Ventilatory demand-capacity imbalance during incremental exercise in COPD: an in silico perspective

Exercise intolerance constitutes a key patient-oriented outcome in COPD [1]. There is mounting evidence that the so-called "ventilatory inefficiency" (as established by the linear minute ventilation (V'E) to carbon dioxide output (V'CO2) relationship during incremental cardiopulmonary exercise testing (CPET)) [2] has an important role in setting the limits of exercise tolerance in this disease [3]. The rationale is straightforward: the faster V'E increases (i.e. the steeper the V'E–V'CO2 slope), and the higher its resting value (~y-intercept) [2], the sooner V'E is expected to reach a lower compared to a higher maximum breathing capacity (MBC) [4]. Recognising that V'E close to MBC cannot be sustained for a prolonged period of time without intolerable dyspnoea [5], it can be hypothesised that peak work rate (WR) would change inversely with V'E–V'CO2 slope and intercept, but directly with MBC. Since the first two parameters are influenced by the fraction of V'E "wasted" in the physiological dead space and the "set-point" for the arterial partial pressure for carbon dioxide [2], whereas MBC is linked to the resting ventilatory capacity [6], it is not surprising that the exertional ventilatory demand–capacity relationship varies markedly among patients with COPD [7].

Source: European Respiratory Journal - September 16, 2020 Category: Respiratory Medicine Authors: Neder, J. A. Tags: Original Articles: Research letters Source Type: research