BLOOD BUFFERS: a program to simulate blood pH The model here presented has three parameters: arterial pH, arterial PCO2 and hemoglobin concentration. It calculates the changes in pH and buffer capacity induced by respiratory or experimental changes in PCO2; for example, if an estimate of the venous PCO2 is provided, it calculates the arterio-venous pH difference and total CO2 difference. The program assumes two buffers: CO2 and a non-carbonic buffer (B) with pK=6.8 that represents proteins, phosphate, etc. In this model Hb, being the principal blood buffer is used to estimate the total concentration of B; moreover, given that protons are exchanged between the two buffers, the program assumes that the sum of deprotonated buffer components (Sdp=[HCO3-]+[B]) is constant. A more detailed explanation of the model is provided on request of the user. arterial blood pH (normal value: 7.4) arterial PCO2 (in mmHg; normal value: 38) hemoglobin concentration (g/dL; normal value 14) other PCO2 (in mmHg; e.g. venous PCO2, normal value: 45; or standard PCO2: 40) Should I explain the model? no yes