how sphygmomanometer works
The diagram should not occupy more than half a page as it needs to show the details of each part.
You may first want to write an introduction paragraph on the importance of measuring/ monitoring blood pressure. Then comes the context of sphygmomanometer. You may do some research on how/ when the equipment was invented (by whom as well) and its working principle. Then you try to make the transition on how it got improved to the one used nowadays (the one with a pump). Attach a figure showing details of such a sphygmomanometer. You may add 1 or 2 sentences as concluding remarks on how physics got involved to medicine (that should be mentioned in the working procedure too).