5 Blood pressure monitoring
High blood pressure (hypertension) is another common problem in people with diabetes, particularly Type 2 diabetes. Along with dyslipidaemia, it is strongly associated with a high risk of developing CHD. As a consequence, blood pressure should be checked at least annually, but is usually checked at every diabetes clinic visit, especially if it is above normal. Blood pressure in people with diabetes should be 140/80 or less, and they may need to take several different tablets to get to this level. (Blood pressure is measured in units of millimetres of mercury (mmHg) but normally the units are not quoted.) If you have diabetes, you may have been advised to try and attain an even lower level, particularly if you know you have diabetes complications. Like blood glucose control, it can be very difficult to achieve the desired target, but again, any reduction in blood pressure is beneficial. The UKPDS (see Box 2) showed that reducing blood pressure was more effective than control of blood glucose in reducing macrovascular disease (such as heart attacks and stroke).
Blood pressure simply means the force with which the blood pushes onto the walls of the blood vessels as it flows through them. This force is produced by the pumping action of the heart pushing the blood around the body, and the elastic nature of the blood vessels which allows them to stretch as the blood is pumped into them, and spring back afterwards when the heart is relaxing to push the blood onwards. If you had no blood pressure you would be dead; this would occur if the heart stopped pumping. However, if the blood vessels become less elastic, the heart has to work harder to pump the blood through them and this can lead to many problems, such as heart failure. People with diabetes are very prone to developing inelastic blood vessels as a result of the build up of atheroma, a fatty substance which causes narrowing of the arteries and also makes them much less elastic. This can then result in problems such as heart attacks and strokes. High blood pressure is an indication that the arteries are becoming less elastic (although there may be other reasons for high blood pressure). This is why it is so important that the blood pressure is checked regularly and accurately, and treatment started if the blood pressure is higher than normal. It is also very important that the equipment is properly maintained so that accurate readings are obtained.
Blood pressure is measured by using a manual or electronic measuring device (a sphygmomanometer), which measures the pressure of blood in the arteries (Figure 10).
The two numbers given when quoting blood pressure refer to the pressure of blood in the artery when the heart is contracting (systolic pressure) and the pressure of blood in the artery when the heart is relaxing (diastolic pressure).
Which do you think is the higher measurement?
The systolic is the higher reading because this is when there is a surge of blood into the arteries.
Many people are used to having their blood pressure measured. However, for some people, the annual review may be the first time their blood pressure has been measured and they may be quite worried about it. Other people who have had their blood pressure measured before may also be worried in case they have high blood pressure. It is important therefore that the person taking the blood pressure explains what is going to happen, and why it is being done, and that the person being checked consents to the procedure. The blood pressure may also be raised if the person tested is very anxious or has been rushing to get to the appointment, so the person should be given time to relax before having their blood pressure measured.
Mrs Ferguson's blood pressure was always higher when Dr Jones took it than when the nurse checked it. Why do you think this could happen?
You may have heard of ‘white coat syndrome’, where a patient's blood pressure is higher when the measurement is taken by a health care professional than when the patient is relaxed in a familiar environment. Perhaps Mrs Ferguson feels more relaxed with the nurse or the nurse talks to her for a few minutes before checking the blood pressure.
Blood pressure is measured by wrapping a cuff round the arm and inflating it, to compress the artery so that there is no blood going through the artery (Figure 11). This means that if the cuff is left inflated, it will be painful as the blood supply to the arm and hand is interrupted. As the cuff is slowly deflated and the pressure in the cuff gradually reduces, blood can start to pass back down the artery. By listening through a stethoscope held over the brachial artery in the antecubital fossa, the person doing the procedure can hear sounds from the time the blood re-enters the artery (systolic pressure) until the blood is flowing freely through the artery (diastolic pressure). This is the manual system and for this, a mercury or aneroid (air-filled) sphygmomanometer is used. Mercury, or more specifically its vapour, is highly toxic and therefore mercury sphygmomanometers are being phased out. If an electronic device is used, a cuff is still applied but the reading is taken automatically following automatic inflation and deflation of the cuff.
Once the reading has been taken, it should be documented clearly in the record of the person with diabetes. If it is either too high or too low, the doctor may start treatment or adjust the current medication.
Whenever your blood pressure is taken, it is important you know what the result is. This information will help you to make choices about your diet and exercise, and may give you some incentive to lose weight or try to give up smoking if these are problems for you. If you are concerned about the result, you should be able to discuss your worries with your doctor or nurse.
There are devices available for people to check their blood pressure at home. They can take the blood pressure at the arm or wrist. The normal range of measurements varies according to the site where the blood pressure is taken and the age of the person. As with the use of blood glucose meters, it is essential that the user knows how to use the device properly, and knows what to do with abnormal results. If you are using one of these devices, you may find it helpful to take it with you when you attend your diabetes clinic appointment. You can then compare the result you obtain with your device with the result obtained at the clinic.
The increased risk of CHD in people with Type 2 diabetes cannot be overemphasised. Any of the factors that cause CHD must be identified and treated if possible, because people with diabetes have such a high risk of developing the condition. Along with identifying hypertension, hyperglycaemia, and dyslipidaemia, lifestyle risk factors need to be assessed, and the person advised on behaviours that increase CHD risk. It may be very difficult to change behaviour, but people need to be aware of the risk involved and empowered to make changes if they choose, through education and initiatives such as support to give up smoking.