Millilitre is the 1,000th part of 1 litre. It is practically the equivalent of a cubic centimetre (1 cm3 = 0·999973 ml); ml is the usual abbreviation.
Patients found to have bacteriuria on SCREENING may never have consulted a doctor but nearly all have a few symptoms, such as frequency or urgency – so-called ‘covert bacteriuria’.
Men have longer urethras and fewer urinary tract infections (UTIs) than women. Risk factors include diabetes mellitus, pregnancy, impaired voiding and genito-urinary malformations. Over 70 per cent of UTIs are due to E. coli, but of UTIs in hospital patients, only 40 per cent are caused by E. coli.
Treatment Patients should be encouraged to drink plenty of water, with frequent urination. Speci?c antibiotic therapy with trimethoprim or amoxicillin may be needed.... bacteriuria
A high blood-cholesterol level – that is, one over 6 mmol per litre or 238 mg per 100 ml – is undesirable as there appears to be a correlation between a high blood cholesterol and ATHEROMA, the form of arterial degenerative disease associated with coronary thrombosis and high blood pressure. This is well exempli?ed in DIABETES MELLITUS and HYPOTHYROIDISM, two diseases in which there is a high blood cholesterol, sometimes going as high as 20 mmol per litre; patients with these diseases are known to be particularly prone to arterial disease. There is also a familial disease known as hypercholesterolaemia, in which members of affected families have a blood cholesterol of around 18 mmol per litre or more, and are particularly liable to premature degenerative disease of the arteries. Many experts believe that there is no ‘safe level’ and that everybody should attempt to keep their cholesterol level as low as possible.
Cholesterol exists in three forms in the blood: high-density lipoproteins (HDLs) which are believed to protect against arterial disease, and a low-density version (LDLs) and very low-density type (VLDLs), these latter two being risk factors.
The rising incidence of arterial disease in western countries in recent years has drawn attention to this relationship between high levels of cholesterol in the blood and arterial disease. The available evidence indicates that there is a relationship between blood-cholesterol levels and the amount of fat consumed; however, the blood-cholesterol level bears little relationship to the amount of cholesterol consumed, most of the cholesterol in the body being produced by the body itself.
On the other hand, diets high in saturated fatty acids – chie?y animal fats such as red meat, butter and dripping – tend to raise the blood-cholesterol level; while foods high in unsaturated fatty acids – chie?y vegetable products such as olive and sun?ower oils, and oily ?sh such as mackerel and herring – tend to lower it. There is a tendency in western society to eat too much animal fat, and current health recommendations are for everyone to decrease saturated-fat intake, increase unsaturated-fat intake, increase daily exercise, and avoid obesity. This advice is particulary important for people with high blood-cholesterol levels, with diabetes mellitus, or with a history of coronary thrombosis (see HEART, DISEASES OF). As well as a low-cholesterol diet, people with high cholesterol values or arterial disease may be given cholesterol-reducing drugs such as STATINS, but this treatment requires full clinical assessment and ongoing medical monitoring. Recent research involving the world’s largest trial into the effects of treatment to lower concentrations of cholesterol in the blood showed that routine use of drugs such as statins reduced the incidence of heart attacks and strokes by one-third, even in people with normal levels of cholesterol. The research also showed that statins bene?ted women and the over-70s.... cholesterol
Normally, there are more than 20 million sperm per millilitre of semen. A low sperm count can be due to various disorders, including orchitis, undescended testis (see testis, undescended), and, infrequently, a varicocele (varicose vein of the testis). Smoking, alcohol abuse, stress, and some drugs may cause temporary oligospermia. Treatment is for the underlying cause. If the cause is unknown, gonadotrophin hormones may be prescribed. (See also azoospermia.)... oligospermia
Severe and extensive burns are most frequently produced by the clothes – for example, of a child – catching ?re. This applies especially to cotton garments, which blaze up quickly. It should be remembered that such a ?ame can immediately be extinguished by making the individual lie on the ?oor so that the ?ames are uppermost, and wrapping him or her in a rug, mat or blanket. As prevention is always better than cure, particular care should always be exercised with electric ?res and kettles or pots of boiling water in houses where there are young children or old people. Children’s clothes, and especially night-clothes, should be made of non-in?ammable material: pyjamas are also much safer than nightdresses.
Severe scalds are usually produced by escape of steam in boiler explosions. Cigarettes are a common cause of ?res and therefore of burns; people who have fallen asleep in bed or in a chair while smoking may set ?re to the bed or chair. Discarded, unextinguished cigarettes are another cause.
Degrees of burns Burns are referred to as either super?cial (or partial-thickness) burns, when there is su?cient skin tissue left to ensure regrowth of skin over the burned site; and deep (or full-thickness) burns, when the skin is totally destroyed and grafting will be necessary.
Symptoms Whilst many domestic burns are minor and insigni?cant, more severe burns and scalds can prove to be very dangerous to life. The main danger is due to SHOCK, which arises as a result of loss of ?uid from the circulating blood at the site of a serious burn. This loss of ?uid leads to a fall in the volume of the circulating blood. As the maintenance of an adequate blood volume is essential to life, the body attempts to compensate for this loss by withdrawing ?uid from the uninjured areas of the body into the circulation. If carried too far, however, this in turn begins to affect the viability of the body cells. As a sequel, essential body cells, such as those of the liver and kidneys, begin to suffer, and the liver and kidneys cease to function properly. This will show itself by the development of JAUNDICE and the appearance of albumin in the urine (see PROTEINURIA). In addition, the circulation begins to fail with a resultant lack of oxygen (see ANOXIA) in the tissues, and the victim becomes cyanosed (see CYANOSIS), restless and collapsed: in some cases, death ensues. In addition, there is a strong risk of infection occurring. This is the case with severe burns in particular, which leave a large raw surface exposed and very vulnerable to any micro-organisms. The combination of shock and infection can all too often be life-threatening unless expert treatment is immediately available.
The immediate outcome of a burn is largely determined by its extent. This is of more signi?cance than the depth of the burn. To assess the extent of a burn in relation to the surface of the body, what is known as the Rule of Nine has been evolved. The head and each arm cover 9 per cent of the body surface, whilst the front of the body, the back of the body, and each leg each cover 18 per cent, with the perineum (or crutch) accounting for the remaining 1 per cent. The greater the extent of the burn, the more seriously ill will the victim become from loss of ?uid from his or her circulation, and therefore the more prompt should be his or her removal to hospital for expert treatment. The depth of the burn, unless this is very great, is mainly of import when the question arises as to how much surgical treatment, including skin grafting, will be required.
Treatment This depends upon the severity of the burn. In the case of quite minor burns or scalds, all that may be necessary if they are seen immediately is to hold the part under cold running water until the pain is relieved. Cooling is one of the most e?ective ways of relieving the pain of a burn. If the burn involves the distal part of a limb – for example, the hand and forearm – one of the most e?ective ways of relieving pain is to immerse the burned part in lukewarm water and add cold water until the pain disappears. As the water warms and pain returns, more cold water is added. After some three to four hours, pain will not reappear on warming, and the burn may be dressed in the usual way. Thereafter a simple dressing (e.g. a piece of sterile gauze covered by cotton-wool, and on top of this a bandage or adhesive dressing) should be applied. The part should be kept at rest and the dressing kept quite dry until healing takes place. Blisters should be pierced with a sterile needle, but the skin should not be cut away. No ointment or oil should be applied, and an antiseptic is not usually necessary.
In slightly more severe burns or scalds, it is probably advisable to use some antiseptic dressing. These are the cases which should be taken to a doctor – whether a general practitioner, a factory doctor, or to a hospital Accident & Emergency department. There is still no general consensus of expert opinion as to the best ‘antiseptic’ to use. Among those recommended are CHLORHEXIDINE, and antibiotics such as BACITRACIN, NEOMYCIN and polymixin. An alternative is to use a Tulle Gras dressing which has been impregnated with a suitable antibiotic.
In the case of severe burns and scalds, the only sound rule is immediate removal to hospital. Unless there is any need for immediate resuscitation, such as arti?cial respiration, or attention to other injuries there may be, such as fractures or haemorrhage, nothing should be done on the spot to the patient except to make sure that s/he is as comfortable as possible and to keep them warm, and to cover the burn with a sterile (or clean) cloth such as a sheet, pillowcases, or towels wrung out in cold water. If pain is severe, morphine should be given – usually intravenously. Once the victim is in hospital, the primary decision is as to the extent of the burn, and whether or not a transfusion is necessary. If the burn is more than 9 per cent of the body surface in extent, a transfusion is called for. The precise treatment of the burn varies, but the essential is to prevent infection if this has not already occurred, or, if it has, to bring it under control as quickly as possible. The treatment of severe burns has made great advances, with quick transport to specialised burns units, modern resuscitative measures, the use of skin grafting and other arti?cial covering techniques and active rehabilitation programmes, o?ering victims a good chance of returning to normal life.
CHEMICAL BURNS Phenol or lysol can be washed o? promptly before they do much damage. Acid or alkali burns should be neutralised by washing them repeatedly with sodium bicarbonate or 1 per cent acetic acid, respectively. Alternatively, the following bu?er solution may be used for either acid or alkali burns: monobasic potassium phosphate (70 grams), dibasic sodium phosphate (70 grams) in 850 millilitres of water. (See also PHOSPHORUS BURNS.)... burns and scalds
Haemoglobin exists in two forms: simple haemoglobin, found in venous blood; and oxy-haemoglobin, which is a loose compound with oxygen, found in arterial blood after the blood has come into contact with the air in the lungs. This oxyhaemoglobin is again broken down as the blood passes through the tissues, which take up the oxygen for their own use. This is the main function of haemoglobin: to act as a carrier of oxygen from the lungs to all the tissues of the body. When the haemoglobin leaves the lungs, it is 97 per cent saturated with oxygen; when it comes back to the lungs in the venous blood, it is 70 per cent saturated. The oxygen content of 100 millilitres of blood leaving the lungs is 19·5 millilitres, and that of venous blood returning to the lungs, 14·5 millilitres. Thus, each 100 millilitres of blood delivers 5 millilitres of oxygen to the tissues of the body. Human male blood contains 13–18 grams of haemoglobin per 100 millilitres; in women, there are 12–16 grams per 100 millilitres. A man weighing 70 kilograms (154 pounds) has around 770 grams of haemoglobin circulating in his red blood corpuscles.... haemoglobin
Treatment In severely affected fetuses, a fetal blood transfusion may be required and/or the baby may be delivered early for further treatment. Mild cases may need observation only, or the reduction of jaundice by phototherapy alone (treatment with light, involving the use of sunlight, non-visible ULTRAVIOLET light, visible blue light, or LASER).
Whatever the case, the infant’s serum BILIRUBIN – the bilirubin present in the blood – and its HAEMOGLOBIN concentration are plotted regularly so that treatment can be given before levels likely to cause brain damage occur. Safe bilirubin concentrations depend on the maturity and age of the baby, so reference charts are used.
High bilirubin concentrations may be treated with phototherapy; extra ?uid is given to prevent dehydration and to improve bilirubin excretion by shortening the gut transit time. Severe jaundice and anaemia may require exchange TRANSFUSION by removing the baby’s blood (usually 10 millilitres at a time) and replacing it with rhesus-negative fresh bank blood. Haemolytic disease of the newborn secondary to rhesus incompatibility has become less common since the introduction of anti-D (Rho) immunoglobulin. This antibody should be given to all rhesus-negative women at any risk of a fetomaternal transfusion, to prevent them from mounting an antibody response. Anti-D is given routinely to rhesus-negative mothers after the birth of a rhesus-positive baby, but doctors should also give it after threatened abortions, antepartum haemorrhages, miscarriages, and terminations of pregnancy.
Occasionally haemolytic disease is caused by ABO incompatibility or that of rarer blood groups.... haemolytic disease of the newborn
Shape and size In adults the heart is about the size and shape of a clenched ?st. One end of the heart is pointed (apex); the other is broad (base) and is deeply cleft at the division between the two atria. One groove running down the front and up the back shows the division between the two ventricles; a circular, deeper groove marks o? the atria above from the ventricles below. The capacity of each cavity is somewhere between 90 and 180 millilitres.
Structure The heart lies within a strong ?brous bag, known as the pericardium. Since the inner surface of this bag and the outer surface of the heart are both covered with a smooth, glistening membrane faced with ?at cells and lubricated by a little serous ?uid (around 20 ml), the movements of the heart are accomplished almost without friction. The main thickness of the heart wall consists of bundles of muscle ?bres, some of which run in circles right around the heart, and others in loops, ?rst round one cavity, then round the corresponding cavity of the other side. Within all the cavities is a smooth lining membrane, continuous with that lining the vessels which open into the heart. The investing smooth membrane is known as epicardium; the muscular substance as myocardium; and the smooth lining membrane as endocardium.
Important nerves regulate the heart’s action, especially via the vagus nerve and with the sympathetic system (see NERVOUS SYSTEM). In the near part of the atria lies a collection of nerve cells and connecting ?bres, known as the sinuatrial node or pacemaker, which forms the starting-point for the impulses that initiate the beats of the heart. In the groove between the ventricles and the atria lies another collection of similar nerve tissue, known as the atrioventricular node. Running down from there into the septum between the two ventricles is a band of special muscle ?bres, known as the atrioventricular bundle, or the bundle of His. This splits up into a right and a left branch for the two ventricles, and the ?bres of these distribute themselves throughout the muscular wall of the ventricles and control their contraction.
Openings There is no direct communication between the cavities on the right side and those on the left; but the right atrium opens into the right ventricle by a large circular opening, and similarly the left atrium into the left ventricle. Into the right atrium open two large veins, the superior and inferior venae cavae, with some smaller veins from the wall of the heart itself, and into the left atrium open two pulmonary veins from each lung. One opening leads out of each ventricle – to the aorta in the case of the left ventricle, to the pulmonary artery from the right.
Before birth, the FETUS’s heart has an opening (foramen ovale) from the right into the left atrium through which the blood passes; but when the child ?rst draws air into his or her lungs this opening closes and is represented in the adult only by a depression (fossa ovalis).
Valves The heart contains four valves. The mitral valve consists of two triangular cusps; the tricuspid valve of three smaller cusps. The aortic and pulmonary valves each consist of three semilunar-shaped segments. Two valves are placed at the openings leading from atrium into ventricle, the tricuspid valve on the right side, the mitral valve on the left, so as completely to prevent blood from running back into the atrium when the ventricle contracts. Two more, the pulmonary valve and the aortic valve, are at the entrance to these arteries, and prevent regurgitation into the ventricles of blood which has been driven from them into the arteries. The noises made by these valves in closing constitute the greater part of what are known as the heart sounds, and can be heard by anyone who applies his or her ear to the front of a person’s chest. Murmurs heard accompanying these sounds indicate defects in the valves, and may be a sign of heart disease (although many murmurs, especially in children, are ‘innocent’).
Action At each heartbeat the two atria contract and expel their contents into the ventricles, which at the same time they stimulate to contract together, so that the blood is driven into the arteries, to be returned again to the atria after having completed a circuit in about 15 seconds through the body or lungs as the case may be. The heart beats from 60 to 90 times a minute, the rate in any given healthy person being about four times that of the respirations. The heart is to some extent regulated by a nerve centre in the MEDULLA, closely connected with those centres which govern the lungs and stomach, and nerve ?bres pass to it in the vagus nerve. The heart rate and force can be diminished by some of these ?bres, by others increased, according to the needs of the various organs of the body. If this nerve centre is injured or poisoned – for example, by lack of oxygen – the heart stops beating in human beings; although in some of the lower animals (e.g. frogs, ?shes and reptiles) the heart may under favourable conditions go on beating for hours even after its entire removal from the body.... heart
Insulin is extracted mainly from pork pancreas and puri?ed by crystallisation; it may be made biosynthetically by recombinant DNA technology using Escherichia coli, or semisynthetically by enzymatic modi?cation of porcine insulin to produce human insulin. The latter is the form now generally used, although some patients ?nd it unsuitable and have to return to porcine insulin.
The hormone acts by enabling the muscles and other tissues requiring sugar for their activity to take up this substance from the blood. All insulin preparations are to a greater or lesser extent immunogenic in humans, but immunological resistance to insulin action is uncommon.
Previously available in three strengths, of 20, 40, and 80 units per millilitre (U/ml), these have now largely been replaced by a standard strength of 100 U/ml (U100). Numerous different insulin preparations are listed; these differ in their speed of onset and duration of action, and hence vary in their suitability for individual patients.
Insulin is inactivated by gastrointestinal enzymes and is therefore generally given by subcutaneous injection, usually into the upper arms, thighs, buttocks, or abdomen. Some insulins are also available in cartridge form, which may be administered by injection devices (‘pens’). The absorption may vary from di?erent sites and with strenuous activity. About 25 per cent of diabetics require insulin treatment: most children from the onset, and all patients presenting with ketoacidosis. Insulin is also often needed by those with a rapid onset of symptoms such as weight loss, weakness, and sometimes vomiting, often associated with ketonuria.
The aim of treatment is to maintain good control of blood glucose concentration, while avoiding severe HYPOGLYCAEMIA; this is usually achieved by a regimen of preprandial injections of short-acting insulin (often with a bedtime injection of long-acting insulin). Insulin may also be given by continuous subcutaneous infusion with an infusion pump. This technique has many disadvantages: patients must be well motivated and able to monitor their own blood glucose, with access to expert advice both day and night; it is therefore rarely used.
Hypoglycaemia is a potential hazard for many patients converting from porcine to human insulin, because human insulin may result in them being unaware of classical hypoglycaemic warning symptoms. Drivers must be particularly careful, and individuals may be forbidden to drive if they have frequent or severe hypoglycaemic attacks. For this reason, insurance companies should be warned, and diabetics should – after taking appropriate medical advice – either return to porcine insulin or consider stopping driving.... insulin
Preparation of milk Milk may be prepared for food in various ways. Boiling destroys the bacteria, especially any Mycobacteria tuberculosis which the milk may contain. It also partly destroys vitamin C and thiamine, as does pasteurisation. Curdling of milk is e?ected by adding rennet, which carries out the initial stage of digestion and thus renders milk more suitable for people who could not otherwise tolerate it. Souring of milk is practised in many countries before milk is considered suitable for food; it is carried out by adding certain organisms such as the LACTIC ACID bacillus, the Bulgarian bacillus, and setting the milk in a warm place for several hours. Sterilisation, which prevents fermentation and decomposition, is usually carried out by raising the milk to boiling temperature (100 °C) for 15 minutes and then hermetically sealing it. Condensed, unsweetened milk – usually known as evaporated milk – is concentrated in vacuo at low temperature; the milk is then placed in tins, which are sealed, and is sterilised by heat at a temperature of 105 °C. This destroys 60 per cent of the vitamin C and 30–50 per cent of the thiamine. Sweetened condensed milk is not exposed to such a high temperature. The sugar, which prevents the growth of micro-organisms, is added before the condensing, and ?nally reaches a concentration of about 40 per cent.
Dried milk is prepared by evaporating all the ?uid so that the milk is reduced to the form of powder. Humanised milk is cow’s milk treated to render it closely similar to human milk.... milk
The cause of the pulsation lies in the fact that, at each heartbeat, 80–90 millilitres of blood are driven into the AORTA, and a ?uid wave, distending the vessels as it passes, is transmitted along the ARTERIES all over the body. This pulsation falls away as the arteries grow smaller, and is ?nally lost in the minute capillaries, where a steady pressure is maintained. For this reason, the blood in the veins ?ows steadily on without any pulsation. Immediately after the wave has passed, the artery, by virtue of its great elasticity, regains its former size. The nature of this wave helps the doctor to assess the state of the artery and the action of the heart.
The pulse rate is usually about 70 per minute, but it may vary in health from 50 to 100, and is quicker in childhood and slower in old age than in middle life; it is low (at rest) in physically ?t athletes or other sports people. Fever causes the rate to rise, sometimes to 120 beats a minute or more.
In childhood and youth the vessel wall is so thin that, when su?cient pressure is made to expel the blood from it, the artery can no longer be felt. In old age, however, and in some degenerative diseases, the vessel wall becomes so thick that it may be felt like a piece of whipcord rolling beneath the ?nger.
Di?erent types of heart disease have special features of the pulse associated with them. In atrial FIBRILLATION the great character is irregularity. In patients with an incompetent AORTIC VALVE the pulse is characterised by a sharp rise and sudden collapse. (See HEART, DISEASES OF.)
An instrument known as the SPHYGMOGRAPH registers the arterial waves and a polygraph (an instrument that obtains simultaneous tracings from several di?erent sources such as radial and jugular pulse, apex beat of the heart and ELECTROCARDIOGRAM (ECG)) enables tracings to be taken from the pulse at the wrist and from the veins in the neck and simultaneous events in the two compared.
The pressure of the blood in various arteries is estimated by a SPHYGMOMANOMETER. (See BLOOD PRESSURE.)... pulse
The principal function of saliva is to aid in the initial processes of digestion, and it is essential for the process of mastication (chewing), whereby food is reduced to an homogeneous mass before being swallowed. In addition, the ptyalin in the saliva initiates the digestion of starch in the food.
An excessive ?ow of saliva known as salivation occurs as the result of taking certain drugs. Salivation also occurs as the result of irritation in the mouth – as for instance, in the teething child – and from DYSPEPSIA. De?ciency of saliva is known as XEROSTOMIA.... saliva
Once ejaculated during intercourse the spermatozoon travels at a rate of 1·5–3 millimetres a minute and remains mobile for several days after insemination, but quickly loses its potency for fertilisation. As it takes only about 70 minutes to reach the ovarian end of the uterine tube, it is assumed that there must be factors other than its own mobility, such as contraction of the muscle of the womb and uterine tube, that speed it on its way.... spermatozoon
TUBERCULIN PURIFIED PROTEIN DERIVATIVE (TUBERCULIN PPD) is the active principle of OT (see above), and is prepared from the ?uid medium on which the Mycobacterium tuberculosis has been grown. It is supplied as a liquid, a powder, or as sterile tablets. The liquid contains 100,000 units per millilitre, and the dry powder contains 30,000 units per milligram. It is distributed in sterile containers sealed so as to exclude micro-organisms. It is more constant in composition and potency than OT.
Uses The basis of the tuberculin reaction is that any person who has been infected with the Mycobacterium tuberculosis gives a reaction when a small amount of tuberculin is injected into the skin. A negative reaction means either that the individual has never been infected with the tubercle bacillus, or that the infection has been too recent to have allowed of sensitivity developing.
There are various methods of carrying out the test, of which the following are the most commonly used. The Mantoux test is the most satisfactory of all, and has the advantage that the size of the reaction is a guide to the severity of the tuberculous infection: it is performed by injecting the tuberculin into the skin on the forearm. The Heaf multiple puncture test is reliable: it is carried out with the multiple puncture apparatus, or Heaf gun. The Vollmer patch test, using an impregnated ?lter paper, is useful in children because of the ease with which it can be carried out.... varieties
Mechanism of respiration For the structure of the respiratory apparatus, see AIR PASSAGES; CHEST; LUNGS. The air passes rhythmically into and out of the air passages, and mixes with the air already in the lungs, these two movements being known as inspiration and expiration. INSPIRATION is due to a muscular e?ort which enlarges the chest, so that the lungs have to expand in order to ?ll up the vacuum that would otherwise be left, the air entering these organs by the air passages. The increase of the chest in size from above downwards is mainly due to the diaphragm, the muscular ?bres of which contract and reduce its domed shape and cause it to descend, pushing down the abdominal organs beneath it. EXPIRATION is an elastic recoil, the diaphragm rising and the ribs sinking into the position that they naturally occupy, when muscular contraction is ?nished. Occasionally, forced expiration may occur, involving powerful muscles of the abdomen and thorax; this is typically seen in forcible coughing.
Nervous control Respiration is usually either an automatic or a REFLEX ACTION, each expiration sending up sensory impulses to the CENTRAL NERVOUS SYSTEM, from which impulses are sent down various other nerves to the muscles that produce inspiration. Several centres govern the rate and force of the breathing, although all are presided over by a chief respiratory centre in the medulla oblongata (see under BRAIN – Divisions). This in turn is controlled by the higher centres in the cerebral hemispheres, so that breathing can be voluntarily stopped or quickened.
Quantity of air The lungs do not completely empty themselves at each expiration and re?ll at each inspiration. With each breath, less than one-tenth of the total air in the lungs passes out and is replaced by the same quantity of fresh air, which mixes with the stale air in the lungs. This renewal, which in quiet breathing amounts to about 500 millilitres, is known as the tidal air. By a special inspiratory e?ort, an individual can draw in about 3,000 millilitres, this amount being known as complemental air. By a special expiratory e?ort, too, after an ordinary breath one can expel much more than the tidal air from the lungs – this extra amount being known as the supplemental or reserve air, and amounting to about 1,300 millilitres. If an individual takes as deep an inspiration as possible and then makes a forced expiration, the amount expired is known as the vital capacity, and amounts to around 4,000 millilitres in a healthy adult male of average size. Figures for women are about 25 per cent lower. The vital capacity varies with size, sex, age and ethnic origin.
Over and above the vital capacity, the lungs contain air which cannot be expelled; this is known as residual air, and amounts to another 1,500 millilitres.
Tests of respiratory e?ciency are used to assess lung function in health and disease. Pulmonary-function tests, as they are known, include spirometry (see SPIROMETER), PEAK FLOW METER (which measures the rate at which a person can expel air from the lungs, thus testing vital capacity and the extent of BRONCHOSPASM), and measurements of the concentration of oxygen and carbon dioxide in the blood. (See also LUNG VOLUMES.)
Abnormal forms of respiration Apart from mere changes in rate and force, respiration is modi?ed in several ways, either involuntarily or voluntarily. SNORING, or stertorous breathing, is due to a ?accid state of the soft palate causing it to vibrate as the air passes into the throat, or simply to sleeping with the mouth open, which has a similar e?ect. COUGH is a series of violent expirations, at each of which the larynx is suddenly opened after the pressure of air in the lungs has risen considerably; its object is to expel some irritating substance from the air passages. SNEEZING is a single sudden expiration, which di?ers from coughing in that the sudden rush of air is directed by the soft palate up into the nose in order to expel some source of irritation from this narrow passage. CHEYNE-STOKES BREATHING is a type of breathing found in persons suffering from stroke, heart disease, and some other conditions, in which death is impending; it consists in an alternate dying away and gradual strengthening of the inspirations. Other disorders of breathing are found in CROUP and in ASTHMA.... respiration
Dosage may vary from herb to herb but today’s standard doses are as follows unless stated otherwise. Dried herbs may be swallowed with water (Psyllium seeds) or drunk as a tea or decoction. Dosage is usually thrice daily for chronic conditions and every 2 hours for acute cases.
Refer to appropriate entries for dosage of teas (infusions), decoctions, powders, liquid extracts, tinctures.
Children. 5 to 12 years. One quarter to half adult dose except where otherwise stated. Medical opinion is that after 12 years a child is regarded as an adult. For babies and children, teas and decoctions have much to commend them. Alcohol-based preparations should be avoided where possible.
Babies. 1 to 5 years. 1 to 5 teaspoons tea or decoction. Should a baby fail to take extract internally, a strong tea or decoction may be prepared and used as a footbath or poured into the bath water. This would need to be ten times as strong as for an internal dose. In this way medicaments may indirectly enter the circulation by absorption through a baby’s soft receptive tissue. Other liquid medicines: one drop for each year of age to 5 years; two drops thereafter to 12 years.
Measurement. 1 millilitre = 15 drops. 1 teaspoon = 5ml (5 millilitres or 75 drops liquid medicine). For liquid medicines always use a medicine glass graduated in millilitres, or a standard dropper. Take liquid extracts or tinctures in water (25ml) or honey. ... dosage
Action: Digitalis stimulates the vagus nerve thus slowing the heart rate. Prolongs diastole which increases the heart’s filling-time and improves coronary circulation. Effects of digitalis are cumulative. The herbalist uses an alternative: Lily of the Valley for the failing heart.
Preparation. Tincture B.P. Each millilitre possesses one unit of activity and is equivalent to 0.1 gramme of the International Standard digitalis powder. Prepared from the leaf in 70 per cent alcohol by a pharmacist. Dose: 0.3ml to 1ml (5-15 drops). Used only under medical supervision.
Digoxin toxicity occurs at levels above 2.6m mol/litre. Schedule 1 P. (POM) (UK) ... foxglove
Strength: “One part by volume of liquid is equal to 1 part by weight of herb.” Thus, one ounce of fluid is equal to one ounce of crude material. For instance, 1oz Stone root liquid extract would have the same therapeutic potency as 1oz Stone root.
In the making of liquid extracts there is often a loss of valuable volatile constituents which is believed to reduce efficacy of a plant. For this reason tinctures are becoming popular among practitioners. Dosage of L.E.s may vary from 5 to 60 drops according to the plant. For instance, the maximum dosage of Goldenseal is 15, Black Cohosh 30, and Yarrow 60 drops. A general average would appear to be 15-60 drops, though a practitioner would be more specific. The bottle should be shaken vigorously before use to remix any natural sediment.
One millilitre = 15 drops. One teaspoonful = 5ml (5 millilitres) or 75 drops liquid medicine. For liquid medicines, always use medicine glass graduated in millilitres, or standard dropper. ... liquid extract (l. e.)
Health Encyclopedia