# Electrical impedance tomography reveals regional lung dysfunction in adults with preserved ratio impaired spirometry: an observational cross-sectional study

## TL;DR

This study shows that electrical impedance tomography can detect lung dysfunction in people with a condition called PRISm, which is not captured by standard spirometry.

## Contribution

The study demonstrates that EIT can reveal regional lung dysfunction in PRISm patients, offering a new diagnostic tool beyond traditional spirometry.

## Key findings

- EIT detected significant regional lung function differences in PRISm subjects compared to healthy volunteers.
- EIT parameters like rOR and τmed were significantly worse in PRISm subjects.
- EIT-based parameters correlated with spirometry FEV1/FVC in PRISm subjects.

## Abstract

Preserved ratio impaired spirometry (PRISm) is a condition characterized by abnormal spirometry results despite a normal forced expiratory volume in the first second (FEV1)/forced vital capacity (FVC) ratio. We hypothesized that electrical impedance tomography (EIT) would detect regional decreases in lung function in subjects with PRISm. The study aimed to explore the regional lung function differences between subjects with preserved ratio impaired spirometry (PRISm) and healthy volunteers.

In this observational study, subjects with respiratory symptoms visiting Xijing Hospital in May 2024 were rescreened for eligibility. Subjects meeting the PRISm criteria were included in the study. Electrical impedance tomography (EIT) and spirometry were conducted simultaneously. The same number of healthy subjects were studied, matching the gender, height, and weight in frequency. The regional lung function parameters were compared. A P-value of < 0.05 was considered statistically significant.

A total of 16 subjects with PRISm, and 16 healthy volunteers were included in the study and evaluated. Functional EIT images provided information about the location of the dysfunctional lung regions. All evaluated EIT-based parameters were worse in the subjects with PRISm. Statistically significant differences were found in the regional obstructive ratio (rOR) and the median of the regional time constant τmed (p < 0.05). EIT-based parameters did not correlate with spirometry-based parameters, except for spirometry FEV1/FVC, which showed correlations with rOR (r = −0.53, p = 0.03) and τmed (r = −0.62, p = 0.01) in subjects with PRISm. Both τmed and rOR values were quite low in healthy volunteers, whereas substantial changes were observed in subjects with PRISm.

EIT-based regional lung function provides additional information to traditional spirometry, which visualizes and localizes regional lung function defects.