Changes in operating lung volume and symptoms during daily activity in COPD

Patients with moderate-severe COPD perform low levels of daily physical activity and both breathlessness and leg fatigue are important symptoms limiting exercise. It is now possible to accurately measure daily physical activity using accelerometers. Less is known about symptoms and hyperinflation measured during laboratory exercise testing relate to daily activity. We studied 20 stable COPD patients (15 male, mean (SD) age 67 (7) yrs, FEV1 0,96 (0,4) l, 36 (12) % predicted, IC 1,7 (0,4) l, 62 (14) % predicted during a time-limited endurance cycle exercise test at 70 % VO2 max. IC, dyspnoea intensity and leg fatigue on a Borg scale were recorded every 2 minutes. We calculated the individual slope of the change in these variables expressed as IC absolute. We assessed daily physical activity using both AW (Actiwatch) and SW (SenseWear) that subjects wore for 3-4 consecutive days from waking until going to bed. There was a good relationship between AW mean activity score and AW mean activity moving (r2=0,7; p<0,01) and a close relationship between SW step count and AW mean activity score (r2=0,8; p<0,001). We found a good relationship between the AW mean activity score and the rate of increase of dyspnoea (r2=0,5; p