Electrical percutaneous tibial stimulation modulates within-a-breath respiratory drive in man

A sharp intake of breath followed by a strong vocalisation is widely observed in response to acute pain although its function and mechanism is poorly understood. This study investigated the effect of percutaneous (overlying the tibial bone) electrical stimulation delivered early (20-30% of inspiratory time) during inspiration (INSP) or expiration (EXP) (20-30% of expiratory time) at sensory intensities at (100%), above (125%) and below (50% and 75%) the pre-determined pain threshold (PT), upon within-a-breath respiratory parameters (via pneumotachography). All INSP stimulation intensities provoked significant inspiratory time shortening thereby elevating mean inspiratory flow. Tidal volume, but not peak flow was increased in response to 100% PT and 125% PT stimulation (vs. PRE). Shortening and increased tidal volume combined to evoke significant mean inspiratory airflow increments. In contrast, EXP stimulation failed to evoke any effect. Thus, our study provides evidence of a within-a-breath inspiratory-specific, augmentory response to noxious stimulation.