[Estimating forced expiratory volume in one second based on breath holding in healthy subjects]

Cross sectional study to evaluate a linear correlation model to calculate forced expiratory volume in one second (FEV1) on the basis of breath-holding time (BHT) in healthy subjects aged 16 years or older. BHT was defined as the maximum time in seconds that a person can voluntarily hold his or her breath measured between the end of a deep breath until he or she begins to exhale in the third of three consecutive maneuvers. To calculate FEV1 on the basis of BHT (FEV1-BHT) the general straight-line equation (y = a + bx) was applied, with x being Logn of BHT and y being FEV1. The a and b values had been previously estimated by gender using multiple linear regression in which FEV1 measured spirometrically was the dependent variable and the age and Logn of BHT were the independent variables. One hundred ninety-seven subjects [97 women (49.2%) and 100 men (50.8%)] were enrolled. Mean FEV1 measured by spirometry (FEV1-Sp) and FEV1-BHT were similar. The correlation (R2) between FEV1 and BHT for women and men was 0.585 (95% CI 0.213-0.753) and 0.702 (95% CI 0.630-1.496), respectively. The ratio FEV1-BHT:FEV1-Sp was higher than 80% for 96 women (98.96%) and 98 men (98.0%). FEV1 can be reliably estimated using BHT.