| 
      * 10-day mortality; ** ICU mortality; # 60-day mortality
        | Authors | Year | 28-day Mortality
            Prone Supine | P Value | N° Patients
            Prone Supine | Hours/day in 
            Pone position |  
        | Gattinoni L et    al.* [17] | 2001 | 21% 25% | 0.65 | 152 152 | 7 h |  
        | Guerin C et al. [12] | 2004 | 32% 32% | 0.77 | 413 378 | 8 h |  
        | Voggenreiter et al.    [18] | 2005 | 23.8% 84% | 0.27 | 21 19 | 11 h |  
        | Manchebo et al. ** [19] | 2006 | 43% 58% | 0.12 | 76 60 | 17 h |  
        | Fernandez R et al.# [12] | 2008 | 38% 53% | 0.36 | 21 19 | ≥ 20 h |  
        | Taccone P et al.    [13] | 2009 | 31% 32.8% | 0.72 | 168 174 | 20 h |  
        | Guerin C et al. [12] | 2013 | 16%    32.8% | <    0.001 | 240 234 | 16 h |  |