Neuromuscular blockade enhances phrenic nerve activity during high-frequency ventilation

Abstract

Phrenic nerve activity was monitored in anesthetized cats during high-frequency ventilation (HFV). Rhythmic phrenic discharge disappeared during HFV in all animals at normal arterial PCO2 [CO2 partial pressure] levels. Rhythmic activity returned after neuromuscular blockade in the vagally intact animal. Although vagotomy alone also restored phrenic discharge, this activity was further enhanced by subsequent neuromuscular blockade. Evidently, apnea during HFV results from inspiratory inhibition mediated by both chest wall and vagal afferent mechanisms.