A random binomial number list (zeroes and ones) will be generated with the statistical software SPSS 16.0 for Windows and the list will be used for allocation of 124 patients between intervention and control groups in a 1:1 proportion. Each one of the 62 pairs of wooden prisms will be marked with a consecutive number coming from an HBE-allocated patient and the prisms will be stored keeping the marked number out of reach from the sight of the researcher in charge of patient recruiting.