The 6-Minute Walk Test as a Tool for Determining Exercise Capacity and Prognosis in Patients with Silicosis

Abstract

Objective: To evaluate exercise capacity using the 6-minute walk test (6MWT) in patients with complicated silicosis, and to determine how results shape the prognostic value of 6MWT for hospitalization and mortality.

Method: Prospective observational study in 143 patients with complicated silicosis who performed the 6MWT in our outpatient pulmonology clinic between 2009 and the end of 2016. Lung function tests, computed tomography findings and 6MWT parameters (distance walked and oxygen desaturation) were evaluated.

Results: Patients with complicated silicosis walked 387±92m. Results deteriorated as silicosis severity increased; category A: 407±97m, B: 370±88m, and C: 357±68m (P=.022). The 6MWT correlated positively with lung function and inversely with dyspnea determined by mMRC (P<.001). Patients with moderate/severe emphysema and greater CT90 presented a worse result on 6MWT. Patients who walked<350m had more hospitalizations (3.7±4.0) than those who walked>350m (1.1±2.9). There was an impact on survival: non-survivors walked 327.9±73.0m, while survivors walked 404.5±89.7m (P<.001).

Conclusions: Spirometry values and category of complicated silicosis correlated with 6MWT and distance walked was a prognostic factor for hospitalization and mortality. The 6MWT is a useful tool in occupational health for monitoring patients with silicosis.

Keywords: Lung function tests; Prueba de la marcha de 6 minutos; Pruebas de función respiratoria; Silicosis; Six-minute walk test.