Functional classification of chronic airflow limitation based on flow-volume and single-breath nitrogen washout...

A simple means of functional classification of the individual patient has been devised. The performance of a forced flow-volume manoeuvre in concert with a single-breath nitrogen washout procedure in 54 comprehensively investigated patients with chronic airflow limitation yielded two parameters which could be employed in classification. A normalized alveolar nitrogen slope (FEV1/FVC X delta N2%) greater than 4.0% per litre clearly delineated emphysema. The peak flow ratio (PEFR/PIFR%) categorized other subgroupings: a value in excess of 100% strongly suggests primary bronchial disease, while a lower value almost certainly indicates a mixed functional disorder.