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Results OHS was identified in 55 of the 611 patients with OSAS (9%). OHS patients were younger, heavier, and more somnolent than non-OHS patients and displayed more severe OSAS, liver dysfunctions, higher total cholesterol, and impaired pulmonary function. However, these differences were resolved except for pulmonary function after correction for obesity. Daytime hypercapnia was associated with impaired pulmonary function. Percent vital capacity (%VC) was most closely correlated with PaCO2 in OHS.Conclusion OHS patients display numerous abnormalities due to obesity compared with non-OHS patients. Impaired pulmonary function, particularly %VC, may play an important role in the development of daytime hypercapnia independent of obesity in OHS patients.

Pharyngeal dilator muscles are clearly important in the pathogenesis of obstructive sleep apnea syndrome. Substantial data support the role of local mechanisms in mediating pharyngeal dilator muscle activation in normal humans during wakefulness. Using a recently reported iron lung ventilation model, we sought to determine the stimuli modulating genioglossus activity, dissociating the influences of pharyngeal negative pressure, from inspiratory airflow, resistance, and CO(2). To achieve this aim, we used two gas densities at several levels of end-tidal CO(2) and a number of intrapharyngeal negative pressures. The correlations between genioglossus electromyography (GGEMG) and epiglottic pressure across a breath remained robust under all conditions (R values range from 0.71 +/- 0.07 to 0.83 +/- 0.05). In addition, there was no significant change in the slope of this relationship despite variable gas density or CO(2) levels. Although flow also showed strong correlations with genioglossus activity, there was a significant change in the slope of the GGEMG/flow relationship with altered gas density. For the group averages across conditions (between breath analysis), the correlation with GGEMG was robust for negative pressure (R(2) = 0.98) and less strong for other variables such as flow and resistance. These data suggest that independent of central pattern generator activity, intrapharyngeal negative pressure itself modulates genioglossus activity both within breaths and between breaths.

Objective To assess changes in response to nasal continuous positive airway pressure (CPAP) in patients with obstructive sleep apnea syndrome (OSAS) concerning excessive daytime sleepiness (EDS), depressive state, and quality of life (QOL).Patients and Methods We assessed for EDS using the Epworth sleepiness scale (ESS), for mood using The Zung self-depression scale (SDS), and for QOL using ShortForm 36 (SF-36) in 132 patients with obstructive sleep apnea syndrome (OSAS) and control subjects. Patients had severe OSAS (apnea-hypopnea index, 59.4±23.8/h) and were more hypersomnolent and depressed, and had poorer QOL than 38 age-and gender-matched controls.Results

Upper airway dilator muscles are phasically activated throughout breathing by respiratory pattern generator neurons. Studies have shown that non‐physiological upper airway mechanoreceptive stimuli (e.g. rapidly imposed pulses of negative pressure) also activate these muscles. Such reflexes may become activated during conditions that alter airway resistance in order to stabilise airway patency. To determine the contribution of ongoing mechanoreceptive reflexes to phasic activity of airway dilators, we assessed genioglossal electromyogram (GG EMG: rectified with moving time average of 100 ms) during slow (physiological) oscillations in negative pressure generated spontaneously and passively (negative pressure ventilator). Nineteen healthy adults were studied while awake, during passive mechanical ventilation across normal physiological ranges of breathing rates (13–19 breaths min−1) and volumes (0.5–1.0 l) and during spontaneous breathing across the physiological range of end‐tidal carbon dioxide (PET,CO2; 32–45 mmHg). Within‐breath phasic changes in airway mechanoreceptor stimuli (negative pressure or flow) were highly correlated with within‐breath phasic genioglossal activation, probably representing a robust mechanoreceptive reflex. These reflex relationships were largely unchanged by alterations in central drive to respiratory pump muscles or the rate of mechanical ventilation within the ranges studied. A multivariate model revealed that tonic GG EMG, PET,CO2 and breath duration provided no significant independent information in the prediction of inspiratory peak GG EMG beyond that provided by epiglottic pressure, which alone explained 93 % of the variation in peak GG EMG across all conditions. The overall relationship was: Peak GG EMG = 79.7 − (11.3 x Peak epiglottic pressure), where GG EMG is measured as percentage of baseline, and epiglottic pressure is in cmH2O. These data provide strong evidence that upper airway dilator muscles can be activated throughout inspiration via ongoing mechanoreceptor reflexes. Such a feedback mechanism is likely to be active on a within‐breath basis to protect upper airway patency in awake humans. This mechanism could mediate the increased genioglossal activity observed in patients with obstructive sleep apnoea (i.e. reflex compensation for an anatomically smaller airway).

To assess the acute effects of nasal continuous positive airway pressure (CPAP) on the 24-hour blood pressure and the secretion of catecholamines in urine and plasma, we investigated the changes in the 24-hour blood pressure and urinary and plasma concentrations of epinephrine (E) and norepinephrine (NE) in 26 men with obstructive sleep apnea (OSA) with and without nasal CPAP. Nasal CPAPresulted in significant decreases in the daytime diastolic pressure (from 86 ± 16 mmHgto 83 ± 12 mmHg), the nighttime diastolic pressure (from 81 ± 12 mmHgto 77 ±9 mmHg) and the nighttime systolic pressures (from 125 ± 15 mmHgto 120 ± 10 mmHg). There was no significant difference between patients with and without CPAPin the daytime or nighttime urinary E level, but patients who received CPAPshowed a significant decrease in daytime urinary NElevel (from 156± 112 |ig/14h to 119 ± 101 |0g/14h) and nighttime urinary NE level (from 143 ±91 |ig/10h to 112 ± 65 |ig/10h). The morning plasma level of NE also decreased (from 371 ± 181 pg/ml to 273 ± 148 pg/ml) in patients who received nasal CPAP (p<0.02), but the plasma level of E remained unchanged. There were no correlations between PSGparameters and the reductions in blood pressure and the catecholamine levels induced by nasal CPAP.These findings suggest that OSA contributes, at least in part, to the development of systemic hypertension by increasing sympathetic nervous activity.

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BackgroundCardiovascular diseases, osteoporosis, and depression are identified comorbidities of chronic obstructive pulmonary disease (COPD), but there have been few reports of chronic kidney disease (CKD) as a comorbidity of COPD. The objective of this study was to investigate the prevalence of CKD in COPD patients using estimated glomerular filtration rate (eGFR) based on creatinine (Cr) and cystatin C (Cys) levels.MethodsThe prevalence of CKD and the values of various CKD-related parameters were compared between 108 stable COPD outpatients (COPD group) and a non-COPD control group consisting of 73 patients aged 60 years or more without a history of COPD or kidney disease. CKD was defined as an eGFR less than 60 mL/min/1.73 m2.ResultsThe Cr level was significantly higher in the COPD group, but eGFR based on serum Cr (eGFRCr) was not significantly different between the two groups (73.3±25.3 vs 79.7±15.5 mL/min/1.73 m2). The Cys level was significantly higher and eGFR based on serum Cys (eGFRCys) was significantly lower in the COPD group (60.0±19.4 vs 74.0±13.5 mL/min/1.73 m2, P<0.0001). The prevalence of CKD evaluated based on eGFRCr was 31% in the COPD group and 8% in the non-COPD group with an odds ratio of 4.91 (95% confidence interval, 1.94–12.46, P=0.0008), whereas the evaluated prevalence based on eGFRCys was 53% in the COPD group and 15% in the non-COPD group with an odds ratio of 6.30 (95% confidence interval, 2.99–13.26, P<0.0001), demonstrating a higher prevalence of CKD when based on eGFRCys rather than on eGFRCr.ConclusionCKD is a comorbidity that occurs frequently in COPD patients, and we believe that renal function in Japanese COPD patients should preferably be evaluated based not only on Cr but on Cr in combination with Cys.