Blood pressure and its variability: classic and novel measurement techniques

Abstract

Current hypertension guidelines recommend using the average values of several blood pressure (BP) readings obtained both in and out of the office for the diagnosis and management of hypertension. In-office BP measurement using an upper-arm cuff constitutes the evidence-based reference method for current BP classification and treatment targets. However, out-of-office BP evaluation using 24 h ambulatory or home BP monitoring is recommended by all major medical associations for obtaining further insights into the BP profile of an individual and how it relates to their daily activities. Importantly, the highly variable nature of office and out-of-office BP readings has been widely acknowledged, including the association of BP variability with cardiovascular outcomes. However, to date, the implications of BP variability on cardiovascular outcomes have largely been ignored, with limited application in clinical practice. Novel cuffless wearable technologies might provide a detailed assessment of the 24 h BP profile and behaviour over weeks or months. These devices offer many advantages for researchers and patients compared with traditional BP monitors, but their accuracy and utility remain uncertain. In this Review, we outline and compare conventional and novel methods and techniques for assessing average BP levels and BP variability, and reflect on the utility and potential of these methods for improving the treatment and management of patients with hypertension.

Fig. 1. History of blood pressure assessment and technology development.

a | The timeline depicts the key milestones in the history of blood pressure (BP) measurement, beginning with the first recorded measurement of BP levels, performed in a horse in 1733. b | The number of registered patents with the words ‘blood pressure’ in their title has risen steadily since 1897. The data for the graph were extracted from www.scopus.com. ABPM, ambulatory blood pressure monitoring; HBPM, home blood pressure monitoring.

Fig. 2. Short-term and long-term blood pressure variability.

Blood pressure (BP) patterns are evident across both the short term and the long term, with overall higher BP levels in colder versus warmer months, in daytime versus the night-time and during exposure to acutely stressful events. The different ranges of BP variability are presented in two individuals (with BP readings shown as red and blue circles) over seconds, hours and months.

Fig. 3. The concept of time at target blood pressure levels.

As blood pressure (BP) levels increase with age, the systolic BP of two individuals (depicted by the red and blue lines) might present similar average levels (black line), but owing to a greater BP load, the individual with the BP depicted by the red line will have a greater risk of cardiovascular disease over their lifetime. Adapted with permission from ref., Wolters Kluwer.

Fig. 4. Advantages and disadvantages of classic and novel blood pressure monitoring methods and capacity to capture blood pressure variability.

Blood pressure (BP) monitoring methods enable the assessment of BP during static or dynamic conditions over different time windows, and thus can capture different aspects of BP variability.

Fig. 5. Capacity of classic blood pressure monitoring methods to assess blood pressure variability.

Classic methods to measure blood pressure (BP) are inadequate to capture BP variability across the spectrum of very short-term to long-term variability.