O2 delivery to tissues depends on all of the following factors, EXCEPT:

The fundamental purpose of the cardiorespiratory system is to deliver O2 and nutrients to cells and to remove CO2 and other metabolic products from them. Proper maintenance of this function depends not only on intact cardiovascular (cardiac output) and respiratory systems but also on an adequate number of red blood cells and hemoglobin and a supply of inspired gas containing adequate O2. Affinity of hemoglobin for 02 also determine the oxygen delivery. Ref: Loscalzo J. (2012). Chapter 35. Hypoxia and Cyanosis. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison's Principles of Internal Medicine, 18e.