Ultrasound could become a new way to treat high blood pressure, a new study shows.

About 70 million American adults (29 percent) have high blood pressure—that's 1 of every 3 adults. Only about half (52 percent) of people with high blood pressure have their condition under control.

In a new study, Japanese researchers found that applying 20 minutes of ultrasound to the forearm of patients resulted in a significant drop in blood pressure.

Japanese researchers at Tohoku University enrolled 212 patients with type 2 diabetes, the most common form of the disease, who also had treatment resistant high blood pressure. Treatment resistant high blood pressure means that people are unable to control their condition despite the use of multiple medications.

They were divided into four groups. One received 20 minutes of low frequency (800 kHz), low-intensity ultrasound radiation to the forearm. Another received 500 kHz of low-intensity radiation for 20 minutes. The other two groups were used as controls, receiving a placebo procedure.

They found that the patients' blood pressure and pulse rates were significantly reduced after both 800kHz and 500kHz irradiation sessions compared to pre-treatment levels.

Blood pressure levels were also lower than those of the placebo groups, but significantly so in the case of the 500kHz treatment. No adverse effects were found in either group as a result of the ultrasound treatment.

How ultrasound improves blood pressure in these patients is still unclear, but it might suppress sympathetic nerve activity, responsible for the “fight or flight response” by means of nerve pathways from the forearm to the cardiovascular system, the researchers say. 

The “flight or fight” response is a biological reaction in the body that releases hormones that quickens the heartbeat, constricts the blood vessels and increases blood pressure.

"We do not have specific treatments for resistant hypertension. The cost of anti-hypertensive agents for patients is high. Ultrasound has the advantage of being cheap and non-invasive,” says researcher Katsunori Nonogaki of the study, which appears in the International Journal of Cardiology.