Patients in this cohort who have GOLD stage 2 to 4 ( post-bronchodilator FEV1/FVC < 0.7 and FEV1 < 80 % of predicted ) , who receive reimbursement by health insurance companies for physical therapy ( post-bronchodilator Tiffeneau-index < 0.6 ) and who experience a COPD exacerbation will be asked within 56 days to participate in a cohort-nested prospective randomised controlled trial ( RCT ) .