Author: Jonathan V. Roth, M.D.
Anesthesiology 12 2016, Vol.125, 1253-1254.
The results of the study of management of one-lung ventilation by Blank et al. suggest that adequate positive end-expiratory pressure (PEEP) is an important factor in reducing pulmonary complications. Blank et al.1 provide an excellent discussion of the mechanical mechanisms and implications. I suggest an alternative or additional possible explanation of the beneficial effects of PEEP. The ventilated lung is subjected to increased blood flow, and this hyperemia may create additional shear stress, resulting in damage to the endothelial glycocalyx, which can then result in clinically significant respiratory complications.2–4 Studies support the concept that increased pulmonary blood flow may induce lung injury or aggravate a preexisting injury state.5–9 PEEP to the ventilated lung may reduce this hyperemia and hence reduce complications. Lower tidal volumes and the resultant reduced inspiratory pressure may result in more hyperemia, thus offsetting any potential beneficial effect of the expected reduced volutrauma. If we find a way to protect the glycocalyx or otherwise reduce the hyperemia to the ventilated lung, it is possible that lower tidal volumes may have a net beneficial effect. Larger tidal volumes to the ventilated lung may increase inspiratory pressure, resulting in less hyperemia and less damage to the glycocalyx, but damage from volutrauma could still occur.
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