Gas Exchange

(gaseous interchange), exchange of gases between an organism and the environment. Oxygen, which is required by all cells, organs, and tissues, enters the organism from the environment; the organism releases carbon dioxide, which it produces, and a small quantity of other gaseous metabolic products. Gaseous interchange is necessary for almost all organisms; without it normal metabolism, energy transfer, and consequently life itself, would be impossible.

The oxygen that enters the tissues is used in the oxidation of the products formed as the result of the long chain of chemical conversion of carbohydrates, fats, and proteins. Carbon dioxide, water, and nitrogenous compounds are formed during this process, and energy is freed to be used in the maintenance of body temperature and in the expenditure of work. The quantity of CO₂ formed in the organism and finally released by it depends not only on the quantity of O₂ consumed but also on the predominant substance being oxidized (carbohydrates, fats, or proteins). The relationship between the CO₂ released by the organism and the O₂ absorbed for the same amount of time is called the respiratory coefficient and is equal to approximately 0.7 for the oxidation of fats, 0.8 for proteins, and 1.0 for carbohydrates. The amount of energy liberated per liter of O₂ consumed (the caloric equivalent of oxygen) is 20.9 kilojoules (kJ), or 5 kilocalories (kcal), for the oxidation of carbohydrates and 19.7 kJ (4.7 kcal) for the oxidation of fats. Thus, it is possible to calculate the amount of energy liberated in the organism by the consumption of O₂ per unit of time and by means of the respiratory coefficient.

Gaseous interchange (and energy expenditure) in poikilothermic (cold-blooded) animals decreases with a decrease in body temperature. The same temperature dependence is observed in homoiothermic (warm-blooded) animals when heat regulation is shut off (under conditions of natural or artificial hypothermia); gaseous interchange increases with an increase in body temperature (upon overheating and in the case of various illnesses).

As the temperature of the surroundings drops, gaseous interchange in warm-blooded animals (especially in small animals) increases as a result of increased heat production. It also increases after the intake of food that is particularly protein-rich (the so-called specifically dynamic effect of food); it attains its greatest magnitude during muscular activity. In humans under moderate exertion, gaseous interchange increases and, three to six minutes after the commencement of activity, reaches a specific level, which is then maintained throughout the period of activity. When performing work requiring great exertion, gaseous interchange increases continuously; soon after a given individual attains his maximum level (maximum aerobic work), he must stop working, since the body’s need for O₂ exceeds this level. Increased O₂ consumption continues after the end of exertion and is used to cover the oxygen debt—that is, to oxidize the metabolic products that formed during the work. The consumption of O₂ can increase from 200-300 milliliters per minute (ml/min) at rest to 2,000-3,000 ml/min during work and, for athletes in good condition, to 5,000 ml/min. At the same time, the liberation of CO₂ and the expenditure of energy increase, and changes in the respiratory coefficient associated with changes in metabolism, acid-base equilibrium, and pulmonary ventilation take place.

The calculation of the total daily expenditure of energy among people of different professions and ways of life is based on determinations of gaseous interchange and is important for fixing dietary levels. Studies of changes in gaseous interchange during standard physical work are used in studying the physiology of work and sports and under clinical conditions for the evaluation of the functional state of systems that participate in gaseous interchange.

The comparative constancy of gaseous interchange with considerable changes in the partial pressure of O₂ in the surroundings, disruptions of the function of the respiratory organs, and so on is ensured by compensatory reactions of the systems that participate in the interchange and are regulated by the nervous system.

Gaseous interchange in humans and animals is usually studied under conditions of complete rest, on an empty stomach, and at a comfortable temperature (18°-22° C). The quantity of O₂ consumed and energy released under these conditions characterizes the basal metabolism. Methods based on the principle of an open or closed system are used in the study of gaseous interchange. In the first instance, the amount and composition of the air expired are determined by means of chemical or physical gas analyzers, which makes it possible to calculate the quantities of O₂ consumed and CO₂ liberated. In the second instance, respiration takes place in a closed system (a hermetically sealed chamber or from a spirograph connected to the respiratory tracts), in which the CO₂ liberated is absorbed and the quantity of O₂ consumed from the system is determined either by measuring the quantity of O₂ entering the system automatically, which is equal to the quantity of O₂ consumed, or by decreasing the volume of the system.

REFERENCES

Ginetsinskii, A. G., and A. V. Lebedinskii. Kurs normal’ noi fiziologii. Moscow, 1956.
Ginetsinskii, A. G., and A. V. Lebedinskii. Fiziologiia cheloveka. Moscow, 1966. Pages 134-56.
Berkovich, E. M. Energeticheskii obmen v norme i patologii. Moscow, 1964. (Contains a bibliography.)
Prosser, L., and F. Brown. Sravnitel’naia fiziologiia zhivotnykh. Moscow, 1967. Pages 186-237. (Translated from English.)

L. L. SHIK

gas exchange

exchange

[eks-chānj´] 1. the substitution of one thing for another.2. to substitute one thing for another.gas exchange the passage of oxygen and carbon dioxide in opposite directions across the membrane" >alveolocapillary membrane.health care information exchange in the nursing interventions classification, a nursing intervention defined as providing patient care information to health professionals in other agencies.impaired gas exchange a nursing diagnosis approved by the North American Nursing Diagnosis Association, defined as excess or deficit in oxygenation and/or carbon dioxide elimination at the membrane" >alveolocapillary membrane (see exchange" >gas exchange). Etiological and contributing factors include an altered oxygen supply, changes in the alveolar-capillary membrane, altered blood flow, and altered oxygen-carrying capacity of the blood. Defining characteristics include changes in mental status such as confusion, somnolence, restlessness, and irritability; ineffective coughing and inability to move secretions from the air passages; hypercapnia; and hypoxia. For specific medical treatments and nursing interventions, see airway clearance, ineffective" >airway clearance, ineffective; patterns, ineffective" >breathing patterns, ineffective; chronic airflow limitation" >chronic airflow limitation; and anemia.plasma exchange see plasma exchange." >plasma exchange.

gas exchange

gas carriage

the transfer of gases between an organism and the environment. In RESPIRATION, oxygen is taken in and carbon dioxide given out. Photosynthesis in plants complicates this system in that during the process carbon dioxide is required by the plant and oxygen given off (see COMPENSATION PERIOD). In plants and small animals such as PROTOZOANS and PLATYHELMINTHS, gas exchange occurs by DIFFUSION. In higher animals, special respiratory surfaces have been developed, for example, internal and external gills, lungs and trachea.

Gas exchange

The process by which oxygen is extracted from inhaled air into the bloodstream, and, at the same time, carbon dioxide is eliminated from the blood and exhaled.Mentioned in: Respiratory Failure

单词	gas exchange
释义	gas exchange gas exchange The movement of gases from an area of higher concentration to an area of lower concentration, especially the exchange of oxygen and carbon dioxide between an organism and its environment. In plants, gas exchange takes place during photosynthesis. In animals, gases are exchanged during respiration. Translations Gas Exchange Gas Exchange (gaseous interchange), exchange of gases between an organism and the environment. Oxygen, which is required by all cells, organs, and tissues, enters the organism from the environment; the organism releases carbon dioxide, which it produces, and a small quantity of other gaseous metabolic products. Gaseous interchange is necessary for almost all organisms; without it normal metabolism, energy transfer, and consequently life itself, would be impossible. The oxygen that enters the tissues is used in the oxidation of the products formed as the result of the long chain of chemical conversion of carbohydrates, fats, and proteins. Carbon dioxide, water, and nitrogenous compounds are formed during this process, and energy is freed to be used in the maintenance of body temperature and in the expenditure of work. The quantity of CO₂ formed in the organism and finally released by it depends not only on the quantity of O₂ consumed but also on the predominant substance being oxidized (carbohydrates, fats, or proteins). The relationship between the CO₂ released by the organism and the O₂ absorbed for the same amount of time is called the respiratory coefficient and is equal to approximately 0.7 for the oxidation of fats, 0.8 for proteins, and 1.0 for carbohydrates. The amount of energy liberated per liter of O₂ consumed (the caloric equivalent of oxygen) is 20.9 kilojoules (kJ), or 5 kilocalories (kcal), for the oxidation of carbohydrates and 19.7 kJ (4.7 kcal) for the oxidation of fats. Thus, it is possible to calculate the amount of energy liberated in the organism by the consumption of O₂ per unit of time and by means of the respiratory coefficient. Gaseous interchange (and energy expenditure) in poikilothermic (cold-blooded) animals decreases with a decrease in body temperature. The same temperature dependence is observed in homoiothermic (warm-blooded) animals when heat regulation is shut off (under conditions of natural or artificial hypothermia); gaseous interchange increases with an increase in body temperature (upon overheating and in the case of various illnesses). As the temperature of the surroundings drops, gaseous interchange in warm-blooded animals (especially in small animals) increases as a result of increased heat production. It also increases after the intake of food that is particularly protein-rich (the so-called specifically dynamic effect of food); it attains its greatest magnitude during muscular activity. In humans under moderate exertion, gaseous interchange increases and, three to six minutes after the commencement of activity, reaches a specific level, which is then maintained throughout the period of activity. When performing work requiring great exertion, gaseous interchange increases continuously; soon after a given individual attains his maximum level (maximum aerobic work), he must stop working, since the body’s need for O₂ exceeds this level. Increased O₂ consumption continues after the end of exertion and is used to cover the oxygen debt—that is, to oxidize the metabolic products that formed during the work. The consumption of O₂ can increase from 200-300 milliliters per minute (ml/min) at rest to 2,000-3,000 ml/min during work and, for athletes in good condition, to 5,000 ml/min. At the same time, the liberation of CO₂ and the expenditure of energy increase, and changes in the respiratory coefficient associated with changes in metabolism, acid-base equilibrium, and pulmonary ventilation take place. The calculation of the total daily expenditure of energy among people of different professions and ways of life is based on determinations of gaseous interchange and is important for fixing dietary levels. Studies of changes in gaseous interchange during standard physical work are used in studying the physiology of work and sports and under clinical conditions for the evaluation of the functional state of systems that participate in gaseous interchange. The comparative constancy of gaseous interchange with considerable changes in the partial pressure of O₂ in the surroundings, disruptions of the function of the respiratory organs, and so on is ensured by compensatory reactions of the systems that participate in the interchange and are regulated by the nervous system. Gaseous interchange in humans and animals is usually studied under conditions of complete rest, on an empty stomach, and at a comfortable temperature (18°-22° C). The quantity of O₂ consumed and energy released under these conditions characterizes the basal metabolism. Methods based on the principle of an open or closed system are used in the study of gaseous interchange. In the first instance, the amount and composition of the air expired are determined by means of chemical or physical gas analyzers, which makes it possible to calculate the quantities of O₂ consumed and CO₂ liberated. In the second instance, respiration takes place in a closed system (a hermetically sealed chamber or from a spirograph connected to the respiratory tracts), in which the CO₂ liberated is absorbed and the quantity of O₂ consumed from the system is determined either by measuring the quantity of O₂ entering the system automatically, which is equal to the quantity of O₂ consumed, or by decreasing the volume of the system. REFERENCES Ginetsinskii, A. G., and A. V. Lebedinskii. Kurs normal’ noi fiziologii. Moscow, 1956. Ginetsinskii, A. G., and A. V. Lebedinskii. Fiziologiia cheloveka. Moscow, 1966. Pages 134-56. Berkovich, E. M. Energeticheskii obmen v norme i patologii. Moscow, 1964. (Contains a bibliography.) Prosser, L., and F. Brown. Sravnitel’naia fiziologiia zhivotnykh. Moscow, 1967. Pages 186-237. (Translated from English.) L. L. SHIK gas exchange exchange [eks-chānj´] 1. the substitution of one thing for another.2. to substitute one thing for another.gas exchange the passage of oxygen and carbon dioxide in opposite directions across the membrane" >alveolocapillary membrane.health care information exchange in the nursing interventions classification, a nursing intervention defined as providing patient care information to health professionals in other agencies.impaired gas exchange a nursing diagnosis approved by the North American Nursing Diagnosis Association, defined as excess or deficit in oxygenation and/or carbon dioxide elimination at the membrane" >alveolocapillary membrane (see exchange" >gas exchange). Etiological and contributing factors include an altered oxygen supply, changes in the alveolar-capillary membrane, altered blood flow, and altered oxygen-carrying capacity of the blood. Defining characteristics include changes in mental status such as confusion, somnolence, restlessness, and irritability; ineffective coughing and inability to move secretions from the air passages; hypercapnia; and hypoxia. For specific medical treatments and nursing interventions, see airway clearance, ineffective" >airway clearance, ineffective; patterns, ineffective" >breathing patterns, ineffective; chronic airflow limitation" >chronic airflow limitation; and anemia.plasma exchange see plasma exchange." >plasma exchange. gas exchange or gas carriage the transfer of gases between an organism and the environment. In RESPIRATION, oxygen is taken in and carbon dioxide given out. Photosynthesis in plants complicates this system in that during the process carbon dioxide is required by the plant and oxygen given off (see COMPENSATION PERIOD). In plants and small animals such as PROTOZOANS and PLATYHELMINTHS, gas exchange occurs by DIFFUSION. In higher animals, special respiratory surfaces have been developed, for example, internal and external gills, lungs and trachea. Gas exchange The process by which oxygen is extracted from inhaled air into the bloodstream, and, at the same time, carbon dioxide is eliminated from the blood and exhaled.Mentioned in: Respiratory Failure FinancialSeeexchange
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