Pathophysiology of dyspnoea

 

The process 

 

 The respiratory centre is responsible for the coordination of muscles involved in respiration which includes the diaphragm, accessory muscles and intercostal muscles. It receives sensory information i.e pH, pO2 and pCO2  or stretching of respiratory muscles from central and peripheral chemoreceptors as well as vagal afferents which is subsequently combined with emotional factors to be processed by the cortex. 

 

Increased resistance

Pulmonary vagal afferents receive information from receptors located in the aortic and carotid bodies, medulla, lungs, diaphragm and chest wall. Dyspnoea arises when there is mismatch in the information between the need for ventilation (afferent) and actual respiration (efferent) i.e the ventilatory need is not met by respiration due to weakened respiratory muscles or increased resistance .

 

 Furthermore, in the lungs, 3 types of stretch receptors are present; fast reacting stretch receptors (involved in the modulation of inspiration), slow reacting stretch receptors (sensitive to irritants and mechanical stimuli) and C fibre receptors (sensitive to changes increased fluid build up between cells). Activation of mechanoreceptors due to irritants or oedema produces afferent input to the cortex to result in the sensation of dyspnoea.