Relevance of hypoxia in sleep disordered breathing: distinct clinical, sleep, and autonomic features in obstructive sleep apnea with and without hypoxia

Introduction Some patients with obstructive sleep apnea do not exhibit hypoxemia. However, there is a lack of studies characterizing this subgroup of patients. We aimed to analyze the clinical, sleep, and autonomic features of a group of patients with obstructive sleep apnea without hypoxia (OSAwh). Materials and methods Twenty-eight patients with OSAwh, 32 patients with OSA with hypoxia, and 22 control subjects were studied. Patient groups were matched in matched in age and gender. Clinical and sleep features were analyzed. Besides, time- and frequency-domain heart rate variability (HRV) measures (mean R–R interval, SDNN, LF oscillations, HF oscillations, and the LF/HF ratio) were calculated across all sleep stages during a one- night polysomnography. Results We found that OSAwh patients had a lower body mass index, a lower waist circumference, and a higher frequency of previous naso-pharyngeal surgery when compared to OSA with hypoxia patients. In terms of heart rate variability, OSA had increased LF oscillations (i.e., baroreflex function) during N1-N2 and REM sleep when compared to OSAwh and controls. OSA and OSAwh had decreased HF oscillations (i.e., vagal inputs) during N1-N2, N3 and REM sleep when compared to controls. The LF/HF ratio was increased during N1-N2 and REM sleep, only in patients with OSA. Conclusion In conclusion, patients with OSAwh exhibit distinctive clinical, sleep, and autonomic features when compared to obstructive sleep apnea with hypoxia. These differences must be taken into account in future studies when analyzing therapeutic approaches for sleep apnea patients. Acknowledgements Clinica Universidad de Navarra.