Functional sympatolysis in respiratory and locomotor muscles in patients with chronic obstructive pulmonary disease

• Grant number: 18/03501-4
• Support type: Scholarships in Brazil - Master
• Effective date (Start): November 01, 2018
• Effective date (End): April 30, 2020
• Field of knowledge: Biological Sciences - Physiology - Physiology of Effort
• Cooperation agreement: Coordination of Improvement of Higher Education Personnel (CAPES)
• Principal Investigator: Bruno Moreira Silva
• Grantee: Indyanara Cristina Ribeiro
• Home Institution: Escola Paulista de Medicina (EPM). Universidade Federal de São Paulo (UNIFESP). Campus São Paulo. São Paulo , SP, Brazil

Abstract

Patients with moderate-to-severe chronic obstructive pulmonary disease (COPD) have low blood flow in the intercostal and locomotor muscles during exercise, but the underlying mechanisms are unclear. Muscle blood flow adjustment during exercise depends on the balance between sympathetic vasoconstriction and local vasodilatory mechanisms, which is known as functional sympatholysis. However, this phenomenon tends to be altered in individuals who have high sympathetic activity and vascular dysfunction, which are characteristics of patients with COPD. Therefore the objective of this project is to test the hypothesis that patients with COPD present impaired functional sympatolysis in respiratory and locomotor muscles. Patients with COPD and healthy control subjects will be assessed under three conditions: i) rest (i.e., control), ii) isocapnic hyperpnea (i.e., increased respiratory muscle work), and iii) physical exercise on a cycle ergometer (i.e., increased work of respiratory and locomotor muscles). Ventilation during the isocapnic hyperpnea will be paired with the level observed during exercise. At end of each condition, a sympathoexcitatory maneuver will be conducted, which will consist of immersing one hand in cold water (1-3ºC). Circulating catecholamines will be quantified in a venous blood sample. The microvascular blood flow of intercostal and vastus lateralis muscles will be measured by near-infrared spectroscopy, associated with infusion of green indocyanine contrast, before and after the sympathoexcitatory maneuver, in each of the experimental conditions.