Chung-Hsin Chiu

Work of Breathing in Eucapnic and Hypercapnic Sleep Apnea Syndrome

Background: Upper airways in patients with obstructive sleep apnea syndrome (OSAS) are more likely narrower than those of normal subjects, a factor in increasing the work of breathing (WOB) in these individuals. Objectives: To evaluate WOB while sitting and while supine, both awake and during stage 2 sleep, in patients with hypercapnic or eucapnic OSAS. Method: Twenty normal control subjects without OSAS, 20 patients with eucapnic moderate or severe OSAS and another 8 patients with hypercapnic severe OSAS were studied. WOB was measured by esophageal manometry with the subjects seated and then with the subjects supine, both while awake and during stage 2 sleep. Results: In both the control and the eucapnic group, WOB was normal in the sitting position. When the eucapnic subjects lay supine, their WOB increased, both while awake and asleep. In contrast, the hypercapnic subjects had an abnormally high WOB both sitting and supine, whether awake or asleep. Conclusion: WOB was increased in subjects with hypercapnic OSAS in both the sitting and supine positions. While eucapnic individuals with OSAS have increased WOB when supine, it is normal when they are sitting upright.

Effect of Treatment by Nasal Continuous Positive Airway Pressure on Serum High Mobility Group Box-1 Protein in Obstructive Sleep Apnea

BACKGROUND Serum levels of high mobility group box-1 protein (HMGB1) are increased in a variety of inflammatory disorders. Obstructive sleep apnea syndrome (OSAS) is associated with inflammation secondary to chronic intermittent hypoxia, but HMGB1 levels in treated and untreated OSAS have not been evaluated. METHODS Twenty healthy subjects and 30 subjects with moderately severe or severe OSAS who desired nasal continuous positive airway pressure (CPAP) treatment were enrolled. Serum levels of HMGB1 and nitric oxide derivative (NO(x)) from peripheral blood samples were measured, and all subjects underwent a sleep study. These studies were repeated 2 months after nasal CPAP treatment in the patients with OSAS. RESULTS In OSAS before nasal CPAP treatment, the serum level of HMGB1 was higher but that of NO(x) was lower than those levels of normal subjects. The HMGB1 levels correlated negatively with NO(x) levels in subjects with OSAS. After nasal CPAP treatment, the HMGB1 and NO(x) returned to normal levels. CONCLUSION Elevated HMGB1 levels and reduced NO(x) levels in patients with OSAS normalized after nasal CPAP treatment.

Effect of uvulopalatopharyngoplasty on endothelial function in obstructive sleep apnea

Objectives: This study evaluates the effects of uvulopalatopharyngoplasty (UPPP) on serum levels of nitric oxide derivatives (NOx) and endothelial function by endothelium dependent flow-mediated dilation (FMD) in obstructive sleep apnea syndrome (OSAS). Study Design: Prospective study. Subjects and Methods: Fifteen healthy subjects and 30 subjects with moderately severe to severe OSAS who desired UPPP were prospectively enrolled. FMD was measured by high-resolution B-mode ultrasonography; serum level of NOx from peripheral blood samples was also measured. All subjects participated in sleep studies. These studies were repeated 3 months after UPPP in OSAS patients. Results: For healthy patients, there was no difference in serum level of NOx and FMD between baseline and 3 months later. The serum levels of NOx in 14 of 30 patients with OSAS – designated surgical responders – increased from 13.9 ± 5.5 μM preoperation to 28.9 ± 8.2 μM postoperatively. FMD increased from 5.2 ± 5.0 preoperatively to 10.0 ± 4.7 postoperatively. For the 16 unresponsive patients, serum NOx and FMD remained impaired after UPPP. Conclusion: Successful treatment of OSAS with UPPP leads to restoration of FMD and normal serum levels of NOx.

Effect of uvulopalatopharyngoplasty on work of breathing during wakefulness in obstructive sleep apnea syndrome

Objectives: We evaluated the effects of uvulopalatopharyngoplasty (UPPP) on the work of breathing (WOB) in obstructive sleep apnea syndrome (OSAS). Methods: Fifteen healthy subjects and 30 subjects with OSAS who desired UPPP were prospectively enrolled. All underwent measurement of WOB while awake as well as in a sleep study. These studies were repeated 3 months after UPPP in the patients with OSAS. Results: In OSAS before UPPP, the WOB while supine was increased above that of normal subjects. After UPPP, the WOB while supine remained elevated in those whose OSAS did not respond to surgery, and it returned to normal levels in patients whose OSAS improved after UPPP. Conclusions: Abnormal WOB in patients with OSAS returns to normal if UPPP results in amelioration of OSAS.

Effect of uvulopalatopharyngoplasty on leptin and endothelial function in sleep apnea.

Objectives: This study evaluated the effects of uvulopalatopharyngoplasty (UPPP) on serum leptin levels and endothelial function in patients with obstructive sleep apnea syndrome (OSAS). Methods: Fifteen healthy subjects and 35 patients with moderate to severe OSAS who desired UPPP were prospectively enrolled. The serum levels of leptin and nitric oxide derivative (NOx) from their peripheral blood samples were measured by enzyme-linked immunosorbent assay. All subjects participated in sleep studies, which were repeated 3 months after UPPP in the patients with OSAS. Results: Before UPPP, the patients with OSAS had a higher serum level of leptin and a lower NOx level than did the control subjects. The serum leptin levels in the 17 of the 35 patients with OSAS who were surgical responders decreased from 24.2 ± 6.1 ng/mL before operation to 15.9 ± 6.0 ng/mL after operation. The serum NOx levels in these 17 patients increased from 18.5 ± 7.5 µmol/L before operation to 27.3 ± 8.2 µmol/L after operation. In the 18 patients who were unresponsive to surgery, the serum leptin and NOx levels remained impaired after the UPPP. Conclusions: Successful treatment of OSAS with UPPP leads to the normalization of serum leptin and NOx levels.

Effects of nasal CPAP on exhaled SIRT1 and tumor necrosis factor-α in patients with obstructive sleep apnea.

Exhaled breath condensate (EBC) has been used to examine airway inflammation and oxidative stress. This study aimed to evaluate if there were abnormal Sirtuin 1 (SIRT1) protein and tumor necrosis factor (TNF)-α levels in EBC and to determine if these levels could be improved after nasal continuous positive airway pressure (CPAP) treatment. Thirty-five patients with moderately severe to severe obstructive sleep apnea syndrome (OSAS) who wanted nasal CPAP treatment and 20 healthy controls were prospectively enrolled. The EBC SIRT1 protein levels and EBC TNF-α protein levels were assessed by ELISA. All patients underwent sleep studies that were repeated 3 months after nasal CPAP treatment in patients with OSAS. Results showed that in OSAS before nasal CPAP treatment, the EBC SIRT1 protein levels were lower than that in normal subjects, whereas the EBC TNF-α protein levels were higher. After nasal CPAP treatment, the EBC SIRT1 levels increased and EBC TNF-α levels decreased. In conclusion, successful treatment of OSAS by nasal CPAP can normalize the levels of EBC SIRT1 and EBC TNF-α.