Correlation of the Distance Saturation Product with spirometric and Diffusion Capacity for Carbon Monoxide data in patients with Interstitial Lung disease

Abstract

<b>Background:</b> The Distance-Saturation Product (DSP) is one of the composite indexes used to predict prognosis in patients with Interstitial Lung Disease (ILD). <b>Aim of study:</b> We aimed to evaluate the correlation of DSP index with spirometry and Diffusion Capacity for Carbon Monoxide (DLCO) in patients with ILD. <b>Methods:</b> This study included 80 patients (35 males, 45 females) diagnosed with ILD and referred to Pulmonary Function Tests Department during 2 years (2018- 2020). Spirometry and Six-Minute Walk Test (6MWT) were performed for all study population. We recorded data of Forced Vital Capacity (FVC), Forced Expiratory Volume in the first second (FEV1) and Diffusing Capacity for Carbon Monoxide (DLCO), Distance Walked (6MWD) in meters and lowest oxygen Saturation value (SpO2). The DSP was calculated by multiplying 6MWD by lowest SpO2 obtained during the 6MWT. <b>Results:</b> The mean age of patients was 54 ± 10 years old. The mean values of FEV1, FVC and DLCO were respectively 78.22 ± 16.34%; 78.57± 15.15% and 60 ± 19.53%. The mean DSP was 419.16 ± 93.43. Statistical analysis revealed that DSP data were significantly correlated with % of FEV1 (r=0.23; p=0.037), FVC (r=0.3; p=0.006) and DLCO (r=0.65; p&lt;0.001). <b>Conclusion:</b> Given that DSP can reliably reflect the mechanical and diffusional abnormalities observed in ILD, pulmonologists should give more importance to 6MWT which, in addition to its simplicity, helps them to better predict the prognosis of this lung disease.