Blood pressure is the force of the blood when moving throughout the vasculature and circulatory system, and is responsible for the transport of blood to areas where nutrients and waste products are delivered and removed. Blood pressure, in a normal individual, is incredibly variable to changes in temperature, exercise status, sleep, caffeine and other parameters which dictate the rate at which blood is distributed around the body.
A majority of the pressure of the blood is dictated by the cardiac output of the heart – the force at which the left ventricle of the heart discharges blood out of major arteries to respiring organs, muscles and tissues around your body. The walls of arteries, arterioles and, to some extent – veins – are responsive to hormones and cell messengers which dictate the dilation or constriction of the vessel, which increases or decreases the diameter of the vessel, subsequently increasing or reducing the pressure at which blood flows through. Think of it as a garden hose – a hose with a large diameter will allow more water to flow smoothly with less pressure – but placing your thumb on the hose and applying force increases the pressure, and causes a much quicker flow of water – this is a basic analogy of what happens in our vessels on a beat to beat basis.
When measuring blood pressure manually or automatically, we get certain numbers which give us information about the cardiac cycle and how the heart and vasculature are working in response to stresses and resting conditions. We often hear of the ‘top’ number and ‘bottom’ number in relation to blood pressure – such as 121/79 – the top number being the systolic, and bottom number representing diastolic blood pressure. Systolic blood pressure reflects the pressure of the blood in the arteries during a contraction of the heart, whilst diastolic blood pressure reflects the residual pressure in the vessels during relaxation of the heart in the cardiac cycle. Since the early 20th century, clinicians have monitored blood pressure in individuals and began to piece together the puzzle of how our blood pressure affect mortality, prevalence and risk of diseases, as well as the affect this has on our everyday health.
What is a normal blood pressure? A commonly accepted classification for blood pressure is that below 120/80mmHg is a normal, health blood pressure for individuals over the age of 18. There are also classifications of higher blood pressure described as ‘hypertension’, which exist in stage 1 hypertension and stage 2 hypertension, all of which describe relative risk for the development of cardiovascular disease and cardiac events such as heart attacks and strokes.
As blood pressure changes on a beat to beat, diurnal and even day to day basis, it is a good idea to collect your blood pressure variables in the morning, lunchtime and evening, and average these over a week or so of collection to get a good idea of your average blood pressure. So what do these risks mean for our health?
Even moderate increases of blood pressure of around 130-139/80-89mmHg doubles your risk for developing serious cardiovascular disease, as well significantly increasing your risk of a heart attack or stroke. At this stage, doctors now recommend lifestyle changes and the addition of an anti-hypertensive drug, such as beta-blockers, or more commonly a newer class of medication known as ACE inhibitors or angiotensin IIa inhibitors. Theses medicines work to reduce the action of specific enzymes and cell signalling molecules which cause constriction of the vessels, increasing blood pressure in your circulatory system. A significant risk of high blood pressure is the rupturing of atheromas (fat and cholesterol build ups in arteries and arterioles, a natural process of aging), which cause blockages and strokes, though commonly cause coronary heart attacks due to blockage of the coronary vasculature, which supplies the heart with the blood needed to maintain function.
It is important to regularly check your blood pressure, coming as part of a national campaign to ‘know your numbers’. It is also important to take steps to reducing your blood pressure if you have a higher than expected reading, something which can be achieved in a variety of ways;
Weight management – there is a strong correlation between body weight and blood pressure, particularly as body mass places strain on the body and heart, as well as increasing the chance of occlusion of arteries and vessels in the lower limbs. Even modest weight loss can greatly improve your blood pressure readings, along with reducing your changes for other non-communicable diseases such as metabolic disease and diabetes.