23.1 System of blood oxygen transport
23.2 Physiological hypoxia
23.3 Intensity of function disorders and bodys?s sensitivity to hypoxia
23.4 Hypoxia stages
23.5 Stages of adaptation to hypoxia
23.6 Mechanisms of adaptation response to hypoxia of physiological systems
23.7 Factors influencing resistance to hypoxia
23.8 Causes and mechanisms of different types of hypoxic states
23.9 Functional-metabolic impairment in hypoxia
23.10 Principles of elimination and prevention of hypoxic effects
Control questions Situational tasks
23.1. System of blood oxygen transport
Oxygen is dissolved in plasma and diffused in blood oxyhemoglobin. The higher oxygen pressure in the blood, the higher amount of oxygen chemically binds to hemoglobin. Binding of oxygen to hemoglobin is a specific chemical process called oxygenation. At optimum pH, temperature, and electrolyte balance, 1 g of hemo-
globin binds 1.34-1.36 ml of O2. The volume of oxygen (ml) that can bind hemoglobin in 1 l of blood is called oxygen capacity of blood.
Oxygen blood capacity (OBC) depends on the hemoglobin (Fe2+) of the blood. The content of hemoglobin in arterial blood averages 120-160 g/l, and its oxygen capacity is 180-200 ml O2/l. There is certain dependence between oxygen pressure (pO2) in plasma and oxyhemoglobin content (% HbO2) which is called the oxyhemoglobin dissociation curve (Fig. 23.1).
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Fig. 23.1. Oxyhemoglobin dissociation curve: left shift - increased oxygen saturation: <t, <pCO2, <2,3-BPG, >pH, right shift - increased oxygen release: >t, >pCO2, >BPG; <pH
Deviations of the curve in the coordinate system are called shifts of the dissociation curve. Such shifts are most marked in various hypoxic states. A relatively steep slope of the curve with diminishing partial pressure of oxygen (up to 50-60 mm Hg) implies sufficiently