A vital parameter that tells our condition

Answer: The term blood pressure refers trivially to the force with which our blood is pushed through the cardiovascular system and can reach all the different regions of our body. Its value depends on a series of multiple, closely integrated factors that allow the blood to move efficiently within the arteries, enabling the body to receive an adequate amount of blood to cope with the situations we face in daily life.

The discovery of arterial pressure as we understand it formally began with the research of William Harvey (De motu cordis, 1628) who first demonstrated the possibility of making the movement of blood within the cardiovascular system objective by generating the idea of a thrust that made blood circulate within a system of conduits quite similar to the one that supports many of the daily activities of our lives. Blood pressure is what is known as a 'vital parameter' from which it is very often possible to infer the clinical and health condition of a subject, especially in emergency-urgency situations. In fact, blood pressure values are directly or indirectly influenced by the balance of numerous factors, both cardiovascular and general (e.g. anaemia, oxygenation, etc.) and this makes the estimation of blood pressure a parameter of absolute importance for the well-being of the organism. An excessive increase in blood pressure beyond normal limits can cause the development of a wide range of cardiovascular, cerebral and renal complications that can be prevented by normalising values, while an excessive reduction in blood pressure can result in malfunctioning of the organs themselves, which can be corrected by bringing blood pressure values back to normal. Blood pressure values are usually expressed in numerical terms by referring to a characteristic conventional unit of measurement called the millimetre of mercury (mmHg), the use of which dates back to the initial measurement based on the vertical displacement of a column of mercury according to a method that we will describe in detail later. Arterial pressure can be defined in three ways: the systolic pressure (or maximum pressure) which expresses the highest value reached during the measurement, the diastolic pressure (or minimum pressure) which represents the lowest value during the cardiac cycle phase, the differential pressure (the arithmetic difference between the value of the systolic and diastolic pressure) and the mean pressure which represents a value calculated arithmetically (diastolic pressure+1/3 of the differential pressure) which represents the least used value and also the one that offers the least number of implications in clinical and therapeutic terms. Of course, the difference between systolic, diastolic and differential pressure is not only numerical, but has differentiated clinical implications that can be roughly summarised by a closer relationship between maximum pressure and pumping capacity of the heart, minimum pressure and function of the kidney and differential pressure and elasticity of the arterial system. This subdivision appears coarse because pressure values are, in reality, multi-determined, although in some clinical situations, it is possible to correlate certain specific diseases predominantly with changes in a certain type of pressure values (e.g. hyperthyroidism and systolic pressure, aortic valvulopathy and differential pressure, etc.) whose alterations can help in terms of diagnostic accuracy. Blood pressure thus represents a kind of easily accessible summary of our health condition and our potential to develop cardiovascular and renal complications. Blood pressure values that are too high or too low, or values that undergo unexplained changes, are almost always suggestive of some underlying pathological abnormality, not necessarily cardiovascular, in respect of which changes in blood pressure represent an alarm bell that must draw attention to the patients' general clinical condition.