The Effect of High‐frequency Ventilation on Pattern of Breathing of Anaesthetized Rabbits

Abstract

SUMMARYThe lungs of anaesthetized rabbits were ventilated with a frequency of 30 Hz and a displacement of 5 ml. High-frequency ventilation (HFV) was superimposed on static inflation or deflation pressures of 2 5 and 5 cmH20 and was maintained for 10 s. Changes in pattern of breathing in response to this procedure were recorded before and during block of pulmonary stretch receptors by SO2. With lung stretch receptors intact apnoea or extended duration of expiration demonstrated the predominant role of pulmonary stretch receptors in the response to HFV. Block of stretch receptors exposed effects of other pulmonary afferents, presumably rapidly adapting receptors, during HFV, and demonstrated the influence of their sustained stimulation on pattern of breathing as augmented breaths and the reduction of duration of expiration. High-frequency ventilation may represent a useful experimental method of stimulating rapidly adapting receptors.

Heterogeneous activity of pulmonary vagal receptors during high-frequency oscillation ventilation

“…High-frequency oscillation ventilation (HFO) has been shown to induce a normocapnic vagally mediated apnea [24], and subsequent findings confirmed the Offprint requests to: Jana Kohl effect of vagal nerves in mediating other respiratory responses to HFO, such as lengthening of expiration, induction of tonic diaphragmatic activity, increase of breathing frequency, and elicitation of augmented breaths [2,3,5,8,25]. Therefore, information about vagal afferent activity during HFO was considered essential to understand the mechanisms underlying the effects of HFO on breathing control.…”

“…Therefore, reflex effects of both SAR and RAR stimulation may occur during HFO. Although the most often reported effect of HFO on respiration is SAR-mediated inhibition of spontaneous breathing, expressed as prolonged expiration, the maximum response being apnea [2][3][4]24], RAR-mediated excitatory effects expressed by induction of tonic diaphragmatic activity, increase of breathing frequency, and elicitation of augmented breaths were also observed during HFO [5,[8][9][10]25]. The resulting respiratory response to HFO depends obviously on the balance between SAR and RAR activity.…”