S Keranov, O Dörr, CW Hamm and H Nef contributed toward study design. S Keranov and O Dörr contributed toward study conduct and data collection. S Keranov, O Dörr, L Jafari, J Riehm, C Liebetrau, T Keller, C Troidl, W Rutsatz, S Kriechbaum, S Voss, MJ Richter, K Tello, H Gall, HA Ghofrani, S Guth, W Seeger, CW Hamm and H Nef contributed toward analysis and interpretation. S Keranov, O Dörr, L Jafari, J Riehm, C Liebetrau, T Keller, C Troidl, W Rutsatz, S Kriechbaum, S Voss, MJ Richter, K Tello, H Gall, HA Ghofrani, S Guth, W Seeger, CW Hamm and H Nef contributed toward manuscript preparation.