[1] Univ Birmingham, Birmingham Med Sch, Birmingham, W Midlands, England
[2] Univ Birmingham, Birmingham Acute Care Res Grp, Inst Inflammat & Ageing, Birmingham, W Midlands, England
[3] Univ Hosp Birmingham NHS Fdn Trust, Queen Elizabeth Hosp Birmingham, Dept Resp Med, Birmingham, W Midlands, England
[4] Birmingham Resp Clin Trials Unit, Birmingham, W Midlands, England
[5] Univ Hosp Birmingham NHS Trust, Queen Elizabeth Hosp Birmingham, Dept Crit Care Med, Birmingham, W Midlands, England