Determination of tissue volume and carbon dioxide dissociation slope of the lungs in man

Abstract

The volume of N2O absorbed by the lung can be measured during inspiration before the gas is taken up in significant amounts by the capillary blood flow by a plethysmographic technique. If the alveolar fraction of N2O and its solubility coefficient are known, the combined pulmonary tissue and capillary blood volume (Vt+c) can be calculated. Vt+c averaged 517 ml, sd 61 ml, in nine adult males, values in good agreement with those obtained by other methods. The pulmonary tissue volume alone, Vt, in six of these subjects was 438 ml, sd 58 ml. A modification of the technique, using CO2 as the test gas, permitted calculation of the CO2 dissociation slope of the lung tissue. In five subjects, the CO2 dissociation slope of the lung, without the buffering effect of pulmonary capillary blood, over a range of PaCOCO2 from 31 to 55 mm Hg, averaged 0.30 ml CO2 STPD/100 ml lung tissue per mm Hg, or including physically dissolved CO2, 0.38 ml CO2 STPD/100 ml lung tissue per mm Hg. Because Vt is about four times larger than Vc, the lung tissue is of greater importance than the pulmonary capillary blood in buffering fluctuations in alveolar carbon dioxide during respiration. pulmonary tissue volume; pulmonary tissue space for N2O Submitted on August 26, 1963

Rate of disappearance of labeled carbon dioxide from the lungs of humans during breath holding: a method for studying the dynamics of pulmonary CO2 exchange

“…This is a determination with an experimental error which we believe is less than 20%o of the measurement. Other investigators using different techniques have also noted similar variations in these quantities (19,20). Therefore, the pulmonary intracellular CO2 concentration most likely has a wider range of normal values than observed in plasma.…”

“…Techniques for the determination of the CO2 dissociation curve of the lung tissues have included a plethysmographic method (19), direct measurement of the CO2 content in vitro after equilibration with known concentrations of CO2 (20), and methods based on the collection of alveolar gas samples after varying breath holding periods (21,22). In this study a modification of the breath holding methods described by DuBois (21) and Fenn and Dejours (22) was used.…”

“…This equilibration takes place in less than 1-2 sec and the amount of CO2 entering the alveoli will be a function of the CO2 dissociation curves of Vti. and Vc (5,19). The CO2 contained in the residual volume (RV), Vti., and Vc before inspiration plus any C02 contained in the inspired gas will equal the CO2 contained in the alveolar volume, Vti.…”

Minimum Alveolar Concentration of Isoflurane and Arterial Blood Gas Values in Anesthetized Green Iguanas, Iguana iguana

“…P aC 02 is the partial pressure of carbon dioxide in the alveoli as measured in the end-tidal expired gases. defined response, and 3) measurem ent o f equilibrated endtidal anesthetic concentration (Sackner, et al, 1964). All three requirements were met in this study.…”

“…A coaxial Mapleson D non-rebreathing circuit (Bain Breathing Circuit; Respiratory Care Inc., Arlington Heights, Illinois) was used to prevent rebreathing o f gases and facilitate the quick change o f isoflu rane concentrations. Initial values for end tidal CO2 were low er than the desired range (35 m m Hg) (Sackner, et al, 1964). Once the end-tidal carbon dioxide (P aC 02) was stable and the appropriate core temperature was achieved, end-tidal isoflurane concentrations were monitored and allowed to sta b iliz e for at least 25 m in u n til the en d -tid al iso flu ran e concentration was equal to the inspired concentration o f isoflurane.…”