The results of this study can be summarized as follows: (1) serum levels of NT–proBNP are not influenced by tidal volume size in patients without ARDS at onset of mechanical ventilation; (2) serum levels of NT–proBNP are dependent on the development of ARDS; and (3) serum levels of NT–proBNP are dependent on cumulative fluid balances, both in patients with and without HF, and on development of AKI. Here, NPPB is linked to acute kidney injury.