Describe the factors that affect mixed venous oxygen saturation.
Mixed venous oxygen saturation is used as a surrogate marker for the overall balance between oxygen delivery and oxygen consumption. A good answer stated this, described the importance of where it is measured and went on to describe the various factors that affect oxygen delivery and consumption. Descriptions of the factors that affect oxygen saturation of haemoglobin, partial pressure of oxygen in the blood and position of oxygen-haemoglobin dissociation curve were necessary to score well. Important omissions were factors that increased and decreased oxygen consumption. While many candidates were able to correctly write the equations for oxygen content and oxygen flux, they then failed to describe how the variables within these equations were related to mixed venous oxygen saturation.
Leach, R. M., and D. F. Treacher. "The pulmonary physician in critical care• 2: Oxygen delivery and consumption in the critically ill." Thorax 57.2 (2002): 170-177.
Rivers, Emanuel P., Douglas S. Ander, and Doris Powell. "Central venous oxygen saturation monitoring in the critically ill patient." Current opinion in critical care 7.3 (2001): 204-211.
Pearse, R. M., and A. Rhodes. "Mixed and central venous oxygen saturation." Yearbook of Intensive Care and Emergency Medicine 2005. Springer, New York, NY, 2005. 592-602.
Reinhart, K. "Mixed venous oxygen saturation." Applied Cardiopulmonary Pathophysiology 2 (1989): 315-325.