Background Dyspnoea 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.
Methods We 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).
Results In healthy volunteers, pressure pain thresholds increased significantly in the deltoid during ITL6 (p<0.05) and ITL8 (p<0.05) and in the trapezius during ITL8 (p<0.05), validating the use of pressure pain thresholds to study dyspnoea-pain counter-irritation. In patients with ALS, the pressure pain thresholds measured in the deltoid during unassisted breathing decreased by a median of 24.5%–33.0% of baseline during NIV30 and NIV60 (p<0.05).
Conclusion Relieving dyspnoea by NIV in patients with ALS having respiratory failure is associated with decreased pressure pain thresholds. Clinical implications have yet to be determined, but this observation suggests that patients with ALS could become more susceptible to pain after the institution of NIV, hence the need for reinforced attention towards potentially painful diagnostic and therapeutic interventions.
- Non invasive ventilation
- Perception of Asthma/Breathlessness
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TS and CM-P are co-last authors.
Contributors LD, LL, TS and CM-P conceived the study design and the experimental plan. LD, LL, MG, JG-B, CM-P contributed to data acquisition and analysis. LD, CM-P and TS drafted and elaborated the manuscript. IR supervised the statistical analysis. All authors contributed to the final version of the manuscript and approved it.
Funding Study was supported by the non-profit Association pour le Développement et l'Organisation de de la Recherche en Pneumologie et sur le Sommeil, a grant Legs Poix from the Chancellerie de l'Université de Paris, Paris, France’ and by the programme ‘Investissement d'Avenir ANR-10-AIHU 06’ of the French Government.
Competing interests None declared.
Ethics approval Comité de Protection des Personnes Ile-de-France 6, La Pitié-Salpêtrière.
Provenance and peer review Not commissioned; externally peer reviewed.