Renin is a enzyme that plays a major role in the production of Hypertension. Roughly Renin causes blood vessels to constrict and raises blood pressure. Renin levels can be measured in the blood and they lead to three types of hypertension.

1) Puzzling variety about 1/4 to 1/3 of patients with hypertension actually have low Renin.
2) About 1/4 to 0 of hypertension patients have normal Renin levels.
3) About 1/2 to 2/3 of hypertension patients or so have high Renin levels.

http://en.wikipedia.org/wiki/Renin

These different Renin levels suggest that there may be different mechanisms acting in various kinds of hypertension and that certain kinds of blood pressure drugs and treatments may work better in some folks than others.

In those patients with high Renin levels - a machine like resperate that stimulates nervous system probably causes Renin levels and production to fall. The direct side-effect is significant lowering of blood pressure. However. in patients that have high hypertension but low Renin values -- my hypothesis is that resperate type process will have less impact. This doesn't mean that resperate isn't helpful, only that it unlikely by itself to be able to reverse hypertension difficulties. It may also be a clue as to why some hypertensives find no improvement from resperate machine.

Patients with low Renin values are likely suffering from water retention and cause of water retention tends to be excess salt. Excess salt in diet forces the kidneys to hold water. Sugar has effect of raising human insulin and higher insulin levels make it harder for the body to get rid of salt, which then triggers water retention which raises blood pressure. So, folks with low Renin values often respond well to having diets low in salt and low in sugar. Various substances in protein seem to aid in the promotion of flood removal, and if you are on a low calorie diet, or if you a diabetic it more important to have some protein in your limited calorie intake to overcome tendency to hold water.

In patients with normal renin levels it probably safe to suggest that some other mechanism other than salt or renin production is at work. Some patients might be low in nitrates and ability to produce nitrogenoxide NO. A food like wieners, and heavy green vegetables like brocalli and spinach that are high in nitrates - often trigger significant blood pressure drops in some patients. Renin production is only one of a complex variety of blood pressure mechanisms in the human body.

Exercise has interesting possible secondary effects. For example, it stimulates the lymphatic system .... and helps promote drainage and lower fluid retention. This is probably one benefit of exercise in the hypertension puzzle.

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