Inspiratory muscle load and capacity in chronic heart failure

Background: Although breathlessness is common in chronic heart failure (CHF), the role of inspiratory muscle dysfunction remains unclear. We hypothesised that inspiratory muscle endurance, expressed as a function of endurance time (Tlim) adjusted for inspiratory muscle load and inspiratory muscle capacity, would be reduced in CHF. Methods: Endurance was measured in 10 healthy controls and 10 patients with CHF using threshold loading at 40% maximal oesophageal pressure (Poesmax). Oesophageal pressure-time product (PTPoes per cycle) and Poesmax were used as indices of inspiratory muscle load and capacity, respectively. Results: Although Poesmax was slightly less in the CHF group (−117.7 (23.6) v −100.0 (18.3) cm H2O; 95% CI −37.5 to 2.2 cm H2O, p = 0.1), Tlim was greatly reduced (1800 v 306 (190) s; 95% CI 1368 to 1620 s, p