REFLEX REVERSAL OF APNEIC EPISODES BY ELECTRICAL-STIMULATION OF UPPERAIRWAY IN CATS

Respiratory effects of electrical stimulation of the upper airways (UA W) before and during apnoeic episodes induced by nitrogen inhalation w ere studied in 9 anaesthetized cats. In eupnoeic animals these electri cally-evoked reflexes comprise rapid and powerful inspiratory efforts characterized by strong maximal airway occlusion pressures (Pmax = 635 +/- 39 mm H2O) and rapid peak inspiratory flow rates (PIF = 536 +/- 3 6 ml.sec(-1)) similar to the sniff-like aspiration reflex elicited mec hanically. Electrical stimulation of the UAW mucosa can elicit reflex inspirations and sniff-like aspiration reflexes even during reversible hypoxic apnoea but their intensity and reproducibility are transientl y reduced. When repeated adequately, the electrically-induced reflexes can increase the reactivity of respiratory centre and interrupt or te rminate apnoeic episodes as do other types of UAW stimulation. Reflex mechanisms and respiratory centre activations seem to be involved in t hese effects. The results suggest that electrical stimulation of UAW c ould be useful for testing the respiratory centre reactivity as well a s for reflex reversal of apnoeic episodes and restoration of normal br eathing in animal experiments and clinico-physiological studies. Such investigation of the role of UAW reflexes in the pathogenesis and ther apy of apnoeic syndromes might also be possible by using a cardiostimu lator adapted as respiratory pacemaker.