[Oxygen affinity of haemoglobin 3 hours after passive increase in altitude from 400 to 1800 metres (author's transl)].

An investigation was undertaken in 9 male subjects of the effect of short exposure to moderate altitude on the oxygen affinity of haemoglobin and other parameters. Initial measurements were performed at 425 m and repeated 3 hours after ascent by cable car to an altitude of 1800 m (Untersberg, Salzburg), no muscular activity being allowed (first period). The same protocol was repeated 3 days subsequently except that after ascent the individuals were exercised on an ergometer bicycle (second part). Altitude exposure without exercise leads to a small, but significant increase in the pH corrected P50 value (= half-saturation tension), whereas the non-corrected P50 value showed no significant change. In the second part of the study the corrected and non-corrected P50 values both increased significantly. The whole body pH and the intraerythrocytic pH rose, whereas PCO2 decreased significantly. The intraerythrocytic 2,3-DPG concentration showed a significant increase (1.2 mumol/gHb) after 3 hours of altitude exposure with and without muscular exercise. The prealtitude DPG concentration and the P50 values in the second period were higher than the first control values. The red blood count and sodium and chloride concentration showed no changes. Potassium rose in both experimental periods, whereas inorganic plasma phosphates decreased. These findings show that 3 hours after cable-car ascent to a medium altitude a DPG increase occurs which is able to counteract the Bohr effect. This means that the expected impairment of tissue oxygenation, caused by the alkalosis-induced shift of the dissociation curve to the left, is prevented. These findings also indicate that a repeated "passive" ascent to moderate altitude can lead to an increased oxygen delivery to the tissue.