Incomplete Forced Expiration – Estimating Vital Capacity by a Mathematical Method

Abstract

Background: Vital capacity is a key parameter in the determination of lung function, usually assessed by means of a forced expiration maneuver. This maneuver can be exhausting, and patients often cannot complete it. Objectives: This study evaluates a method to estimate forced vital capacity (FVC) based on the extrapolation of volume-time curves from forced expiration. Methods: The algorithm was applied to 2,363 volume-time curves from patients with and without respiratory disease. 416 of these spirograms originated from incomplete maneuvers. For each spirogram, estimated (FVC_est) and measured FVC were compared with inspiratory vital capacity. Results: Reliable FVC_est were obtained for 82% of all and for 76% of the incomplete maneuvers. Regardless of the category of respiratory disease and acceptability of forced expiration, FVC_est were close to inspiratory vital capacities. Conclusions: When assessing the lung function of patients who cannot complete forced expiration, this method could help to reduce the duration of maneuvers required to provide a reliable estimate for vital capacity.

Analysis of Forced Expiratory Flow Signals Using the New Luus–Jaakola Optimization Procedure

“…To estimate FVC, Steltner et al used multiexponential models to analyze forced expired volume-time curves. Because the appropriateness of the model is only considered from a statistical point of view, there are some great differences between estimated and measured FVC [30]. Moreover, Ioachimescu et al proposed a regression equation for estimating FVC from measured values of FEV 2 and FEV 3 , and used FEV 1 /estimated FVC to detect airflow obstruction.…”