Reflex reversal of apnoeic episodes by electrical stimulation of upper airway in cats

Respiratory effects of electrical stimulation of the upper airways (UAW) before and during apnoeic episodes induced by nitrogen inhalation were studied in 9 anaesthetized cats. In eupnoeic animals these electrically-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 +/- 36 ml.sec-1) similar to the sniff-like aspiration reflex elicited mechanically. 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 transiently reduced. When repeated adequately, the electrically-induced reflexes can increase the reactivity of respiratory centre and interrupt or terminate apnoeic episodes as do other types of UAW stimulation. Reflex mechanisms and respiratory centre activations seem to be involved in these effects. The results suggest that electrical stimulation of UAW could be useful for testing the respiratory centre reactivity as well as for reflex reversal of apnoeic episodes and restoration of normal breathing in animal experiments and clinico-physiological studies. Such investigation of the role of UAW reflexes in the pathogenesis and therapy of apnoeic syndromes might also be possible by using a cardiostimulator adapted as respiratory pacemaker.