Background: People with chronic obstructive pulmonary disease (COPD) often experience exacerbations and impaired gas exchange, leading to hypoxemia that may require hospitalization. Pattern analysis of capillary oxygen saturation (SpO2) variability can provide valuable insight into the adaptive capacity of the respiratory control system under this condition. Therefore, this study tested the hypothesis that the adaptability of the respiratory control system is reduced in patients with COPD.
Methods: In this study we utilized entropy and fractal-like correlation properties of SpO2 time series in patients with COPD. We analyzed pulse oximetry data from 13 patients with COPD during hospitalization and discharge time and compared them to 16 age- and sex-matched control subjects. SpO2 variability analysis of 25 mins time series was performed using sample entropy, multiscale entropy, and detrended fluctuation analysis.
Results: Entropy analysis revealed a complex pattern of SpO2 variability in healthy controls and patients with COPD. Both short-term (α1) and long-term fractal-like exponent (α2) were higher in patients with COPD compared to healthy controls. SpO2 entropy and mean were significantly lower in patients with COPD in comparison with controls. There was no statistically significant difference in SpO2 complexity measures between the hospitalization and discharge phases in these patients.
Conclusion: The respiratory control system in patients with COPDs exhibit less complexity and information processing. These non-invasive analytical methods have potential for future clinical application to monitor the integrity of respiratory control in individuals suffering from chronic respiratory diseases.