, could even suggest the opposite: a detrimental effect of increasing PEEP.

First, it is not clear how the authors interpret the largely increased tidal volumes in the HP/LP group, compared to the HP/HP group. In our opinion, it is not likely that adding 7 cm H2O PEEP, reduces the tidal volume to such extent. The extremely large mean tidal volumes and the large standard errors (HP/LP) could rather suggest that the results of these measurements might be unreliable.

If the results in the HP/LP group would be left out of the analysis, the results from the control group and the HP/HP group can be compared. Both groups have similar (moderate) tidal volumes, and similar %I-E∆. The pathological studies, however, show more edema in the HP/HP compared to the control group. Based on this result, we would argue that, given an stable moderate tidal volume, increasing PEEP may have negative consequences.

(1) Injurious mechanical ventilation in the normal lung causes a progressive pathologic change in dynamic alveolar mechanics. Pavone et al Critical Care 2007 11: R64

MML Stikkelbroeck, MD PhD

JMM Verwiel, MD

JG van der Hoeven, MD PhD

Dept. of Intensive Care, University Medical Center Nijmegen, PO Box 9101, 6500 HB, Nijmegen, The Netherlands,

Competing interests

None declared

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