Relieving dyspnoea by non-invasive ventilation decreases pain thresholds in amyotrophic lateral sclerosis

BackgroundDyspnoea is a threatening sensation of respiratory discomfort that presents many similarities with pain. Experimental dyspnoea in healthy subjects induces analgesia. This ‘dyspnoea-pain counter-irritation’ could, in reverse, imply that relieving dyspnoea in patients with chronic respiratory diseases would lower their pain thresholds.MethodsWe first determined pressure pain thresholds in 25 healthy volunteers (22–31 years; 13 men; handheld algometer), during unloaded breathing (BASELINE) and during inspiratory threshold loading (ITL). Two levels of loading were used, adjusted to induce dyspnoea self-rated at 60% or 80% of a 10 cm visual analogue scale (ITL6 and ITL8). 18 patients with chronic respiratory failure due to amyotrophic lateral sclerosis (ALS) were then studied during unassisted breathing and after 30 and 60 min of non-invasive ventilation—NIV30 and NIV60—(same dyspnoea evaluation).ResultsIn healthy volunteers, pressure pain thresholds increased significantly in the deltoid during ITL6 (p