Regional lung function assessment using electrical impedance tomography in COPD, PRISm, and normal spirometry subjects: insights into early diagnostic potential

Abstract

Purpose

This study utilizes electrical impedance tomography (EIT) to explore spatial–temporal heterogeneity in regional lung function among patients with chronic obstructive lung disease (COPD), preserved ratio impaired spirometry (PRISm), and those with normal lung function.

Methods

Subjects who had pulmonary function test at Sir Run Run Shaw Hospital from 28 December 2023 to 30 March 2024 were screened. Regional lung functions were accessed with EIT regarding spatial distribution, abnormal area size, and expiratory time. The correlations between smoking index, SGRQ score, and EIT-related parameters were also evaluated.

Results

A total of 194 patients were screened and 161 patients were included (56 COPD, 21 PRISm, and 84 normal). Spatial distribution of regional FEV1EIT (P < 0.001), FVCEIT (P = 0.025), FEV1/FVCEIT (P < 0.001), MMEFEIT (P = 0.012), T-75EIT (P < 0.001), and FIVCEIT (P = 0.020) showed significant differences among the three groups. The percentage of abnormal FEV1/FVCEIT areas detected via EIT was 83.40% (25–75% percentiles 52.29%-98.39%) in the COPD group, 25.46% (17.31%-41.31%) in the PRISm group, and 10.37% (3.34%-19.04%) in the normal group. The time constant map revealed that the patients with COPD exhibited the longest exhalation times. Elevated smoking index and SGRQ scores were associated with increased heterogeneity and larger areas of abnormal FEV1/FVCEIT.

Conclusion

Through EIT-based pulmonary function assessment, it is possible to sensitively identify the spatio-temporal heterogeneity in COPD and PRISm patients. Regional lung function impairments, particularly in PRISm patients with an FEV1/FVC ratio ≥ 0.7, were detected using EIT, highlighting its potential for early COPD diagnosis.