A Technique for Estimating the Position of the Oxygen-Hemoglobin Dissociation Curve

Abstract

A nomogram was constructed which allows estimation of the P(50) value from the Po(2) and per cent O(2) saturation of a single venous blood sample. There was excellent correlation between 50 estimated P(50) values obtained in 27 severely ill patients when compared with P(50) values determined from constructed OH-DC's (correlation coefficient 0.92). The mean of the differences between the estimated and determined P(50) values was 1.5 mm Hg with a standard deviation of +/-1.1, and the maximum difference was 4 mm Hg.

The in-vivo oxyhaemoglobin dissociation curve at sea level and high altitude

“…This nomogram (Canizaro et al, 1974), which has been validated against the mixing technique mentioned above, estimates P 50 based on the PO 2 and SO 2 values of a single venous blood sample. Because it relies on interpolation based on two measurements, the caveat of this method is that the two measurements must be extremely accurate, or the resulting P 50 may be very inaccurate.…”

A simple method to calculate P50 from a single blood sample

“…The square root of the average square error (root-mean-square error) is 1.27 mmHg. The method was also evaluated using sample data from Mountcastle [6] (Table 1), where the results of our method are compared with the nomogram developed by Canizaro et al [3]. As can be seen, our method is comparable in accuracy.…”

“…Several methods to estimate Pso have been reported [1][2][3], but none is simple enough for speedy calculation using a pocket calculator. Here we report on a very simple method for estimating Pso from a single arbitrary point on the oxyhemoglobin dissociation curve.…”

“…Comparison of this method (Doyle Pso) with the methodofCanizaro et al[3] (Canizaro Pso) for data obtained from Mountcastle[6]. (The Canizaro data is presented with less precision because it was obtained from a nomogram)…”

Effects of massive transfusion on oxygen availability

“…PvO 2 was determined in the blood collected from the distal part of Swan-Ganz catheters. (6,7) . Arteriovenous oxygen difference (avDO 2 ), oxygen availability (DO 2 ), oxygen extraction ratio (O 2 ER), and oxygen consumption (VO 2 ) were determined by standard equations.…”