Cardiopulmonary exercise testing in obstructive sleep apnea syndrome.

To investigate whether cardiac dysfunction or abnormal measurements on cardiopulmonary exercise testing (CPET) are present in patients with obstructive sleep apnea syndrome (OSAS) and what factors are responsible for exercise limitation in these patients. We enrolled 20 patients with moderate or severe OSAS in the OSA group and 20 subjects without OSAS in the control group. All subjects underwent a sleep study and cardiac evaluation by radionuclide scanning and CPET. There was no difference in left ventricular ejection fraction (VEF) between the two groups, but the OSA group had a lower right VEF. Patients in the OSA group had a lower VO2(peak), VO2(peak/kg) and workpeak than the control group. The OSA group had a higher breathing reserve and a greater decrease in anaerobic threshold (AT) and oxygen pulse. In conclusion, patients with moderate to severe OSAS had abnormal CPET results. These abnormalities may be due to cardiac disease, pulmonary vascular disease, or possible lack of fitness.

Effect of laser-assisted uvulopalatoplasty on oral airway resistance during wakefulness in obstructive sleep apnea syndrome.

The aim of the study was to evaluate the effects of successful laser-assisted uvulopalatoplasty (LAUP) on oral airway resistance (R(OA)) during wakefulness in patients with OSAS. Fifteen healthy subjects (group I) and 25 subjects (group II) with moderately severe or severe obstructive sleep apnea syndrome (OSAS) proven by an overnight sleep study and who desired LAUP were enrolled. All underwent an overnight sleep study, pulmonary function testing and measurement of oral airway resistance [R(OA) (including impedance (Zrs), resistance (R) and reactance (X)] measurement by Impulse Oscillometry (IOS) (MasterScreen IOS, VIASYS Healthcare GmbH, Germany) in the upright (seated) position and then in the supine position while awake. Group II subjects had these measurements twice, both before and 3 months after LAUP. Based on the assessment of their sleep study after LAUP, they were divided into two groups: responders (group IIa) and nonresponders (group IIb). Zrs was normal in the sitting position both before and after LAUP in both groups IIa and IIb and comparable to that of group I controls. There was an increase in Zrs in the supine position in both groups IIa and IIb subjects before LAUP. After LAUP, the Zrs in group IIb subjects remained elevated, while that in group IIa subjects returned to levels comparable to those in the normal controls. OSAS patients before LAUP have abnormal R(OA) in the supine position as reflected by a high Zrs. The Zrs is improved after LAUP that successfully ameliorates OSAS.

Effect of treatment by laser-assisted uvulopalatoplasty on cardiopulmonary exercise test in obstructive sleep apnea syndrome.

OBJECTIVES: To evaluate the effects of successful laser-assisted uvulopalatoplasty (LAUP) on cardiopulmonary exercise testing (CPET) in patients with obstructive sleep apnea syndrome (OSAS). STUDY DESIGN AND SETTING: Twenty-five subjects with moderately severe or severe OSAS who desired LAUP were enrolled. All patients had an overnight sleep study and CPET before and 3 months after LAUP. Patients were divided into 2 groups based on the success (group I) or failure (group II) of LAUP to improve their sleep apnea. RESULTS: Successful LAUP in group I was followed by improvement in right ventricular ejection fraction, maximal work rate (WRmax), VO2max/kg, anaerobic threshold, oxygen pulse, and a lower breathing reserve. CPET results were unchanged after LAUP in group II subjects. CONCLUSION: Patients with OSAS before LAUP had abnormal CPET as reflected by low VO2peak/kg, WRmax, anaerobic threshold, and oxygen pulse. All of these variables improved after LAUP that successfully ameliorated OSAS.

Oral airway resistance during wakefulness in eucapnic and hypercapnic sleep apnea syndrome.

The purpose of this study was to evaluate whether there was an abnormal increase of upper airway resistance in the sitting and supine positions in hypercapnic obstructive sleep apnea syndrome (OSAS) patients compared with eucapnic OSAS or normal controls as measured by impulse oscillometry (IOS) while awake. Twenty subjects without OSAS served as controls (group I), and 20 patients with moderate or severe eucapnic OSAS (group II) and another eight hypercapnic severe OSAS patients (group III) were studied. Group II was further divided into two subgroups. Group IIa consisted of 14 subjects whose BMI was less than 35 and group IIb of six subjects whose BMI was greater than 35. All subjects also had an overnight sleep study. Oral airway resistance (AR) (including impedance (Zrs), resistance (R) and reactance (X)) was measured by impulse oscillometry (IOS) (MasterScreen IOS, VIASYS Healthcare GmbH, Germany) in the upright (seated) position and then in the supine position while awake. The results demonstrated that in both group I and group II, Zrs was normal in the sitting position. However, there was a high Zrs in the supine position for group II patients. In contrast, in group III patients, there was a high Zrs in both the sitting and supine positions. In conclusion, upper airway resistance was increased both sitting and supine in the hypercapnic OSAS patients; this would presumably increase the work of breathing and might explain why these subjects were hypercapnic while awake, while eucapnic OSAS patients and normal controls were not. Secondly, the increased upper airway resistance in the supine position in the eucapnic OSAS patients may contribute to their OSAS.

Effect of treatment by nasal CPAP on cardiopulmonary exercise test in obstructive sleep apnea syndrome.

This study was done to evaluate whether cardiac dysfunction or abnormal measurements on cardiopulmonary exercise testing (CPET) can be improved after 2 months of nasal CPAP treatment. Twenty patients with moderate or severe OSAS received nasal CPAP treatment. All subjects also underwent blood pressure, simple spirometric, and arterial blood gas (ABG) measurements; cardiac evaluation by radionuclide scanning and CPET; and an overnight polysomnography sleep study before and after nasal CPAP treatment. No difference in left ventricular ejection fraction (LVEF) was found after 2 months of nasal CPAP treatment, but higher right ventricular ejection fraction (RVEF), VO2peak, VO2peak/kg and workpeak were observed. After 2 months of nasal CPAP treatment, these patients had a lower breathing reserve and a greater increase in anaerobic threshold and oxygen pulse. Moderate to severe OSAS patients before nasal CPAP treatment had abnormal CPET as reflected by lower RVEF, VO2peak/kg, workpeak, anaerobic threshold and oxygen pulse. These abnormalities can be improved after 2 months of nasal CPAP treatment.