Randomization and allocation concealment
A prior randomization list was drawn based on computergenerated random numbers before the study commenced. It was then sealed in a database file with security password. In order to achieve a balanced number of treatment and control subjects at every single point of time, a randomization strategy according to ‘‘permuted blocks’’ was adopted.19 According to the ‘‘permutated blocks’’ strategy, the possible
combination sequences for every block of 4 subjects were as follows: (1) TTCC, (2) TCTC, (3) TCCT, (4) CCTT, (5) CTCT, and (6) CTTC, where T indicated ‘‘Treatment’’ and C indicated ‘‘Control.’’ Based on the random number drawn for the first of every four allocations, the particular sequence of T and C out
of the six possible combinations was selected for these 4 subjects. In case the random number for the first subject was beyond the range from 1 to 6, the random number for the second subject was adopted. On the ninth training session of the pulmonary rehabilitation training program for each potential subject, the occupational therapist who was blind to the list opened the file and assigned the subject to either the
treatment or the control group accordingly. A home exercise program was usually introduced to our patients with COPD on the ninth session of our conventional PRP.