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CHAPTER 23. PHYSIOLOGY OF HYPOXIA

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).

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

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