Vitamin D status and parathyroid hormone levels in patients with obstructive sleep apnea.

BACKGROUND: Vitamin D insufficiency and high levels of parathyroid hormone (PTH) appear to be emerging risk factors for metabolic syndrome (MS), diabetes and cardiovascular disease, conditions that occur frequently in patients with obstructive sleep apnea syndrome (OSAS). OBJECTIVES: This study examined whether serum concentrations of 25-hydroxyvitamin D [25(OH)D] and PTH were associated with the presence of MS, diabetes and hypertension among an OSAS population. METHODS: A total of 826 patients (635 men and 191 women) with newly diagnosed OSAS were studied. The occurrence of the MS was analyzed according to the National Cholesterol Education Program Adult Treatment Panel III clinical criteria. Serum levels of 25(OH)D, PTH, glucose, triglycerides, cholesterol, HDL cholesterol, creatinine and uric acid were determined. RESULTS: In 55.3% of the men and in 63.2% of the women, the serum 25(OH)D level was less than 30 ng/ml (insufficient status). After adjusting for age, sex and seasonality, there was a significant trend of decreasing odds for diabetes [odds ratio (OR) 0.55, 95% confidence interval (CI) 0.33-0.94, ptrend = 0.038] and MS (OR 0.34, 95% CI 0.21-0.56, ptrend < 0.001) with increasing vitamin D levels. Higher PTH levels were associated with a higher prevalence of obesity (OR 2.05, 95% CI 1.06-3.09, ptrend < 0.001) and hypertension (OR 1.83, 95% CI 1.01-3.05, ptrend = 0.049). CONCLUSIONS: These data suggest an inverse association of 25(OH)D with diabetes and MS and a positive association of PTH with obesity and hypertension among patients with OSAS. Based on our observational study, the causative nature of the associations cannot be established. These findings require further examination in prospective studies including clinical trials.

Automatic CPAP performance in patients with sleep apnea plus COPD.

BACKGROUND: Automatic CPAP devices have demonstrated good results in obtaining optimal fixed CPAP pressure to eliminate respiratory events in patients with sleep apnea-hypopnea syndrome (SAHS). However, automatic CPAP has not been fully studied in patients with COPD plus SAHS. OBJECTIVES: To analyse the performance of an automatic CPAP in severe COPD patients compared with SAHS patients with no associated co-morbidity. METHODS: We compared 10 consecutive patients with SAHS and no associated co-morbidity and 10 patients with SAHS plus severe COPD who required CPAP titration. Automatic CPAP performance was studied during full-night PSG. Inadequate pressure increase periods, absence of pressure increases in reaction to respiratory events, air leak periods, and pressure behaviour in the face of erratic breathing periods were analysed. RESULTS: The SAHS patients without co-morbidities vs. SAHS plus COPD patients presented: mean sleep efficiency, 80.2 (11.5)% vs. 76.5 (12.1)%; residual AHI, 6.3 (5.2) vs. 5.1 (7.7); residual CT90, 1 (3)% vs. 14 (1)%. The device´s performance demonstrates a mean of 1.2 (1.5) vs. 1.3 (1.2) periods of inadequate pressure increases; absence of pressure increases in reaction to respiratory events, 4.1 (5.4) vs. 0.6 (0.7) times; periods of air leaks, 1.3 (3.8) vs. 13.9 (11.7); mean optimal pressure, 9.1 (1.4) vs. 9.0 (1.9) cm H(2)O. CONCLUSION: Titration with automatic CPAP could be as effective in patients with SAHS plus severe COPD as in patients with SAHS without COPD. However, the presence of more leakages must be taken into account.

Visual analogical well-being scale for sleep apnea patients: validity and responsiveness : a test for clinical practice.

INTRODUCTION: Health-related quality-of-life (HRQL) tests used in sleep apnea-hypopnea syndrome (SAHS) are time-consuming, complicating their application in clinical practice. The objective was to examine the validity and responsiveness of a simple visual analogical well-being scale (VAWS) for the clinical use. METHOD: The subjects proceed from a cohort of SAHS patients treated with CPAP for 12 weeks. We correlated the VAWS with other HRQL tests, related clinical and polysomnographic measures to concurrent and construct validities. Responsiveness by: (1) comparison of HRQL tests between before and after treatment and effect size. (2) Association of the change with treatment between VAWS with other HRQL tests and between VAWS with clinical parameters. RESULTS: At baseline, VAWS correlated with all HRQL tests but better with functional outcomes in sleep questionnaires (FOSQ) and European quality-of-life questionnaire (EuroQol) thermometer. VAWS and FOSQ correlated better with clinical variables than other HRQL tests. VAWS captures the magnitude change with treatment similarly to FOSQ but better than other HRQL tests. CONCLUSION: VAWS is a very simple test which measures HRQL in SAHS. It could be a useful tool in clinical practice, primarily for the responsiveness of treatment.

Non-synonymous polymorphism in the neuropeptide S precursor gene and sleep apnea.

BACKGROUND: Obstructive sleep apnea syndrome (OSAS) is a complex disease with a strong genetic basis. One of the primary molecular domains affected by OSAS is sympathetic activity. Neuropeptide S (NPS) plays an important role in the regulation of the sleep-wakefulness cycle, anxiety states, and daytime sleepiness. It is important to study neuropeptides related to sympathetic activity regulation and how their function could be modified by genetic variants affecting the expression of these molecules. OBJECTIVES: We investigated the association of the non-synonymous polymorphism rs4751440 in the NPS precursor gene with OSAS and certain variables related to OSAS (daytime sleepiness, body mass index (BMI), insulin resistance, and blood pressure). This polymorphism causes an amino acid substitution in exon 3 of the human NPS precursor gene. PATIENTS AND METHODS: We included 253 OSAS patients and 70 healthy subjects. Genotyping was done by polymerase chain reaction using specific flanking primers and agarose gel electrophoresis. Daytime sleepiness, BMI, plasma levels of high-density lipoprotein, glucose, total cholesterol, insulin, triglycerides, and the homeostasis model assessment index were also determined. RESULTS: A similar genotypic and allelic distribution was found in OSAS patients and controls. The risk of OSAS was not associated with the rs4751440 polymorphism. There was no significant interaction between daytime sleepiness or metabolic variables and the rs4751440 polymorphism. CONCLUSION: Genotypic and allelic frequency distribution of the rs4751440 polymorphism was similar in OSAS patients and controls. In this population-based study, we could not show a significant association between rs4751440 polymorphism and susceptibility to OSAS or certain phenotypes related to OSAS (daytime sleepiness, BMI, systolic blood pressure, and insulin resistance) with the exception of diastolic blood pressure.

Sleep breathing flow characteristics as a sign for the detection of wakefulness in patients with sleep apnea.

BACKGROUND: To improve the performance of simplified sleep studies, it is essential to properly estimate the sleep time. OBJECTIVES: Our aim is to estimate sleep efficiency on the basis of flow breathing signal characteristics. METHODS: Twenty subjects with sleep apnea-hypopnea syndrome diagnosed by polysomnography were studied. A characteristic pattern of flow signal defined our criteria for wakefulness and sleep. Sleep was analyzed in 2 different runs: (1) in the usual manner (neurological and respiratory variables), and (2) only the nasal cannula flow signal was displayed on the computer screen and the sleep and wakefulness periods were scored according to our criteria. At the end of the scoring process, all the signals were displayed on the screen to analyze the concordance. RESULTS: Three thousand and sixty-nine screens were analyzed. The polysomnography sleep efficiency measured was 80.8%. The estimated sleep efficiency measured by nasal prongs was 78.9%. The detection and concordance of wakefulness had a sensitivity of 58.7%, a specificity of 96.4%, a positive predictive value of 81.3% and a negative predictive value of 89.6%. CONCLUSIONS: Our criteria for sleep and wakefulness based on airflow waveform morphology are a helpful parameter for estimating sleep efficiency in a simplified sleep study.

Daytime sleepiness and polysomnography in obstructive sleep apnea patients.

BACKGROUND: Excessive daytime sleepiness (EDS) is the major complaint in subjects with obstructive sleep apnea syndrome (OSAS). However, EDS is not universally present in all patients with OSAS. The mechanisms explaining why some patients with OSAS complain of EDS whereas others do not are unknown. OBJECTIVE: To investigate polysomnographic determinants of excessive daytime sleepiness (EDS) in a large multicenter cohort of patients with obstructive sleep apnea (OSAS). METHODS: All consecutive patients with an apnea-hypopnea index greater than 5h(-1) who were evaluated between 2003 and 2005. EDS was assessed using the Epworth Sleepiness Scale (ESS), and patients were considered to have EDS if the ESS was >10. RESULTS: A total of 1649 patients with EDS ((mean [+/-SD] Epworth 15+/-3) and 1233 without EDS (Epworth 7+/-3) were studied. Patients with EDS were slightly younger than patients without EDS (51+/-12 vs 54+/-13 years, p<0.0001), had longer total sleep time (p<0.007), shorter sleep latency (p<0001), greater sleep efficiency (p<0.0001) and less NREM sleep in stages 1 and 2 (p<0.007) than those without EDS. Furthermore, patients with EDS had slightly higher AHI (p<0.005) and arousal index (p<0.001) and lower nadir oxygen saturation (p<0.01). CONCLUSIONS: Patients with OSAS and EDS are characterized by longer sleep duration and increased slow wave sleep compared to those without EDS. Although patients with EDS showed a mild worsening of respiratory disturbance and sleep fragmentation, these results suggest that sleep apnea and sleep disruption are not the primary determinants of EDS in all of these patients.

Alternative methods of titrating continuous positive airway pressure: a large multicenter study.

Standard practice for continuous positive airway pressure (CPAP) treatment in sleep apnea and hypopnea syndrome (SAHS) requires pressure titration during attended laboratory polysomnography. However, polysomnographic titration is expensive and time-consuming. The aim of this study was to ascertain, in a large sample of CPAP-naive patients, whether CPAP titration performed by an unattended domiciliary autoadjusted CPAP device or with a predicted formula was as effective as CPAP titration performed by full polysomnography. The main outcomes were the apnea-hypopnea index and the subjective daytime sleepiness. We included 360 patients with SAHS requiring CPAP treatment. Patients were randomly allocated into three groups: standard, autoadjusted, and predicted formula titration with domiciliary adjustment. The follow-up period was 12 weeks. With CPAP treatment, the improvement in subjective sleepiness and apnea-hypopnea index was very similar in the three groups. There were no differences in the objective compliance of CPAP treatment and in the dropout rate of the three groups at the end of the follow-up. Autoadjusted titration at home and predicted formula titration with domiciliary adjustment can replace standard titration. These procedures could lead to considerable savings in cost and to significant reductions in the waiting list.

The effect of the "inert" counteranions in the deprotonation of the dihydrogen complex trans-[FeH(eta 2-H2)(dppe)2]+: kinetic and theoretical studies.

Kinetic studies indicate that trans-[FeH(H2)(dppe)2]+ reacts with an excess of NEt3 to form cis-[FeH2(dppe)2] in a single kinetic step. The second-order rate constant is strongly affected by the presence of added salts, an acceleration being observed with BF4- and PF6- salts and a deceleration with BPh4-. Theoretical calculations indicate that the role of the accelerating anions consists of the formation of ion pairs that provide a more effective reaction pathway for deprotonation. However, for the ion pair with the bulky BPh4- anion, steric crowding in the proximities of the dihydrogen ligand hinders the approach of the base, and the reaction is decelerated.

Mechanisms of Reactions of Dihydrogen Complexes: Formation of trans-[RuH(H(2))(dppe)(2)](+) and Substitution of Coordinated Dihydrogen.

The reactions between cis-[RuH(2)(DPPE)(2)] and a number of acids in THF solution (DPPE = Ph(2)PCH(2)CH(2)PPh(2)) show biphasic kinetics, with initial formation of trans-[RuH(H(2))(DPPE)(2)](+) followed by slower substitution of coordinated dihydrogen by the anion of the acid. The formation of the dihydrogen complex is a second-order process that occurs with an inverse kinetic isotope effect and rate constants k(HX) strongly dependent on the nature of the acid. There is a linear correlation between the values of log k(HX) for cis-[RuH(2)(DPPE)(2)] and the related cis-[FeH(2)(PP(3))] [PP(3) = P(CH(2)CH(2)PPh(2))(3)] that leads to two parameters, S and R, that can be used as a measure of the selectivity and intrinsic reactivity of the dihydride toward acids. The possible contributions to the values of these parameters are discussed, especially the role of the isomerization of the starting complex and the basicity of the reacting species. The substitution of coordinated dihydrogen in trans-[RuH(H(2))(DPPE)(2)](+) occurs through a simple dissociative mechanism instead of the more complicated one previously proposed for substitutions in the analogous Fe complex; the mechanistic change is associated with the relative strength of the M-H(2) and M-P(chelate) bonds.