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A morphometric study was carried out on biopsy specimens taken from 40 smokers (27 with chronic bronchitis and 13 asymptomatic) submitted to bronchoscopy to identify and quantify the possible structural differences between the two groups. The chronic bronchitic group had a mean age of 65.67 years and 57.04 pack-years of smoking, the asymptomatic group had a mean age of 44.69 years and 22.62 pack-years of smoking. 70 biopsy specimens (45 from chronic bronchitics and 25 from asymptomatic smokers), in which large areas of best-preserved and perpendicularly cut epithelium were present, were considered suitable for the study and examined by light and transmission electron microscopy. The mean thickness of surface epithelium (p < 0.001), the number of layers of basal cells (p < 0.001), the intercellular space of the superficial zone of the epithelium (p < 0.05) and the percentage of abnormal bronchial cilia (p < 0.05) were significantly greater in patients with chronic bronchitis than in asymptomatic smokers. No significant difference between the two groups was observed in the thickness of the lamina reticularis of the basement membrane. Goblet cell hyperplasia was more marked in chronic bronchitics than in the asymptomatic smokers (p < 0.001), whereas the frequency of epidermoid metaplasia did not show a significant difference. The morphological study of the bronchial epithelium has allowed the identification of transitional cells, which gives rise to the concept that epidermoid metaplasia may result from conversion of mucous cells. This finding suggests that the different histologic types appearing in lung tumours may originate from one undifferentiated pluripotential stem cell, which is able to differentiate into different histogenetic types.

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There is now sufficient evidence that non-invasive positive pressure ventilation (NIPPV) in selected patients with severe hypercapnic acute respiratory failure due to chronic obstructive pulmonary disease (COPD) is more effective than pharmacological therapy alone. The aim of this study was to identify prognostic factors to predict the success of this technique. Fifty-nine consecutive patients with COPD admitted to a respiratory ward for 75 episodes of acute respiratory failure treated with NIPPV were analysed: success (77%) or failure (23%) were evaluated by survival and the need for endotracheal intubation. There were no significant differences in age, sex, cause of relapse and lung function tests between the two groups. Patients in whom NIPPV was unsuccessful were significantly underweight, had an higher Acute Physiology and Chronic Health Evaluation (APACHE) II score, and a lower serum level of albumin in comparison with those in whom NIPPV was successful. They demonstrated significantly greater abnormalities in pH and PaCO2 at baseline and after 2h of NIPPV. The logistic regression analysis demonstrated that, when all the variables were tested together, a high APACHE II score and a low albumin level continued to have a significant predictive effect. This analysis could predict the outcome in 82% of patients. In conclusion, our study suggests that low albumin serum levels and a high APACHE II score may be important indices in predicting the success of NIPPV.

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