Mean PAP is a flow-dependent variable. Despite well-known limitations of the model,36‐38,47 the mPAP-cardiac output linear relationship is the most popular way to describe pulmonary circulation. Studies from our group have documented major redundancy between mPAP on the one hand and sPAP,10,12 PA mean ejection pressure (Pej = 1.25 mPAP),48 and PA end-ejection pressure or notch pressure (Pnotch = mPAP)49 on the other hand. Such pressure redundancy has been also documented on exercise11,13,48 and during the Valsalva maneuver.49 Thus, it may be hypothesized that a single pressure-powered function is reflected in any of these four pressures (mPAP, sPAP, Pej, Pnotch), all reflecting the steady component of arterial load. As a result, it may be kept in mind that there exists a family of pressure-flow relationships using any of these four pressures. Conceptually, each representation is similar, in that the abscissa is mean cardiac output and the ordinate is some representative measure of the steady pressure component opposing to flow (mPAP, sPAP, Pej, Pnotch). This approach may be useful to describe the steady-state, time-independent coupling between the ventricle and its load.50 Both dPAP and PA pulse are also linearly related to mPAP,10‐13 with mPAP explaining approximately 90% of variance of the two pressures. However, the linear relationship appears slightly less strong, such that the small remaining part of dPAP and PA pulse pressure variance may be explained by mechanisms related to the pulsatile component of PA load.