Effect of early and later prone positioning on outcomes in invasively ventilated COVID-19 patients with acute respiratory distress syndrome: analysis of the prospective COVID-19 cr... by Simpkin, AJ, McNicholas, BA, Hannon, D, Bartlett, R, Chiumello, D, Dalton, HJ, Gibbons, K, White, N, Merson, L, Fan, E, Panigada, M, Grasselli, G, Motos, A, Torres, A, Barbé, F, Ng, PY, Fanning, JP, Nichol, A, Suen, JY, Bassi, GL, Fraser, JF, Laffey, JG