Devices and methods for control of blood pressure
Apparatus is provided for reducing hypertension of a subject. A selective circumferential pressure applicator ( 60 ) includes at least two surfaces ( 61 ) that increase baroreceptor activity of the subject, by applying pressure to an artery ( 20 ) of the subject at two or more respective non-contiguous regions around the circumference of the artery, at a longitudinal site of the artery, such that between the non-contiguous regions, at the longitudinal site (a) there is at least one region ( 22 ) of the artery that is more relaxed than in the absence of the device, and (b) there is at least one region ( 21 ) of the artery that is more tense than in the absence of the device. A joint ( 63 ) couples the surfaces to each other. For at least a portion of the subject's cardiac cycle, the joint does not to contact the subject's artery. Other applications are also provided.
1. An apparatus for stimulating baroreceptors to treat hypertension of a subject, the apparatus comprising:
a selective circumferential pressure applicator, comprising:
at least two non-contiguous pressure application surfaces that are configured to increase baroreceptor activity of the subject by applying pressure to an artery of the subject at two or more respective non-contiguous regions around a circumference of the artery at a longitudinal site of the artery, such that between the non-contiguous regions, at the longitudinal site:
there is at least one region of the artery that is more relaxed than in the absence of the apparatus, and
there is at least one region of the artery that is more tense than in the absence of the apparatus; and
a joint configured:
to couple the at least two surfaces to each other on the circumference of the artery at the longitudinal site, and
for at least a portion of a cardiac cycle of the subject, not to contact the artery of the subject on the circumference of the artery at the longitudinal site
wherein the at least two non-contiguous pressure application surfaces and the joint are configured to apply forces passively to the artery during systole and diastole of a cardiac cycle in order to increase the baroreceptor activity and maintain blood flow through the artery.
2. The apparatus according to claim 1 , wherein the joint is a rigid joint.
3. The apparatus according to claim 1 , wherein the joint is a flexible joint.
4. The apparatus according to claim 1 , wherein the at least two-non-contiguous pressure application surfaces are configured to apply the pressure to the artery such that the region of the artery that is more tense is between the joint and the region of the artery that is more relaxed.
5. The apparatus according to claim 1 , wherein the at least two-non-contiguous pressure application surfaces are configured to apply the pressure to the artery such that the region of the artery that is more relaxed is between the joint and the region of the artery that is more tense.
6. The apparatus according to claim 1 , wherein the at least two non-contiguous pressure application surfaces are slidably coupled to each other.
7. The apparatus according to claim 1 , wherein the at least two non-contiguous pressure application surfaces are oriented in general opposition with respect to each other.
8. The apparatus according to claim 7 , wherein an angle between two of the at least two surfaces is less than 20 degrees.
9. The apparatus according to claim 8 , wherein the angle between two of the at least two surfaces is less than 10 degrees.
10. The apparatus according to claim 1 , wherein the at least two non-contiguous pressure application surfaces and the joint are configured to compress the artery and stimulate the baroreceptors without reducing blood flow through the artery.
11. A method for stimulating baroreceptors to treat hypertension of a subject, the method comprising:
using at least two non-contiguous pressure application surfaces that are coupled to each other by a joint, applying pressure to an outer wall of an artery of the subject at two or more respective non-contiguous regions around a circumference of the artery at a longitudinal site of the artery, such that between the non-contiguous regions, at the longitudinal site:
there is at least one region of the artery that is more relaxed than in the absence of the at least two non-contiguous pressure application surfaces, and
there is at least one region of the artery that is more tense than in the absence of the at least two non-contiguous pressure application surfaces, and
placing the joint such that for at least a portion of a cardiac cycle of the subject the joint does not contact the artery of the subject on the circumference of the artery at the longitudinal site
wherein the at least two non-contiguous pressure application surfaces and the joint apply forces to the artery passively during systole and diastole of a cardiac cycle in order to stimulate the baroreceptors and maintain blood flow through the artery.
12. The method according to claim 11 , wherein applying the pressure comprises applying the pressure to the artery such that the region of the artery that is more tense is between the joint and the region of the artery that is more relaxed.
13. The method according to claim 11 , wherein applying the pressure comprises applying the pressure to the artery such that the region of the artery that is more relaxed is between the joint and the region of the artery that is more tense.
14. The method according to claim 11 , wherein applying the pressure to the artery comprises applying pressure to the artery at a region of the artery that is rich in baroreceptors.
15. The method according to claim 11 , wherein applying the pressure to the artery comprises applying pressure to the artery at a location selected from the group consisting of an upstream location, and a downstream location from a region of the artery that is rich in baroreceptors.
16. The method according to claim 15 , further comprising selecting a location as the selected location such that at least a portion of a pressure change induced in the artery at the location, by the at least two surfaces, reaches the region of the artery that is rich in baroreceptors after a time delay from when the pressure change was induced at the location, the time delay being such that baroreceptor stimulation at the region of the artery that is rich in baroreceptors, as a result of the portion of the pressure change that reaches the region of the artery that is rich in baroreceptors, is greater than if the pressure change was induced by the at least two surfaces at the region of the artery that is rich in baroreceptors.
17. The method according to claim 11 , wherein applying the pressure to the artery comprises applying the pressure using the at least two non-contiguous pressure application surfaces oriented in general opposition with respect to each other.
18. The method according to claim 17 , wherein applying the pressure to the artery comprises applying the pressure using the at least two non-contiguous pressure application surfaces oriented such that an angle between the two surfaces is less than 20 degrees.
19. The method according to claim 18 , wherein applying the pressure to the artery comprises applying the pressure using the at least two non-contiguous pressure application surfaces oriented such that the angle between the two surfaces is less than 10 degrees.
20. The method according to claim 11 , wherein the at least two non-contiguous pressure application surfaces and the joint compress the artery and stimulate the baroreceptors without reducing blood flow through the artery.