de Courson H, Ferrer L, Cane G, et al. - Using pulse contour analysis (ProAQT®, Pulsion Medical System, Germany), researchers assessed the least significant change (ie, the minimal change that needs to be measured by a device to recognize a real change) of cardiac index, stroke volume index, stroke volume variation and pulse pressure variation obtained. Participants in the study were 50 mechanically ventilated patients undergoing neurosurgery in the operating room. For cardiac index, stroke volume index, pulse pressure variation and stroke volume variation, the least significant changes statistically differed over time. Least significant changes for cardiac index ranged from 1.3 to 0.7%, for stroke volume index from 1.3 to 0.8%, for pulse pressure variation from 10 to 4.9% and for stroke volume variation from 10.8 to 4.3%. The results obtained from the observational study indicate that pulse contour analysis is capable of detecting rapid and small changes in the index of cardiac and stroke volume, but the definition of rapid and small changes in pulse pressure variation and stroke volume variability must be carried out with care.