Values of the slope of VE vs VCO2 relationship, VEYint, RRYint and volume of dead space in heart failure patients (upper panel) and healthy subjects (lower panel) with 0 mL, 250 mL and 500 mL of additional dead space.

Data are presented as means ± SD; RRYint = respiratory rate calculated as Y intercept of RR vs VCO2 relationship; VCO2 = carbon dioxide production; VDYint = dead space volume calculated as VEYint/RRYint; VDmeas = dead space volume measured by PaCO2 in heart failure patients and estimated by PETCO2 in healthy subjects; VE = ventilation; VEYint = ventilation at VCO2 = 0, calculated as Y intercept of VE vs VCO2 relationship.†p§p*p&p$p©p