The carbon monoxide dissociation curve of human blood

Abstract

The complete dissociation curve of carboxyhaemoglobin has not been studied since Douglas et al. (1912), using the more accurate and convenient methods available at the present time. COHb dissociation curves have therefore been determined in the absence of oxygen, at three different C02 pressures, for the blood of three normal subjects. These curves have been compared with the corresponding 02Hb curves. METHODSFor each experiment 20-25 ml. of venous blood was freshly drawn into a syringe, the dead space of which was filled with heparin solution.Deoxygenation of the blood. Before determining the carboxyhaemoglobin dissociation curves, the blood was deoxygenated as completely as possible, to exclude the effect of any residual oxyhaemoglobin on the uptake of carbon monoxide. 17 ml. of the blood was introduced into a 410 ml. tonometer which was evacuated to a pressure of 50 mm Hg. Further lowering of the pressure was found to cause boiling of the blood and undue haemoconcentration. Nitrogen was then admitted to the tonometer to restore the pressure to atmospheric. This was followed by a second evacuation and restoration of the pressure with nitrogen, after which the tonometer was rotated for 5 min in a water-bath at 370 C. The whole cycle was repeated four times making a total of eight evacuations and four 5 min periods of equilibration with nitrogen at 370 C. The

The Bohr effect on the reaction of carbon monoxide with fully oxygenated haemoglobin.

“…Further precise data of Joels & Pugh (1958) and Roughton (1965) confirmed that the equilibrium curve for 02 cannot be obtained from that for CO by using a simple scale factor, M. The same conclusion was also reached on the basis of kinetic studies (Gibson, 1959). The value of M is sensitive to temperature and varies with pH (Roughton, 1954;Joels & Pugh, 1958). The results of Allen & Root (1957) suggest that M reaches a maximum value in whole blood at a plasma pH of 7-4.…”

“…The estimation of the four individual equilibrium constants for CO, by Roughton (1954), and for 02 by Roughton, Otis & Lyster (1955), supported this argument. Further precise data of Joels & Pugh (1958) and Roughton (1965) confirmed that the equilibrium curve for 02 cannot be obtained from that for CO by using a simple scale factor, M. The same conclusion was also reached on the basis of kinetic studies (Gibson, 1959). The value of M is sensitive to temperature and varies with pH (Roughton, 1954;Joels & Pugh, 1958).…”

The kinetics of the reaction of carbon monoxide with fully oxygenated haemoglobin in solution and erythrocytes

“…P0oand pressure. The data of Rodney et al (1969) would suggest that neither pH nor pressure has any effect on M. They discount earlier data of Roughton (1954), Allen & Root (1957) and Joels & Pugh (1958) …”

The optimised CO-rebreathing method: a new tool to determine total haemoglobin mass routinely

“…Godin and Shephard (1972) calculated the diffusion coefficient of CO to Mb to be 0.1 ml CO s À1 mmHg À1 . Assuming an increase in HbCO content by 5%, the increase in pCO in blood is 0.02 mmHg [Joels and Pugh 1958; i.e. that within 300 s (mean time of minutes 4 and 6) after starting the CO-rebreathing of 60 ml CO, 0.6 ml CO is bound to Mb].…”