Compatibility analysis of total lung capacity values measured by segmentation with computed tomography and helium dilution method.

Abstract

Background: Accurate assessment of lung volumes is essential for diagnosing ventilatory defects and managing pulmonary diseases such as interstitial lung diseases (ILDs) and chronic obstructive pulmonary disease (COPD). Although body plethysmography is the standard method, it can be limited by patient tolerance and complexity. Helium dilution method (HDM) is a portable and cost-effective alternative, while chest computed tomography (CT) offers noninvasive volume assessment through imaging. This study aimed to evaluate the agreement and potential interchangeability between TLC values measured by CT (TLC_CT) segmentation and the TLC_HDM in patients with ILD and COPD.

Materials and methods: In this retrospective study, patients who underwent HDM and chest CT were evaluated. Based on pulmonary function tests (PFTs), patients were grouped as having restrictive or obstructive ventilatory defects. TLC_CT and HDM were compared using Bland-Altman analysis to assess agreement and bias.

Results: The study included 213 patients. In the overall cohort, TLC_CT was slightly lower than TLC_HDM (mean difference = -0.32 L, 95% confidence interval [CI] -0.50 to -0.14 L, P = 0.0007). In subgroup analyses, the mean bias was -0.67 L (95% CI -0.84 to -0.51 L, P < 0.001) for ILD and +0.78 L (95% CI 0.35-1.21 L, P = 0.0007) for COPD, indicating underestimation and overestimation by CT, respectively. The overall 95% limits of agreement ranged from -3.0 to +2.25 L.

Conclusion: Both HDM and CT provide valuable lung volume data. CT may serve as a reliable alternative in patients unable to undergo PFTs. Prospective studies are warranted to confirm clinical utility.