Prediction of Lung Vital Capacity Value from Thoracoabdominal Expansion in Young Adults

Background: Vital capacity (VC) is a fundamental indicator of pulmonary health, but its routine assessment often depends on spirometry devices that may be unavailable (i.e. because of access, cost) in many clinical or community settings. In contrast, lower costal (LC) and upper abdominal (AB) expansions are simple, equipment-free methods commonly used in physiotherapy. Method: This cross-sectional study was aimed at developing prediction equations for VC using LC or upper AB expansion alongside demographic and anthropometric variables. The study involved 116 healthy nonsmokers (53 male and 63 female individuals) aged 18–39 years. VC was measured via spirometry using a forced vital capacity manoeuvre, while LC and upper AB expansions were measured using a nonstretchable tape. Results: VC was moderately correlated with LC (r = 0.570) and upper AB (r = 0.581), highly correlated with height (r = 0.871), and moderately correlated with body weight (r = 0.690). Lower correlations were found with waist circumference (r = 0.446) and age (r = –0.268). The resulting equations were VC = -4.713 + 0.047 × height - 0.666 × gender + 0.146 × LC and VC = -5.060 + 0.051 × height - 0.606 × gender + 0.094 × upper AB, with gender = 0 for male and 1 for female. Conclusion: These equations offer accessible alternatives for estimating VC and may be useful in settings where spirometry is not feasible. Keywords: Vital capacity; Predict vital capacity; Thoracoabdominal expansion; Lower costal expansion; Upper abdominal expansion