Breathing pattern and ventilatory response to exercise in patients with Chronic Obstructive Pulmonary Disease.

Background: Patients with Chronic Obstructive Pulmonary Disease (COPD) show ventilatory limitation to exercise due to dynamic hyperinflation (DH). Breathing pattern can be expressed by T/T (inspiratory time/total time) and V/T (tidal volume/inspiratory time). Both parameters significantly increase during exertional hyperpnea in healthy subjects, but they have never been studied in COPD. In a large cohort of COPD patients, we analysed T/T and V/T at rest and during maximal exercise.

Methods: We enrolled clinically stable COPD patients with wide degree of airflow obstruction. All participants underwent spirometry and cardiopulmonary exercise testing (CPET) on a cycle ergometer.

Results: In 234 COPD patients (75 females; age range 41-89 years), T/T and V/T values significantly increased during exercise, from 0.259 ± 0.040-0.304 ± 0.038 and from 854.1 ± 229,6 ml/s to 2100 ± 622.5 ml/s respectively (p < 0.05). T/T and V/T were positively related (p < 0.05) with VO (ml/min/kg), maximal workload (Watt). T/T, but not V/T values showed a positive correlation (p < 0.05) with the peak-rest difference of inspiratory capacity (ΔIC, in ml). When related to minute ventilation T/T and V/T rest values in patients with DH (ΔIC ≥150 ml), compared with those without DH, did not differ between the two groups, though T/T, but not V/T values, significantly increased during exercise in patients without DH CONCLUSIONS: T/T and V/T values significantly increase during maximal exercise in COPD. T/T values were significantly correlated with dynamic hyperinflation. Our results suggest that T/T and V/T assessment may provide further information on exercise ventilatory limitation in COPD.