Relationship between CO2 drive and characteristics of apneas in obstructive and central sleep apnea

Previously we showed that CO2 drive is increased in patients with obstructi ve sleep apnea (OSA). In the present study we would like to evaluate a poss ible relationship between CO2 drive and characteristics of apneas in obstru ctive and central sleep apnea (CSA). We compared the hypercapnic ventilator y response (HCVR) between patients with OSA and CSA. HCVR was correlated wi th total event time and mean event duration in both groups. 17 normocapnic patients in each group and 14 controls were studied. The apnea patients wer e matched for apnea-hypopnea index, age, sex, and BMI. SHCVR (slope) tended to be higher in apnea patients than in controls without statistical signif icancy: controls 1.65 (0.16), CSA 2.17 (0.22), OSA 2.55 (0.35) (l/min per m mHg) (P = 0.13). A significant correlation was found between HCVR and event time in CSA (0.52, P = 0.04) and between HCVR and apnea mean duration in O SA (r = 0.52, P = 0.04). We conclude that while CO2 drive was not statistic ally increased in both apnea types, small changes can contribute to breathi ng instability and may increase the total event time tin CSA) but may also shorten the apnea duration tin OSA). (C) 1998 Elsevier Science B.V. All rig hts reserved.