We read with interest the article entitled 'Benefit of a single recruitment maneuver after an apnea test for the diagnosis of brain death' by Paries and colleagues .
The 'ideal' apnea test (AT) should permit an increase in PaCO2 (partial pressure of carbon dioxide in arterial blood) but prevent a detrimental decrease in PaO2 (partial pressure of oxygen in arterial blood). We agree that a recruitment maneuver (RM) after the AT can improve oxygenation and result in protection of donor organs. However, we have two comments.
First, changes in PaCO2 are not reported in the article. It has been shown that RM can affect CO2 elimination in different ways . We think that the course of - already elevated - PaCO2 after RM would be of interest, and may also have clinical consequences. The structure of the study is appropriate to report the changes in PaCO2.
Second, we have shown in an animal model that a RM prior to AT followed by apneic oxygenation was associated with an increase in PaO2 without affecting the increase in PaCO2. RM plus apneic oxygenation also improved the survival time during AT, and there was no change in PaCO2 (which is a warranted result).
We think that the 'optimal' method for the AT should also consider changes in PaCO2. A RM before (likewise after) the AT could prevent hypoxemia. Whether a 'combination' of RM's before and after the AT would have additive effects should also be examined in further clinical studies.
AT: apnea test; PaCO2: partial pressure of carbon dioxide in arterial blood; PaO2: partial pressure of oxygen in arterial blood; RM: recruitment maneuver.
The authors declare that they have no competing interests.