Blood pressure (also called arterial pressure, or abbreviated as BP) refers to the pressure exerted by circulating blood on the walls of blood vessels, and constituted one of the principal vital signs of life.
Under certain conditions, people were known to alter their blood pressure, lower their body temperature, and manifest tumors as a result of psychological stimuli. Julian Bashir, being genetically enhanced, could control his vital signs, including his blood pressure. (DS9: "Things Past", "Extreme Measures")
In 2373, when Elim Garak experienced claustrophobia after having to work in a tight space to help rescue himself and others from Internment Camp 371, Doctor Julian Bashir commented that Garak's pulse was racing and he didn't want to think about his blood pressure. (DS9: "By Inferno's Light")
In 2374, The Doctor found that Seven of Nine's blood pressure was slightly off, but within tolerance. This was recorded rather airily due to his preoccupation with Kovin's death, which Seven shared. (VOY: "Retrospect")
In 2377, The Doctor listed elevated blood pressure among the physiological responses that were indicated when one person had romantic feelings for another. This information was supplied to Icheb, who was laboring under a misapprehension involving B'Elanna Torres. (VOY: "Nightingale")