I was reading through a long topic here on Blood Pressure, I see they are in Boots for 2-3000B

Is there any difference in quality of reading form the compact wrist ones compared to the bulky upper arms ones?

As a bit of a back up, would the adult upper arm ones do a boy as well, (body of a 6yo) as an accurate indication of BP?

(Purely as more info how fast we have to get him to hospital when he gets sick at home - the lad has a medical condition)

Wrist monitors are harder to use correctly, but if used correctly can be as accurate as upper arm ones. The wrist type is particularly sensitive to body position. Generally the upper arm ones are recommended for home use.

You can use the same monitor for adults and children. However, you would need to have a cuff appropriate to the boy's size. (The same applies to adults, too. The cuff that comes as standard is too small for fat/muscular adults with large arms.) I'd recommend you measure the circumference of the boy's upper arm and check for the availability of an appropriate cuff before purchasing the monitor. You'll probably have to order the smaller cuff from overseas.

As with most of the commercially bought medical devices, buy the best you can afford.

Comment above from AyG very valid.

I have both a cuff and a wrist monitor. I use the cuff version more often, but in reality there is still a wide variation in repeat readings as with the wrist version. The Omron wrist machine I have has an ingenious way of leveling your arm with your heart. Can't for the life of me work out how it does it, but it does ensure that the arm is always in the same position.

Maybe one reason I like the cuff version more is that I can take alternate readings from each arm. Whereas with the wrist monitor you have to set the machine for one side. Changing the setting every time for each arm is too much of a pain.

I paid about 100 British pounds for my machine about 10 years ago. so should be available for less now.

I bought a Microlife BP 3AP1-3E cuff one and it came with a large cuff which fits a fat farang like me comfortably.

It cost 2,700 baht. You can specify what size cuff you require when you order, Sm, Med or Large. The price will be the same.

I ordered mine through the paharmacy in Nakhon Sawan and they sent it to me EMS as I live 125 km away for 100 baht and that EMS included my meds as well.

Do a quick Google search then narrow it down to what you want.