"Exercise intolerance in pulmonary arterial hypertension: insight into central and peripheral pathophysiological mechanisms." S. Malenfant, M. Lebret, É. Breton-Gagnon, et al. Eur Respir Rev 2021; 30: 200284

Abstract

Unfortunately, an error was made in labelling figure 4 of this manuscript. The solid black line should have been labelled “Fick principle” not “Fick Law”. The equation associated with this label should have read “Vʹ_O2=CO×P_a–vO2” not “Vʹ_O2=CO×a–vO₂ PO₂”. The corrected version of figure 4 is shown below.

FIGURE 4

The Wagner diagram. Oxygen uptake is plotted as a function of microvascular oxygen pressure. Black line: diffusive (Fick law) and convective (Fick principle) components that interact to determine peak oxygen uptake (Vʹ_O2peak). The Fick principle line is not straight because it directly represents the haemoglobin dissociation curve (greater haemoglobin O₂ affinity), resulting in a lower venous O₂ partial pressure [130]. The slope of the straight line (Fick law) is determined by the diffusing capacity of the muscles [130]. Red line: in patients with heart failure, a left-shifted haemoglobin dissociation curve (greater haemoglobin O₂ affinity), resulting in a lower venous O₂ partial pressure, and a lower slope of the Fick law line results in earlier bisection of both diffusive and convective components and reduced Vʹ_O2peak. P_a–vO2: arterio-venous difference in partial pressure of oxygen; D_O2: oxygen delivery; HFrEF: heart failure with reduced ejection fraction; P_O2: partial pressure of oxygen; CO: cardiac output.