title: Analgesic effects of dyspnoea: "Air hunger" does not inhibit the spinal nociception reflex in humans.
abstract: Dyspnoea has distinct sensory modalities, including air hunger and the sensation of excessive breathing "work/effort". Both have analgesic properties. In the case of work/effort, spinal mechanisms have been documented (inhibitory effect on the spinal nociceptive flexor reflex, RIII). This mechanism involves C-fibres. As C-fibres are unlikely to play a major role in air hunger, we hypothesised that inducing this type of dyspnoea would not result in RIII inhibition. Eight healthy volunteers were exposed to a hypercapnic hyperoxic gas mixture (5% CO2 and 95% O2) and asked to voluntarily fight the corresponding ventilatory reflex response by reducing tidal volume below its spontaneous level. Ventilatory variables and dyspnoea intensity (ordinal scale) were measured. Electromyography of the biceps femoris was used to record the amplitude of RIII in response to painful electrical sural nerve stimulation. Air hunger failed to inhibit the RIII reflex. We conclude that the mechanisms of air hunger induced analgesia do not include a spinal contribution and are therefore mostly central.
authors.affiliation: Assistance Publique - Hôpitaux de Paris, Service de Pneumologie et Réanimation Médicale, Groupe Hospitalier Pitié Salpétrière, Paris, France; Université Paris 6, ER10UPMC, Paris, France. Electronic address: capucine.morelot@psl.ap-hop-paris.fr.
authors.forename: Capucine
authors.initials: C
authors.lastname: Morélot-Panzini
authors.forename: Julien
authors.initials: J
authors.lastname: Mayaux
authors.forename: François
authors.initials: F
authors.lastname: Hug
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Willer
authors.forename: Thomas
authors.initials: T
authors.lastname: Similowski
mesh_terms: D000328:Adult; D000698:Analgesia; D002245:Carbon Dioxide / Q000008:administration & dosage; D004417:Dyspnea / Q000139:chemically induced / Q000503:physiopathology*; D004576:Electromyography; D005260:Female; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology; D008297:Male; D009433:Neural Inhibition; D059225:Nociception / Q000187:drug effects / Q000502:physiology*; D012018:Reflex / Q000187:drug effects; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology*
chemical_list: D002245:Carbon Dioxide
keywords: Air hunger; C-fibres; Dyspnoea; Nociceptive flexor reflex; Pain