What are appropriate values of relative krogh diffusion Constant of NO against CO and of theta-NO in alveolar septa?

OBJECTIVES

To propose new physical constants for NO and CO (Krogh diffusion constant ratio (KD) and specific blood conductance for NO (θ)) for calculating DMCO and Vc, according to Roughton-Forster's equation (Roughton and Forster, J. Appl. Physiol. 11: 290-302, 1957) from simultaneous DLNO and DLCO measurements.

RESULTS AND CONCLUSIONS

(1) The Graham's law is unacceptable for determining KD because CO does not fulfil all the conditions of an "ideal" gas. We have re-estimated KD in a new way based on difference in molar volumes of two gases (molar volume theory). The KD thus decided is 2.34. (2) θ measured with rapid-reaction, constant-flow method by Carlsen and Comroe (J. Gen. Physiol. 42: 83-107, 1958) may be underestimated by about 40 % due to unstirred water layer surrounding the erythrocyte. (3) Erythrocyte θ can be harvested from O release kinetics in presence of high concentration of dithionite, which effectively removes the unstirred water layer-elicited effect. Multiplication of erythrocyte θ by erythrocyte KD equals erythrocyte θ, the value of which is 6.2 mL/min/mmHg/(mL⋅blood). According to the concepts of Kang et al. (RESPNB. 241: 62-71, 2017) and Borland et al. (RESPNB. 241: 58-61, 2017), in vitro θ decided from rapid-mixing experiments may mirror bulk absorption of NO by erythrocytes. (4) In pulmonary capillaries, NO uptake takes place predominantly in the surface rim of the erythrocyte. This surface absorption of NO increases the θ 10-fold versus bulk absorption of NO to about 60 mL/min/mmHg/(mL⋅blood).