Modulation of laryngeal and respiratory pump muscle activities with upper airway pressure and flow

The hypothesis that upper airway (UA) pressure and flow modulate respirator y muscle activity in a respiratory phase-specific fashion was assessed in a nesthetized, tracheotomized, spontaneously breathing piglets. We generated negative pressure and inspiratory flow in phase with tracheal inspiration o r positive pressure and expiratory flow in phase with tracheal expiration i n the isolated UA. Stimulation of UA negative pressure receptors with body temperature air resulted in a 10-15% enhancement of phasic moving-time-aver aged posterior cricoarytenoid electromyographic (EMG) activity above tonic levels obtained without pressure and flow in the UA (baseline). Stimulation of UA positive pressure receptors increased phasic moving-time-averaged th yroarytenoid EMG activity above tonic levels by 45% from baseline. The same enhancement of posterior cricoarytenoid or thyroarytenoid EMG activity was observed with the addition of flow receptor stimulation with room temperat ure air. Tidal volume and diaphragmatic and abdominal muscle activity were unaffected by UA flow and/or pressure, whereas respiratory timing was minim ally affected. We conclude that laryngeal afferents, mainly from pressure r eceptors, are important in modulating the respiratory activity of laryngeal muscles.