24 Hour monitoring: ambulatory blood pressure

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By wearing a small portable device for 24 hours, doctors can obtain an overview of your blood pressure, as it varies during the day.  Although not routinely used, it can provide valuable information under certain circumstances.

This little device is usually carried in a pouch, and doesn’t interfere with daily activities. Typically, it is programmed to take readings every 15 to 30 minutes during the day and night. The information is stored and printed out by the doctor. The patients are asked to keep a diary during the period and write down their activities, emotions, time of medication and meal times.

ABPM for White Coat Hypertension
Ambulatory blood pressure monitoring, called ABPM, is often used in patients with suspected "white coat hypertension".  Blood pressure is then raised when taken by the doctor, but consistently normal when taken outside of the clinical setting. 

It is also used in certain cases of borderline hypertension, where the true extent of the possible hypertension is very significant.  This is when clinical signs of organ damage are found, for example, abnormal kidney function or an enlarged heart.

It can be helpful in assessing the effectiveness of drug treatment, and whether it may be responsible for hypotensive episodes. Hypotension means that the patient experiences a sharp fall in blood pressure.  The type of drug or dosage can then be changed accordingly.

Some patients have a wide range of pressure readings at the doctor or clinic.  The 24-hour information can then help to determine the average blood pressure. ABPM can also help diagnose patients with pheochromocytoma, an adrenal gland tumor, where episodic spikes of high blood pressure are recorded. 

Autonomic dysfunction is another condition that may be uncovered with 24-hour monitoring. Heart rate and breathing are some of the functions of the autonomic nervous system that controls involuntary body systems. These patients have low blood pressure when awake and raised readings when asleep.  They can also experience an abrupt drop in blood pressure after meals. 

(Dr Kathleen Coetzee, MBChB)

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