Breath-by-breath variation of FRC: effect on VO2 and VCO2 measured at the mouth

1979 ◽  
Vol 46 (6) ◽  
pp. 1122-1126 ◽  
Author(s):  
H. U. Wessel ◽  
R. L. Stout ◽  
C. K. Bastanier ◽  
M. H. Paul

We examined breath-by-breath (B-B) variations of FRC (delta FRC) and their effect on measured O2 and CO2 gas exchange in 52 2- to 4-min segments of continuous air breathing obtained in 29 patients (age range 6--50 yr). Respiratory frequency ranged from 13 to 43 breaths/min, VE from 6.7 to 22.5 l/min (BTPS), and expired VT from 234 to 1,370 ml (BTPS). Computer analysis was based on the following source data measured at the mouth: inspired (VI) and expired (VE) gas flow, FN2, FO2 and FCO2. The analysis provides B-B evaluation of VI, VE, delta FRC in terms of VN2, and VO2 and VCO2 at the mouth and at the alveolar level, i.e., after correction for delta FRC. Significant B-B variations of FRC were found in all studies. delta FRC ranged from +360 to -360 ml (BTPS). For single respiratory cycles VI - VE is primarily a function of N2 exchange at the mouth (VMN2). VO2 and VCO2, uncorrected for delta FRC, are significantly more dispersed about mean values than the corrected gas uptakes (P less than 0.0005). The data support the view that the assumption of VIN2 = VEN2 is invalid for single respiratory cycles. Determination of breath-by-breath VO2 and VCO2 should therefore, not be based on steady-state gas uptake equations. It requires measurement of both inspired and expired breath volumes and evaluation of N2 gas exchange.

Planta ◽  
1991 ◽  
Vol 183 (2) ◽  
Author(s):  
Marie-H�l�ne Avelange ◽  
JeanM. Thi�ry ◽  
Fr�d�ric Sarrey ◽  
Pierre Gans ◽  
Fabrice R�beill�

2001 ◽  
Vol 91 (1) ◽  
pp. 10-16 ◽  
Author(s):  
Philip J. Peyton ◽  
Gavin J. B. Robinson ◽  
Bruce Thompson

Ventilation-perfusion (V˙a/Q˙) inhomogeneity was modeled to measure its effect on overall gas exchange during maintenance-phase N2O anesthesia with an inspired O2 concentration of 30%. A multialveolar compartment computer model was used based on physiological log normal distributions of V˙a/Q˙ inhomogeneity. Increasing the log standard deviation of the distribution of perfusion from 0 to 1.75 paradoxically increased O2 uptake (V˙o 2) where a low mixed venous partial pressure of N2O [high N2O uptake (V˙n 2 o)] was specified. With rising mixed venous partial pressure of N2O, a threshold was observed where V˙o 2 began to fall, whereas V˙n 2 o began to rise with increasing V˙a/Q˙ inhomogeneity. This phenomenon is a magnification of the concentrating effects thatV˙o 2 andV˙n 2 o have on each other in low V˙a/Q˙ compartments. During “steady-state” N2O anesthesia,V˙n 2 o is predicted to paradoxically increase in the presence of worseningV˙a/Q˙ inhomogeneity.


1986 ◽  
Vol 61 (6) ◽  
pp. 2238-2242 ◽  
Author(s):  
P. Webster ◽  
A. S. Menon ◽  
A. S. Slutsky

Constant-flow ventilation (CFV) is a ventilatory technique in which physiological blood gases can be maintained in dogs by a constant flow of fresh gas introduced via two catheters placed in the main-stem bronchi (J. Appl. Physiol. 53: 483–489, 1982). High-velocity gas exiting from the catheters can create uneven pressure differences in adjacent lung segments, and these pressure differences could lead to gas flow through collateral channels. To examine this hypothesis, we studied CFV in pigs, animals known to have a high resistance to collateral ventilation. In three pigs we examined steady-state gas exchange, and in six others we studied unsteady gas exchange at three flow rates (20, 35, and 50 l/min) and three catheter positions (0.5, 1.5, and 2.5 cm distal to the tracheal carina). During steady-state runs we were unable to attain normocapnia; the arterial CO2 partial pressure (PaCO2) was approximately 300 Torr at all flow rates and all catheter positions, compared with 20–50 Torr at similar flows and positions in dogs studied previously. The initial unsteady gas-exchange experiments indicated no consistent effect of catheter position or flow rate on the rate of rise of PaCO2. In three other pigs, the rates of rise of PaCO2 were compared with the rates observed with apneic oxygenation (AO). At the maximum flow and deepest position, the rate of rise of PaCO2 was lower during CFV than during AO. These data suggest that flow through collateral channels might be important in producing adequate gas transport during CFV; however, other factors such as airway morphometry and the effects of cardiogenic oscillations may explain the differences between the results in pigs and dogs.


2001 ◽  
Vol 91 (1) ◽  
pp. 3-9 ◽  
Author(s):  
Philip J. Peyton ◽  
Gavin J. B. Robinson ◽  
Bruce Thompson

Ventilation-perfusion (V˙a/Q˙) inhomogeneity was modeled to measure its effect on gas exchange in the presence of inspired mixtures of two soluble gases using a two-compartment computer model. Theoretical studies involving a mixture of hypothetical gases with equal solubility in blood showed that the effect of increasing inhomogeneity of distributions of either ventilation or blood flow is to paradoxically increase uptake of the gas with the lowest overall uptake in relation to its inspired concentration. This phenomenon is explained by the concentrating effects that uptake of soluble gases exert on each other in low V˙a/Q˙ compartments. Repeating this analysis for inspired mixtures of 30% O2and 70% nitrous oxide (N2O) confirmed that, during “steady-state” N2O anesthesia, uptake of N2O is predicted to paradoxically increase in the presence of worsening V˙a/Q˙ inhomogeneity.


1970 ◽  
Vol 6 (1) ◽  
pp. 184-193
Author(s):  
Ольга Віговська

У статті теоретично обґрунтовано феномен конструктивного самозбереження особистості як ознаки самоактуалізації, розкриття власного потенціалу і побудови перспективи розвитку особистості та емпірично виявлено ознаки психологічної детермінації домінуючого інстинкту у конструктивній самореалізації жінок з різним соціальним статусом. Зазначено, що проблема самозбереження асоціюється з особливостями прояву інстинкту самозбереження людини, але потреби вищого порядку зумовлюють соціальну природу її поведінки, яка локалізована у найвищій точці самореалізації. Теоретично обгрунтовано, що самореалізація визначає тенденцію раціональної організації життя людини та проявляється у її почутті задоволеністю життям. З’ясовано, що психологічну основу конструктивного самозбереження становлять індивідуально-типологічні характеристики людини, які відображають психофізіологічні та психосоціальні резерви самореалізації особистості. Розроблена програма емпіричного дослідження, а також комплекс використаних методів математичної обробки результатів дослідження дає змогу конкретизувати психологічний зміст детермінації домінуючого інстинкту у конструктивній самореалізації жінок вікового діапазону 35-45 років та з різним соціальним статусом. У жінок, які виховують проблемну (хвору) дитину, домінує інстинкт "егофільного типу", що виражається у їх надмірному егоцентризмі і супроводжується низькими показниками самоактуалізації, на відміну від досліджуваних жінок, які виховують здорових дітей і у яких на фоні вираженої тенденції до самоактуалізації домінує базовий інстинкт "дослідницького типу" та "лібертофільного типу". This article theoretically proves constructive phenomenon of self identity as signs of self-disclosure own potential and prospects of development of individual construction. In addition, it empirically showes signs of psychological determination of the dominant instinct in a constructive self-determination of women with different social statuses. It was noted that the issue of self-preservation is associated with the peculiarities of manifestation of self-preservation instinct of man, but it needs higher-order cause social nature of the behavior that is localized at the highest point of self-realization. It theorized that self-realization determines the trend of rational organization of human life and manifests itself in its sense of life satisfaction. It was found that the psychological basis of constructive self-preservation of the individual make individually-typological characteristics of a person that reflect physiological and psychosocial reserves of self-realization. The developed program of empirical research, as well as the methods used complex mathematical processing of results of research allows to specify the content of the psychological determination of the dominant instinct of constructive self-realization а women age range of 35-45 years and with different social status. Women who bring up the problem child dominates the instinct of self-preservation, which is reflected in their excessive self-centeredness, and is accompanied by low levels of self-actualization, as opposed to the study of women who are raising healthy children and that against the backdrop of a pronounced tendency to self-actualization, dominated by basic instinct "research type" and "independent type."


Clean Air ◽  
2007 ◽  
Vol 8 (4) ◽  
pp. 359-371
Author(s):  
A. Medeiros ◽  
R. Edenhofer ◽  
K. Lucka ◽  
H. Kohne

1989 ◽  
Vol 20 (2) ◽  
pp. 85-96 ◽  
Author(s):  
Gunnar Jacks ◽  
Göran Åberg ◽  
P. Joseph Hamilton

Strontium isotopes in precipitation, soil and runoff water can be used to establish a ratio of wet plus dry deposited Sr to Sr released by weathering. This ratio is especially enhanced in areas with old acid Proterozoic rocks (0.6-2.5 Ga) and Archean rocks (>2.5 Ga). Since Sr and Ca behave in an analogous way in the coniferous forest ecosystem the results for Sr can be used for the determination of Ca. If the deposition of calcium can be calculated reasonably accurately the weathering rate can also be estimated. Five catchments have been investigated using this approach. Three of them seem to be close to a steady state, wherein the losses and gains of calcium to the system are equal. In the two southern-most catchments there seems to be an ongoing loss of exchangeable calcium. The loss by runoff occurs with sulphate being the dominant anion. Weathering rates of 1.5 to 4.8 kg Ca/ha year have been estimated.


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