Lung function in asymptomatic cigarette smokers--the single breath nitrogen test.

The modified single breath nitrogen (SBN) test and simple spirometry were used to study the lung function (LF) of 101 asymptomatic, cigarette smoking and 20 non-smoking men aged 18 to 39 years. Abnormal LF was demonstrated in 39% of smokers. An abnormal SBN test was found in 28% of the light and 56% of the heavy smokers but only 3% were spirometrically abnormal. Only one non-smoker had an abnormal SBN test. Closing volume and slope of the alveolar plateau, which are both measured from the SBN test, correlated poorly suggesting that the abnormality caused by smoking may differ among smokers. The SBN test is a simple test which is sensitive enough to detect LF abnormalities in young smokers. The significance of the detected abnormalities in relation to the development of chronic obstructive lung disease is not presently known.