Considerations for implementing an antibiotic policy in hospital practice

An antibiotic policy should aim for the safe, effective and economical use of antimicrobial drugs, and to prevent their indiscriminate use and development of resistant bacterial strains. The term 'antibiotic' is used as a general term for all antimicrobial drugs. Antibiotics prescriptions should be based on clinical evidence of bacterial infection, preferably substantiated by appropriate laboratory culture and sensitivity tests. Viral infections are not an indication for antibiotic prescriptions. Patient factors to be considered for choice and dose of an antibiotic are age, pregnancy, lactation, renal and hepatic impairment. Immunodeficient patients should receive only bactericidal drugs. Severity of infection determines the route of administration. Duration of therapy should not exceed five days, unless specifically prescribed by the physician. An antibiotic should, if started as an empirical therapy not be changed before a minimum of three days trial. Prescriptions of drugs such as aztreonam, imipenem, vancomycin, piperacillin and amphotericin are to be restricted due to cost and toxicity and should be reviewed by the microbiologist (AU)

Respiratory conditions, including asthma, and height in primary school

The National Study of Health and Growth (NSHG) of primary school children has examined the relationships between height and each of six separate respiratory conditions, one of which was asthma, in children aged 5-11 years, allowing for a number of genetic and enviromental confounding factors, in particular for parental height. The relationships were investigated in a 'representative' sample of 4974 Caucasian English children in 1984 and in an 'ethnic/inner city' sample of 3419 Afro-Caribbean/Indian and Pakistani/Caucasian English children in 1985. None of the respiratory conditions was found to be related to height except for wheeze most days', whether or not it was accompanied by an asthma attack in the last 12 months. The Caucasian children in the 'representative' sample who had 'wheeze most days', were 0.17 height standard deviation score (95 percent confidence interval 0.03 to 0.31) less (approximately 1cm) than those with no wheeze. Comparisons with previous results for NSHG 'representative' Caucasian English children in 1973 showed good agreement except for children with three or more asthma attacks who were found to be shorter in 1973, but not in 1984, which may reflect improved treatment, or milder asthma being reported in 1984. It was concluded that, in the 1980s, the respiratory conditions were not related to height. The exception was 'wheeze most days'. It is suggested that this is an indicator of sickness, most likely asthma, which is being experienced with sufficient severity to affect growth slightly (AU)

Chronic obstructive lung disease: a role for theophylline?

Asthma, chronic obstructive bronchitis, and emphysema represent different forms of chronic obstructive pulmonary disease (COPD). Because they have different causes and are based on different pathophysiology, it is reasonable to suspect they may respond differently to treatment. In particular, bronchodilators, such as theophylline, which are purported to act by preventing the spasm of bronchial smooth muscle, should work in asthma but not in chronic bronchitis or emphysema. However, theophylline and other bronchodilators do improve breathing in all three forms of COPD, although to different degrees. Theophylline's effectiveness in chronic bronchitis and emphysema is attributed, in part, to the observation that these forms of COPD commonly have a reversible component (bronchospastic). Furthermore, it is now known that theophylline's mechanism of action includes a strengthening of the diaphragm and other muscles of respiration. These additional mechanisms may explain theophylline's effectiveness in those forms of COPD that lack a bronchospastic component. (AU)

Comparative observations of mucus transport velocity in health and disease

The present study evaluated mucus transport velocity (MTV) in different areas of the tracheobronchial tree in vitro in normal, acute and chronic bronchitic animals. The average MTV in animals ranged from 11.5 mm/min in the trachea to 0.64 mm/min in the pre-terminal bronchus. Chronic bronchitic animals showed mucus hypersecretion, areas of ciliary abnormality and mucus stagnation. The mean transport velocities ranged from 21.2 mm/min in the trachea to 4.1 mm/min in the pre-terminal bronchus. In the acutely ill animals, MTV ranged from 2.5 mm/min in the trachea to zero below the upper lobar bronchus. It is postulated that the higher than normal values in chronic bronchitis are due to altered mucus rheology, increased peristalsis and linear acceleration; whereas those in acute bronchitis were attributed to an early phase of viral or bacterial infection. (AU)

Effect of cigarette smoking and marihuana on respiratory tract function

Studies were conducted to elucidate the effect of tobacco smoking and marihuana on respiratory functions in both animals and human subjects. The airway resistance (Raw) was measured in apparently healthy Wistar rats using whole body plethysmograph. Histopathological and histochemical observations were also made to ascertain the damage induced by the inhalation of tobacco or marihuana smoke. Various pneometric tests viz. Vital capacity (VC), Functional Residual Capacity (FRC), Residual Volume (RV), Total Lung Capacity (TLC), Forced Expiratory Volume in one second (FEV1.0), Mean Transit Time (MTT), Peak Expiratory Flow Rate (PEFR) and Closing Volume (CV) were carried out in chronic tobacco, marihuana smokers and clinically assessed asthmatic patients. The effect of crude aqueous marihuana extract on specific airway resistance (sRaw) as well as on various pneometric parameters were observed both in animals and human subjects respectively. Animal Studies - inhalation of either marihuana or tobacco smoke significantly increased (p<0.01) airway resistance (Raw), functional residual capacity (FRC) and specific airway resistance (sRaw) as compared to the control rats. Apparent increases in the airway resistance were observed after the first week of exposure but significant differences were only noted in rats exposed for a period of 12 weeks or more. The smoking of either marihuana or tobacco increased the sensitivity of airways to acetylcholine from 18 weeks of exposure onwards. Attempts to elucidate the mechanism of action suggested that the increase in airway responsiveness of alpha adrenoceptors and increased vagal activity which may have resulted in the narrowing of the airways. This has been suggested on the basis of the following observations: i) Intraperitoneal administration of adrenaline (400 ug/kg body weight) following propranolol (2 mg/kg body weight) resulted in an increase in sRaw, whereas a decrease was observed following phentolamine (2 mg/kg body weight). ii) Intramuscular administration of atropine (2 mg.kg body weight) decreased sRaw. Bilateral vagotomy of marihuana or tobacco smoke to exposed rats. iii) The administration of subthreshold concentrations of acetycholine (0.25 ug and 0.5 ug Ach) in 36 weeks smoke exposed rats significantly increased sRaw in contrast to control rats. The administration of atropine prior to acetypcholine in subthreshold concentrations prevented such increase in sRaw in smoke exposed rats indicating the involvement of vagus in inducing the hypersensitivity. The possible existence of bronchitis in marihuana and tobacco smoke to rats from 12 weeks onwards has been further supported by histopathological and histochemical changes which include inter alia catarrhal inflammation resulting in ulceration of the bronchial mucosa, squamous cell metaplasia, increased goblet cell, increased sulphation of mucus, focal alveolitis and alveolar collapse. The interperitoneal administration of 1 ml aqueous crude marihuana extract (1.27 gm/100 ml) significantly decreased the value of sRaw in both marihuana and tobacco smoke exposed rats. This is suggestive of its bronchodilatory effect and has been further demonstrated to be acting through beta adrenoceptors. The cessation of smoking for one month resulted in a decreasing trend of sRaw in rats exposed to either marihuana or tobacco smoke for a period of 36 weeks. This suggests that improvement in the lung picture may be achieved if a longer recovery period is allowed. Human Studies - the comparison of lung functions in chronic marihuana smokers and non-smokers indicated narrowing of both central and peripheral airways as demonstrated by slight decreases in FEV1.0 percent and PEFR and increases in RV/TLC percent, CV/VC percent and CC/TLC percent. These lung functions were found to be more affected in chronic smokers. The bronchodilatory effect observed immediately after smoking a single dose of marihuana to the chronic marihuana smokers may be due to the presence of THC. This bronchodilation was followed by bronchoconstriction when observed after 60 minutes of marihuana smoking. The mechanism of initial bronchodilation is at present unclear but may be due to a direct effect of THC on the bronchial smooth muscle. The bronchoconstrictory effect of marihuana or tobacco smoke is probably due to increased vagal activity and increased responsiveness of alpha adrenoceptors as observed in the animal studies. The presence of a low responsive and a high responsive group of subjects in chronic marihuana smokers has been demonstrated. The high responsive group seems to be more susceptible to marihuana smoke as exemplified by greater decrease in FEV1.0 percent and increase in CV/VC percent. These changes further indicate that the impairment occurs predominantly in the larger airways even though there are signs of onset of small airway disease. The decreases in FEV1.0 percent and PEFR in the asthmatic subjects indicated abnormalities in the larger airways. Significant increases in MTT, CV/VC percent and CC/TLC percent is suggestive of obstruction in the peripheral airways. Administration of 30 mls aqueous extract (200 mg/100 mls) of marihuana to asthmatic subjects resulted in the improvement in lung functions after 30 minutes with the maximum improvement being observed at 60 minutes post administration. The bronchodilatory effect of marijuana extract was quite comparable to a known bronchodilator, ventolin (Salbutamol 200 ug), used in this study. However, the effect of ventolin was faster than aqueous marihuana extract. The bronchodilatory effect of aqueous marihuana extract may be due to the presence of some active ingredients other than THC and may be partly due to the increased activity of beta adrenoceptors (AU)

Tracheobronchial function in health and disease: effect of mucolytic substances

The effect of mucolytic and expectorant substances on ciliary beat frequency, mucus transport velocity and mucus production, was investigated in normal and bronchitic rats. The results showed that: (i) N-acetylcysteine and S-carboxymethylcysteine were mildly cilioexcitatory at low and ciliodepressive at higher concentrations in both normal and bronchitic rats. A similar pattern was seen in mucus transport velocity. (ii) Bisolvan enhanced all aspects of muciciliary activity in both groups of animals. Sobrepin was less effective than Bisolvan and more effective than Tachoquilin. (iii) Geleomytrol, Ozothin and prostaglandin E1 were all cilioexcitatory in rats with bronchitis. Mucus transport velocity was similarly stimulated by both Geleomyrtol and Ozothin. (iv) Ammonium chloride and potassium iodide enhanced mucociliary activity in normal and bronchitic rats. (v) All substances stimulated mucus production, however, the most potent was prostaglandins E1. The mechanisms for increased mucociliary activity involve inter alia the probable cleaving of disulphide bridges, decreased mucosal swelling, altered rheological characteristics and stimulation of adenylate cyclase (AU)

Cigarette smoking and irreversible airways obstruction in the West Indies

Two communities, one in Jamaica and one in Guyana, have been surveyed in order to investigate the relationships between cigarette smoking and respiratory symptoms, and lung function in the West Indies. Cigarette consumption was less than that reported in the United Kingdom, particularly among women. Smoking was associated with cough, phleghm, increases in total lung capacity and residual volume, and reductions in FEV percent, transfer coeffecient (Kco), and aveolar capillary blood volume (Vc). Vital capacity (VC) and the diffusion capacity of the alveolar membranes (Dm) were normal. After allowing for differences in age and tobacco consumption, less cough, phleghm and airways obstruction occurred in the West Indies than has been reported in the United Kingdom. Forty-seven patients in Jamaica with chronic obstructive lung disease were followed for three years. All except six female asthmatics were either current smokers or ex-smokers. Smoking in patients was associated with a similiar but more severe pattern of lung disease to that found in survey subjects with, in addition, reductions in VC, and Dm. In the non-smoking asthmatics Kco, Dm, and Vc were normal. The lung function of these 47 patients was similiar to that reported for UK patients even though both chronic bronchitis and hypercapnia were considerably less common in Jamaica. Emphysema was present in all six patients who died and came to necropsy. It is suggested that in the West Indies emphysema contributes more than bronchitis to airways obstruction in smokers. There was also evidence that subjects of African origin were less susceptible to the emphysema-producing effect of cigarettes than were other ethnic groups (AU)

The lipoid pneumonia of blackfat tobacco smokers in Guyana

In Guyana, a large number of patients have been diagnosed as having a diffuse pulmonary fibrosis of unknown aetiology, characterized by typical radiological appearances, dyspnoea, cough, weight loss, and eventually pulmonary heart disease. Investigation of 56 patients showed that all had smoked a tobaco known as 'blackfat' or 'black tobacco'. In a community survey 20.4 per cent of the population aged 55 years and over smoked this tobbaco. 19.6 per cent of the blackfat smokers but no non-blackfat smokers showed definite radiological evidence of pulmonary fibrosis. Smokers with, but not those without fibrosis, had severe airway obstruction. Immunological studies made it unlikely that an extrinsic allergic aveolitis had caused the radiological changes. Three post-mortem open-lung specimens were obtained and in each case the histology showed a diffuse interstitial fibrosis and vasculitis associated with large deposits of lipid surrounded by black amorphous material. Blackfat is a tobacco leaf to which mineral oil and vaseline is added for flavouring and as humectants. The presence of oil in the tobacco, and the post-mortem findings of oil in the lungs, indicate that the diffuse pulmonary fibrosis can be more accurately described as a lipoid pneumonia caused by the inhalation of mineral oils when blackfat is smoked. The potential health hazards of many tobacco additives, particularly oils, employed by the tobacco industry should be recognized. A similar type of disease as that found in Guyana may be present in other parts of the world where blackfat, or related tobacco, are smoked.(Summary)

A community survey of respiratory disease among East Indian and African adults in Guyana

The belief that chronic bronchitis is more prevalent among Indians than Africans in the Caribbean area was investigated by a community survey in Guyana. Respiratory symptoms were assessed by a standard questionnaire, ventilatory capacities were measured, and chest radiographs were taken of some 800 African and Indian men and women aged 35 to 54 years living in adjacent and similar communities. Histories of morning cough, chronic cough, morning phlegm, and chronic phlegm (chronic bronchitis) were more common in Indians than Africans. Although these respiratory symptoms were much more common in smokers than non-smokers, the higher prevalence rates in Indians could not be explained by smoking habits which were similar in the two races. Chronic bronchitis occurred in 17.3 percent of Indian and 2.4 percent of African male smokers and in 6.1 percent and 2.2 percent of Indian and African female non-smokers respectively. Judging by the history, lung infection, and clinical signs, chronic bronchitis was more severe in Indians than Africans. The condition was more common among field labourers on sugar estates but, although the majority of field labourers were Indian, this occupational difference only partially explained the difference in prevalence between Indians and Africans. Indians, for reasons unknown, appear to have a greater susceptibility than Africans to chronic bronchitis.(AU)

Distribution of bronchial gland measurements in a Jamaican population

Measurements of the gland thickness and Reid index have been made on bronchi obtained at necropsy on 53 male and 52 female Jamaicans. The mean values for the Reid index and mucous gland thickness obtained were 0.314 and 0.192mm. for males, and 0.302 and 0.170mm. for females respectively. No significant increase in values was seen with age, although the data suggest this trend. The results have been compared with data published from Montreal and the same overall Gaussian distribution is seen. This supports the suggestion that the gland measurements in non-bronchitic and bronchitic subjects do not fall into two distinct groups but are part of a continous distribution. The similarity of the two studies is also of interest as the populations are drawn from two distinct environments, one from a non-industrialized tropical island, the other from a large city in the northern hemisphere.(AU)

Bagassosis: an epidemiological, environmental, and clinical survey

An epidemiological and environmental survey of 170 bagasse workers employed by a raw sugar producing company in Trinidad was carried out in order to assess the prevalence of respiratory symptoms and to determine if exposure to bagasse was associated with alterations in ventilatory capacity. The epidemiological survey failed to reveal a significantly increased prevalence of respiratory symptoms in the more exposed group but showed that the group of Indian workers who were regularly and continously exposed to bagasse had a significantly lower ventilatory capacity than the control group. This diminished ventilatory capacity was demonstrated despite negligible dust concentrations in the plant. However, the possibility that persistence exposure to low concentrations of bagasse may be the cause must be considered. During a five-year period, 17 patients with bagassosis were seen, the clinical picture being similar to that described in extrinsic allergic alveolitis from other causes. The systematic variations demonstrated in some indices of ventilatory function in different racial groups is discussed.(AU)