Used without further specification, “blood pressure” usually refers to the blood pressure journal pdf in large arteries of the systemic circulation. It is one of the vital signs, along with respiratory rate, heart rate, oxygen saturation, and body temperature.
Traditionally, blood pressure was measured non-invasively using a mercury manometer and this is still generally considered the gold standard. More recently other semi-automated methods have become common, largely due to concerns about potential mercury toxicity, although cost and ease of use have also influenced this trend. Early alternatives to mercury sphygmomanometers were often inaccurate, but more modern validated devices have similar accuracy to mercury devices.
In the short term it is regulated by baroreceptors which act via the brain to influence nervous and endocrine systems. Blood pressure that is low due to a disease state is called hypotension, and pressure that is consistently high is hypertension. Both have many causes and may be of sudden onset or of long duration. Long term hypertension is a risk factor for many diseases, including heart disease, stroke and kidney failure.
Long term hypertension is more common than long term hypotension. Long term hypertension often goes undetected because of infrequent monitoring and the absence of symptoms.
In practice blood pressure is considered too low only if noticeable symptoms are present. Observational studies demonstrate that people who maintain arterial pressures at the low end of these pressure ranges have much better long term cardiovascular health. There is an ongoing medical debate over what is the optimal level of blood pressure to target when using drugs to lower blood pressure with hypertension, particularly in older people. The table shows the classification of blood pressure adopted by the American Heart Association for adults who are 18 years and older.
It assumes the values are a result of averaging resting blood pressure readings measured at two or more visits to the doctor. In November 2017 the American Heart Association announced revised definitions for blood pressure categories that increased the number of people considered to have high blood pressure. Blood pressure fluctuates from minute to minute and normally shows a circadian rhythm over a 24-hour period, with highest readings in the early morning and evenings and lowest readings at night. Loss of the normal fall in blood pressure at night is associated with a greater future risk of cardiovascular disease and there is evidence that night-time blood pressure is a stronger predictor of cardiovascular events than day-time blood pressure.
Various other factors, such as age and sex, also influence a person’s blood pressure. In children, the normal ranges are lower than for adults and depend on height. Reference blood pressure values have been developed for children in different countries, based on the distribution of blood pressure in children of these countries.
As adults age, systolic pressure tends to rise and diastolic pressure tends to fall. Consequently, in the elderly, systolic blood pressure often exceeds the normal adult range, this is thought to be due to increased stiffness of the arteries. Differences between left and right arm blood pressure measurements tend to be small.
Curve of the arterial pressure during one cardiac cycle. The closing of the aortic valve causes the notch in the curve. The up and down fluctuation of the arterial pressure results from the pulsatile nature of the cardiac output, i. By expanding under pressure, the aorta absorbs some of the force of the blood surge from the heart during a heartbeat.