The peak systemic arterial blood pressure is produced by transmission of left ventricular systolic pressure. Vascular tone and an intact aortic valve maintain the diastolic blood pressure. How to take the blood pressure is outlined in Practical box 13.1.

Variations in blood pressure

Practical Box 13.1 Taking the blood pressure

The blood pressure is taken in the (right) arm with the patient relaxed and comfortable. The sphygmomanometer cuff is wrapped around the upper arm with the inflation bag placed over the brachial artery. The cuff is inflated until the pressure exceeds the arterial pressure – when the radial pulse is no longer palpable. The diaphragm of the stethoscope is positioned over the brachial artery just below the cuff. The cuff pressure is slowly reduced until sounds (Korotkoff sounds) can be heard (phase 1). This is the systolic pressure. The pressure is allowed to fall further until the Korotkoff sounds become suddenly muffled (phase 4). The pressure is allowed to fall still further until they disappear (phase 5).

The diastolic pressure is usually taken as phase 5 because this phase is more reproducible and nearer to the intravascular diastolic pressure. The Korotkoff sounds may disappear (phase 2) and reappear (phase 3) between the systolic and diastolic pressures. Do not mistake phase 2 for the diastolic pressure or phase 3 for the systolic pressure.

The systolic blood pressure varies by up to 10 mmHg between the right and left brachial arteries. Standing usually causes a slight reduction of the systolic pressure (< 20 mmHg) and an increase in the diastolic pressure (< 10 mmHg). In postural (orthostatic) hypotension, a large postural fall of both the systolic and diastolic pressures is associated with dizziness. When an irregular heart rhythm such as atrial fibrillation is present, the blood pressure is variable. Because the blood pressure is normally liable to variation, it must be estimated on several occasions before it can be declared elevated.

Obese people are at a higher risk of early death, mostly because of diabetes, coronary heart disease, cerebrovascular disease and otehr cardiovascular deseases. The higher the level of obesity is the greater morbidity and mortality rates are. For example, men who are 10% overweight have a 13% increased risk of death, while the increase in mortality for those 20% overweight is 25%. The rise is less in women, and in men over 65 obesity is not an independent risk factor. Weight reduction reduces this mortality and therefore should be strongly encouraged. The benefits are probably greater in more obese subjects (Table 5.14).

Clinical features

Most patients recognize their own problems, although often they are unaware of the main foods that cause obesity. Many symptoms are related to psychological problems or social pressures, such as the woman who cannot find fashionable clothes to wear.

Box 5.4 Ranges of body mass index (BMI) used to classify degrees of overweight and associated risk of co-morbidities

WHO classification	BMI (kg/m2)	Risk of co-morbidities
Overweight	25-30	Mildly increased
Obese	> 30
Class I	30-35	Moderate
Class II	35-40	Severe
Class III	> 40	Very severe

Table 5-14. Potential benefits that may result from the loss of 10 kg in patients who are initially 100 kg and suffer from co-morbidities

Mortality	20-25% fall in total mortality
	30-40% fall in diabetes-related deaths
	40-50% fall in obesity-related cancer deaths
Blood pressure	Fall of about 10 mmHg (systolic and diastolic)
Diabetes	Reduces risk of developing diabetes by > 50%
	Fall of 30-50% in fasting blood glucose
	Fall of 15% in HbA1c
Serum lipids	Fall of 10% in total cholesterol
	Fall of 15% in LDL cholesterol
	Fall of 30% in triglycerides
	Increase of 8% in HDL cholesterol

The degree of obesity can be assessed by comparison with tables of ideal weight for height, from the BMI (Box 5.4), and by measuring skinfold thickness. The latter should be measured over the middle of the triceps muscle; normal values are 20 mm in a man and 30 mm in a woman. A central distribution of body fat (a waist/hip circumference ratio of > 1.0 in men and > 0.9 in women) is associated with a higher risk of morbidity and mortality than is a more peripheral distribution of body fat (waist/hip ratio < 0.85 in men and < 0.75 in women). This is because fat located centrally, especially inside the abdomen, is more sensitive to lipolytic stimuli, with the result that the abnormalities in circulating lipids are more severe.

Table 5.15 shows the conditions and complications that are associated with obesity.

Table 5-15. Conditions and complications associated with obesity

Psychological	Hypertension
Osteoarthritis of knees and hips	Breathlessness
Varicose veins	Ischaemic heart disease
Hiatus hernia	Stroke
Gallstones	Diabetes mellitus (type 2)
Postoperative problems	Hyperlipidaemia
Back strain	Menstrual abnormalities
Accident proneness Obstructive sleep apnoea	Increased morbidity and mortality
	Increased cancer risk
	Heart failure

The metabolic syndrome (syndrome X) is a cluster of cardiovascular risk factors associated with excess fat. A commonly used definition (NCEP ATP III) defines the syndrome as the coexistence of three or more of the following five abnormalities: high blood pressure (>130/85 mmHg); elevated serum triglycerides (>1.5 g/L); serum LDL cholesterol > 0.4 g/L (men) or > 0.5 g/L (women); increased abdominal circumference > 102 cm (men) or > 88 cm (women); and impaired fasting glucose (> 1.1 g/L or > 6.1 mmol/L). It is estimated that it affects up to about a quarter of adults in the USA.

The relationship between cardiovascular disease (hypertension or ischaemic heart disease), hyperlipidaemia, smoking, physical exercise and obesity is complex. Difficulties arise in interpreting mortality figures because of the number of factors involved. Many studies do not differentiate between the types of physical exercise taken or take into account the cuff-size artefact in the measurement of blood pressure (an artefact will occur if a large cuff is not used in patients with a large arm). Nevertheless, obesity almost certainly plays a part in all of these diseases and should be treated. An exception is that stopping smoking, even if accompanied by weight gain, is more beneficial than any of the other factors. Physical fitness is also helpful, and there is some evidence to suggest that a fit obese person may have similar or even lower cardiovascular risk than a leaner unfit person.

This is an ophthalmic emergency. In this type of glaucoma there is a sudden rise in intraocular pressure to levels greater than 50 mmHg. This occurs due to reduced aqueous drainage as a result of the ageing lens pushing the iris forward against the trabecular meshwork. People most at risk of developing AACG are those with shallow anterior chambers such as hypermetropes and women. The attack is more likely to occur under reduced light conditions when the pupil is dilated.

AACG causes sudden onset of a red painful eye and blurred vision. Patients become unwell with nausea and vomiting and complain of headache and severe ocular pain. The eye is injected, tender and feels hard. The cornea is hazy and the pupil is semi-dilated. Table 20.8 shows the differential diagnosis of the acute red eye.

Prompt treatment is required to preserve sight and includes i.v. acetazolamide 500 mg (provided there are no contraindications) to reduce IOP, and instillation of pilocarpine 4% drops to constrict the pupil to improve aqueous outflow and prevent iris adhesion to the trabecular meshwork. Other topical drops such as beta-blockers and prostaglandin analogues can also be instilled if available, provided there are no contraindications. Analgesia and antiemetics are given as required.

These patients must be referred to an ophthalmologist immediately so that reduction in IOP can be monitored and other agents such as oral glycerol or i.v. mannitol can be administered to non-responding patients. Definitive treatment involves making a hole in the periphery of the iris of both eyes either by laser or surgically.

This refers to a group of diseases where the pressure inside the eye is sufficiently elevated to cause optic nerve damage and result in visual field defects. Normal intraocular pressure (IOP) is between 10 and 21 mmHg. Some types of glaucoma can result in an IOP exceeding 70 mmHg. Glaucoma as a disease entity is the second commonest cause of blindness word-wide and the third commonest cause of blind registration in the UK.

Primary open-angle glaucoma (POAG)

Table 20-8. Differential diagnosis of the acute red eye

Cause	Conjunctival injection	Unilateral or bilateral	Pain	Photophobia	Vision	Pupil	Intraocular pressure
Conjunctivitis	Diffuse	Bilateral	Gritty	Occasionally with adenovirus	Normal	Normal	Normal
Anterior uveitis	Circum-corneal	Unilateral	Painful	Yes	Reduced	Constricted	Normal or raised
Acute glaucoma	Diffuse	Unilateral	Severe pain	Mild	Reduced	Mid-dilated	Raised

This is the commonest form of glaucoma. High intraocular pressures result from reduced outflow of aqueous humour through the trabecular meshwork. The cause of this increased resistance to aqueous outflow at the level of the meshwork is not fully understood. Common risk factors include age (0.02% of 40-year-olds vs 10% of 80-year-olds), race (black Africans are at five times greater risk than whites), positive family history and myopia.

POAG causes a gradual, insidious, painless loss of peripheral visual field. The central vision remains good until the end-stage of the disease. Diagnosis is only made if the IOP is measured. The optic disc is inspected and shows an enlarged cup with a thin neuroretinal rim. Visual fields are performed and show a normal blind spot with scotomas. Most patients are identified as having glaucoma whilst undergoing a routine ophthalmic examination.

Treatment

Treatment aims to reduce the IOP and this is achieved either by reducing aqueous production or increasing aqueous drainage. Beta-blockers such as timolol, carteolol, levobunolol, reduce aqueous production and are the commonest prescribed topical agents. These drugs are contraindicated in patients with COPD, asthma or heart block. Prostaglandin analogues such as latanoprost, travoprost, increase aqueous outflow and are fast becoming the treatment of choice for POAG as they can reduce IOP by 30%. Carbonic anhydrase inhibitors such as acetazolamide reduce aqueous production and are available in both topical and oral form. In its oral form acetazolamide is the most potent drug for reducing ocular pressure. It should not be used in patients with sulphonamide allergy.

Paradoxical pulse is a misnomer, as it is actually an exaggeration of the normal pattern. In normal subjects, the systolic pressure and the pulse pressure (the difference between the systolic and diastolic blood pressures) fall during inspiration. The normal fall of systolic pressure is less than 10 mmHg, and this can be measured using a sphygmomanometer. It is due to increased pulmonary intravascular volume during inspiration. In severe airflow limitation (especially severe asthma) there is an increased negative intrathoracic pressure on inspiration which enhances the normal fall in blood pressure. In patients with cardiac tamponade, the fluid in the pericardium increases the intrapericardial pressure, thereby impeding diastolic filling of the heart. The normal inspiratory increase in venous return to the right ventricle is at the expense of the left ventricle, as both ventricles are confined by the accumulated pericardial fluid within the pericardial space. Paradox can occur through a similar mechanism in constrictive pericarditis but is less common.