Dan Stănescu

A normal FEV1/VC ratio does not exclude airway obstruction

Background: A decreased forced expiratory volume in 1 s/vital capacity (FEV1/VC) ratio is the hallmark of the definition of airway obstruction. We recently suggested that a lung function pattern, we called small airways syndrome (SAOS), has a normal FEV1/VC and total lung capacity (TLC) and reflects obstruction of small airways. Objectives: To substantiate our hypothesis we measured and compared lung function tests including maximal expiratory flow rates (MEFR), sensitive indicators of airway obstruction, in SAOS subjects and in matched controls. Methods: We selected 12 subjects with the pattern of SAOS, but without chronic lung or heart disease (average age: 40.7 ± 7.8 years) and 36 age-matched subjects with normal lung function (42.8 ± 6.3 years). We measured static and dynamic lung volumes, MEFR and lung diffusing capacity (DLCO). Results: SAOS subjects were heavier smokers (p < 0.05) and body mass index was less than in control subjects (p < 0.01). Both FEV1/VC ratio and TLC were comparable in the two groups. However, FEV1, VC, DLCO, and MEFR were lower and residual volume (RV) and RV/TLC ratio were higher (p < 0.05) in the SAOS group than in the control one. Furthermore, the MEFR curve of the SAOS group was displaced to the left without any change in slope, suggesting premature airway closure. Conclusion: Our results suggest that a normal FEV1/VC ratio does not exclude airway obstruction. A decrease of FEV1, provided TLC is normal, reflects small airway obstruction.

Pulmonary resistance and maximal expiratory flow-rates following isoprenaline in patients with chronic obstructive lung disease

Stănescu, D. C., Clément, J., and van de Woestijne, K. P. (1973).Thorax, 28, 716-720. Pulmonary resistance and maximal expiratory flowrates following isoprenaline in patients with chronic obstructive lung disease. Pulmonary resistance, maximal expiratory flowrates (measured from flow-volume curves), and lung volumes were measured in 17 patients with chronic obstructive lung disease before and 20 minutes after isoprenaline aerosols. Forced vital capacity, maximum expiratory flowrates, and pulmonary resistance all changed significantly following isoprenaline. Using a discriminant analysis, we showed that the bronchodilator effect was reflected almost completely by only two indices, pulmonary resistance and maximum expiratory flowrate at 25% of the control vital capacity. The information provided by each was independent. When the change following bronchodilatation is expressed as a percentage, pulmonary resistance carried most of the information and for practical purposes this index may be used alone.

In long-term smokers and former smokers the bronchodilator response is not related to the fall in FEV1

Background: Cigarette smoking is the cardinal cause of chronic obstructive pulmonary disease (COPD), but only a relatively small percentage of smokers are developing clinically overt disease, suggesting, therefore, that other risk factors than smoking are involved. Several studies have shown that the bronchodilator response (BR) is related to the progress of COPD, as assessed by the fall in forced expiratory volume in 1 s (FEV1). However, the relationship between BR and fall in FEV1, is a disputed one. Objective: To assess the relationship between BR and fall in FEV1 in a group of long-term smokers and ex-smokers who were 60 years old on the average. Methods: Questionnaire, spirographic tests and BR were assessed in 56 smokers and ex-smokers of mean age 62.5 ± (SD) 2.7 years at the end of a 13-year follow-up period. BR was expressed as a percentage change of the prebronchodilator value (‘% initial’) and as a percentage change of predicted value (‘% predicted’). Results: The FEV1/VC vital capacity was 68.9 ± 7.6% at the start and 64.5 ± 11.3% at the end of the study. The average fall in FEV1 over 13 years was 26 ± 25 ml/year. The FEV1 increased after albuterol on the average with 5.9 ± 6.6%, 4.5 ± 3.9% of predicted, and the vital capacity with 2.5 ± 6.5%, 2.3 ± 6.4% of predicted. BR and fall in FEV1 were correlated: the greater the BR, the more rapid the fall in FEV1 (r = 0.4 and p < 0.01 for FEV1% and r = 0.3 and p < 0.05 for FEV1 predicted). However, when adjusting for prebronchodilator FEV1, the BR was no more related to the fall in FEV1 (r = 0.15, p > 0.05). Conclusions: In long-term smokers and ex-smokers, the BR measured at the end of the follow-up period was correlated with the fall in FEV1. However, after adjusting for prebronchodilator FEV1 values, BR was no more related to the decline in FEV1. The BR appears not to be associated with the development of COPD.