Of all the organs of our body the heart is without doubt the most critical and rightly so as, if it stops pumping blood around the body and delivering vital oxygen to the other organs, including the brain, death will occur very quickly.

Despite its importance however many of us pay little if any attention to the health of our heart until forced to do so, when it is often too late. And yet keeping a check on the heart by simple routine measurement of our blood pressure could not be easier.

As with most things in life, if the heart starts to run into problems then there will be warning signs giving us time to take remedial action and these warning signs often come in the form of abnormally high or low blood pressure.

The principle role of the heart is to take freshly oxygenated blood and pump it through the main arteries and then through a network of smaller blood vessels to all parts of the body. As the heart contracts forcing blood out into the arteries pressure is exerted on the walls of the arteries. Then, as the heart relaxes and its chambers refill ready to pump again the pressure in the arteries falls.

By measuring these two pressure levels we can get an indication of just how well the heart is pumping blood around the body and thus see whether or not it is working normally.

Until quite recently it was necessary to visit the doctor's office to have your blood pressure measured. The doctor would place a cuff around your upper arm roughly at the level of the heart. He would then place his stethoscope over the brachial artery where it runs close to the surface of the skin on the inside of your arm at the elbow and proceed to inflate the cuff.

As the cuff is inflated it tightens around the arm preventing blood from flowing through the brachial artery. The pressure in the cuff, which is indicated by a mercury manometer attached to the cuff, is slowly released and the point at which blood starts flowing through the artery, and which the doctor hears as a "whoosing" sound through his stethoscope, is noted. This is the point at which the pressure in the cuff equals the pressure in the artery as the heart pumps blood through it and is known as the systolic pressure.

The doctor then continues to slowly release the pressure in the cuff and to monitor the sound of blood being pumped through the artery until no sound at all is detected. At this point the manometer indicates the pressure in the artery as the heart is at rest and refilling ready to pump again. This lower pressure is known as the diastolic pressure.

Blood pressure will vary from person to person and will also rise and fall within each of us depending on a variety of factors such as the time of day, our level of activity, whether we are feeling stressed, our general state of health and whether or not we are currently taking particular forms of medication.

For the average person at rest however systolic blood pressure will be around 120 mm Hg (millimeters of mercury) and diastolic blood pressure will be 80 mm Hg. As an indication of the degree of variation between individuals, and within any one person, the normal range of systolic pressure is considered to be 90