Describe the physiological factors that affect PaCO2.
Candidates who scored well generally defined PaCO2 and proceeded to describe factors in terms of those related to production and elimination. Good answers described the key production factor as being rate of production through aerobic metabolism which is in turn influenced by substrate and BMR. Those who scored well described elimination as being dependent upon minute ventilation, which in turn is influenced by CO2 detection by chemoreceptors, specifically detailing the difference between peripheral and central. Many candidates detailed pathophysiological factors which unfortunately did not gain any marks.