Responses of pulmonary vagal mechanoreceptors to high-frequency oscillatory ventilation

The discharge of 57 slowly adapting pulmonary stretch receptors (PSR's) and 16 rapidly adapting receptors (RAR's) was recorded from thin vagal filaments in anesthetized dogs. The receptors were localized and separated into three groups: extrathoracic tracheal, intrathoracic tracheal, and intrapulmonary receptors. The influence of high-frequency oscillatory ventilation (HFO) at 29 Hz on receptor discharge was analyzed by separating the response to the associated shift in functional residual capacity (FRC) from the oscillatory component of the response. PSR activity during HFO was increased from spontaneous breathing (49%) and from the static FRC shift (25%). PSR activity during the static inflation was increased 19% over spontaneous breathing. RAR activity was also increased with HFO. These results demonstrate that 1) the increased activity of PSR and RAR during HFO is due primarily to the oscillating action of the ventilator and secondarily to the shift in FRC associated with HFO, 2) the increased PSR activity during HFO may account for the observed apneic response, and 3) PSR response generally decreases with increasing distance from the tracheal opening.