Authors’ reply to the comment by Drs. Bellani and Musch

Excerpt

Sir: We thank Drs. Bellani and Musch for their comments regarding our recent contribution [1]. Their hypothesis of altered distribution of perfusion caused by different regional pulmonary vascular resistances is attractive, but it can neither be supported nor rejected by our study since we did not measure regional perfusion. However, although the correlation between oxygenation and the amount of nonaerated lung has been demonstrated previously [2], no such relationship has been proven for the changes in lung aeration and venous admixture. In fact we have shown that the fractional changes in venous admixture and PaO₂ are not correlated with the fractional change in nonaerated lung volume [3]. Thus the deterioration in oxygenation cannot be predicted by the increase in nonaerated lung as seen in the computed tomography. The mechanism by which the regional perfusion is diverted is still not fully understood, and the possibility that individuals may behave differently must at least be considered. …