Effect of pulmonary congestion on vagal afferent activity

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Abstract
Pulmonary venous occlusion was shown to increase the activity of slowly-adapting pulmonary stretch receptors by mechanical alterations within the lung parenchyma. Two types of response were evident: a) stimulation throughout the respiratory cycle; b) stimulation only during low lung volumes. Pulmonary arterial occlusion caused both significant increases and decreases in fiber activity. Two fibers demonstrated cardiac-triggered impulses superimposed upon a basic respiratory rhythm, an effect dependent upon pulsation of the pulmonary arterial tree. The results of this investigation indicate a twofold responsiveness of the pulmonary stretch receptors, i.e. to the volume of air in the lungs and, to a lesser extent, to the degree of distention of the pulmonary vasculature. The latter effect is suggested as an important factor in the decreased depth of respiration during pulmonary congestion.