Chest
Clinical Investigations: Airways ObstructionContribution of the Respiratory Muscles to the Lactic Acidosis of Heavy Exercise in COPD
Section snippets
Patients
A group of eight patients with moderate to severe COPD (FEV1 <65% of predicted) took part in this study after giving written informed consent. Before entering the study, full pulmonary function testing and incremental cardiopulmonary exercise testing were performed. Patients were included when they fulfilled the following criteria: (1) irreversible obstructive airway disease (<10% improvement in FEV1 after inhalation of ß2-agonist); (2) ability to exercise beyond the lactic acidosis threshold
Healthy Subjects
Average physical characteristics of the healthy subjects were as follows: age, 28.3±4.7 years; height, 174.4±4.7 cm; and weight, 78.6±13.9 kg. There were two women and three men in this group. In the incremental exercise test, average peak was 2.32±0.56 L/min and peak minute ventilation ( ) was 89.4±16.7 L/min. The lactic acidosis threshold averaged 1.27± 0.37 L/min.
The work rate chosen for the CWR averaged 94±22 W. The upper panel in Figure 1 shows the ventilatory time
Discussion
Impaired exercise tolerance is a prominent complaint of patients with obstructive lung disease. Unlike healthy subjects, patients with obstructive lung disease are often limited in their exercise tolerance by the level of ventilation they are able to sustain. Strategies to improve exercise tolerance have focused on either reducing the high ventilatory requirement for a given level of exercise or increasing the amount of ventilation that can be sustained. Improving the function of the
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2010, Current Opinion in Pulmonary Medicine
Supported by an Established Investigator Award from the American Lung Association of California.