Respiratory pattern, thoracoabdominal motion and ventilation in chronic airway obstruction

Background. Patients with chronic obstructive pulmonary disease (COPD) present abnormal respiratory mechanics, but its relation to ventilation variables at rest is not fully understood. Methods. We evaluated breathing pattern, thoracoabdominal motion, and ventilation in moderate and severe COPD patients by means of respiratory inductive plethysmograph and analysis of respiratory metabolism in semirecumbent position at rest. Diaphragmatic movement was measured using radiographs. Results. COPD patients showed an increase in mean inspiratory flow, minute ventilation, dead space ventilation, oxygen and carbon dioxide ventilatory equivalents and reduction of respiratory times and pulse oxymetry. These findings were more pronounced in severe COPD. Changes in ventilatory efficiency were correlated with decreased respiratory times, reduced diaphragmatic movement, and lower oxygen uptake. Conclusions. Rapid shallow breathing and reduced diaphragmatic movement have led to ventilatory inefficiency without changes in thoracoabdominal motion.