[Nomogram for the determination of arterial oxygen partial pressure of man in relation to high altitude and in dependence from age (author's transl)].

If somebody ascends from sea level to higher altitude within a short time, the change of the atmospheric conditions can be a danger for his life. Therefore, a nomogram was constructed which allows to read off the arterial oxygen partial pressures and the corresponding arterial oxygen saturation in relation to altitude. On the basis of the oxygen partial pressure of the atmosphere determined by steps of 500 m from sea level up to an antitude of 10,000 m, we calculated the decrease of the oxygen partial pressure from the inspired air to the arterial blood. When passing our airways, the inspired oxygen partial pressure is dimished by the adaptation to BTPS conditions and by the increasing CO2 partial pressure when approaching the alveolar gas exchanging zone. Another oxygen partial pressure gradient formed by inhomogeneities of ventilation to perfusion, diffusing capacity to perfusion and shunt perfusion is found at the alveolar-arterial barrier. The value of this alveolar-arterial oxygen partial pressure difference is closely correlated to age. With the values of the single steps, the nomogram was constructed. Seven abscissas show the oxygen partial pressure gradients from the inspired air at a distinct altitude to the arterial blood. In relation to a lot of CO2-depending oxygen dissociation curves, it is possible to read off additionally the corresponding arterial oxygen saturation for a person in rest up to an altitude of 10,000 m.