Lost in interpretation: should the highest VC value be used to calculate the FEV1/VC ratio?

Spyridon Fortis Department of Medicine, Division of Pulmonary, Critical Care and Occupational Medicine, University of Iowa, Iowa City, IA, USA Airflow obstruction or obstructive ventilatory defect (OVD) is defined as low forced expiratory volume in 1 second (FEV1) to vital capacity (VC) ratio. VC can be measured in various ways, and the definition of “low FEV1/VC” ratio varies. VC can be measured during forced expiration before bronchodilators (forced vital capacity [FVC]) and after bronchodilators (post-FVC), and during slow expiration (slow vital capacity [SVC]) and during inspiration (inspiratory vital capacity [IVC]). Theoretically, in a healthy person, VC values should be the same regardless of the maneuver used. Nevertheless, SVC is usually larger than FVC except in patients with no OVD and body mass index LLN, only 64% have restriction in lung volumes. The rest 36% have a nonspecific Pulmonary Function Test pattern.4 Approximately, 15% of patients with this nonspecific PFT pattern develop OVD in follow-up PFTs.4 It is possible that a portion of patients with obstructive lung disease remain underdiagnosed when FVC is used to compute FEV1/FVC ratio. View the original paper by Torén and colleagues.