Chest wall distortion and discharge of pulmonary slowly adapting receptors

Abstract

We assessed the effects of chest wall distortion, changes in lung volume, and abolition of airway smooth muscle tone on the discharge patterns of 92 pulmonary slowly adapting receptors (SAR) in decerebrate, spontaneously breathing cats. Distortion resulted from their inspiratory efforts against an occluded airway at functional residual capacity and at increased end-expiratory lung volumes. Approximately 40% of SAR increased discharge frequencies during occlusions. Modulation of SAR discharge during occlusions persisted after administration of atropine to eliminate airway smooth muscle tone. Phasic modulation of SAR discharge was eliminated during no-inflation tests after paralyzing the cats and ventilating them on a cycle-triggered pump. We conclude 1) parasympathetic modulation of airway smooth muscle tone makes no obvious contribution to SAR discharge in spontaneously breathing cats; 2) the no-inflation test (withholding of lung inflation during neural inspiration) in paralyzed and ventilated cats is a valid test for the presence of projections from SAR to medullary respiratory neurons; and 3) in the absence of tidal volume changes, distortion stimulates some SAR. Sensory feedback from receptors in the lung, not just those in the chest wall, may therefore provide information about abnormal chest wall configurations.

A Joint Computational Respiratory Neural Network-Biomechanical Model for Breathing and Airway Defensive Behaviors

“…Pulmonary stretch receptors (PSRs) became more active with increasing lung volume V (membrane bias = 0.5 V mV/%VC) and mediated the Hering–Breuer reflex. Deflation-sensitive lung receptors were also implemented (Paintal, 1955; Luck, 1970; Wei and Shen, 1985; Iscoe and Gordon, 1992; Bergren and Peterson, 1993; Matsumoto et al, 2002; Yu et al, 2003). A low threshold population (Def_1, membrane bias = − 0.225( V  − 70) mV/%VC) and its afferent pathway introduced in Poliaček et al (2011) was used to represent a class of possible network mechanisms for generating an inhibitory bias on E-Dec neurons.…”

“…A higher threshold “distortion” (Dis_1) receptor population (cf. Iscoe and Gordon, 1992) excited the ELM population when lung volume was below FRC (membrane bias = −1.75( V  − 10) mV/%VC if V  < 10, 0 otherwise). We note that the synaptic strength and firing rates of this speculative Dis_1 population, added for development purposes in other work (Hutchison and Lindsey, 2009), resulted in negligible modulation of ELM population activity under the conditions of the present study (see “Influence of Some Added Network Connections”).…”

Respiratory-related evoked potentials elicited by inspiratory occlusions in double-lung transplant recipients

“…As the inspiratory muscles contract against the closed airway, there is a large negative pressure change in mouth, resulting in decompression of the gas within the lung and trachobronchial tree. It has been found by several studies that vagal afferent played a role in response to inspiratory airway occlusion (6,19,35). Afferent projections from the vagus nerve to cerebral cortex have been found in both cats and monkeys (26).…”

Phrenic motoneuron discharge during sustained inspiratory resistive loading

“…Although there are no data to support or refute this hypothesis, the smaller inspired volumes, lower flows, and reduced end-expiratory lung volumes during IRL (19) should all cause less SAR feedback. However, the increased transpulmonary pressures during IRL and distortion of the rib cage associated with breathing against loads are associated with activation of SAR with atypical discharge patterns (15), the effects of which on phrenic motoneuron discharge are unknown.…”