title: Ventilatory and cerebrovascular responses to hypercapnia in patients with obstructive sleep apnoea: effect of CPAP therapy.
abstract: The purpose of this study was to assess whether the cerebrovascular response to hypercapnia is blunted in OSA patients and if this could alter the ventilatory response to hypercapnia before and after CPAP therapy. We measured the cerebrovascular, cardiovascular and ventilatory responses to hypercapnia in 8 patients with OSA (apnoea-hypopnoea index=101+/-10) before and after 4-6 weeks of CPAP therapy and in 10 control subjects who did not undergo CPAP therapy. The cerebrovascular and ventilatory responses to hypercapnia were not different between OSA and controls at baseline or follow-up. The cardiovascular response to hypercapnia was significantly increased in the OSA group by CPAP therapy (mean arterial pressure response: 1.30+/-0.16 vs. 2.04+/-0.36 mmHg Torr(-1); p=0.007). We conclude that in normocapnic, normotensive OSA patients without cardiovascular disease, the ventilatory, cerebrovascular, and cardiovascular responses to hypercapnia are normal, but the cardiovascular response to hypercapnia is heightened following 1 month of CPAP therapy.
authors.affiliation: Department of Physiology and Biophysics, Faculty of Medicine, University of Calgary, Alberta T2N 4N1, Canada.
authors.forename: Glen E
authors.initials: GE
authors.lastname: Foster
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Hanly
authors.forename: Michele
authors.initials: M
authors.lastname: Ostrowski
authors.forename: Marc J
authors.initials: MJ
authors.lastname: Poulin
mesh_terms: D000293:Adolescent; D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology; D002320:Cardiovascular Physiological Phenomena; D016022:Case-Control Studies; D002560:Cerebrovascular Circulation / Q000502:physiology*; D045422:Continuous Positive Airway Pressure / Q000379:methods*; D005500:Follow-Up Studies; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D017286:Polysomnography / Q000379:methods; D012123:Pulmonary Ventilation / Q000502:physiology*; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology* / Q000628:therapy*; D055815:Young Adult