Measuring Blood Pressure- Techniques and Devices

To measure blood pressure and to measure it accurately is an extremely important part of a medical examination. Blood pressure is measured not only in cases of hypertension or hypotension but it is a general indicator of the smooth functioning of the heart. In any serious case, the blood pressure of a patient is monitored periodically to assess the overall condition of the patient. Not to say, in specific case of patients suffering from hyper or hypotension, the BP readings obviously determine the course of treatment to be taken.

The most common method to measure blood pressure is a non-invasive procedure. It is known as the Ausculatory method in medical terms. Sitting position is the ideal position for measuring the blood pressure of a patient. In that position, the brachial artery is at the same level as of the heart. A cuff is wrapped around the brachial artery which passes through our arms. The cuff is inflated to 180mm Hg followed by gradual deflation. A stethoscope placed on the surface of the arm allows the doctor to hear a particular sound. The quality of the sound and the count at which the sound ceases is determined as the BP level of the patient.

Measuring the blood pressure level is a very delicate process and a trained person is required to measure it correctly. There are five phases of the sound which tell about the BP count. It is known as Korotkoff sound. The systolic pressure is determined by the first sound. It is a sharp tapping sound. Then the last sound which sounds like a blow is the diastolic count. The tapping sound is preceded by silence while the blowing sound is followed by silence.

Another technique to measure the blood pressure levels is the oscillometric technique. It is a much sophisticated way to measure blood pressure levels. It records the oscillation of the contraction and expansion of the heart. The maximal point of oscillation corresponds to the mean of the arterial pressure. The systolic and diastolic pressure are at the opposite ends of this oscillation. The recorder then derives the BP count by an algorithm.

The ausculatory technique is used in manual devices while the oscillometric technique is used only in semi automated and automated devices.

The modern devices are very user friendly devices that only use the oscillometric technique. There has been a raging debate on the accuracy of these devices. The advantage of the automated devices is that the patient can use hem to measure his own blood pressure easily. This helps him keep a self track of his BP count. In case of any complications, the readings can always be tallied with the measurement taken at the hospital.

Other potential advantages of the oscillometric method for ambulatory monitoring are that it is less susceptible to external noise (but not to low-frequency mechanical vibration), and that the cuff can be removed and replaced by the patient himself. The main disadvantage is that such recorders do not work well during physical activity, when there may be considerable movement.