Small Airway Obstruction Research Articles

Pulmonary effects of exposure to fine fibreglass: irregular opacities and small airways obstruction.

Man made mineral fibres imitate asbestos and produce tumours of the pleura in animals. To answer the question, Does prolonged exposure to fibreglass adversely affect pulmonary function or produce radiographic abnormalities in human subjects? we studied workers in a midwestern appliance plant where refrigerator doors and previously entire cabinets were insulated with fibreglass sheeting and loose rotary spun fibreglass. Spirometry and lung volumes were measured, respiratory and occupational questionnaires were administered, and chest x-ray films were read for pneumoconiosis using International Labour Office (ILO) 1980 criteria in 284 workers with exposure of 20 years or more. Expiratory flows were reduced including FEV1 (mean 90.3% of predicted (pr), FEF25-75 (85.5% pr), and FEF75-85 (76.2% pr). Forced vital capacity was significantly reduced (92.8% pr) and total lung capacity was significantly increased (109.2% pr). In white male smokers, a group large enough for comparisons, parameters of pulmonary function were reduced further in the presence of irregular opacities. Forty three workers (15.1%) had evidence of pneumoconiosis on chest radiographs: 26 of these (9.1%), had no known exposure to asbestos and 17 (6.0%) had some exposure. The best judgement was that in 36 (13.0%), pulmonary opacities or pleural abnormalities were due to fibreglass. Commercial rotary spun fibreglass used for insulating appliances appears to produce human disease that is similar to asbestosis.

Evaluation of mean transit time in children as an indicator of airways obstruction

Mean transit time was evaluated as a test of pulmonary function in normal and asthmatic children. It was found to be independent of body size and negatively correlated with PEFR, FEV1 and FVC in normal children. Mean transit time was less sensitive in detecting the effects of bronchodilator therapy in asthmatic children than other simpler tests of lung function. The range of normal was so wide that there was no clear demarcation between normal and abnormal. The degree of overlap makes isolated tests of mean transit time of little diagnostic value. It is therefore concluded that mean transit time though it theoretically offers the attractive advantage of being a sensitive indicator of both large and small airways obstruction, is unlikely to play a major part in the routine evaluation of lung function in asthmatic children.

Sequential respiratory, psychologic, and immunologic studies in relation to methyl isocyanate exposure over two years with model development.

Of 113 methyl isocyanate (MIC)-exposed subjects studied initially at Bhopal, India, 79, 56, 68, and 87 were followed with clinical, lung function, radiographic, and immunologic tests at 3, 6, 12, 18, and 24 months. Though our cohort consisted of subjects at all ages showing a varied severity of initial illness, fewer females and young subjects were seen. Initially all had eye problems, but dominant symptoms were exertional dyspnea, cough, chest pain, sputum, and muscle weakness. A large number showed persistent depression mixed with anxiety, with disturbances of personality parameters. The early radiographic changes were lung edema, overinflation, enlarged heart, pleural scars, and consolidation. The persistent changes seen were interstitial deposits. Lung functions showed mainly restrictive changes with small airway obstruction; there was impairment of oxygen exchange. Oxygen exchange improved at 3-6 months, and spirometry improved at 12 months, only to decline later. The expiratory flow rates pertaining to large and medium airway function improved, but those for small airways remained low. There were changes of alveolitis in bronchoalveolar lavage fluid on fiber optic bronchoscopy, and in 11 cases positive MIC-specific antibodies to IgM, IgG, and IgE were demonstrated. On follow up, only 48% of the subjects were clinically stable, while 50% showed fluctuations. Thirty-two percent of the subjects had lung function fluctuations. Detailed sequential behavior over 2-4 years was predicted for dyspnea, forced vital capacity, maximum expiratory flow rate (0.25-0.75), peak expiratory flow rate, VO2, and depression score. A model for clinical behavior explained a total variance of 52.4% by using the factors of cough, PCO2 and X-ray zones in addition to above five parameters. The behavior of the railway colony group (1640 patients) revealed a similar pattern of illness. When this observed pattern of changes was transferred to the affected Bhopal city sections (with an equitable age-sex distribution), our model results were again validated. Thus the picture of MIC-induced disease seems similar despite the differences for age-sex and initial severity of illness in our cohort and in the population of Bhopal city as predicted by our model.

Sequential Respiratory, Psychologic, and Immunologic Studies in Relation to Methyl Isocyanate Exposure over Two Years with Model Development

Of 113 methyl isocyanate (MIC)-exposed subjects studied initially at Bhopal, India, 79, 56, 68, and 87 were followed with clinical, lung function, radiographic, and immunologic tests at 3, 6, 12, 18, and 24 months. Though our cohort consisted of subjects at all ages showing a varied severity of initial illness, fewer females and young subjects were seen. Initially all had eye problems, but dominant symptoms were exertional dyspnea, cough, chest pain, sputum, and muscle weakness. A large number showed persistent depression mixed with anxiety, with disturbances of personality parameters. The early radiographic changes were lung edema, overinflation, enlarged heart, pleural scars, and consolidation. The persistent changes seen were interstitial deposits. Lung functions showed mainly restrictive changes with small airway obstruction; there was impairment of oxygen exchange. Oxygen exchange improved at 3-6 months, and spirometry improved at 12 months, only to decline later. The expiratory flow rates pertaining to large and medium airway function improved, but those for small airways remained low. There were changes of alveolitis in bronchoalveolar lavage fluid on fiber optic bronchoscopy, and in 11 cases positive MIC-specific antibodies to IgM, IgG, and IgE were demonstrated. On follow up, only 48% of the subjects were clinically stable, while 50% showed fluctuations. Thirty-two percent of the subjects had lung function fluctuations. Detailed sequential behavior over 2-4 years was predicted for dyspnea, forced vital capacity, maximum expiratory flow rate (0.25-0.75), peak expiratory flow rate, VO2, and depression score. A model for clinical behavior explained a total variance of 52.4% by using the factors of cough, PCO2 and X-ray zones in addition to above five parameters. The behavior of the railway colony group (1640 patients) revealed a similar pattern of illness. When this observed pattern of changes was transferred to the affected Bhopal city sections (with an equitable age-sex distribution), our model results were again validated. Thus the picture of MIC-induced disease seems similar despite the differences for age-sex and initial severity of illness in our cohort and in the population of Bhopal city as predicted by our model.

Bronchoalveolar Lavage Cell Findings in Patients with BOOP and Related Diseases

Bronchiolitis obliterans with organizing pneumonia (BOOP) is a clinicopathologic entity. 1 Epler GR Colby TV McLoud TC Carrington CB Gaensler EA. Bronchiolitis obliterans organizing pneumonia. N Engl J Med. 1985; 312: 152-158 Crossref PubMed Scopus (862) Google Scholar It is pathologically defined as granulation tissue plugs within lumens of small airways, sometimes with complete obstruction of small airways and granulation tissues extending into alveolar ducts and alveoli. Findings such as extensive fibrosis and honeycombing, hyaline membranes, extensive fibrinous exudates, necrosis, acute inflammation, vasculitis, prominent eosinophils, and prominent granulomas should not be included. 2 Colby TV Lombard C Yousem SA Kitaichi M. Interstitial diseases. In: Atlas of pulmonary surgical pathology. WB Saunders, Philadelphia1991: 228-306 Google Scholar Above findings are nonspecific and common in various lung injuries of either definite or idiopathic etiology. Furthermore, clinical features show a subacute onset and the duration is less than 2 months in 75% of the patients. 3 Epler GR Bronchiolitis obliterans organizing pneumonia: definition and clinical features. Chest. 1992; 102: 2S-6S Abstract Full Text Full Text PDF PubMed Google Scholar

Pulmonary Inflammation Associated with Aspirated Meconium and Epithelial Cells in Calves

"Meconium aspiration syndrome" is a condition resulting in respiratory distress and the occasional death of newborn human beings. A retrospective study was conducted on 52 calves that were submitted for postmortem examination to the Atlantic Veterinary College, Charlottetown, Prince Edward Island, Canada. These calves died of infectious and noninfectious diseases within the first 2 weeks of life due to a variety of causes. The most common cause of death was infectious enteric disease. Histologic examination of lungs revealed that 42.5% of calves had evidence of meconium, squamous cells, or keratin in the lung. There was considerable variation in the magnitude of histologic changes in lungs containing aspirated material. Typically, affected lungs had only a few inconspicuous pieces of meconium, keratin, and squamous cells within bronchoalveolar spaces. Sporadically, the entire lumen of airways was obliterated by aspirated material. Lungs with aspirated material had a mild but diffuse alveolitis characterized by exudation of a few neutrophils, macrophages, and occasional multinucleated giant cells. Obstruction of small airways and focal atelectasis were also observed. Similar lesions have been reported in human meconium aspiration syndrome. It is concluded that histologic changes similar to those of human meconium aspiration syndrome occur commonly in calves that die within 2 weeks of birth. Further studies involving healthy age-matched calves are required to evaluate the clinicopathologic significance of meconium aspiration in this species.

Small airways function of silica-exposed workers.

Small airways obstruction may be present for many years before chronic airway obstruction becomes evident. Several spirometric indices, especially flow rates at low lung volumes, may reflect the status of small airways. Time domain indices, by using moments analysis of the volume time spirogram, have also been shown to be sensitive indicators of small airways obstruction. In this study, we have applied the various spirometric indices as well as time domain indices to a group of granite quarry workers without radiographic evidence of silicosis or physiological evidence of obstruction to the larger airways. The aim was to evaluate small airways function in relation to dust exposure in subjects with normal ratio of the forced expiratory volume in one second to the forced vital capacity (FEV1/FVC) and normal FVC. The volume-time spirograms of 140 quarry workers were digitized using an electronic digitizer connected to a microcomputer where flow and time domain indices were computed. The workers were divided into three exposure groups based on their occupational history. With adjustment for age, height, and smoking status, all the time domain indices showed significant small airways obstruction with increasing dust exposure. Smokers had greater degree of airways obstruction than the non-smokers, with a similar trend of increase in small airways obstruction in relation to higher exposure. Our present study suggests that small airways obstruction is present among silica exposed workers in the absence of radiological evidence of silicosis and large airways obstruction. There was also evidence of increasing small airways obstruction in higher dust exposure group. Our study also suggests that time domain indices are more sensitive to small airways obstruction.

Respiratory function in patients with perennial nasal allergy and pollinosis

There are many patients with allergic rhinitis who have no lower airway symptoms. The question arises as to whether or not the lower airway is involved in such cases, but the results of investigations in this field remain controversial. To answer this question, I performed various respiratory function tests in patients with perennial nasal allergy or pollinosis with or without a history of bronchial asthma. In addition, physiological changes in lower airway lesions were evaluated after challenge with antigen and histamine in these patients. In the present study, respiratory function was examined by autospirometry and the following results were obtained. 1. The group with perennial nasal allergy and a history of bronchial asthma showed significantly lower FEV1.0%, PER, %VC, V75, V50, and V25 values than the group with perennial nasal allergy without history of bronchial asthma, indicating an obstructive lesion in the lower airway. The group with perennial nasal allergy alone showed lower V75, V50, and V25 values than the control group, suggesting small airway obstruction. 2. The group with perennial nasal allergy and a history of bronchial asthma showed marked hypersensitivity in the lower airway after histamine inhalation. The group with perennial nasal allergy alone showed marked changes in V75, V50, and V25: the degree was between that of the control group and that in the group with a history of asthma. 3. In patients with pollinosis, various respiratory function tests showed no abnormalities during the in-season of pollinosis and the out-seasons. However, inhalation of antigen or histamine decreased various parameters, significantly V50 and V25, during the symptomatic season.(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnosing COPD

Chronic obstructive pulmonary disease (COPD) is seen often in primary care offices. Its hallmark is dyspnea with obstruction. Smoking is the leading risk factor. Smokers should be counseled at every encounter to quit smoking to prevent development of COPD and lower the rate of decline of pulmonary function. Office spirometry detects the early changes of small airways obstruction. All patients with symptoms should receive baseline spirometry and follow-up spirometry once they have received maximal medical therapy. If evidence of obstruction is found and spirometric abnormality persists after therapy, COPD is present. Treatment early in the clinical course can markedly improve COPD and avoid the severe disability of end-stage disease.

Denervation of transplanted porcine lung causes airway obstruction

Lung transplantation can be complicated by a form of small airway obstruction known as bronchiolitis obliterans. We tested the hypothesis that lung denervation causes small airway obstruction in young pigs (10 ± 1 weeks). Control pigs had an innervated native lobe, and study pigs had either a denervated native lobe or a denervated transplant lobe. Transplanted pigs received standard immunosuppression. At 10 weeks we measured isolated left lobe pulmonary mechanics. Dynamic resistance in both study groups was significantly higher than in the lobectomy group, whereas dynamic compliance in both study groups was significantly lower than in the lobectomy group. No significant difference in resistance or compliance was noted between the transplant and reimplant groups. Histologic changes consistent with rejection were noted in the transplant lobes. We conclude that the small airway obstruction noted in this model is due to operative denervation rather than to immunosuppression or rejection.

Long term effects of smoke inhalation in survivors of the King's Cross underground station fire.

In most accidents causing smoke inhalation only a few victims actually inhale the smoke. The fire at King's Cross provided an opportunity to assess the long term effects of smoke inhalation in a larger number of patients. Fourteen survivors from the King's Cross underground station fire were assessed for respiratory disability six months after the disaster and 10 were reassessed at two years. All had inhaled substantial quantities of smoke and 10 had skin burns of differing severity. Six months after the fire nine survivors admitted to one or more symptoms, which included hoarseness (two cases), cough (five cases), and breathlessness (six cases); and a survivor with asthma noted a worsening of his symptoms. The remaining five denied new symptoms. Peak expiratory flow, spirometric indices, and transfer factor for carbon monoxide were within the predicted normal ranges. The mean residual volume, however, was greater than the predicted value and the mean maximum expiratory flow at 25% of vital capacity (V25) less than predicted, with no significant differences between smokers (n = 7) and non-smokers (n = 7). At least one of these ventilatory defects, suggesting small airways obstruction, was present in 11 survivors at six months and they had persisted in the seven patients who were reassessed at two years. Smoke inhalation may be associated with injury to the small airways.

Domiciliary nocturnal nasal intermittent positive pressure ventilation in COPD: mechanisms underlying changes in arterial blood gas tensions

The improvement in arterial blood gas tensions following assisted ventilation in chronic obstructive pulmonary disease (COPD) has usually been attributed to the relief of incipient or established respiratory muscle fatigue. The contribution of changes in the load placed upon and the drive to the respiratory muscle pump have not been evaluated. We have investigated the contribution of changes in respiratory muscle strength, the ventilatory response to CO2 and ventilatory function to changes in arterial blood gas tensions in eight patients with severe COPD completing six months domiciliary nasal intermittent positive pressure ventilation. Six patients showed a reduction and two an increase in arterial carbon dioxide tension (PaCO2), median (range) for eight patients, -0.9 kPa (-1.5 to +0.4) (p less than 0.05) and seven showed an improvement in arterial oxygen tension (PaO2), +0.7 kPa (-0.4 to +1.7) (p less than 0.05) during daytime spontaneous breathing. The reduction in PaCO2 was not related to increased inspiratory muscle strength but was correlated with a decrease in gas trapping (Spearman rank correlation coefficient (r(S)) 0.85, p less than 0.05) and in the residual volume (r(s) 0.78, p less than 0.05), suggesting reduced small airway obstruction and, therefore, a reduction in load. The change in PaCO2 also correlated with the increase in ventilation at an end-tidal CO2 of 8 kPa during rebreathing (r(s) -0.76, p less than 0.05) suggesting improved chemosensitivity to CO2. Our data do not support the hypothesis that improvements were due to the relief of muscle fatigue. We suggest that the contribution of changes in load and central drive warrant further investigation.

Auscultated Forced Expiratory Time as a Clinical and Epidemiologic Test of Airway Obstruction

Seeking an inexpensive, readily available, clinical, screening, and field surveillance test of airway obstruction, we determined the validity of current dogma that forced expiratory time (FET) is a good clinical test of airway obstruction yet is of no epidemiologic use given excessive intrasubject variability. Two hundred twenty-nine white male plumbers and pipefitters were evaluated by spirometry, chest roentgenography, and a standardized respiratory questionnaire during a union-sponsored asbestos screening program. Subjects were classified as having large airway obstruction (LAO), small airway obstruction (SAO) alone, or no obstruction, on the basis of standard spirometric prediction equations. Two physicians, blinded to clinical and spirometric data, independently measured FET while auscultating the trachea with a stethoscope. The FET was defined as the time taken for an individual to forcefully exhale through an open mouth from total lung capacity until airflow became inaudible. Five such times were recorded for each subject. The mean of the three times having the narrowest range was deemed the FET for calculating test sensitivity and specificity. Based on previous literature, an FET greater than or equal to 6 s was considered abnormally prolonged. Two hundred five subjects completed both spirometry and FET testing; 67 had LAO, 5 SAO, and 133 no obstruction. A total of 83 percent had three FETs reproducible within a range of less than or equal to 1 s. The sensitivity and specificity of FET for LAO were 92 and 43 percent, respectively, while for SAO alone, 60 and 44 percent, respectively. Overall, FET misclassified 56 percent of nonobstructed subjects. Adjusting the normal-abnormal cutoff points for both FET and SAO minimally improved the performance of FET. Although FET is a simple, inexpensive, sensitive, and fairly reproducible clinical test of LAO, it cannot be recommended as a clinical or an epidemiologic tool because of its extremely low specificity.

Carcinogen mmetabolism and DNA adducts in human lung tissues as affected by tobacco smoking or metabolic phenotype: a case-control study on lung cancer patients

Individual variations in activity of pulmonary enzymes that metabolize tobacco-derived carcinogens may affect an individual's cancer risk from cigarette smoking. To investigate whether some of these enzymes (e.g., cytochrome P450IA-related) can serve as markers for carcinogen-induced DNA damage accumulating in the lungs of smokers, non-tumorous lung tissue specimens were taken during surgery from middle-aged men with either lung cancer (n = 54) or non-neoplastic lung disease (n = 20). Phase I (AHH, ECDE) and phase II (EH, UDPGT, GST) enzyme activities, glutathione and malondialdehyde contents were determined in lung parenchyma and/or bronchial tissues; some samples were analyzed for DNA adducts, using 32P-postlabeling.Data analysis of subsets or the whole group of patients yielded the following results. (1) Phase I and II drug-metabolizing enzyme (AHH, EH, UDPGT, GST) activities in histologically normal surgical specimens of lung parenchyma were correlated with the respective enzyme activities in bronchial tissues of the same subject. (2) In lung parenchyma, enzyme (AHH, ECDE, EH, UDPGT) activities were significantly and positively related to each other, implying a similar regulatory control of their expression. (3) Mean activities of pulmonary enzymes (AHH, ECDE) were significantly (2- and 7-fold, respectively) higher in lung cancer patients who had smoked within 30 days before surgery (except GST, which was depressed) than in cancer-free subjects with a similar smoking history. (4) In the cancer patients, the time required for AHH, EH and UDPGT activities to return to the level found in non-smoking subjects was several weeks. (5) Bronchial tree and peripheral lung parenchyma preparations exhibited a poor efficiency in activating promutagens to bacterial mutagens in Salmonella. However, they decreased the mutagenicity of several direct-acting mutagens, an effect which was more pronounced in tissue from recent smokers. GSH concentration and GST activity were positively correlated with mutagen inactivation in the same sample. (6) In recent smokers, AHH activity in lung parenchyma was positively correlated with the level of tobacco smoke-derived DNA adducts. (7) Pulmonary AHH and EH activity had prognostic value in tobacco-related lung cancer patients. (8) An enhanced level of pro-oxidant state in the lungs was associated with recent cigarette smoking. Malondialdehyde level in lung parenchyma was associated with the degree of small airway obstruction, suggesting a common free radical-mediated pathway for both lung cancer induction and small airway obstruction.These results demonstrate the pronounced effect of recent cigarette smoke exposure on pulmonary xenobiotic metabolism and lipid peroxidation and lend further support to the hypothesis that the inducibility of pulmonary AHH activity (cytochrome P450IA1 levels) in tobacco smokers is associated with lung cancer risk. Results on DNA adducts in smokers' lung tissue may help to explain why a certain metabolic phenotype accumulates more DNA damage in lung cells.

The effects of diuresis and transfusion on pulmonary function in children with thalassemia major

Previous pulmonary function studies in subjects with thalassemia major (TM) who were on regular transfusion programs have demonstrated results ranging from small airway obstruction to a restrictive pattern. Ten subjects with TM were studied pre- and postdiuresis, and again 24 hr after transfusion, in order to evaluate the role of possible fluid overload in altering pulmonary function. Subjects underwent spirometry and had lung volume and flow volume curves (MEFVC) measured in a volume displacement plethysmograph while breathing air and a mixture of 80% helium and 20% oxygen (HeO2). Six patients had pulmonary mechanics measured with esophageal balloons in place. Baseline function was normal and no change occurred following diuresis. Following transfusion, the volume of isoflow (VisoV) decreased, but other parameters did not change. Subsequent analysis revealed 5 subjects with an initial VisoV greater than 20 (% FVC) but, paradoxically, less evidence of flow limitation in the small airways than those with a VisoV less than 20 (% FVC). Posttransfusion, in those subjects with an initially high VisoV, the Vmax25(air) tended to fall without a change of MEFVC in HeO2, resulting in a decreased VisoV. This was interpreted as evidence of subtle abnormalities in the small airways caused by volume expansion, raising doubts about the value of the VisoV as a measure of small airway disease. As a group, our subjects did not demonstrate any abnormalities in baseline function. Some subjects had mild flow limitation in small airway while other developed comparable levels of flow limitation following the volume expansion associated with transfusion.

Effects of Hemodialysis and Anemia on Pulmonary Diffusing Capacity, Membrane Diffusing Capacity and Capillary Blood Volume in Uremic Patients

The study aimed at investigating pulmonary function in uremic patients, emphasizing the lung diffusing capacity for CO (DLCO) and its membrane and pulmonary capillary blood volume (Vc) components. The study sample comprised 25 uremic patients without clinical/radiological evidence of lung disease. They were enrolled in a chronic hemodialysis (HD) program and had anemia requiring transfusions. The subjects were tested for their lung function before and after both a first HD and a HD with blood transfusion (BT) that followed a few days later. After HD-induced removal of body fluid, and increase in pre-HD reduced forced vital capacity, alveolar volume and mid-expiratory flow rate (FEF25-75%) was observed. HD-induced DLCO decrease (p less than 0.005) was observed and was related to decreased Vc. The second HD with BT increased DLCO, due to partially normalized Hb. On average, a 7.2% DLCO increase corresponded to each 10-g/l Hb rise. In conclusion, (1) the beneficial effect of HD in uremic patients reverts the small-airway obstruction; (2) the lower values of DLCO in these patients are due to reduced Hb and HD causes further DLCO reduction via decrease of Vc, and (3) HD with BT still increases DLCO because improvement of Hb predominates.

Assessment of respiratory diseases and therapeutic intervention by the forced oscillation technique in feedlot cattle

The forced oscillation technique was used to study pulmonary function in bulls during naturally acquired pulmonary-gastrointestinal disease complex known as shipping fever and as it was treated with two different antibiotics. Fifteen double-muscled bulls of the Belgian White and Blue breed were investigated. Clinical, serological and pulmonary function values were recorded during and after naturally occurring respiratory disease. Total respiratory resistance (R rs) and reactance (X rs) were measured by the forced oscillation technique. The antibiotic ceftiofur (group A, n =10) and oxytetracycline (group B, n = 5) were given over three days. A large increase of R rs at low frequencies with a marked negative frequency dependence, an increase of the resonant frequency, and a decrease of X rs were recorded in the initial stage of the disease. The parameters returned to normal values seven days later. Clinical evidence of recovery was more marked in group A than in group B. These results show that moderate shipping fever induces acute small and large airway obstruction which responds to appropriate antibiotic therapy.

Pulmonary Lipid Peroxidation in Cigarette Smokers and Lung Cancer Patients

Lipid peroxidation (LPO) was studied in lung tissues of patients with lung cancer (LC, n = 37) or nonlung cancer (NLC, n = 13) and its relationships with the smoking habits and the degree of airway obstruction were investigated. Specimens of peripheral lung parenchyma, free of tumor tissue, were taken and the malondialdehyde (MDA) content was measured in the S-12 fractions. Airway obstruction was assessed by flow-volume curves, and data were expressed as percentage of the predicted values. Cigarettes smoked were expressed as pack-years. The patients with LC and NLC did not differ by MDA content, age, and number of pack-years. On the contrary, FEF75-85 and MEF75 were significantly lower in LC than in NLC patients (p less than 0.05). The MDA content was inversely correlated to number of days patients had refrained from smoking (r = -0.66, p less than 0.001). The MDA content was higher in recent smokers (ie, people smoking during the last 30 days before surgery) than in the other patients (0.136 +/- 0.007 vs 0.116 +/- 0.007 mumol/g of tissue, p less than 0.05) and, by considering only recent smokers, MDA content was higher in LC patients (0.144 +/- 0.008 mumol/g of tissue) than in NLC patients (0.113 +/- 0.014 mmol/g tissue, p = 0.059). When patients were divided into "high MDA" and "low MDA" groups, MEF75 was much lower in the high MDA group (35.1 +/- 3.4 percent) than in the low MDA group (55.1 +/- 8.1 percent) (p less than 0.01). These results suggest the following: (1) enhanced level of prooxidant state in the lungs is associated with recent cigarette smoking; (2) LC patients may be more prone than respective NLC patients to oxidative stress; (3) MDA level and degree of small airway obstruction were associated and differed between LC and NLC patients even though these groups did not differ in the percentage of recent smokers; and (4) a common free-radical mediated pathway may be active for both LC and small airway obstruction.

House dust mite allergen levels and an anti‐mite mattress spray (natamycin) in the treatment of childhood asthma

Natamycin, a fungicide marketed as Tymasil, is claimed to reduce house dust mite numbers and would therefore be expected to improve asthma in children with mite sensitivity. We have tested this assertion by a double-blind, placebo-controlled trial. There was no significant effect on levels of Der p I in mattress dust between active and placebo groups at the end of the spraying period. Histamine inhalation challenge PC20, clinic visit symptom scores and lung function tests reflecting either large or small airways obstruction were also unchanged. Therefore this product is not a therapeutic option for mite-allergic patients using the manufacturer's recommended dose and method of administration. Other factors influencing the Der p I levels were also investigated. Of these, only month of measurement and bedroom wall humidity showed any association.

FEV1 decline in asymptomatic young adults: relationships with some tests of small airways function

The aim of this study is to determine whether some tests proposed as diagnostic of small airways obstruction (SAO) are useful in identifying the subjects at risk of developing chronic airflow limitation. Eighty five healthy male workers (46 nonsmokers and 39 smokers, aged 21-41 yrs), living in the same area and not exposed to occupational pollutants were re-examined after an interval of 6 yrs. At the first survey 39 had functional evidence of SAO as determined by the presence of one of: maximal mid-expiratory flow (MMEF) less than 65% of predicted value (pred); maximal expiratory flow when 25% forced vital capacity remains to be expired (Vmax25) less than 60% pred; closing capacity (CC) greater than 130% pred; 46 had all functional values in the normal range. We considered four subgroups: smokers and nonsmokers with and without SAO. The rate of decline in FEV1, the decline in %delta FEV1 and delta FEV1.height-3, have been evaluated and compared in the subgroups. Initial values of specific tests (MMEF, Vmax25, CC and slope of phase III) have been examined for a possible relationship with decline of FEV1. Statistical analysis of our data showed that only CC was related to FEV1 decline. However, there were no significant differences in FEV1 decline among the subgroups. We conclude that in young adult subjects functional characteristics of SAO have no predictive value for development of chronic airways obstruction.