Arterial oxygen partial pressure

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The arterial oxygen partial pressure (p a O 2 ) is the partial pressure ( partial pressure ) of the oxygen dissolved in the arterial blood as a proportion of the total pressure of all gases dissolved in the blood. The oxygen partial pressure corresponds to the proportion of oxygen in the total pressure within a gas mixture. This follows from Dalton's law , according to which the partial pressures of the individual gases in a mixture add up to the total pressure.

physiology

Normal values ​​(with 21% oxygen in the inhaled air) are measured arterially about 70 to 90 mm Hg (8–12 kPa), mixed venous approx. 35–40 mm Hg (4.6–5.3 kPa); in old age, the values ​​drop to 60 mmHg (arterial). The arterial oxygen partial pressure in mm Hg is approximately 103.4 minus (0.42 times the age in years).

The p a O 2 is an important measure for the assessment of the pulmonary diffusion with regard to the loading of the erythrocytes (red blood cells) with oxygen, the concentration gradient, the gas exchange area, the permeability and thickness of the alveolocapillary membrane and the contact time of the erythrocytes with depends on the membrane.

The difference between the alveolar oxygen partial pressure (p A O 2 ) and that of the arterial blood (p a O 2 ) is also referred to as the alveolo-arterial oxygen pressure difference (AaDO 2 ).

In the atmospheric air, the individual gas components are present in different concentrations and thus also in partial pressures. However, they are by no means identical to the alveolar breathing gas mixture. In the breathing gas mixture is z. B. still water vapor.

Pathophysiology

A disturbance of the arterial oxygen status can be described according to clinical aspects as follows: Hypoxia , that is the decrease in the p a O 2 and is to be distinguished from a hypoxemia , that is a decrease in the arterial oxygen content. A hypoxygenation would correspond to a reduction in the arterial oxygen saturation (S a O 2 ). However, it ultimately leads to a decrease in the oxygen content (hypoxemia).

literature

  • RF Schmidt, G. Thews (Hrsg.): Physiologie des Menschen. Springer publishing house.
  • WF Ganong: Textbook of Medical Physiology. Springer publishing house.
  • DU Silverthorn: Physiology. Pearson.
  • R. Larsen, T. Ziegenfuß: Ventilation. Springer, Berlin / Heidelberg 1997.

Individual evidence

  1. ^ P. Lotz: Symbols, Terminology, Formulas. In: J. Kilian, H. Benzer, FW Ahnefeld (ed.): Basic principles of ventilation. Springer, Berlin a. a. 1991, ISBN 3-540-53078-9 , 2nd, unchanged edition, ibid 1994, ISBN 3-540-57904-4 , p. 425 f.