What is blood pressure?
The heart pumps blood around the body, which travels through blood vessels called arteries (imagine water flowing through a pipe). The pressure of the blood flow through the arteries as the heart squeezes (systolic) and relaxes (diastolic) is measured as blood pressure.
Thus, there are 2 numbers to blood pressure:
- a 'top' number (systolic) which represents the pressure when the heart is squeezing and pumping blood
- a 'bottom' number (diastolic) which represents the pressure when the heart is relaxing
You will normally see blood pressure recorded as 135/85 mmHg for example (mmHg is the unit of measurement - millimetres of mercury). You will often see this read as 135 'over' 85.
Why is blood pressure important?
Blood is vital in supplying oxygen to the vital organs of the body to keep them working. Going back to the analogy of water flowing through a hose pipe, if the pressure is turned too low, flow will be inadequate in supplying blood to the organs. In fact, this is the reason why severe blood loss will eventually lead to death.
Turn the pressure too high and you risk the water jet damaging its target, which will be the major organs of the body.
Symptoms of low blood pressure might include:
- Lightheadedness and dizziness
- Blurry vision
- Fainting
- Feeling sick
- Confusion
- General weakness
On the other hand, note most people with high blood pressure (when not extreme) do not experience any symptoms at all. However, it is important to bear in mind that damage is still being done silently in the background - hence high blood pressure is often called 'the silent killer'.
When blood pressure gets very high then symptoms might include:
- Severe headaches
- Chest pain
- Dizziness
- Blurry vision
- Feeling sick
- Nosebleeds
Over time, uncontrolled high blood pressure can lead to:
- Heart disease
- Kidney disease
- A sudden stroke
- Dementia
Prevention of high blood pressure is key.
What is a normal blood pressure?
Remember, blood pressure is dynamic and there will always be some individual to individual variation (to a degree).
Blood pressure is also reactive and it is normal that it will go up and down as blood flow is maintained (you should be worried if it didn't) e.g. with exercise, stress/emotions, caffeine, smoking, following a large meal etc.
Therefore, blood pressure is context dependent and a single one off reading that is high does not necessarily equate to hypertension. It is when blood pressure is consistently high that it becomes a problem and important that it is managed.
Generally speaking, measuring blood pressure when at home and most relaxed is the ideal circumstance.
- Normal blood pressures are between 90/60mmHg to 120/80mmHg
- An ideal blood pressure is less than 120/80
- Blood pressures less than 90/60mmHg are low (hypotension)
- Blood pressures greater than 120/80mmHg but less than 140/90mmHg would be considered at risk of developing high blood pressure (referred to as pre-hypertension)
- Blood pressures consistently greater than 140/90mmHg is considered as high blood pressure (hypertension). However, this is where it gets a little bit more tricky - if measuring blood pressure at home, the targets are more strict as you are assumed to be most relaxed - so blood pressures of 135/85mmHg are considered as high blood pressure
How do you measure blood pressure?
To ensure the reading is accurate, relax 30 minutes before taking a reading and avoid:
- Eating or having any caffeine intake
- Exercise
- Smoking
When taking a blood pressure reading:
- Sit in a neutral position with legs uncrossed/flat on the floor and with arm placed at approximately chest (heart) level
- Place the cuff approximately one inch above the bend of the elbow on bare skin or over thin fabric only
- Do not talk or move while the reading is taken
- Take three measurements 1-2 minutes apart and record the readings down - do this morning and evening. Taking regular measurements over a more prolonged period e.g. over a week will help to obtain more accurate average readings