Autonomic and cerebrovascular abnormalities in mild COPD are worsened by chronic smoking

Abstract

Patients with chronic obstructive pulmonary disease (COPD) may develop hypercapnia and hypoxia, two main determinants of cerebral blood flow. The current authors tested whether cerebrovascular regulation was altered in mild COPD, modified by manoeuvres acutely improving autonomic cardiovascular modulation or influenced by smoking habit. In 15 eucapnic normoxic mild COPD patients (eight smokers) and 28 age-matched controls (14 smokers), midcerebral artery blood flow velocity (MCFV), end-tidal carbon dioxide tension (P(ET,CO2)), arterial oxygen saturation (S(a,O2)), ECG and blood pressure at rest were monitored during progressive hypercapnic hyperoxia, isocapnic hypoxia, slow breathing and oxygen administration. MCFV, arterial baroreflex and dynamic MCFV-blood pressure relationships were compared by phase analysis. COPD and control smokers showed higher MCFV (when corrected for P(ET,CO2)), lower cerebrovascular resistance index and lower sensitivity to hypercapnia than nonsmokers, with equal sensitivity to S(a,O2) and similar phase analysis. Arterial baroreflex was depressed in all COPD patients. Slow breathing and oxygen administration improved baroreflex sensitivity and reduced MCFV in all COPD patients. Patients with mild chronic obstructive pulmonary disease show autonomic dysfunction. Chronic smoking induces cerebral vasodilation and impairs cerebrovascular control. All abnormalities can be partly corrected by improving the cardio- and cerebrovascular autonomic modulation, suggesting that functional autonomic abnormalities are already present at an early stage of disease.