Mmhg Health Dictionary

The pressure exerted by the flow of blood through the main arteries. The pressure at 2 different phases is measured. Systolic, the higher pressure, is created by the contraction of the heart. Diastolic, the lower, is recorded during relaxation of the ventricles between heartbeats; it reflects the resistance of all the small arteries in the body and the load against which the heart must work. The pressure wave that is transmitted along the arteries with each heartbeat is easily felt as the pulse.

Blood pressure is measured using a sphygmomanometer and is expressed as millimetres of mercury (mmHg).

Blood pressure varies with age, between individuals, and at different times in the same individual but a healthy young adult usually has a blood pressure reading, at rest, of about 120/80 (that is 120 mmHg systolic and 80 mmHg diastolic).

Abnormally high blood pressure is called hypertension; abnormally low pressure is termed hypotension.... blood pressure

The lowest level of blood pressure measured in the main arteries. Diastolic pressure is the pressure between heartbeats when the ventricles are relaxed and filling with blood. Systolic pressure, the highest level of blood pressure in the arteries, occurs when the ventricles contract. The normal range varies with age and between individuals, but a young adult usually has a diastolic pressure of about 80 mmHg (mm of mercury) and a systolic pressure of around 120 mmHg. A persistently high diastolic pressure occurs in most cases of hypertension.... diastolic pressure

Persistently raised blood pressure exceeding about 140 mmHg

(systolic) and 90 mmHg (diastolic) at rest. Hypertension is very common, particularly in men, and its incidence is highest in middle-aged and elderly people.

Hypertension is usually symptomless but may cause headaches and visual disturbances when severe. It increases the risk of stroke, coronary artery disease, and heart failure, and may eventually lead to kidney damage and retinopathy.

In many cases, there is no obvious cause. Factors associated with hypertension include high alcohol intake, a high-salt diet, obesity, a family history of the condition, a sedentary lifestyle, a high degree of stress, and smoking.

Specific causes include various kidney disorders, certain disordes of the adrenal glands, pre-eclampsia, coarctation of the aorta, and use of certain drugs. Taking the combined contraceptive pill can increase the risk.

With mild to moderate hypertension, if no underlying cause is found, lifestyle changes are recommended, for example, introducing regular exercise and

stopping smoking. Biofeedback training and relaxation techniques can help reduce blood pressure. If self-help measures have no effect, or hypertension is severe, 1 or a combination of antihypertensive drugs may be given.... hypertension

n. reduction of the oxygen concentration in the arterial blood, recognized clinically by the presence of central and peripheral *cyanosis. When the partial pressure of oxygen (pO2) falls below 8.0 kPa (60 mmHg), the condition is defined as respiratory failure.... hypoxaemia

n. a unit of volume equal to the volume occupied by 1 kilogram of pure water at 4°C and 760 mmHg pressure. In *SI units the litre is treated as a special name for the cubic decimetre, but is not used when a high degree of accuracy is required (1 litre = 1.0000028 dm3). For approximate purposes 1 litre is assumed to be equal to 1000 cubic centimetres (cm3), therefore 1 millilitre (ml) is often taken to be equal to 1 cm3. This practice is now deprecated.... litre

dangerously high blood pressure (diastolic pressure >130 mmHg) associated with necrosis of small arteries and arterioles. Retinal haemorrhage and *papilloedema are present. Untreated, malignant hypertension causes severe organ damage, targeting the central nervous and cardiovascular systems and the kidneys (malignant *nephrosclerosis). Causes include complications of essential and secondary *hypertension and pregnancy and the use of certain drugs (e.g. MAO inhibitors).... malignant hypertension

(OHT) a constantly raised intraocular pressure (greater than 21 mmHg by Goldmann applanation *tonometry) registered on two or more occasions in one or both eyes with the absence of evidence of optic nerve damage or visual field defect. Intraocular pressure increases slowly with age and OHT can increase the risk of developing glaucoma. It is treated with eye drops and surgery if indicated.... ocular hypertension

(PIH) raised blood pressure (>140/90 mmHg) developing in a woman during the second half of pregnancy. It usually resolves within six weeks of delivery and is associated with a better prognosis than *pre-eclampsia.... pregnancy-induced hypertension

n. an instrument for measuring *blood pressure in the arteries. It consists of an inflatable cuff connected to a graduated scale gauge calibrated in millimetres of mercury (mmHg). The cuff is applied to a limb (usually the arm) and inflated to exert pressure on a large artery until the blood flow stops. The pressure is then slowly released and, with the aid of a stethoscope to listen to the pulse, it is possible to determine both the systolic and diastolic pressures (which can be read on the scale). Automated electronic devices are increasingly used.... sphygmomanometer