Functional Classification of Chronic Airflow Limitation Based on Flow-Volume and Single-Breath Nitrogen Washout Criteria

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 · ΔN2%) 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