The overall prevalence of COPD in Saudi Arabia is 4.2%. Male, increasing age and smoking were the main risk factors for COPD.

BACKGROUNDAsthma and chronic obstructive pulmonary disease (COPD) are chronic conditions with an increasing prevalence in developing countries. The evaluation of endobronchial biopsies has emerged as a tool to differentiate between both conditions via the measurement of the reticular basement membrane (RBM) thickness with various conclusions drawn from different studies.OBJECTIVESCompare the thickness of the RBM between asthma and COPD and evaluate other histomorphological features in both groups.DESIGNProspective, descriptive and analytical.SETTINGUniversity teaching hospital.PATIENTS AND METHODSThe study included patients with COPD and irreversible and reversible asthma with diagnosis based on clinical assessment, pulmonary function tests and high-resolution computed tomography scans. Endobronchial biopsies were obtained from all patients and, using a light microscope and a computerized image analyzer, the thickness of the reticular basement membrane was calculated in all patients. We also made a qualitative assessment of other histomorphological features.MAIN OUTCOME MEASURESMean RBM thickness.SAMPLE SIZEThirty male patients.RESULTSThe mean RBM thickness in asthmatic patients was 8.9 (2.4) μm. The mean RBM thickness in COPD patients was 5.3 (1.1) μm. However, there was no thickening of the RBM in patients with reversible asthma. The RBM was significantly thicker in patients with irreversible asthma than in patients with COPD or reversible asthma. There were no significant differences in epithelial desquamation or metaplasia, mucosal or submucosal inflammation, the presence of eosinophils, submucosal glandular hyperplasia or submucosal smooth muscle hyperplasia between groups.CONCLUSIONSThe thickness of the RBM is the only reproducible histopathological feature to differentiate COPD from irreversible asthma.LIMITATIONSThe study included a limited number of patients. A qualitative approach was used to compare epithelial cell injury, inflammation, submucosal glandular and muscular hyperplasia.

Endoscopic palliation of tracheobronchial malignancies I read with interest the review by Drs M R Hetzel and S G T Smith (May 1991;46:325-33). I think that cryotherapy is almost unknown in England, and used in only one centre.' There are some errors regarding cryotherapy. The bronchial probes now use nitrous oxide and not liquid nitrogen. The temperature obtained on the tip of the probe reaches-700 (or-80'C) but the tumour or tissues are frozen at-40'C. No cases of perforation have been reported with this technique. Flexible probes were not described by Sanderson;' he used rigid cryosurgical probes (I was the first to use flexible probes in 1985). The authors say that no comparative studies of laser treatment and cryotherapy have been published but there is one study in a French journal,' and others."°T his technique is well known in France and used more widely than laser therapy. There are at the moment 75 cryotherapists and 1500-2000 patients have been treated.