Further studies of rimiterol and salbutamol administered by intermittent positive-pressure ventilation, and an important observation on the technique of using the Bennett ventilator.

1. Using the same technique of administering drugs by intermittent positive-pressure ventilation as used in previous studies a source of contamination of solutions nebulized was discovered. This was rectified by using a new ventilator and completely separate patient circuits for each solution nebulized. 2 Salbutamol 0.5% and 0.25% solutions achieved the same degree of bronchodilatation, but there was a significantly greater increase in heart rate produced by salbutamol 0.5%. 3 Rimiterol 0.5% and salbutamol 0.25% produced similar peak mean improvements in FEV and also induced the same degree of tachycardia, but the duration of these effects were significantly shorter in the case of rimiterol. 4 The sustained degree of bronchodilatation achieved by salbutamol 0.25% could not be mirrored by giving two doses of rimiterol 0.5%, the second dose 2 h after the first. 5 Rimiterol 0.5% induced a degree of tachycardia which was similar in peak effect to that observed after salbutamol 0.25%. However, in the controls the second dose of rimiterol, given 2 h after the first, was responsible for only a small increase in heart rate which was not significantly different than that after saline in the other three treatment groups.