Can a self-management plan, which includes a four-fold increase in inhaled corticosteroid dose, reduce severe asthma exacerbations: a randomised, pragmatic trial by Mckeever, T, Mortimer, K, Duley, L, Bradshaw, L, Swinden, R, Skeggs, A, Pavord, I, Higgins, B, Walker, S, Thomas, M, Devereux, G, Wilson, A, Brightling, C, Price, D, Oborne, J, Mitchell, E, Harrison, T, Haydock, R