Janelle McAlpine MMRes BA (Human Bioscience) BMid
Registered Midwife
Blood pressure is the pressure of your blood on the walls of your arteries as your heart pumps it around your body. It’s a vital part of how your heart and circulation works.
Once the blood leaves your heart it continues to move through the rest of your body via your arteries under two forces:
- The blood that is pumped out of the heart by your next heartbeat keeps it moving away from your heart, and
- The muscles in the walls of your arteries contract and relax, moving your blood in the right direction.
Arteries play an active role in moving blood around your body. This is why they have a thick muscle layer. The muscular artery walls are elastic and can stretch to accommodate higher volumes of blood; for instance when your heart beats faster or you are exercising. This regulates how much pressure the artery walls are under while doing their job.
Veins, on the other hand, are almost passive bystanders in returning blood to your heart. They don’t need to pump it back – its more like a shuffle really. It is for this reason that they have valves, rather than thick muscle walls. The valves close and let blood go one way – toward your heart – but not the other (when they work properly).
Like any other muscle the more you use your arteries the better they work. When your arteries need to work hard to pump enough blood around your body (such as when you exercise), they get better at what they do. Regular exercise trains your artery muscles, and they stay strong and flexible because they are used to their full capacity regularly. It is because your arteries are constantly adjusting to their workload the your blood pressure goes up and down all the time, adjusting to your heart’s needs depending on what you are doing.
Blood pressure is usually reported as two numbers – a top and a bottom (120/70). The top number is the systolic reading – a fancy name for the pressure on your artery walls when your heart is contracting (or squeezing the blood out). The normal range for this is between 90 and 120. The bottom number is the diastolic reading. This is the pressure on your artery walls when your heart is relaxing (or refilling), and is normal if your reading is between 60 and 80.
In 2011-12, just over one in five people (21.5%) aged 18 years and over had measured high blood pressure (systolic blood pressure greater than or equal to 140mmHg and/or diastolic blood pressure greater than or equal to 90mmHg)(1).
Low blood pressure (readings lower than these numbers), in otherwise healthy people is not associated with any long term health risks. When your blood pressure is low you may feel dizzy or lightheaded, unsteady on your feet, or faint. It can happen when we have been standing a long time or we get up too quickly.
Any changes in position need to be detected by our body and our blood diverted accordingly. If you are prone to low blood pressure take your time getting up, and take a seat every now and then. It is more likely to happen when we are hot. This is because our body diverts more blood to your skin to try and cool you down. While uncomfortable it is easily treatable – a big drink of water and taking a moment to adjust will make you feel better quickly. If this does resolve your situation then please see your doctor.
When your arteries have been damaged, clogged or just basically neglected they lose their ability to stretch. This affects their elasticity and the ability to ‘absorb’ the pressure the blood travelling through them. This increases the force of the blood moving through the artery and the pressure on the artery walls, resulting in high blood pressure.
High blood pressure is when your blood pressure is persistently higher than normal. If your systolic is between 120-140, or your diastolic between 80-90, it is still considered in normal range. However it may indicate that high blood pressure is just around the corner and extra surveillance may be necessary. Measurements over 140 systolic and/or 90 diastolic are abnormal and require further review. If this high blood pressure does not resolve and becomes your usual reading the condition is termed chronic. The medical name for high blood pressure over a long period of time is chronic hypertension.
Chronic hypertension is one of the main risk factors for heart disease. Your risk for this increases as you get older, but it is now not uncommon to find young adults with hypertension. Please get your blood pressure checked regularly. If it’s persistently high it needs to be managed in order to minimise your risk of other health complications. Uncontrolled high blood pressure can lead to a heart attack, stroke, or kidney damage.
References:
- Australia Bureau of Statistics, Australian Health Survey updated results 2011-2012