Forced Expiratory Time: Added Value in Diagnosing Obstructive Ventilatory Defects

<bold>Introduction:</bold> Forced expiratory time (FET) is a spirometrically derived variable reflecting the time required to completely empty the lungs. The utility of FET in various ventilatory defects, remains unclear compared with traditional spirometry parameters. We aimed in this study to investigate the utility of FET as a measure to identify Obstructive Ventilatory Defects(OVD). <bold>Methods:</bold> This cross-sectional study included patients with chronic respiratory diseases who were referred to our department from March 2023 to December 2023. All subjects underwent spirometry with measurement of Forced Expiratory Volume in one second (FEV1), Forced Vital Capacity (FVC), FEV1/FVC ratio and FET. OVD was defined by a low FEV1/FVC ratio. The Receiver Operator Curve (ROC) analysis was used to look for the cut off value of FET to identify OVD. <bold>Results:</bold> We included 255 patients, of whom 114(44.7%) were males. Mean age was 50.95 ± 16.44 years. OVD was observed in 62 (24.3%) distributed as follows: 31 with asthma, 26 with COPD, 3 with sarcoidosis and 2 with bronchial dilatation. When comparing lung function of patients with OVD with the rest of the study population, we found that they had lower FEV1% (OVD: 58.88± 20.8 vs rest: 86.11± 18.65 ; p<0.0001) and FEV1/FVC ratio (OVD: 56.45± 11.59 vs rest: 79.73± 6.3 ; p<0.0001) and higher FET (OVD: 7.96 ± 1.97s vs rest: 5.48± 1.45s ; p<0.0001). ROC analysis showed that the area under curve was 0.85 (p<0.001). The cut-off level for FET to identify OVD was 6.74s with sensitivity of 71% and specificity of 82%. <bold>Conclusion:</bold> Our findings highlight the significance of incorporating FET into pulmonary function testing protocols to improve the sensitivity and specificity of diagnosing OVD.