That is the study of the “European Society of Hypertension recommendations for conventional, ambulatory and home blood pressure measurement.” Over 28 densely packed pages you get comprehensive information about the pros, cons, pitfalls and considerations of when, how to take and how to interpret blood pressure (BP). And the DIY chartrooms are like a horror story concerning health (here blood pressure) issues; they truly are the stronghold of incompetence and a malicious endangerment of the help seeker´s health.
More and more people nowadays measure their BP at home, thus it is not surprising that many different ways of how to take the BP and how to interpret it have emerged. A growing number of patients for example take their BP first thing in the morning, a few times in a row, being upset that it varies widely and then averaging the result. This is an example of a bit of truth in everything, but in total it’s wrong.
Although the recommendations were written 10 years ago, hardly anything has changed in assessing BP. BP is recorded e.g. 120/80 which means the pressure in the arteries is measured when the heart is contracting (systolic) and when it is relaxed (diastolic). BP can be highly variable even in short periods of time and to minimize errors the reading should be taken with an empty bladder sitting or lying after a few minutes of rest (also resting from tobacco, coffee or exercise for at least 30 minutes) with the BP cuff and the forearm at the level of the heart. The weight of the arm should be supported, one should not speak during the measurement of the BP and a further reading should not be repeated within a minimum of one minute, because the artery has to rest, too. The BP should not be taken during the first 30 minutes after getting up, but before taking ones BP medication. BP checks should be repeated at least in the evening, a time when it tends to rise naturally anyway.
One BP result is absolutely meaningless and diagnosing high BP via visits to the doctor´s surgery is often unhelpful, because results may be artificially elevated and high is everything above 140/90. Results of 160/100 and higher nowadays are termed stage II hypertension and immediate treatment without further evaluation is warranted with values above 180/110. But don´t think that a BP of 135/85 is normal; no it is called pre-hypertension, only a BP of 120/80 and below is now considered as normal. Fortunately in otherwise healthy persons pre-hypertension does not need treatment.
Unfortunately, life is never as straightforward and a lot of people will have results requiring treatment mingling with normal results. Then BP assessment at home becomes of utmost importance; either ambulatory measuring which records the BP automatically every 30 minutes over a 24-hour period or frequent self-measurements throughout a few days at home. A mean BP of 135/85 (120/70 whilst asleep) and above is considered as hypertension or a quarter of a representative number of results (e.g. 25 to 30 readings). If in doubt the readings of the first day can be discarded to assure that the novelty of checking the BP does not affect the result adversely.
Finally, we only have to make sure that the cuff is fitted correctly… and just as a reminder, less salt, less stress, more exercise, healthy eating, a normal weight, not smoking and not drinking excessively helps keeping the BP down.