Inspiratory and expiratory CT analyses of the diaphragmatic crus in chronic obstructive pulmonary disease

This study aimed to investigate the association between the results of pulmonary function tests (PFTs) in patients with chronic obstructive pulmonary disease (COPD) and the size of their diaphragmatic crus (DC) using inspiratory and expiratory CT.

Thirty-three patients who underwent inspiratory and expiratory CT and PFTs between July and December 2019 were studied retrospectively. The short axis, long axis, and cross-sectional area (CSA) of the bilateral DC were measured, and the percentage change of the DC after expiration (% change of DC) in the size was calculated. The correlation between the results of the PFTs (forced expiratory volume in 1 s [FEV₁], FEV₁/forced vital capacity [FVC], and percent predicted FEV₁ [%FEV₁]) and the size and % change of DC was statistically analyzed.

Significant correlations were observed between the short axis of the right and left DC at expiration and PFTs (FEV₁, r = -0.35, -0.48, p = 0.04, .007; FEV₁/FVC, r = -0.52, -0.65, p = 0.002, < .001; %FEV₁, r = -0.56, -0.60, p < 0.001, < 0.001; respectively), between the CSA of the right DC at expiration and PFTs (FEV₁/FVC, r = -0.42, p = 0.01; %FEV₁, r = -0.41, p = 0.017; respectively), and between the % change of the short axis of the left DC and the CSA of the left DC and PFTs (FEV₁, r = 0.64, 0.56, p < 0.001, .001; %FEV₁, r = 0.52, 0.51, p = 0.004, 0.004; respectively). The smaller the short axis of the DC and CSA at expiration and the larger the % change in DC of the CSA, the lower the airflow limitation.

There were significant correlations between airflow limitation and the short axis of the bilateral DC at expiration, and the % change in the DC of the CSA. Certain CT measurements of the DC may reflect airflow limitation in patients with COPD.