부산대학교 도서관

Purpose: In normotensive patients with obstructive sleep apnea (OSA), the muscle sympathetic nerve activity (MSNA) response to exercise is increased while metaboreflex control of MSNA is decreased. We tested the hypotheses that acute intermittent hypercapnic hypoxia (IHH) in males free from OSA and associated comorbidities would augment the MSNA response to exercise but attenuate the change in MSNA during metaboreflex activation. Methods: Thirteen healthy males (age = 24 ± 4 yr) were exposed to 40 min of IHH. Before and after IHH, the pressor response to exercise was studied during 2 min of isometric handgrip exercise (at 30%maximal voluntary contraction), whereas themetaboreflex was studied during 4min of postexercise circulatory occlusion (PECO).Mean arterial pressure (MAP), heart rate (HR), and fibularMSNA were recorded continuously. MSNA was quantified as burst frequency (BF) and total activity (TA).Mixed effects linear models were used to compare the exercise pressor andmetaboreflex before and after IHH. Results: As expected, IHH led to significant increases in MSNA BF, TA, and MAP at baseline and throughout exercise and PECO. However, during handgrip exercise, the change from baseline inMAP,HR,MSNABF, and TA was similar before and after IHH(All P > 0.31).During PECO, the change from baseline inMSNA BF and TA was similar after IHH, whereas the change from baseline inMAP (Δ14mmHg, 95% CI = 7-19, vs Δ16mmHg, 95% CI = 10-21; P < 0.01) wasmodestly increased. Conclusion: After acute IHH,MSNAresponse to handgrip exercise and metaboreflex activationwere preserved in healthy young males despite overall increases in resting MSNA and MAP. Chronic IHH and comorbidities often associated with OSA may be required to modulate the exercise pressor reflex and metaboreflex. [ABSTRACT FROM AUTHOR]