shahn@hstbme.mit.edu (Sam Hahn) (04/24/91)
Does anyone know of an equation that describes the oxygen saturation/desaturation curve for hemoglobin? Surprisingly, none of my biochemistry or physiology texts seems to have a reference for an actual quantitative relationship between oxygen pressure and hemoglobin saturation. I have tried curve fitting a standard saturation curve with very unsatisfactory results so any help would be appreciated. Please email your responses and I will post a summary if other people are interested. Thanks. Sam Hahn
larry@kitty.UUCP (Larry Lippman) (04/25/91)
In article <6523@husc6.harvard.edu> shahn@hstbme.mit.edu (Sam Hahn) writes: >Does anyone know of an equation that describes the oxygen >saturation/desaturation curve for hemoglobin? Surprisingly, none of my >biochemistry or physiology texts seems to have a reference for an actual >quantitative relationship between oxygen pressure and hemoglobin >saturation. > >I have tried curve fitting a standard saturation curve with very >unsatisfactory results so any help would be appreciated. Hemoglobin saturation in % plotted against PO2 varies depending upon both pH and temperature. If you look in one of the more complete physiology texts, such as "Human Physiology" by Mountcastle, you will see *families* of curves, with significanly different curves resulting from pH variations of as little as 0.1 pH unit. You will also see different curves depending upon temperature, but temperature variation is not much of a problem in say, a clinical setting. Therefore, your curve fitting may be unsatisfactory due to pH (and possibly temperature) variation. It would have been helpful if you had described your application. For example, in the case of an oximeter, curve fitting is not much of a problem since pH and temperature is largely compensated after calculations are performed with both the visible light and NIR spectrophotometric absorption versus saturation curves. Using just two fitted curves (the visible and NIR), oxygen saturation can be measured to within 2% - which is really pretty good. Larry Lippman @ Recognition Research Corp. "Have you hugged your cat today?" VOICE: 716/688-1231 {boulder, rutgers, watmath}!ub!kitty!larry FAX: 716/741-9635 [note: ub=acsu.buffalo.edu] uunet!/ \aerion!larry