Correlation Between Degree of Desaturation and Severity of Obstructive Sleep Apnoea: A Cross-sectional Study

Abstract

Introduction: Obstructive Sleep Apnoea (OSA) is major Non Communicable Disease (NCD) which is becoming very common worldwide. The OSA results in day time hypersomnolence, nocturnal hypoxia and snoring. Repeated desaturation events during sleep results in aerobic metabolism at tissue level changing to anaerobic metabolism, which results in cellular inflammation and insulin resistance further complicating metabolic syndrome. Aim: To study correlation between degree of desaturation and severity of obstructive sleep apnoea. Materials and Methods: This cross-sectional study was conducted in Department of Pulmonary medicine at KS Hegde Medical Academy (tertiary care hospital), Mangaluru, Karnataka, India, from March 2018 to February 2021. Total 54 patients who underwent overnight polysomnography and diagnosed to have OSA were included in the study. The minimum recorded oxygen saturation (SpO2 ) defined as maximum desaturation was noted. Relative desaturation was defined as drop in saturation by 3% or more from the pre-event baseline. Correlation between total number of relative desaturation and Apnoea Hypopnea Index (AHI) was analysed. The correlation between two variables were analysed by Pearson’s correlation and the coefficient was calculated. The p-value was calculated by regression analysis and Analysis of Variance (ANOVA). Results: Total of 54 patients was included in the study. Out of which, 22 were mild, 14 moderate and 18 severe OSA respectively. Number of relative desaturations recorded was from 0 to 636. The correlation between AHI and mean SpO2 in sleep was r-value=-0.4542 (p-value=0.001) and the correlation between AHI and minimum SpO2 was r-value=-0.45577 (p-value=0.001) respectively. Correlation between mean SpO2 and minimum SpO2 was r-value=0.747266 (p-value<0.001) and the correlation between AHI and relative desaturation was r-value=0.876698 (p-value=0.001). Conclusion: As the severity of the obstructive sleep apnoea worsened, there was greater degree of desaturation in sleep and the lowest SpO2 was also observed during severe obstructive sleep apnoea.