RT Journal Article SR Electronic T1 Effects of sildenafil and the association of sildenafil-sixtasentan on the NO/CO transfer factor in low landers exposed to high altitude JF European Respiratory Journal JO Eur Respir J FD European Respiratory Society SP p4743 VO 38 IS Suppl 55 A1 Jean-Benoît Martinot A1 Claire de Bisschop A1 Cristina Scoditti A1 Chantal Dedobbeleer A1 Maria Overbeek A1 Robert. Naeije A1 Hervé Guenard YR 2011 UL http://erj.ersjournals.com/content/38/Suppl_55/p4743.abstract AB Little is known about the CO/NO lung transfer in low landers (LL) exposed to hypoxic environment without previous acclimatisation. The acute expected rise of the arterial pulmonary pressure (sPAP) can modify the capillary lung volume (Vc) and the conductance for CO (DmCO). We studied the effects of sildenafil and the association sildenafil-sixtasentan on the lung diffusion in 26 LL subjects transported to Cerro de Pasco (4300 m) in 2 or 3 days. sPAP was acquired using a Cx50 echocardiographic system. The tests were done at arrival and repeated 5 days later under a placebo, double blind randomised trial. The data are corrected for haemoglobin concentration.Results:View this table:sPAP increased between sea level and altitude from a mean (± sem) of 23.1 (3.9) to 32 (7.6) mmHg without significant differences in cardiac index and mitral E/Ea ratio.Conclusion: Acute exposure to high altitude leads to a recruitment of lung capillaries associated to the expansion of the exchange surface (DmCO/VA) and to a 48% increase in sPAP. Acclimatisation is accompanied by a spontaneous decrease of Vc after one week. The arterial pulmonary vasodilators had no effect on Vc, suggesting that the mean capillary lung pressure remained constant.