Izumi Shibuya

Estimation of the Transfer Coefficients of Oxygen and Carbon Monoxide in the Boundary of Human and Chicken Red Blood Cells by a Microphotometric Method

The reaction rates of O2 and CO with the human and chicken red blood cell (RBC) were measured by using a microphotometric apparatus. In the experiments on the human RBC, a small amount of RBCs were put in an air-tight reaction cuvette. Gas mixtures containing various concentrations of O2 and CO were sequentially injected into the cuvette and the change in O2 and CO saturation of hemoglobin was measured from the change in transmission of the RBCs at 402 and 416.5 nm. The reaction rate of CO with RBCs was significantly influenced by photodissociation of carboxyhemoglobin (COHb). To eliminate this, a short-pass filter (400 to 435 nm) and a sector (100 Hz) were used. By comparing the measured reaction rates of O2 and CO with the theoretical rates obtained from the numerical solutions of the partial differential equations of the diffusions of O2 and CO, the transfer coefficients of O2 and CO (eta O2 and eta CO) in the RBC boundary, including the RBC membrane and water layer around the RBC, were estimated. Both the values showed good agreement, ranging from 0.3 to 2.5 x 10(-6) cm.sec-1.Torr-1. Furthermore, the chorioallantoic capillary of chicken embryo was used for the measurements of the reaction rates of O2 and CO with RBC through the capillary membrane. The reaction rates of O2 and CO in the chorioallantoic capillary were slower than those obtained in the human RBC. By comparing the measured reaction rates and the numerical solutions, the eta O2 and eta CO in the boundary, including the capillary membrane, plasma, and RBC membrane, were estimated. These two values ranged from 0.1 to 0.4 x 10(-6) cm.sec-1.Torr-1 and showed good agreement. These results suggest that the diffusion rates for O2 and CO across the capillary and RBC membrane are similar.

Relation between the contact time and venous and alveolar PCO2 at rest.

The simultaneous partial differential equations for diffusions of O2, CO2, and HCO 3 − ions in the red blood cell (RBC) were solved numerically, taking chemical reactions of Bohr- and Haldane-effects into account. The diffusion equations and the chemical reactions were computed alternatively in an increment time of 2 msec. After solving each of the three diffusion equations, the Po2, O2 saturation (S), Pco2, pH and HCO 3 − content were corrected by using the equations of Bohr- and Haldane-effects, and a modified Henderson-Hasselbalch equation (Kagawa and Mochizuki, 1984). The Bohr-shift was calculated from Hill’s equation by assuming its K value to be a function of the intracellular pH. The change in intracellular Pco2 due to the Haldane effect was also evaluated by means of the modified Henderson-Hasselbalch equation, in which the buffer value was taken as 44 mmol · 1(RBC)−1 · pH c −1 . The computed Pco2 profiles during the Haldane effect in a closed vessel was compatible wit the experimental data of Klocke (1973). The extracellular Po2 profile computed during the Bohr-off-shift in a closed system coincided well with the experimental data of Nakamura and Staub (1964) and Forster and Steen (1968).

Quantitative Relations between Gas Exchange Parameters including Contact Time at Rest and during Treadmill Exercise

Studies on quantitative relations between gas exchange parameters at rest and during exercise have provided many reports on the relation between oxygen uptake (\(\dot V{o_2}\)), arterio-venous 02 differenc.

A Method for Estimating Contact Time of Red Cells in Lung Capillaries from O2 and CO2 Concentrations in Rebreathing Air in Man

In a previous paper (Mochizuki et al., 1986) we described the relation between alveolar- and venous-Pco2 and the contact time (tc). However, at that time, Pco2-dependency of the arterio-venous difference in O2 content ((a-v)Co2), the contact-time-dependency of the Haldane effect, and linearity of the relation between the experimental gas exchange ratio and Pco2 (R-Pco2 line) in rebreathing air were not taken into account. Recently, we have precisely analysed the above correlations from the numerical solutions of the simultaneous O2 and CO2 diffusions in the red blood cell (RBC). Based upon the results we have derived a corrected contact time equation. When the time constant of the reaction rate of the extracellular dehydration reaction was less than 0.2 sec, good agreement was observed between the contact time obtained from the pulmonary diffusing capacity for CO (Uchida, Shibuya and Mochizuki, 1986) and that from the present method.