How to accurately measure blood pressure

Arterial blood pressure is a common parameter assessed in both conscious and anesthetised patients for numerous reasons. These include monitoring disorders, such as renal disease, cardiovascular disease and endocrine disease, and, most commonly, as a parameter to monitor the cardiovascular status of an animal under anaesthesia. Measuring blood pressure is a widely recognised element in patient care because both hypertension and hypotension can significantly affect the health of patients (Sturgess, 2016).

This article summarises both invasive and non-invasive blood pressure (NIBP) techniques available to measure arterial blood pressure in patients and discusses the causes of potential errors that may lead to inaccurate measurements. It describes the proper use of blood pressure measurement devices and interpretation of the measurements obtained from them.

Blood pressure, or more accurately intravascular pressure, is the pressure that blood physically exerts on a vessel wall. This pressure is important because the difference in intravascular pressure at any two points in the vascular network is the driving force for blood circulation. The pressure found at the root of an aorta is much more than the vena cava pressure, ensuring blood will flow from the arterial side to the venous side, delivering nutrients and oxygen to cells located along this path. The most common intravascular pressure measured in small animals is the peripheral arterial blood pressure. This is most commonly measured indirectly via a surface-applied pressure cuff around a limb or tail base using flow detection methods such as oscillometry (Figure 1) or Doppler ultrasound (Figure 2) (Clarke et al, 2015; Haskins, 2015).