Correlation of Six Minute Walk Test and Lung Function Test Variables (% FEV1, % FVC, % DLCO) in Patients with Connective Tissue Disorder – Interstitial Lung Disease

Abstract

BACKGROUND Interstitial Lung Diseases (ILDs) also known as diffuse parenchymal lung disease, include a group of diffuse parenchymal infiltrative lung diseases. A restrictive defect is the most frequent pulmonary abnormality in patients with pulmonary fibrosis which is the usual consequence of many ILDs. Connective tissue disorders are usually rare, but are potentially life threatening conditions. The spectrum of ILD varies from mucocutaneous symptoms, arthralgia / arthritis to impairment of pulmonary and renal function. Systemic Lupus Erythematosus (SLE), Systemic Sclerosis (SSc), Sjogren's Syndrome (SS), inflammatory muscle diseases and overlap-syndromes are grouped together as connective-tissue disorders. Involvement of lung and its function is the most common form of interstitial lung disease, leading to high morbidity and mortality among the group of connective tissue disorders. We wanted to correlate the 6-Min Walk Distance (6MWTD) with the Pulmonary Function Test values such as \% FEV1, \% FVC and FEV1 / FVC, among patients with connective tissue disorder associated Interstitial Lung Disease in SRM Medical College Hospital, a tertiary care hospital in Tamilnadu, South India. METHODS This study was done as a cross sectional analytical study among 31 patients in the Department of Respiratory Medicine, Rheumatology and General Medicine in SRM medical college and hospital. Each patient was explained the purpose of the study and the need for complete co-operation. Those who satisfied the inclusion and exclusion criteria were included. Data was collected using a structured proforma. 6-minute walk test and pulmonary function tests were performed and correlated. RESULTS There appears to be a significant correlation between 6-minute walk test, \% desaturation, 6 Minute Walk Test Distance, 6 Minute Walk Test Pre BDI and 6 Minute Walk Test Post BDI with spirometry values especially with the Spirometry FEV 1 \%, Spirometry FVC \% and \% predicted DLCO. CONCLUSIONS 6MWT can be used as a useful surrogate for pulmonary function tests especially among the population where spirometry is not possible. 6MWT has good reproducibility, is simple to perform and can be used as a screening tool for Interstitial Lung Disease in connective tissue disorder patients.