RELAx - REstricted versus Liberal positive end-expiratory pressure in patients without ARDS: protocol for a randomized controlled trial od Algera, A, Pisani, L, Bergmans, D, Den Boer, S, De Borgie, C, Bosch, F, Bruin, K, Cherpanath, T, Determann, R, Dondorp, A, Dongelmans, D, Endeman, H, Haringman, J, Horn, J, Juffermans, N, Van Meenen, D, Van Der Meer, N, Merkus, M, Moeniralam, H, Purmer, I, Tuinman, P, Slabbekoorn, M, Spronk, P, Vlaar, A, Gama De Abreu, M, Pelosi, P, Serpa Neto, A, Schultz, M, Paulus, F