Dietary magnesium (Mg) intake has been shown to be independently related to lung function, airway reactivity, and respiratory symptoms in the general population. Inhaled Mg and IV Mg administration have been shown to promote bronchodilation and to improve lung function in asthmatic patients. Some studies have suggested that COPD patients exhibit decreased body levels of Mg. The purpose of the present study was to investigate the effects of acute IV Mg loading on parameters of respiratory function and maximal exercise capacity of stable COPD patients.The study hypothesis is that Mg administration will be associated to improvements on airflow and vasodilation leading to improvements of pulmonary function and exercise performance.

Patients are required to have a diagnosis of COPD according to the Global Initiative for Chronic Obstructive Lung Disease criteria.

This is a randomized, double-blind, placebo-controlled, cross-over study. Twenty five patients are going to be included. They are going to come to the laboratory to receive IV placebo or IV Mg sulfate at two distinct occasions about 48 hours apart. Half of the patients are going to receive Mg first and Placebo at the second day, while the other half are going to receive the treatments in an inverse order. Tests are going to be performed before and about 40 minutes after the IV infusions. Tests to be performed are: spirometry, arterial blood gases, Mg plasma level measurements, and a maximal exercise test protocol in cycloergometer.

Inclusion Criteria:

• COPD diagnosis according GOLD criteria
• Men between 45 and 80 years old

Exclusion Criteria:

• History of asthma or atopy, renal failure, heart failure, arrhythmias or cardiac electrical disturbances, and other significant disease other than COPD.
• Individuals on chronic oral steroids, diuretics, or use of mineral supplementation.
• Locomotor impairment.