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    Cardiopulmonary responses to exercise in moderate-to-severe obstructive sleep apnea
    (Turkish Assoc Tuberculosis & Thorax, 2005) Ozturk, Levent; Metin, Gokhan; Cuhadaroglu, Caglar; Utkusavas, Ayfer; Tutluoglu, Bulent
    Information regarding the safety of maximal cardiopulmonary exercise testing (CPET) or the mechanisms of exercise limitation in obstructive sleep apnea (OSA) patients is fairly limited. In the present study, we addressed the problem of exercise capacity in moderate-to-severe OSA patients. Nineteen non-consecutive patients (three female, 16 male) with moderate-to-severe OSA and 11 age and body mass index matched control subjects (four female, seven male) underwent respiratory function tests during pre-exercise resting period and volitionally limited cardiopulmonary exercise testing on an electronically braked cycle ergometer. All participants completed CPET without any complication. Control subjects were exercise limited due to deconditioning. None of the patients revealed mechanical ventilatory limitation to exercise or had evidence of cardiac ischaemia. Five patients had no limitation to exercise. Six patients had low VO2peak, low anaerobic treshold (AT), and low peak O-2 pulse, a pattern consistent with ventricular dysfunction. Six patients had low VO2peak, low AT, and peak heart rate less than 85% predicted. This pattern is consistent with exercise limitation due to peripheral vascular disease. Two patients had low VO2peak, low AT without peak oxygen pulse and peak heart rate abnormalities consistent with deconditioning. We concluded that moderate-to-severe OSA patients have impaired exercise capacity. Exercise limitation seems to originate from cardiovascular reasons namely left ventricular dysfunction and/or peripheral vascular impairment; and finally, maximal CPET can be tolerated by these patient group without serious complications.
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    Effects of Nasal CPAP Treatment on Insulin Resistance, Lipid Profile, and Plasma Leptin in Sleep Apnea
    (Springer, 2009) Cuhadaroglu, Caglar; Utkusavas, Ayfer; Ozturk, Levent; Salman, Serpil; Ece, Turhan
    Background Obstructive sleep apnea has been linked with metabolic syndrome characterized by dyslipidemia, dyscoagulation, hypertension, and diabetes mellitus type 2 and their cardiovascular consequences. This study was designed to determine the effects of 8 weeks of therapy with continuous positive airway pressure (CPAP) on insulin resistance, glucose, and lipid profile, and the relationship between leptin and insulin-resistance parameters in patients with moderate-to-severe obstructive sleep apnea. Methods In 44 patients, serum cholesterol, triglycerides, high-density lipoprotein, low-density lipoprotein, very low-density lipoprotein, leptin, and insulin parameters were measured at baseline and after 8 weeks of CPAP. Insulin resistance index was based on the homeostasis model assessment (HOMA-IR) method. Insulin sensitivity (HOMA-S) and insulin secretion capacity (HOMA-beta) also were calculated. Thirteen patients were excluded from statistical analyses due to noncompliant CPAP usage (<4 h night(-1)). Results In 31 patients who used CPAP for >= 4 h night-1, CPAP therapy reduced total cholesterol (P < 0.05), low-density lipoprotein (P < 0.05), and leptin (P < 0.05). Circulating leptin levels showed significant correlation with both HOMA-S and HOMA-IR at baseline and follow-up (P = 0.03 for all). In addition, there was no correlation between HOMA-IR and the severity of sleep apnea, which was shown by apnea-hypopnea index. Conclusions In patients with moderate-to-severe obstructive sleep apnea, compliant CPAP usage may improve insulin secretion capacity, reduce leptin, total cholesterol, and low-density lipoprotein levels. Leptin showed significant relationship with insulin resistance, and this relationship remained after 8 weeks of CPAP therapy.