Impact of nocturnal oxygen and CPAP on the ventilatory response to hypoxia in OSA patients free of overt cardiovascular disease

• Published in: Experimental neurology 2021-12, Vol.346, p.113852-113852, Article 113852
• Main Authors: Pun, Matiram, Beaudin, Andrew E., Raneri, Jill K., Anderson, Todd J., Hanly, Patrick J., Poulin, Marc J.
• Format: Article
• Language: English
• Subjects: Adult; Apnea; Cardiovascular Diseases; Continuous Positive Airway Pressure - methods; CPAP; Female; Follow-Up Studies; Humans; Hypoxia - physiopathology; Hypoxia - therapy; Male; Middle Aged; OSA; Oxygen; Oxygen - administration & dosage; Oxygen Inhalation Therapy - methods; Random Allocation; Sleep; Sleep Apnea, Obstructive - physiopathology; Sleep Apnea, Obstructive - therapy; Ventilation
• ISSN: 0014-4886; 1090-2430
• DOI: 10.1016/j.expneurol.2021.113852

A primary characteristic of obstructive sleep apnea (OSA) is chronic exposure to intermittent hypoxia (IH) due to repeated upper airway obstruction. Chronic IH exposure is believed to increase OSA severity over time by enhancing the acute ventilatory response to hypoxia (AHVR), thus promoting ventilatory overshoot when apnea ends and perpetuation of apnea during sleep. Continuous positive airway pressure (CPAP), the gold-standard treatment of OSA, reduces the AHVR, believed to result from correction of IH. However, CPAP also corrects ancillary features of OSA such as intermittent hypercapnia, negative intrathoracic pressure and surges in sympathetic activity, which may also contribute to the reduction in AHVR. Therefore, the objective of this study was to investigate the impact of nocturnal oxygen therapy (to remove IH only) and CPAP (to correct IH and ancillary features of OSA) on AHVR in newly diagnosed OSA patients. Fifty-two OSA patients and twenty-two controls were recruited. The AHVR was assessed using a 5 min iscopanic-hypoxic challenge before, and after, treatment of OSA by nocturnal oxygen therapy and CPAP. Following baseline measurements, OSA patients were randomly assigned to nocturnal oxygen therapy (Oxygen, n = 26) or no treatment (Air; n = 26). The AHVR was re-assessed following two weeks of oxygen therapy or no treatment, after which all patients were treated with CPAP. The AHVR was quantified following ~4 weeks of adherent CPAP therapy (n = 40). Both nocturnal oxygen and CPAP treatments improved hypoxemia (p  0.05). However, there was a significant decrease in AHVR with both nocturnal oxygen therapy and CPAP in patients in the highest OSA severity quartile (p