TY - JOUR
T1 - Sympathetic chemoreflex responses in obstructive sleep apnea and effects of continuous positive airway pressure therapy
AU - Imadojemu, Virginia A.
AU - Mawji, Zubina
AU - Kunselman, Allen
AU - Gray, Kristen S.
AU - Hogeman, Cynthia S.
AU - Leuenberger, Urs A.
N1 - Funding Information:
This work was supported in part by grants K23 HL04190 (V.A.I.), R01 HL68699 (U.A.L.), and National Institutes of Health/National Center for Research Resources grant M01 RR10732.
PY - 2007/5
Y1 - 2007/5
N2 - Background: Sympathetic nerve activity is increased in awake and regularly breathing patients with obstructive sleep apnea (OSA). Over time, repetitive hypoxic stress could alter sympathetic chemoreflex function in OSA. Methods: We determined the responses to acute hypoxia (fraction of inspired oxygen of 0.1, for 5 min), static handgrip exercise, and the cold pressor test (CPT) in 24 patients with OSA (age, 50 ± 3 years [mean ± SEM]; apnea-hypopnea index, 47 ± 6 events per hour) and in 14 age- and weight-matched nonapneic control subjects. Muscle sympathetic nerve activity (MSNA) [peroneal microneurography], BP, and ventilation were monitored. Results: Basal MSNA was higher in OSA patients compared to control subjects (45 ± 4 bursts per minute vs 33 ± 4 bursts per minute, respectively; p < 0.05). Furthermore, compared to control subjects, the MSNA responses to hypoxia were markedly enhanced in OSA (p < 0.001). Whereas the ventilatory responses to hypoxia tended to be increased in OSA (p = 0.06), the BP responses did not differ between the groups (p = 0.45). The neurocirculatory reflex responses to handgrip exercise and to the CFT were similar in the two groups (p = not significant). In OSA patients who were retested after 1 to 24 months of continuous positive airway pressure (CPAP) therapy (n = 11), basal MSNA (p < 0.01) and the responses of MSNA to hypoxia (p < 0.01) decreased significantly, whereas the ventilatory responses remained unchanged (p = 0.82). Conclusion: These data suggest that the sympathetic responses to hypoxic chemoreflex stimulation are enhanced in OSA and may normalize in part following CPAP therapy.
AB - Background: Sympathetic nerve activity is increased in awake and regularly breathing patients with obstructive sleep apnea (OSA). Over time, repetitive hypoxic stress could alter sympathetic chemoreflex function in OSA. Methods: We determined the responses to acute hypoxia (fraction of inspired oxygen of 0.1, for 5 min), static handgrip exercise, and the cold pressor test (CPT) in 24 patients with OSA (age, 50 ± 3 years [mean ± SEM]; apnea-hypopnea index, 47 ± 6 events per hour) and in 14 age- and weight-matched nonapneic control subjects. Muscle sympathetic nerve activity (MSNA) [peroneal microneurography], BP, and ventilation were monitored. Results: Basal MSNA was higher in OSA patients compared to control subjects (45 ± 4 bursts per minute vs 33 ± 4 bursts per minute, respectively; p < 0.05). Furthermore, compared to control subjects, the MSNA responses to hypoxia were markedly enhanced in OSA (p < 0.001). Whereas the ventilatory responses to hypoxia tended to be increased in OSA (p = 0.06), the BP responses did not differ between the groups (p = 0.45). The neurocirculatory reflex responses to handgrip exercise and to the CFT were similar in the two groups (p = not significant). In OSA patients who were retested after 1 to 24 months of continuous positive airway pressure (CPAP) therapy (n = 11), basal MSNA (p < 0.01) and the responses of MSNA to hypoxia (p < 0.01) decreased significantly, whereas the ventilatory responses remained unchanged (p = 0.82). Conclusion: These data suggest that the sympathetic responses to hypoxic chemoreflex stimulation are enhanced in OSA and may normalize in part following CPAP therapy.
UR - http://www.scopus.com/inward/record.url?scp=34248578612&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=34248578612&partnerID=8YFLogxK
U2 - 10.1378/chest.06-2580
DO - 10.1378/chest.06-2580
M3 - Article
C2 - 17494791
AN - SCOPUS:34248578612
SN - 0012-3692
VL - 131
SP - 1406
EP - 1413
JO - CHEST
JF - CHEST
IS - 5
ER -