Blood pressure is overwhelmingly the most commonly measured parameter for the assessment of haemodynamic stability. In clinical routine in the operating theatre and in the intensive care unit, blood pressure measurements are usually obtained intermittently and non-invasively using oscillometry (upper-arm cuff method) or continuously and invasively with an arterial catheter. However, both the oscillometric method and arterial catheter-derived blood pressure measurements have potential limitations. A basic technical understanding of these methods is crucial in order to avoid unreliable blood pressure measurements and consequential treatment errors. In the recent years, technologies for continuous non-invasive blood pressure recording such as the volume clamp method or radial artery applanation tonometry have been developed and validated. The question in which patient groups and clinical settings these technologies should be applied to improve patient safety or outcome has not been definitively answered. In critically ill patients and high-risk surgery patients, further improvement of these technologies is needed before they can be recommended for routine clinical use.
