Chemoreflex function in pulmonary diseases - A review.

The chemoreflex is a vital protective reflex that is crucial in restoring normal blood gas and pH levels. The carotid bodies are peripheral chemoreceptors activated by hypoxia (primarily), hypercapnia, acidaemia, temperature, lactate and potassium fluctuations. They are crucial for maintaining physiological conditions based on underlying causes and blood gas abnormalities. Central chemoreceptors in the brain stem are responsive to hypercapnia and contribute to blood gas regulation. Chemoreceptors regained attention during the SARS-CoV-2 (COVID-19) pandemic, potentially contributing to disease severity. In conditions like chronic intermittent hypoxia, chemoreflex sensitization may lead to respiratory disorders, impacting quality of life. There has been substantial research/evidence linking chemoreflex dysfunction to cardiovascular illnesses such as heart failure and hypertension. However, little emphasis has been placed on the role of the chemoreflex in mediating cardiopulmonary dysfunction during and after pulmonary disorders such as acute lung injury. The current review summarizes recent advances in the study of chemoreflex malfunction and the underlying mechanisms in acute and chronic lung diseases such as COVID-19 infection, chronic obstructive pulmonary disease, asthma, obstructive sleep apnoea and acute lung injury.