Effects of chest wall vibration on breathlessness during hypercapnic ventilatory response

Vibratory stimulation applied to the chest wallduring inspiration reduces the intensity of breathlessness, whereas thesame stimulation during expiration has no effect or may increasebreathlessness. The purpose of the present study was to determinewhether vibration reduced the intensity of breathlessness duringprogressive hypercapnia with and without the addition of an externalresistive load. A second objective was to see whether the mouthocclusion pressure at 0.2 s(P_0.2) was reduced by thevibratory stimulation. Hypercapnic ventilatory response was conductedin 10 healthy male volunteers with simultaneous measurement of visualanalog scale, P_0.2, and minuteventilation. Hypercapnic ventilatory response was performed andrandomly combined with or without vibratory stimulation (100 Hz) aswell as with or without inspiratory load. With inspiratory load,in-phase vibration did not cause any significant changes in the slopesof P_0.2 and minute ventilation toCO₂, whereas the slope of visualanalog scale to CO₂ significantlydecreased from 0.47 ± 0.15 to 0.34 ± 0.11 (SE) cm/Torr(P < 0.05). We conclude thatin-phase vibration could decrease the slope of breathlessness elicitedby inspiratory load combined with hypercapnia without changing motoroutput.