Ambulatory Blood Pressure Monitor
Our blood pressure (BP) is quite variable it will go up if we are stressed and be lower when we are relaxed or asleep. It has been known for many years that blood pressure readings in a GP’s surgery or a hospital clinic are usually higher than a person’s blood pressure at home. As we spend more time at home/work the wear and tear on the arteries from the BP is best judged by a reliable home blood pressure record. Patients can take their own blood pressure at home but even then some patients will subconsciously put their blood pressure up if they know they are going to measure their blood pressure even without realising this is what it happening-this is a “white coat” element.
This is why NICE have recommended that before diagnosing a person as having high blood pressure (“Systemic Hypertension” or just “Hypertension”) the individual should have a 24hour blood pressure monitor.
This is a machine that is worn for 24hours at home and will take the blood pressure every ½ hour during the day and every hour at night. As the machine automatically takes the reading without warning there is less chance of the patient subconsciously becoming tense and increasing their blood pressure as they may do when they are preparing to take their own blood pressure.
Indeed it has been found that the 24hr blood pressure readings correlate better with future outcomes such as heart attacks and strokes than do clinic readings.
The monitor is shown in this illustration-
A graph of a 24hour BP in a 44 year old woman whose sister had developed severe hypertension and developed kidney failure. The patient had been started on medication but her own home blood pressures were very high. The blood pressure that I recorded in clinic was fairly normal so having discussed it with her she was happy to have a 24 hour BP to see whether her blood pressure was indeed higher at home than in the clinic (usually it is the other way around ie higher in the clinic). This print out shows that her blood pressure at home was indeed well controlled and that she did not need additional medication.
The blood pressure monitor inflates the cuff which presses on the patient’s arm.
Reasons for having a 24hr Blood Pressure monitor-
- To establish that the patient truly has high blood pressure before potentially starting lifelong treatment
- To check that the treatment that the patient is on is controlling the blood pressure adequately
- To see if symptoms of for instance dizziness are due to low blood pressure
- To check if home blood pressure readings are correct if clinic readings are very different