Role of chemoreceptors in mediating dyspnea

Abstract

Dyspnea, or the uncomfortable awareness of respiratory distress, is a common symptom experienced by most people at some point during their lifetime. It is commonly encountered in individuals with pulmonary disease, such as chronic obstructive pulmonary disease (COPD), but can also be seen in healthy individuals after strenuous exercise, at altitude or in response to psychological stress. Dyspnea is a multifactorial sensation involving the brainstem, cortex, and limbic system, as well as mechanoreceptors, irritant receptors and chemoreceptors. Chemoreceptors appear to contribute to the sensation of dyspnea in two ways. They stimulate the respiratory control system in response to hypoxia and/or hypercapnia, and the resultant increase respiratory motor output can be consciously perceived as unpleasant. They also can induce the sensation of dyspnea through an as yet undetermined mechanism–potentially via direct ascending connections to the limbic system and cortex. The goal of this article is to briefly review how changes in blood gases reach conscious awareness and how chemoreceptors are involved in dyspnea.

Validation of a three-factor measurement model of dyspnea in hospitalized adults with heart failure

“…60-65 Which stimuli and which pathways predominate at any given time may differ between diagnoses or even within diagnoses as clinical condition changes, but there is no compelling evidence that afferent or higher central nervous system pathways differ by diagnosis in patients with cardiopulmonary disease. 66-71 …”

Serotonin Neurons and Central Respiratory Chemoreception

“…However, one must be cautious in accepting those conclusions for several reasons. First, the 5-HT neurons that have been proposed to be respiratory chemoreceptors are in the medulla, not the dorsal raphe of the midbrain, although those in the midbrain may be important for arousal and anxiety/panic to hypercapnia (Buchanan and Richerson 2009, Buchanan and Richerson 2010). Second, the data obtained to make these conclusions were all from neurons in brain slices from P7-P12 mice, which is too young for a mature response.…”

Ventilation and Respiratory Mechanics

“…In this regard, afferents from intercostal muscles have been shown to project directly to the somatosensory cortex and convey proprioceptive and kinesthetic information (114,174). There is some evidence that increased chemoreceptor stimulation by added hypercapnia or hypoxia during exercise can directly influence the intensity of dyspnea, independent of the attendant increases in respiratory motor activity, but the magnitude and direction of this effect appears to be inconsistent across studies (80,297,556).…”