A Cochrane review included 8 studies with a total of 461 patients. Admission to hospital was reduced with continuous beta-agonists (CBA) compared to intermittent beta-agonists (RR: 0.68; 95% CI 0.5 to 0.9); patients with severe airway obstruction at presentation appeared to benefit most from this intervention (RR: 0.64; 95% CI 0.5 to 0.9). Patients receiving CBA demonstrated small but statistically significant improvements in pulmonary function tests when all studies were pooled (greater improvements in % predicted FEV1: SMD 0.3, 95% CI 0.03 to 0.5; and PEFR: SMD 0.33, 95% CI 0.1 to 0.5); this effect was observed by 2–3 hours. The doses of beta-agonists varied between 5 mg and 30 mg, and were generally administered over 120 minutes. One study used a small volume nebuliser and by increasing the amount of normal saline lengthened the nebulisation to 20 minutes, thereby creating back-to-back treatments and an effectively continuous nebulisation under these research conditions. Continuous treatment was generally well tolerated, with no clinically important differences observed in pulse rate or blood pressure between the treatment groups.