The relationship between change in blood pressure, blood pressure and time

Physiological homeostatic mechanisms and interventions by anaesthetists attempt to moderate excessive change in many biological variables during anaesthesia. These mechanisms may have fast or slow response times. This study describes how mean arterial blood pressure changes with time and how the change is dependent upon the pre‐existing blood pressure. The results demonstrate the ‘regression towards the mean’ concept; low arterial blood pressures increase and high pressures decrease. The data are the result of all interactions and have been used to produce an ‘envelope’ into which 80% of all changes fall. Alarm systems using this envelope could warn of excessive changes that occur within short time intervals.