The utility of spirometry and single breath gas transfer measurements to identify low total lung capacity

Measurement of total lung capacity (TLC) requires large and expensive equipment. We aimed to investigate whether spirometric restriction and low alveolar volume measured by single breath gas transfer (V _A) can be used to identify those with a low TLC.

We retrospectively analysed data from adults referred to Cambridge University Hospitals between January 2016 and December 2023. We investigated the utility of spirometric restriction (forced vital capacity (FVC) < lower limit of normal (LLN) with forced expiratory volume in 1 s /FVC ≥LLN) and reduced V _A (pleth V _A to identify TLC_pleth

Data from 7923 patients were included. The majority (94%) of patients were of European ancestry, 51% were female. Mean age was 58 years. 11% of patients had a TLC_pleth V _A pleth pleth V _A pleth V _A pleth

A FVC in the healthy range is an effective tool for ruling out restriction. Low V _A can be used to accurately identify those with a low TLC, negating the need for formal measurement of static lung volumes when identifying restrictive lung disease.