Accuracy of Balloons and Handheld Spirometers as Low-Cost Tools for Measuring Vital Capacity and Air Volume: A Laboratory-Based Validation Study

Introduction: Vital capacity and air volume are key physiological substrates important for voice, speech, cough, and swallowing. The current gold standard equipment to assess vital capacity and air volume is a pneumotachograph. The aim of this study was to characterize the validity of four low-cost, clinically accessible tools as potential alternative methods to accurately assess vital capacity and air volume. Methods: This laboratory-based study examined the accuracy of four low-cost tools to assess vital capacity and air volume: two balloon-based circumference methods ( c), Bland-Altman plots, and linear regression models. Concordance was interpreted as “moderate” if ρc = 0.90 to