Relationships between the pulmonary densitometry values obtained by CT and the forced oscillation technique parameters in patients with silicosis

Abstract

Objective: To evaluate the correlations between pulmonary densitometry values and forced oscillation technique (FOT) parameters in patients with silicosis.

Methods: This cross-sectional study comprised 36 non-smoker patients with silicosis and 20 matched control subjects who were submitted to FOT and multidetector CT (MDCT).

Results: Compared with the control subjects, the MDCT evaluation demonstrated that patients with silicosis exhibited greater total lung mass. These patients also had larger non-aerated and poorly aerated compartments, which included nodules and scarring. Compared with the control subjects, FOT evaluation demonstrated that patients with silicosis exhibited changes in both reactive and resistive properties of the respiratory system. In these patients, there was a greater heterogeneity of the respiratory system and increased work of breathing. Significant correlations between non-aerated compartment size and FOT parameters that reflect the non-homogeneity of the respiratory system were observed. The dynamic compliance of the respiratory system was negatively correlated with non-aerated compartment size, while the impedance at 4 Hz was positively correlated with non-aerated compartment size.

Conclusion: Patients with silicosis have heavier lungs. In these patients, a larger non-aerated compartment is associated with a worsening of lung function. A more significant pulmonary involvement is associated with a loss of homogeneity and increased mechanical load of the respiratory system. Advances in knowledge The findings provided by both pulmonary densitometry and FOT may add valuable information to the subjective analysis of silicosis; however, more studies are necessary to evaluate the potential use of these methods for assessing disease progression.

Figure 1.

Three-dimensional (3D) images of the lungs reconstructed from the binary matrix of the region of interest in the anteroposterior view (top left). The 3D representation (posteroanterior view) of the lung parenchyma and each compartment reveals the hyperaerated compartment (red), the poorly aerated compartment (light grey), the non-aerated compartment (black) and the normally aerated compartment (blue).

Figure 2.

(a) Relationship between the total air volume (TAV) and the total lung capacity (TLC; rs = 0.806; p < 0.001). (b) Relationship between the hyperaerated compartment (hyper) and the TLC (rs = 0.749; p < 0.001).

Figure 3.

(a) Relationship between the non-aerated compartment size, measured by the percentage of total lung volume (non %TLV), and the mean reactance (Xm; rs = −0.582; p < 0.001). (b) Relationship between the non-aerated compartment size, measured by the percentage of TLV (non %TLV), and the dynamic compliance of the respiratory system (Cdyn; rs = −0.548; p < 0.001).