In the walls of the carotid artery of the neck exists a baroreceptor (pressure sensor) called the carotid sinus. The carotid sinus monitors blood pressure by the amount of deformity detected in the walls of the carotid artery. Thus, when the pressure increases there is more stretch on the walls. This information is then sent to the brain via the glossopharyngeal nerve (cranial nerve IX) where it synapses at the nucleus tractus solitarius of the medulla oblongata and indirectly affects the heart rate through the hypothalamus via the vagus nerve (cranial nerve X).
Certain studies suggest that a manual stimulation of the carotid sinus can cause a drop in heart rate and ultimately a drop in blood pressure. For further information regarding the carotid body massage please visit the following link to be redirected to the New England journal of medicine:
This information is important in osteopathy as we sometimes find tissue tone to be increased in the area over the carotid sinus that may be placing pressure on. This pressure may potentially be contributing to a lower blood pressure in an individual as the pressure caused by the increased muscle tone may be interpreted by the sinus as an increase in blood pressure. Thus the body tries to correct this via its connection with autonomic nervous system of the heart to either increase or decrease its rate respectively.
This would mean that not only would a shortening of the overlying musculature place pressure on the carotid sinus, but a back-up of fluid in the neck would also create a similar pressure with a similar outcome.
Therefore, in terms of how this may be addressed with osteopathy is by reducing the amount of tension and pressure in the neck with the intention of changing the physiology based on a change in the anatomy. Please note that osteopathy does not treat blood pressure issues. Osteopathy does, however, treat the body based on objective anatomical findings.
Please note that there is currently no measurable evidence or journal articles that exist to support how osteopathic manipulation can influence blood pressure. However, the anatomical and physiological connection are valid and do exist.