Although dyspnoea has been shown to attenuate pain, whether different forms of dyspnoea exert a similar inhibitory effect on pain has never been tested. We examined the effects of two different forms of dyspnoea, i.e., "air hunger" sensation (AIR HUNGER) and "work/effort" sensation (WORK/EFFORT), on pain induced by a cold-pressor test. Dyspnoea was induced by two different dyspnoea stimuli (i.e., AIR HUNGER and WORK/EFFORT stimuli) and the magnitudes of both sensations were evaluated by using a visual analogue scale (VAS). At equi-dyspneic VAS levels of two different forms of dyspnoea, pain was induced and the unpleasantness of pain was assessed by pain VAS, pain threshold time (PTT) and pain endurance time (PET). Both AIR HUNGER and WORK/EFFORT caused an increase in PTT and an increase in PET or a decrease in maximal pain VAS. Our findings suggest that AIR HUNGER and WORK/EFFORT exert a similar analgesic effect although the WORK/EFFORT-induced analgesia was slightly more effective.
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