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doi: 10.1002/phy2.222 Ventilatory capacity is reduced in chronic obstructive pulmonary disease (COPD) patients. Tidal volume (VT) is lower and breathing frequency higher at a given ventilation (VE) compared to healthy subjects. We examined whether airflow limitation and dynamic hyperinflation in COPD patients were related to breathing pattern. An incremental treadmill exercise test was per-formed in 63 COPD patients (35 men), aged 65 years (48–79 years) with a mean forced expiratory volume in 1 sec (FEV1) of 48 % of predicted (SD = 15%). Data were averaged over 20-sec intervals. The relationship between VE and VT was described by the quadratic equation VT = a + bVE + cVE 2 for each subject. The relationships between the curve parame-ters b and c, and spirometric variables and dynamic hyperinflation measured as the difference in inspiratory capacity from start to end of exercise, wer