Machine Learning-Based Prediction of Pulmonary Function Test Outcomes Using Oscillometry in Patients with COPD

Oscillometry has been recognized as a non-invasive method for assessing respiratory conditions and is increasingly being implemented in routine clinical practice. Currently, a full pulmonary function test (PFT), which requires extensive infrastructure and trained personnel, remains the standard for comprehensive lung function assessment. Furthermore, while a full PFT can be performed by most patients with mild chronic obstructive pulmonary disease (COPD), this can be exceedingly difficult and cumbersome to complete in patients with more advanced disease. The present study sought to investigate the relationship between lung function parameters obtained by oscillometry, a non-invasive technique requiring only quiet breathing, with the parameters obtained from the more technically demanding components of a standard PFT, plethysmography and diffusing capacity, in patients with mild and very severe COPD. Through Spearman analyses, the strongest associations were observed between resistance at 5 Hz (R₅) and the difference in resistance between 5 Hz and 19 Hz (R₅-R₁₉), by oscillometry, with residual volume (RV) to total lung capacity (TLC) ratio (RV/TLC-gas trapping) and diffusing capacity of the lung for carbon monoxide (DLco-diffusing capacity), by PFT (0.69 and -0.74, respectively). To extend the clinical applicability of oscillometry, three machine learning models suitable for small datasets, Extreme Gradient Boosting (XGBoost), Random Forest (RF), and Support Vector Regression (SVR), were implemented to predict these key PFT outcomes from oscillometry metrics and baseline demographic data alone. XGBoost achieved the best performance, with mean absolute errors of 9.7 for RV/TLC and 8.1 for DLco. In contrast, none of the models could accurately predict TLC. Feature importance analysis revealed that age enhanced RV/TLC prediction, while DLco prediction was consistently influenced by the addition of body mass index (BMI). In conclusion, oscillometry has the potential to serve as complementary to PFT for assessing otherwise tedious, resource-intensive, and often unattainable information on gas trapping and gas exchange, especially for older or frail adults with advanced disease, while still offering high accuracy.