Barcroft J. & Orbeli L. The influence of lactic acid upon the dissociation curve of blood. (Digitized Edition of the 1910 Classic)

Abstract / Аннотация 1. Brief Summary / Краткое содержание “The Influence of Lactic Acid upon the Dissociation Curve of Blood” is an experimental study by Joseph Barcroft and Leonid Orbeli, published in The Journal of Physiology in 1910. The authors investigated the effect of lactic acid on the affinity of blood for oxygen and demonstrated that lactic acid alters the blood dissociation curve in a manner analogous to the effect of carbonic acid described by Bohr. The study includes in vitro experiments in which lactic acid was added to defibrinated blood, as well as experiments in animals subjected to progressively reduced oxygen availability. The principal finding was that increasing lactic acid concentration decreases the affinity of blood for oxygen and facilitates oxygen release. In experiments involving oxygen deprivation in animals, the blood dissociation curve progressively shifted as oxygen deficiency increased; the authors attributed this change to an increase in the concentration of lactic acid in the blood. The physiological significance, as formulated by the authors themselves, is that at low oxygen tension in the capillaries, lactic acid facilitates the release of oxygen from the blood. They further emphasized that the concentration of lactic acid is higher in the tissues in which it is produced, and consequently in the capillaries of those tissues, than in the general circulation. Methodologically, the study is significant because the authors examined not only the effect of artificially adding lactic acid to blood, but also changes in the dissociation curve occurring in the living organism during reduced oxygen availability. In experiments on cats, progressively decreasing the oxygen concentration of the inspired gas was accompanied by a decline in arterial blood oxygen saturation and a corresponding alteration of the blood dissociation curve. The study therefore connects three physiological processes: oxygen deficiency → formation of lactic acid → alteration of haemoglobin–oxygen affinity and facilitated oxygen release to the tissues. It extends the physiological principle demonstrated by Bohr for carbonic acid by showing a similar effect of lactic acid on the dissociation of oxygen from blood. 2. Main Findings and Ideas Lactic acid decreases the affinity of blood for oxygen. Addition of lactic acid to blood produced a marked displacement of the dissociation curve, with the effect increasing as the concentration of acid increased. The effect of lactic acid is analogous to that of CO₂/carbonic acid on the dissociation curve. The authors explicitly noted that the resulting curves were analogous to those produced by increasing concentrations of carbonic acid. The effect is also observed during oxygen deficiency in the living organism. As oxygen deficiency increased, the blood dissociation curve became progressively more depressed; the authors associated this change with an increase in lactic acid in the blood. Local production of lactic acid has physiological significance for working tissues. The concentration of lactic acid is higher in the tissues where it is produced, and consequently in their capillaries, than in the general circulation. Its effect on oxygen release is therefore particularly relevant at the tissue level. Acid-mediated changes in haemoglobin–oxygen affinity facilitate oxygen release where it is required. Barcroft and Orbeli regarded lactic acid as a valuable accessory to tissue respiration and as a factor facilitating the release of oxygen from blood when oxygen tension is low. 3. Relevance to the Buteyko Method The principal aspect of this study that is directly relevant to the physiological rationale of the Buteyko Method is the relationship between CO₂, haemoglobin–oxygen affinity, and oxygen release to the tissues through the oxygen dissociation curve. Buteyko incorporated this physiological relationship into a central element of his theoretical framework: a reduction in CO₂ associated with excessive ventilation increases haemoglobin’s affinity for oxygen and impairs its release to the tissues, whereas restoration of CO₂ through reduced ventilation facilitates the normalization of oxygen release. In Buteyko’s own formulation, this mechanism is identified with the Verigo–Bohr effect and forms a direct part of his explanation of the physiological action of the method. The work of Barcroft and Orbeli is important to this line of development because it experimentally demonstrates the general principle of an acid-dependent alteration of haemoglobin–oxygen affinity not only for carbonic acid, but also for lactic acid. The authors explicitly present their finding as an extension, in the case of lactic acid, of what Bohr had already demonstrated for carbonic acid: under conditions of low oxygen tension, the acid factor facilitates the release of oxygen from the blood. In the Buteyko Method, this physiological principle was applied to the regulation of CO₂ through breathing: excessive ventilation removes CO₂, whereas reduced ventilation is intended to retain or restore CO₂. The resulting change in the blood’s CO₂-related physiological state is linked in Buteyko’s model to haemoglobin–oxygen affinity and tissue oxygen release. Thus, for the history of the Buteyko Method, this 1910 study represents an important physiological link in the chain: acid factor → alteration of haemoglobin–oxygen affinity → change in the oxygen dissociation curve → alteration of tissue oxygen release. In the experiments of Barcroft and Orbeli, the experimentally examined acid factor was lactic acid, whereas in the Buteyko physiological model the central respiratory factor is CO₂ and the associated acid–base state of the blood. The historical significance of the study therefore lies in its experimental demonstration of a physiological principle that became important in the Buteyko explanation of CO₂, the oxygen dissociation curve, and tissue oxygen delivery.