[The effect of bilateral vagal blockade on respiration]

Although respiratory regulation has been extensively studied so far, the relation between the vagal nerves and respiratory reflex in man is still open to controversy. This paper describes the effect of bilateral vagal blockade on respiration. 1) Dyspnea due to unilateral bronchial occlusion. This type of dyspnea is caused by extreme depression of the intrabronchial pressure on the occluded side and is accompanied by a rapid increase in respiratory rate and a rapid decrease in tidal volume. This type of dyspnea is relieved by blockade of the ipsilateral cervical vagal nerve. 2) Animal experiments on bilateral lung transplantation, heart-lung transplantation and bilateral cervical vagal blockade. The respiratory changes induced by CO2 inhalation, low O2 inhalation, respiratory stimulant. Loss of blood or fever stimulation in the manipulated dogs were compared with those in normal controls. CO2 inhalation alone produced differences in the respiratory rates and tidal volumes between the two groups. The tidal volume increase under CO2 inhalation was suppressed by the inflation reflex but other afferent vagal nerves seemed to be closely associated with the increased respiratory rate. 3) Vagal nerve reflex in humans. Blockade of the bilateral cervical vagal nerves in an awake state resulted in irregular PETCO2 in cases that had been stable and sometimes produced a pattern of Cheyne-Stokes respiration. Inhalation of 5% CO2 restored the regular rhythm of respiration and enhanced the response to CO2. When subjected to bilateral vagal blockade in an awake state, the patient expressed an unbearbly uneasy dyspneic sensation as if he were pulled into a bottomless abyss. This was demonstrated by the unstable FRC level.