Advice from the BP Measurement Experts
Last week we addressed a report from the Institute of Medicine indicating that high blood pressure is not on the minds of the general public. However, in the most recent issue of the Lancet, a different view of hypertension was posted: what if your physician is looking at the wrong BP values? What if there is more to clinic blood pressure, or the measurement that your physician takes, than the average value?
As reported by many outlets including the BBC and in more detail, Pulse, research from Peter Rothwell at the John Radcliffe Hospital in Oxford, UK proposes that variability and maximum values of BP measured in the clinic can be just as, if not more, informative, especially for those hypertensive or who have had a transient ischaemic attack. This research found that patients with BP readings that change from visit to visit are at greater risk of having a stroke than those with steady average clinic readings. With these findings, Professor Rothwell questions the current guidelines for treatment as they are all based on the "widespread belief... that underlying usual blood pressure can alone account for all blood-pressure-related risk of vascular events" 1. While the current guidelines may not be incorrect, they are not likely to be as comprehensive as needed.
This is particularly interesting given that we have discussed BP variability and, in particular, the factors that contribute to these fluctuations. With the growing popularity of BP monitoring, it begs the question, what levels of variability are acceptable for BP measured outside of the clinic and at home? While these answers are not likely to be easily answered, it is good to have research highlight the nuance and importance to variation in BP measurements especially in light of times when it seems that BP readings may be much different than what is expected, which often prompts the response, "my BP device doesn't seem to be working." It's not to say that BP monitors are always correct but that fluctuations in BP are a physiologic reality; one that seems to warrant a bit more attention.
This is just the attention that is needed to highlight that good, careful manual BP measurement can be complementary to well-designed, thoroughly-validated automated solutions.
1 Rothwell PM. "Limitations of the usual blood-pressure hypothesis and importance of variability, instability, and episodic hypertension." Lancet 2010; 375: 938-48.