Swamp Thing said:
Is it ok to gently squeeze the bulb just after crossing the systolic or diastolic threshold, just to make sure of the exact value?
With the automatic machines which have largely taken over this is probably a bad idea, in fact some will simply go higher still to try and compensate.
It's unlikely you will ever get an exact value, it's always changing depending on a variety of things, and you don't want to become over concerned about the accuracy, that can also distort the results. It's the averages seen over time that provide the most useful information, unless of course you've had an accident or something. It's usually suggested that you will get the most reliable readings (at home) by sitting, supporting the arm at a level similar to heart level, relax, stay still and quiet then start the machine. When it's finished, check the reading and give your arm a rest for at least 5 minutes, then repeat the process. It's usually best to avoid recording your BP after physical activity, eating or drinking (particularly coffee) and it's probably a good idea to be consistent in which arm you use. Take whichever of the two reading is lowest at the measure. Because this can be rather time-consuming, it's usually suggested people record their BP twice a day for 5-7 days, often for diagnosis or following changes in treatment, most people can cope with that.
Drs. do all sorts of variations on this which allows them to use the measures as diagnostic tests for various disorders, but this isn't usually suggested for people doing home measures. Interestingly, your home measures are likely to be the more accurate than the measures done at the Drs. there are too many things going on that cause your BP to rise during a Drs. visit.