[1] Univ Siena, Div Cardiol, Dept Med Biotechnol, I-53100 Siena, Italy
[2] Umea Univ, Dept Publ Hlth & Clin Med, S-90187 Umea, Sweden
[3] St George London Univ, Dept Publ Hlth & Clin Med, London SW17 0RE, England
[4] Brunel Univ, Dept Publ Hlth & Clin Med, Uxbridge UB8 3PH, Middx, England
[5] Royal Brompton & Harefield NHS Fdn Trust, Adult Intens Care Unit, London SW3 6NJ, England
[6] Univ Siena, Le Scotte Hosp, Resp Dis & Lung Transplantat Sect, Dept Clin Med & Neurosci, I-53100 Siena, Italy
[7] Univ Siena, Dept Med Biotechnol Anesthesia & Intens Care, I-53100 Siena, Italy