[1] Lancashire Teaching Hosp NHS Fdn Trust, Dept Med, Resp Med, Preston, Lancs, England
[2] Royal Preston Hosp, Dept Med, Preston, Lancs, England
[3] Lancashire Teaching Hosp NHS Fdn Trust, Dept Med, Emergency & Acute Med, Preston, Lancs, England
[4] Univ Manchester, Inst Cardiovasc Sci, Cardiovasc Sci, Manchester M13 9PL, Lancs, England