Fig. 2
From: Cardiopulmonary exercise testing and echocardiographic exam: an useful interaction
The VE/VCO2 slope during ramp incremental exercise in a normal subject (a) and in a patient with mild (b) and moderate (c) heart failure. A reduced ventilatory efficiency is present in heart failure expressed by a steeper VE/Vco2 slope when compared with that of a normal subject. VE = Ventilation; VCO2 = Volume of exhaled carbon dioxide; HF = Heart failure patient