Influence of sampling interval on the evaluation of nocturnal blood pressure in subjects with and without obstructive sleep apnoea.

Blood pressure (BP) variability during sleep is high in obstructive sleep apnoea syndrome (OSAS). How BP sampling interval affects the estimate of mean nocturnal BP in OSAS and control subjects was investigated. Nine subjects with apnoea/hypopnoea index (AHI) <5 and 18 OSAS patients with AHI >30 underwent nocturnal polysomnography with beat-by-beat BP monitoring. Mean nocturnal BP was evaluated averaging: a) all systolic (Ps) and diastolic (Pd) BP values; b) Ps and Pd sampled every 5, 10, 15, 20, and 30 min. The sampling starting point was repeatedly shifted, and several mean BP estimates for each sampling interval were obtained. Differences (deltaPs and deltaPd) between means obtained by sampling BP and by averaging all BP values were calculated. In both groups deltaPs and deltaPd scatter increased as sampling interval increased; their variance was always higher in OSAS subjects (p<0.001). Over 95% of deltaPs and deltaPd were <5% of the beat-by-beat mean values at all sampling intervals in controls, but this occurred only at sampling intervals < or =10 min in OSAS subjects. To conclude, for each blood pressure sampling time, a larger number of inaccurate nocturnal mean blood pressure estimates are obtained in obstructive sleep apnoea syndrome than in control subjects. Obstructive sleep apnoea syndrome subjects require more frequent blood pressure measurements to obtain a similar accuracy in nocturnal blood pressure evaluation.     

Comparison of autonomic withdrawal in men with obstructive sleep apnea syndrome, systemic hypertension, and neither condition

Obstructive sleep apnea syndrome is characterized by obesity, nocturnal breathing abnormalities, arterial hypertension, and an increased number of cardiovascular events. Sympathetic activity is increased during nocturnal apneic episodes, which may mediate the cardiovascular complications of sleep apnea. We studied 15 male subjects with obstructive sleep apnea syndrome and associated hypertension, 54 subjects with mild to moderate essential hypertension, and 25 healthy normotensive men. Cardiovascular autonomic control was assessed using frequency domain measures of heart rate variability (HRV) during a controlled breathing test and during orthostatic maneuver. Compared with normotensive and hypertensive groups, total power and low- and high-frequency components of HRV during controlled breathing were significantly (analysis of variance, p<0.0001) lower in the obstructive sleep apnea syndrome. During the orthostatic maneuver, the change in total power of HRV was different between the 3 groups (analysis of variance, p = 0.004). The total power of HRV tended to increase in the normotensive (4.11+/-12.29 ms2) and in hypertensive (2.31+/-12.65 ms2) groups, but decreased (1.13+/-1.23 ms2) in the hypertensive group with obstructive sleep apnea syndrome. According to multivariate regression analysis, age and sleep apnea were the major independent determinants of HRV. This study found that an abnormal response to autonomic nervous tests characterizes hypertension in overweight subjects with obstructive sleep apnea syndrome. This could be due to autonomic withdrawal or supersaturation of the end-organ receptors by excessive and prolonged sympathetic stimulation. Our results also show the reduced response of orthostatic maneuver and controlled breathing in the hypertensive group compared with the normotensive group.     

Sleep and daytime sleepiness in upper airway resistance syndrome compared to obstructive sleep apnoea syndrome.

This study has investigated differences in the nocturnal sleep and daytime sleepiness among patients with obstructive sleep apnoea syndrome (OSAS), upper airway resistance (UARS), sleep hypopnoea syndrome, and normal control subjects, using sleep scoring and spectral activity analysis of the electroencephalogram (EEG). Twelve nonobese males with UARS aged 30-60 yrs were recruited. These subjects were strictly matched for age and body mass index with twelve OSAS patients, 12 sleep hypopnoea syndrome patients, and 12 normal controls, all male. Daytime sleepiness was evaluated using the Epworth Sleepiness Scale (ESS) and the Multiple Sleep Latency Test (MSLT). The macrostructure of sleep was determined using international criteria and spectral analysis of the sleep EEG was obtained from a central lead. The sleep macrostructure of OSAS and UARS patients was significantly different from that of controls. These patients were also sleepier during the daytime than controls. Complaints of tiredness and daytime sleepiness, ESS and MSLT scores were similar in the different patient groups. Mild dysmorphia was present in all three patient groups. However, nocturnal sleep was significantly different among the different groups. OSAS patients had significantly more awake time during sleep than the UARS patients. The spectral activity of the total sleep time of the patient groups also differed significantly from that of controls. When the sleep spectral activity of UARS and OSAS patients were compared, OSAS patients had less slow wave sleep activity than UARS patients. UARS patients had a significantly higher absolute power in the 7-9 Hz bandwidth than OSAS patients. The absolute delta power over the different sleep cycles was also different between controls and patients, and between UARS and OSAS patients. There are clear differences in the macrostructure and spectral activity of sleep between upper airway resistance and obstructive sleep apnoea syndrome patients, demonstrated by differences in the cortical activity recorded in the central lead during sleep. Despite these nocturnal sleep differences, the tests of subjective daytime sleepiness are not significantly different.     

Impaired glucose-insulin metabolism in males with obstructive sleep apnoea syndrome.

The aim of this cross-sectional study was to evaluate the frequency of type-2 diabetes and impaired glucose tolerance (IGT) in a large clinic-based male population presenting various degrees of obstructive sleep apnoea syndrome (OSAS) and to analyse the relationship between OSAS and glucose-insulin metabolism. Male patients (n=595) with suspected OSAS underwent both nocturnal polysomnography and a 2-h oral glucose-tolerance test with measurements of fasting and postload blood glucose and plasma insulin. Insulin sensitivity was evaluated by the ratio of fasting glucose to fasting insulin. OSAS was diagnosed in 494 patients, while 101 patients were nonapnoeic snorers. Type-2 diabetes was present in 30.1% of OSAS patients and 13.9% of nonapnoeic snorers. IGT was diagnosed in 20.0% of OSAS patients and 13.9% of nonapnoeic snorers. Fasting and postload blood glucose increased with severity of sleep apnoea. Insulin sensitivity decreased with increasing severity of sleep apnoea. In addition to body mass index and age, the apnoea/hypopnoea index independently influenced postload blood glucose and insulin sensitivity. The authors conclude that in a clinic-based sample of patients, obstructive sleep apnoea syndrome is associated with a high frequency of type-2 diabetes and impaired glucose tolerance. The relationship between sleep-disordered breathing and impaired glucose-insulin metabolism is independent of obesity and age.     

The role of mean inspiratory effort on daytime sleepiness.

This study has investigated the role of average maximum inspiratory effort in excessive daytime sleepiness in patients with obstructive sleep apnoea syndrome (OSAS) and upper airway resistance syndrome (UARS). Fifteen patients diagnosed with UARS and 32 patients with OSAS, with >5.5 h total sleep time (TST) during 8 h of nocturnal polygraphic recordings, were included in the study. Demographical data, polysomnographical data and data about daytime sleepiness, including Epworth sleepiness scale (ESS) and multiple sleep latency test (MSLT), were evaluated. In order to compute the average maximum inspiratory effort from oesophageal pressure (Poes) measurements, maximum Poes was obtained from 20 representative obstructive respiratory events (obstructive apnoeas, hypopnoeas or flow limitations) for each sleep stage in both supine and side positions. From Poes measurements during sleep, the increase in Poes (deltaPoes) during respiratory events was also calculated. The average maximum Poes, deltaPoes, respiratory disturbance index (RDI) and arousal index were significantly correlated with ESS in OSAS patients. In patients with UARS, the only significant correlation was obtained between average maximum Poes and ESS. The MSLT score did not show any significant correlation with arousal index, number of stage variations, RDI, average Poes, deltaPoes, minimum oxygen saturation (Sa,O2) and percentage of TST with an Sa,O2 <90% in both UARS and OSAS patients. The results of multiple regression analysis showed that average maximum Poes correlates best with the variance in ESS for OSAS patients. In conclusion, the data from this study indicate the possible important role of average inspiratory effort in determining subjective sleepiness in both obstructive sleep apnoea syndrome and upper airway resistance syndrome patients.     

Role of nocturnal hypoxaemia in the genesis of systemic hypertension

Two groups of patients with nocturnal arterial oxygen desaturation were compared. The degree of nocturnal oxygen desaturation, as reflected by the percentage of total sleep time spent with an oxygen saturation less than 90 and 80%, was similar in patients with the obstructive sleep apnoea syndrome (OSAS) and in those with nocturnal hypoventilation (NH) secondary to restrictive chest wall disease. Systemic hypertension was present in 16 of the 24 OSAS patients but in only 6 of the 24 with NH (p less than 0.005). Multiple regression analysis demonstrated that this difference remained significant even after adjustment for age, sex, weight and history of smoking. It is likely that factors other than nocturnal hypoxaemia are important in the aetiology of systemic hypertension in patients with sleep-related breathing disorders.     

Cardiovascular risk factors in patients with obstructive sleep apnoea syndrome.

Cardiovascular disorders are common in patients with obstructive sleep apnoea syndrome (OSAS) but there is debate as to whether OSAS is an independent risk factor for their development, since OSAS may be associated with other disorders and risk factors that predispose to cardiovascular disease. In an effort to quantify the risk of OSAS patients for cardiovascular disease arising from these other factors, the authors assessed the future risk for cardiovascular disease among a group of 114 consecutive patients with established OSAS prior to nasal continuous positive airway pressure therapy, using an established method of risk prediction employed in the Framingham studies. Patients were 100 males, aged (mean+/-SD) 52+/-9.0 yrs, and 14 females, aged 51+/-10.4 yrs, with an apnoea/hypopnoea index of 45+/-22 x h(-1). Based on either a prior diagnosis, or a mean of three resting blood pressure recordings >140 mmHg systolic and/or 90 diastolic, 68% of patients were hypertensive. Only 18% were current smokers, while 16% had either diabetes mellitus or impaired glucose tolerance, and 63% had elevated fasting cholesterol and/or triglyceride levels. The estimated 10-yr risk of a coronary heart disease (CHD) event in males was (mean+/-SEM) 13.9+/-0.9%, 95% confidence interval (95% CI) 12.1-16.0, and for a stroke was 12.3+/-1.4%; 95% CI 9.4-15.1, with a combined 10 yr risk for stroke and CHD events of 32.9+/-2.7%; 95% CI 27.8-38.5 in males aged >53 yrs. These findings indicate that obstructive sleep apnoea syndrome patients are at high risk of future cardiovascular disease from factors other than obstructive sleep apnoea syndrome, and may help explain the difficulties in identifying a potential independent risk from obstructive sleep apnoea syndrome.     

Nasal obstruction as a risk factor for sleep apnoea syndrome.

Nasal obstruction has frequently been mentioned as a possible risk factor in obstructive sleep apnoea syndrome (OSAS). Over a 2-yr period, 541 unselected consecutive snorers referred for suspected breathing disorders during sleep were included to undergo posterior rhinomanometry. In addition cephalometric landmarks and body mass index (BMI) were obtained. Polysomnography was used to determine the number of abnormal respiratory events that occurred during sleep. OSAS was defined as 15 episodes, or more, of apnoea or hypopnoea per hour of sleep (AHI). Of the 541 consecutive snorers 528 underwent nasal resistance measurement by posterior rhinomanometry (failure rate: 2.4%). Patients with OSAS (259 patients) had higher nasal resistance than patients without OSAS (2.6+/-1.6 hPa x L x s(-1) versus 2.2+/-1.0 hPa x L x s(-1), respectively, p<0.005). A stepwise multiple regression analysis showed that BMI, male sex, nasal resistance, and cephalometric parameters were contributing factors to the AHI. The r2-value of the multiple regression analysis was 0.183. Nasal resistance contributed 2.3% of the variance (p<0.0001), whereas mandibular plane-hyoid distance, BMI, male sex and age contributed 6.2%, 4.6%, 3% and 1.3% of the variance, respectively. To conclude, daytime nasal obstruction is an independent risk factor for OSAS.     

Respiratory impedance response to continuous negative airway pressure in awake controls and OSAS.

The aim of the study was to determine whether the response of respiratory impedance (Zrs) to decreasing levels of continuous negative airway pressure (CNAP) during wakefulness, differs in controls and subjects with obstructive sleep apnoea syndrome (OSAS). Zrs was measured by the forced oscillation technique (4-32 Hz) in 15 controls and 21 patients with OSAS (apnoea/hypopnoea index >20 per sleep hour) with normal lung function, in the basal state and with application of decreasing CNAP of -5, -10, and -15 hPa. Respiratory resistance was extrapolated to 0 Hz (R0) and estimated at 16 Hz (R16) by linear regression analysis of respiratory resistive impedance versus frequency. Respiratory elastance (Ers) and inertance (Irs) were estimated by multilinear regression analysis of respiratory reactance versus frequency, and resonance frequency (RF) was determined as RF=(1/2pi)(Ers/Irs)0.5. In both groups, R0, R16, Ers and RF significantly increased as the CNAP level decreased (p <0.0001 for all). R0, Ers, and RF increased significantly more in OSAS than in controls (p < 0.01, 0.001, and 0.0001, respectively), independently of the severity of obesity. Receiver operator characteristic curves showed that the parameter which best detected OSAS was RF, with a sensitivity of 81% and 93% specificity for the 13.6 Hz cut-off point. The results of the present study suggest that the response of respiratory impedance to decreasing continuous negative airway pressure levels, might allow detection of obstructive sleep apnoea syndrome in subjects with normal lung function.     

Sleep apnoea as an independent risk factor for cardiovascular disease: current evidence, basic mechanisms and research priorities.

Considerable evidence is available in support of an independent association between obstructive sleep apnoea syndrome (OSAS) and cardiovascular disease, which is particularly strong for systemic arterial hypertension and growing for ischaemic heart disease, stroke, heart failure, atrial fibrillation and cardiac sudden death. The pathogenesis of cardiovascular disease in OSAS is not completely understood but likely to be multifactorial, involving a diverse range of mechanisms including sympathetic nervous system overactivity, selective activation of inflammatory molecular pathways, endothelial dysfunction, abnormal coagulation and metabolic dysregulation, the latter particularly involving insulin resistance and disordered lipid metabolism. The present report, which arose out of a European Union Cooperation in the field of Scientific and Technical Research (COST) action on OSAS (COST B26), reviews the current evidence for an independent association and proposes research priorities to identify the underlying mechanisms involved, with a view to identifying novel therapeutic strategies. Large-scale collaborative studies of carefully defined patient populations with obstructive sleep apnoea syndrome, adequately controlled for potential confounders, are needed. Such studies carry the prospect of evaluating potential interactions between different basic mechanisms operating in obstructive sleep apnoea syndrome and cardiovascular disease, and interactions with other related disorders, such as obesity, diabetes and dyslipidaemia. Furthermore, translational studies involving cell culture and animal models linked to studies of obstructive sleep apnoea syndrome patients are necessary to integrate basic mechanisms with the clinical disorder.     

Daytime sleepiness and polysomnographic variables in sleep apnoea patients.

Excessive daytime sleepiness (EDS) is not invariably present in patients with obstructive sleep apnoea syndrome (OSAS). The aim of the present study was to investigate polysomnographic determinants of EDS in patients with OSAS. EDS was assessed using the Epworth Sleepiness Scale (ESS) and the multiple sleep latency test (MSLT). Patients showed EDS whenever the ESS score was >10 and the MSLT score <5 min. Absence of EDS was defined as having an ESS score of <10 and an MSLT score of >10 min. In total, 23 male patients with EDS (mean+/-sd ESS and MSLT score 17+/-3 and 4+/-1 min, respectively) and 17 without EDS (ESS and MSLT score 5+/-2 and 16+/-3 min, respectively), were studied. Both groups exhibited a similar apnoea/hypopnoea index (62+/-18 versus 60+/-20 events.h(-1)). Patients with EDS exhibited shorter sleep latency (11+/-16 versus 18+/-18 min) and greater sleep efficiency (90+/-7 versus 82+/-13%) than those without EDS. Patients with EDS showed lower oxygenation (lowest arterial oxygen saturation 69+/-12 versus 79+/-8%; mean arterial oxygen saturation 87+/-6 versus 90+/-5%). Sleep stage distribution and arousal index did not differ between the groups. Patients with obstructive sleep apnoea syndrome and excessive daytime sleepiness are characterised by shorter sleep latency, increased sleep efficiency and worse nocturnal oxygenation than those without excessive daytime sleepiness. Nocturnal hypoxaemia can be a major determinant of excessive daytime sleepiness in patients with obstructive sleep apnoea syndrome.     

睡眠呼吸暂停综合征对高血压病患者血压昼夜节律及心率变异性的影响

目的探讨阻塞性睡眠呼吸暂停（OSAS）对高血压病患者血压昼夜节律及心率变异性（HRV）的影响。方法入选62例高血压病患者,根据是否合并OSAS分为：单纯组（无合并OSAS）及合并组（合并OS-AS）,另选择同期30名健康人群作为对照组。比较三组患者呼吸紊乱指数（AHI）、夜间平均血氧水平、昼间及夜间血压水平、非杓型血压的比例、HRV频域指标（SDNN、PNN50）与时域指标（低频谱、高频谱）的差异。结果合并组与单纯组、对照患者比较夜间平均血氧水平、AHI、HRV频域指标（SDNN、PNN50）与时域指标（低频谱、高频谱）差异均有显著统计学意义（P均〈0.01）;合并组非杓型血压的比例显著高于其他两组,差异有显著统计学意义（P〈0.01）。结论 OSAS增加高血压病患者血压昼夜节律异常及心率变异性。     

The cost-effectiveness of nCPAP treatment in patients with moderate-to-severe obstructive sleep apnoea.

The demand for diagnostic and therapeutic services for obstructive sleep apnoea syndrome (OSAS) showed marked growth during the 1990s. This paper analyses the long-term cost-effectiveness of nasal continuous positive airway pressure (nCPAP) treatment in comparison to conventional null treatment. A Markov model was used to represent the natural history of OSAS based upon published evidence. Utility values came from a survey of OSAS patients. Data on health costs were collected from hospitals in the Basque Country, Spain. The incremental cost-effectiveness ratio of nCPAP treatment is <6,000 Euros per quality-adjusted life year. On disaggregated analysis, nCPAP treatment accounts for 86% of incremental costs; 84% of incremental effectiveness is attributable to improved quality of life. Treatment of obstructive sleep apnoea syndrome with nasal continuous positive airway pressure has a cost-effectiveness that is in line with that of other commonly funded treatments such as antihypertensive drugs. The key clinical benefit of nasal continuous positive airway pressure treatment is improvement in the quality of life of patients with obstructive sleep apnoea syndrome. This benefit is also precisely the one for which the evidence base is strongest. The remaining uncertainties concerning the impact of nasal continuous positive airway pressure on long-term mortality have only a relatively small impact on the economics of treatment.     

阻塞性睡眠呼吸暂停综合征心率变异性的变化及其意义

目的 :研究阻塞性睡眠呼吸暂停综合征 （OSAS）患者心率变异性 （HRV ）的变化。方法 :经夜间多导睡眠图（PSG） 7h监测及动态心电图检查 ,选取重度 OSAS患者及正常受试者各 2 0例 ,采用时域法和频域法分析 HRV。结果 :OSAS组与对照组比较时域指标 SDANN ,SDNN ,r MSSD显著增高 ,SDNN- index则显著降低 ,频域指标VL F,L F,HF,L Fnrom,HFnorm及 L F/HF均较对照组显著增高。结论 :OSAS患者交感神经及副交感神经活动均增强 ,交感神经活动增强占优势     

Nocturnal ischemic events in patients with obstructive sleep apnea syndrome and ischemic heart disease: effects of continuous positive air pressure treatment

OBJECTIVES: To investigate the occurrence of nocturnal ischemic events in patients with obstructive sleep apnea syndrome (OSAS) and ischemic heart disease (IHD). BACKGROUND: Although previous reports documented nocturnal cardiac ischemic events among OSAS patients, the exact association between obstructive apneas and ischemia is not yet clear. It is also not known what differentiates between patients showing nocturnal ischemia and those that do not. METHODS: Fifty-one sleep apnea patients (age 61.3+/-8.3) with IHD participated in the study (after withdrawal of beta-adrenergic blocking agents and anti-anginotic treatment). All patients underwent whole-night polysomnography including ambulatory blood pressure recordings (30 min interval) and continuous Holter monitoring during sleep. A control group of 17 OSAS patients free from IHD were also similarly studied. Fifteen of the 51 patients were also recorded under continuous positive airway pressure (CPAP). RESULTS: Nocturnal ST segment depression occurred in 10 patients (a total of 15 events, 182 min), of whom six also had morning ischemia (06-08 am). Five additional patients had only morning ischemia. No ischemic events occurred in the control group. Age, sleep efficiency, oxygen desaturation, IHD severity and nocturnal-double product (DP) values were the main variables that significantly differentiated between patients who had ischemic events during sleep and those who did not. Nocturnal ischemia predominantly occurred during the rebreathing phase of the obstructive apneas, and it is characterized by increased heart rate (HR) and DP values. Treatment with continuous positive airway pressure significantly ameliorated the nocturnal ST depression time from 78 min to 33 min (p<0.001) as well as the maximal DP values (14,137+/-2,827 vs. 12,083+/-2,933, p<0.001). CONCLUSIONS: Exacerbation of ischemic events during sleep in OSAS may be explained by the combination of increased myocardial oxygen consumption as indicated by increased DP values and decreased oxygen supply due to oxygen desaturation with peak hemodynamic changes during the rebreathing phase of the obstructive apnea. Treatment with CPAP ameliorated the nocturnal ischemia.     

Optimal continuous positive airway pressure in patients with obstructive sleep apnoea: role of craniofacial structure

Although nasal continuous positive airway pressure (CPAP) is effective in improving nocturnal obstructive apnoea, daytime sleepiness and well-being in patients with obstructive sleep apnoea syndrome (OSAS), not all patients tolerate this treatment. Since optimal CPAP titration is essential to maintain compliance, it is important to elucidate the factors that help to determine the optimal pressure. However, the determinants of the optimal CPAP level are controversial. The subjects comprised 27 Japanese male patients with OSAS who underwent standard polysomnography (PSG), pulmonary function tests, arterial blood gas analysis, cephalometry and CPAP titration. Twenty normal controls also underwent cephalometric analysis. The apnoea-hypopnoea index (AHI), mean oxygen saturation (mean SaO2) and the lowest SaO2 during sleep were found to be 54.7+/-22.6, 89.0+/-5.6%, and 69.7+/-9.0%, respectively by PSG. The mean optimal CPAP was 9.6+/-1.8 cmH2O. The cephalometric angles (SNA, SNB and NSBa) were similar to those found in the control subjects. but MP-H, and PNS-P were significantly longer than those in the control subjects as shown by cephalometry. The optimal CPAP was correlated with the mean SaO2 (P<0.0001), neck circumference (P<0.05) and three cephalometric variables (NSBa: P<0.01, MP-H: P<0.05, PNS-P: P<0.05). Multiple, step-wise, regression analysis showed that the mean SaO2 and NSBa were independent variables that best predicted the optimal CPAP. These variables accounted for 57.5% of the total variance (R2=0.575, P<0.001). Optimal CPAP was closely correlated with oxygen desaturation during sleep. However, the craniofacial structure had additional effects such as an independent factor in determining the optimal CPAP level.     

Quantification of sleep disordered breathing by computerized analysis of oximetry, heart rate and snoring

Intermittent snoring and cyclic oscillations of heart rate and oxyhaemoglobin saturation (Sao2) are characteristic features of the obstructive sleep apnoea syndrome (OSAS). Thus, overnight recordings of laryngeal sounds and heart rate by a portable device (MESAM) and of Sao2 by oximetry are applicable to screen outpatients for the presence of OSAS. Computerized analysis for time intervals of constant heart rate and intervals between snoring sounds is used by MESAM to quantify respiratory disturbances during sleep. Rapid increases in Sao2 during the postapnoeic hyperventilation period together with the number of desaturations are used by a new software for quantitative analysis of oximetry. To elucidate reliability of results from automatically scored MESAM and oximetry recordings, we compared the four computer calculated respiratory disturbance indices from heart rate (RDIH), snoring (RDIS), resaturations (RDIR) and desaturations (RDID) with the apnoea plus hypopnoea index (AHI) from simultaneously performed polysomnography. The study population consisted of 53 snorers with an AHI of 19.0 +/- 2.6 (median +/- SEM; range 0.7-87.8). Whereas both RDI's from MESAM correlated rather weakly with the AHI from polysomnography (RDIH: r = 0.32, p less than 0.05; RDIS: r = 0.33, p less than 0.05), this correlation was much better for the RDI's from oximetry (RDIR: r = 0.951, RDID: r = 0.93; p much less than 0.0001). Accepting a plus/minus 30 percent difference from the AHI, the RDIR classified 77% of patients correctly, the RDID 62%, the RDIS 32% and the RDIH 23%. In conclusion, results from computerized analysis of oximetry for desaturations and rapid resaturations correlate more closely with polysomnography than those from automatic scoring of MESAM recordings.     

Overdrive atrial pacing does not improve obstructive sleep apnoea syndrome.

The aim of this study was to assess the ability of overdrive atrial pacing to reduce sleep apnoea severity. A total of 17 unselected patients (12 males; mean+/-SD age 71+/-10 yrs; body mass index 27+/-3 kg x m(-2)) who had received permanent atrial-synchronous ventricular pacemakers for symptomatic bradyarrhythmias and not known to have central or obstructive sleep apnoea syndrome (OSAS) were studied. Using a crossover study design, patients were or were not in pacing mode with atrial overdrive (15 beats x min(-1) faster than mean baseline nocturnal cardiac frequency) for 1 month. Patients were paced only during sleep periods, identified by a specific algorithm included in the pacemaker. Patients underwent three overnight polysomnographic evaluations 1 month apart. The first was performed for baseline evaluation. The patients were then randomly assigned to either 1 night in spontaneous rhythm or to 1 night in pacing mode with atrial overdrive. Two patients refused to continue the study after the first polysomnographic evaluation. OSAS was highly prevalent in this population: 10 of the 15 (67%) patients exhibited an apnoea-hypopnoea index of >30 events x h(-1). The nocturnal spontaneous rhythm was 59+/-7 beats x min(-1) at baseline, compared to 75+/-10 beats x min(-1) with atrial overdrive pacing. The apnoea-hypopnoea index was 46+/-29 events x h(-1) in spontaneous rhythm, compared to 50+/-24 events x h(-1) with atrial overdrive pacing. Overdrive pacing changed none of the respiratory indices, or sleep fragmentation or sleep structure parameters. In conclusion, atrial overdrive pacing has no significant effect on obstructive sleep apnoea.     

beta3-Adrenergic receptor Trp64Arg polymorphism and increased body mass index in sleep apnoea.

Obesity is an important risk factor for obstructive sleep apnoea syndrome (OSAS), insulin resistance and cardiovascular disease. The substitution of tryptophan 64 with arginine (Trp64Arg) polymorphism (Arg variant) of the beta(3)-adrenergic receptor (ADRB3) has been associated with obesity. In this study, the prevalence of the Trp64Arg ADRB3 polymorphism in a large group of patients with OSAS and its association with body mass index (BMI), insulin resistance and hypertension were evaluated. ADRB3 genotype was determined in 387 patients with OSAS and 137 healthy subjects recruited from three Spanish tertiary hospitals. The distributions of the ADRB3 genotypes were similar in OSAS and controls, and, in a multivariate model, the risk of OSAS was not associated with the presence of the Arg variant of the ADRB3 gene. However, BMI was higher in those patients with OSAS who carried this genetic variant than in those with the Trp variant. Furthermore, a linear trend for higher BMI was found in those with the Arg variant (56, 75 and 100% for Trp/Trp, Trp/Arg and Arg/Arg, respectively). Insulin resistance, blood pressures and serum levels of lipids and glucose were not associated with the presence of the Arg variant of the ADRB3 gene. The presence of the arginine 64 allele of the beta(3)-adrenergic receptor gene does not increase the risk of obstructive sleep apnoea syndrome, but is associated with the development of obesity in those patients who suffer obstructive sleep apnoea syndrome.     

阻塞性睡眠呼吸暂停综合征患者的心率变异性研究

目的研究阻塞性睡眠呼吸暂停综合征(OSAS)患者心率变异性(HRV)昼夜变化,探讨利用HRV指标筛选OSAS的效果。方法对80例研究对象测量体重、身高、血压、计算体重指数(BMI)、询问有无糖尿病史、心肌梗死病史。对可疑OSAS者用多导睡眠图(PSG)行整夜(至少7h)睡眠检测,同步记录脑电图、眼电图、下颌肌电图、口鼻气流、胸腹呼吸、鼾声、血氧饱和度(SaO2)、血压及脉搏情况。所有研究对象同步进行动态心电图及24h HRV检查。以研究OSAS患者HRV昼夜变化。行PSG检测的50例患者,通过PSG、HRV分析各自的诊断标准在互相不沟通的情况下做出OSAS阳性、阴性诊断。以PSG检测为标准,评介HRV分析筛选OSAS的效果。结果△[昼/夜]OSAS阳性组与OSAS阴性组HRV时域指标的平均夜间SDNN、△[昼/夜]SDNN、夜间RMSSD、△[昼/夜]RMSSD、夜间PNN50、△[昼/夜]PNN50有显著性差异;频域指标的平均夜间ULF、夜间VLF、△[昼/夜]VLF、夜间LF、△[昼/夜]LF、夜间HF、△[昼/夜]HF有显著性差异。平均心率变异四项指标评分,≥1分敏感性为75%,特异性为70%,符合率为74%;≥2分敏感性为70%,特异性为80%,符合率为72%;≥3分敏感性为37.5%,特异性为90%,符合率为48%。结论OSAS患者夜间HRV增强;应HRV分析筛选OSAS有其临床实用价值。