An assessment of forced expiratory volumes and flow rates in the detection of early ventilatory impairment in RN submariners

Abstract

AbstractA prospective study of an early diagnostic test of small airway dysfunction, the forced expiratory flow between 75 and 85% of the forced vital capacity, was carried out in 230 RN submariners. All the subjects were male caucasians, of whom 105 were smokers and 125 non-smokers. Measurements were performed using a single breath wedge spirometer (Vitalograph®) and forced vital capacity (FVC), forced expiratory volume in one second (FEV1), ratio of the FEV1 to the FVC (FEV1/FVC%) and the forced expiratory flow between 75 and 85% of the forced vital capacity (FEF75–85) obtained from the tracings in accordance with the recommendations of the American Thoracic Society. Multiple linear regression analysis of these four measurements together with height, age and smoking habit showed age to be the most significant factor for FEF75–85, followed by height Height was the most significant factor for FVC and FEV1 followed by age. Age was the only significant factor for FEV1/FVC%. FEF75-85 was highly correlated with FEV1/FVC% (r = 0.72) and to a lesser extent with FEV1 and FVC (r = 0.70 and 0.37 respectively). In the presence of age and height no significant effect of smoking habit on FEF75–85 could be demonstrated. However when the FEV1/FYC%, age and smoking habit were examined, there was found to be a significantly greater decrease in FEV1/FYC% with age in the smokers. It would appear that in this study FEV1/FVC% is a more sensitive index of early obstructive changes induced by smoking than measurement of flow at low lung volumes.