NPPB and hydrops fetalis: Two reasons of this observation could be made: first, in an animal study performed on pacing induced HF rabbit, a reduction of peripheral chemoreceptor perfusion by carotid occlusion similar to the one obtained with cardiac output reduction (and potentially expressed by higher level of NT-proBNP), was associated with increased peripheral chemoreceptors, which are also responsive to CO2, thus contributing to HCVR [36,37].