Association between Nocturnal Hypoxemia and COPD Severity: A Cross-sectional Study

Abstract

Introduction: Globally, Chronic Obstructive Pulmonary Disease (COPD) is the third most common cause of mortality. More than 80% of these fatalities happened in low- and middleincome nations. Transient desaturation during sleep occurs in healthy persons during Rapid Eye Movement (REM) sleep. This phenomenon is aggravated in COPD patients. As Nocturnal Desaturation (NOD) in COPD has been suggested to increase mortality, its early identification will aid in early initiation of treatment and prevention of associated complications. Aim: To estimate the prevalence of nocturnal hypoxemia in COPD and determine its association with COPD severity. Materials and Methods: A cross-sectional study was carried out at the Department of General Medicine, Apollo Hospitals, Guwahati, Assam, India during January to December 2021 involving 100 patients who had COPD symptoms. Continuous oxygen saturation monitoring with transcutaneous finger probe was done for the entire duration of sleep at night. Patients whose oxygen saturation falls below 90% for at least 30% of recording time in sleep were classified as desaturators. Statistical Package for Social Sciences (SPSS) Version 26.0 was used for data analysis. Using the Chi-square test, the relationship between the qualitative variables was evaluated. The Mann-Whitney test or the unpaired t-test was used to analyse the quantitative data between the two groups. A p-value of less than 0.05 was considered significant. Results: Prevalence of NOD among cases of COPD was observed as 26% in present study. A significant association was observed between presence of NOD in COPD cases with severity of COPD and with desaturation in 6-Minute Walk Test (6-MWT) (p<0.01). Severe cases had a prevalence of NOD as 65% as compared to 28.2% and 4.9% in moderate and mild cases respectively (p<0.01). A total of 61.9% cases with desaturation during 6-MWT showed NOD as compared to 38.1% without desaturation (p<0.01). Conclusion: One fourth of the normoxemic COPD patients had significant NOD. NOD episodes were observed to be positively associated with increasing severity of COPD. Assessing variations in oxygen saturation during a 6-MWT can be helpful in identifying COPD patients who may be at risk for severe night time desaturation.