Non-linear behaviour of respiratory movement in obstructive sleep apnoea syndrome

In this study we investigated the non-linear properties of respiratory movement in patients with obstructive sleep apnoea syndrome (OSAS) during sleep without and with nasal continuous positive airway pressure (nCPAP). To calculate the correlation dimension (D2) in respiratory movement we applied an algorithm proposed by Grassberger and Procaccia. Non-linearity in respiratory movement was tested by comparing D2 for the original data with that for surrogate data. Respiratory movement was recorded from 10 patients with OSAS. D2 during both wakefulness with eyes closed and during sleep with nCPAP at 8 cm H2O could be computed in all subjects (2.50 +/- 0.69 and 1.68 +/- 0.17, respectively). On the other hand, D2 during sleep with apnoea could not be computed in patients with severe OSAS. These results indicate the abnormal properties of respiratory movement during apnoeic sleep in severe OSAS. Moreover, respiratory movement with nCPAP was shown to be non-linear deterministic behaviour in respiratory movement during sleep. Analysis of D2 for respiratory movement may be useful in adjusting (titrating) nCPAP and classifying severity in OSAS.     

Refractory chronic headache associated with obstructive sleep apnoea syndrome

The aim was to investigate the comorbidity of chronic refractory headache with obstructive sleep apnoea syndrome (OSAs). Seventy-two patients (51 women and 21 men) with chronic and refractory headaches, whose headache occurred during sleep or whose sleep was accompanied by snoring, were submitted to polysomnography. Patients diagnosed with OSAs (respiratory disturbance index > 10) began continuous positive airway pressure (C-PAP) treatment and were followed up for ≥ 6 months. Twenty-one cases of OSAs were identified (29.2% of the total investigated, 13.7% of the women and 66.6% of the men). Headaches were classified into several headache disorders, medication overuse headache and cluster headache being the most prevalent (nine and six of the 21 cases, respectively). In one case (1.4% of the total sample, 4.7% of all the men), the criteria for hypnic headache were fulfilled. Multivariate regression analysis revealed that age, male gender and body mass index were associated with OSAs. C-PAP treatment improved both sleep apnoea and headache in only a third of the cases. Patients suffering from chronic refractory headache associated with sleep or snoring, in particular those who are also middle-aged, overweight men, should be considered for polysomnography. C-PAP treatment alone does not seem to improve headache, but further investigation is needed.     

Reduced cardiac sympathetic autonomic tone after long-term nasal continuous positive airway pressure in obstructive sleep apnoea syndrome

The increased sympathetic activation that occurs in obstructive sleep apnoea (OSA) may play an important role in associated morbidity. We investigated the effect of long-term (3 month) nasal continuous positive airway pressure (CPAP) on the autonomic nervous system assessed by heart rate variability (HRV). Fourteen patients (12 men), mean age 61·4 ± 8·1 years, with OSA underwent continuous synchronized electrocardiographic and polysomnographic monitoring. The apnoea/hypopnoea index (AHI) decreased from 50·6 ± 13·7 to 2·2 ± 2·5 events h^?1 after CPAP. HRV analysis showed significant decreases in low frequency (LF; from 7·12 ± 1·06 to 6·22 ± 1·18 ln ms² Hz^?1; P<0·001), high frequency (HF; from 5·91 ± 0·87 to 5·62 ± 0·92 ln ms² Hz^?1; P<0·05) and LF/HF (from 1·21 ± 0·12 to 1·11 ± 0·15 ln ms² Hz^?1; P<0·001) when the patients were asleep. The decrease in LF/HF was prolonged into the daytime (from 1·33 ± 0·22 to 1·24 ± 0·21 ln ms² Hz^?1; P<0·001). Treatment of OSA by CPAP significantly reduced the parameters of cardiac sympathetic tone, a favourable effect.     

Lung aeration during sleep in patients with obstructive sleep apnoea

Background: Previous studies have indicated that patients with obstructive sleep apnoea (OSA) have altered ventilation and lung volumes awake and the results suggest that this may be a determinant of severity of desaturations during sleep. However, little is known about regional lung aeration during sleep in patients with OSA. Methods: Twelve patients with OSA were included in the study. Computed tomography was used to study regional lung aeration during wakefulness and sleep. Lung aeration was calculated in ml gas/g lung tissue in four different regions of interest (ROI_1–4), along the border of the lung from ventral to dorsal. Results: Lung aeration in the dorsal (dependent) lung region (ROI₄) was lower during sleep compared to wakefulness 0·78 ± 0·19 versus 0·88 ± 0·19 (mean ± SD) ml gas/g lung tissue (P = 0·005). Associations were found between awake expiratory reserve volume and change in lung aeration from wakefulness to sleep in ROI₄ (r = ?0·69; P = 0·012). In addition, the change in lung aeration in the dorsal region correlated to sleep time (r = 0·69; P = 0·014) but not to time in supine position. The difference in lung aeration between inspiration and expiration (i.e. ventilation), was larger in the ventral lung region when expressed as ml gas per g lung tissue. In two patients it was noted that, during on‐going obstructive apnoea, lung aeration tended to be increased rather than decreased. Conclusions: Aeration in the dorsal lung region is reduced during sleep in patients with OSA. The decrease is related to lung volume awake and to sleep time.     

Simultaneous midline laser glossectomy with palatopharyngeal surgery for obstructive sleep apnoea syndrome

We investigate the outcome of performing tongue base reduction surgery and palatopharyngeal surgery in a single stage to determine whether the same-stage midline laser glossectomy (MLG) with extended uvulopalatal flap (EUPF) for obstructive sleep apnoea syndrome (OSAS) is a safe and effective procedure. Six male patients with a history of severe OSAS were recruited into the retrospective study. They were the first patients to undergo the MLG with EUPF procedure. Patients were identified to have retropalatal and hypopharyngeal sites of obstruction on the basis of fiberoptic endoscopy with Muller's manoeuvre and three-dimensional computerised tomography. No significant adverse events occurred. The follow-up polysomnography (6-month follow-up) revealed that the mean respiratory disturbance index from 50.7 to 11.6, snoring index from 230.9 to 137.3 and the minimal oxygen saturation from 76.3 to 88.8. This study confirms that the same-stage MLG with EUPF for OSAS is a safe and effective procedure.     

Inspiratory flow limitation in obstructive sleep apnoea patients

Patients suffering from the obstructive sleep apnoea syndrome (OSAS) experience nocturnal episodes of upper airway obstruction resulting in recurrent oxygen desaturations and arousals. Methods to quantify the nocturnal obstructive events are of interest for characterizing this prevalent sleep disorder. In a study published in this issue of Clinical Science, Bloch and co-workers propose the computation of a new index for objectively quantifying the degree of flow limitation in patients with OSAS. The results obtained in a bench test and in a pilot study in patients suggest that the flow limitation index proposed may help to better characterize the disturbed breathing events undergone by patients with OSAS.     

Changes of serum brain-derived neurotrophic factor in children with obstructive sleep apnoea-hypopnoea syndrome following adenotonsillectomy

Children with obstructive sleep apnoea syndrome (OSAS) have substantial cognitive functional morbidity. Brain-derived neurotrophic factor (BDNF) is a key mediator of memory and cognition, but its regulation in OSAS is unknown. Circulating BDNF, transforming growth factor-β(1) and 5-hydroxytryptamine levels, cognitive ability and overnight polysomnography were evaluated in 44 children with newly-diagnosed OSAS and in 26 healthy children. All parameters were monitored pre-operatively and at 3, 6 and 12 months after adenotonsillectomy. Pre-operative cognitive ability and sleep parameters were significantly poorer in children with OSAS compared with controls, but BDNF levels were similar. At 3 months post-operation, serum BDNF concentrations decreased, but cognitive ability and sleep parameters remained deficient. At 6 months post-operation, serum BDNF levels, sleep parameters and cognitive ability had improved and, by 12 months, there were no differences between the two groups. It is concluded that adenotonsillectomy can rapidly normalize sleep parameters and improve the cognitive ability of children with OSAS, by regulating the circulating level of BDNF.     

Disorders of glucose metabolism and insulin resistance in patients with obstructive sleep apnoea syndrome

Objective: Insulin resistance (IR) and disorders of glucose metabolism (DGM) are risk factors for cardiovascular diseases. There are different reasons for development of DGM in patients with obstructive sleep apnoea syndrome (OSAS) and this association is controversial. We investigated the frequency of DGM and IR in patients with OSAS and determining factors for these disorders. Method: One hundred and twelve untreated patients with OSAS and 19 non‐apnoeic snoring subjects upon polysomnography were included in this study. Oral glucose tolerance test (OGTT) was performed in all subjects who had fasting blood glucose < 125 mg/dl. IR method was analysed using homeostasis assessment model (HOMA‐IR). Diabetes mellitus (DM), impaired glucose tolerance (IGT) and impaired fasting glucose (IFG) were defined according to values of OGTT. DGM was defined as having one of the diagnoses of DM, IGT or IFG. Subjective sleepiness of all subjects was assessed with Epworth Sleepiness Scale (ESS). Excessive daytime sleepiness (EDS) was described as ESS score ≥ 10. Results: Fasting glucose and the rate of DGM in patients with OSAS were higher than in non‐apnoeic snoring subjects. DGM were shown in % 15.7 of non‐apnoeic snoring subjects, 29.6% of mild sleep apnoea, 50% of moderate sleep apnoea and 61.8% of severe sleep apnoea. The rate of DGM in patients with moderate and severe OSAS was higher than in non‐apnoeic snoring subjects and in patients with severe OSAS higher than in patients with mild OSAS. DGM are associated with body mass index (BMI), severity of OSAS, arousal index and EDS. In addition, IR is associated with apnoea hypopnoea index, BMI, arousal index and ESS score. Conclusion: Obstructive sleep apnoea syndrome is associated with high frequency of DGM. In addition, the progression of disease from simple snoring and mild OSAS to severe OSAS increases the rate of DGM. Thus, DGM especially in patients with severe OSAS should be examined in regular periods.     

The effect of a very low-calorie diet-induced weight loss on the severity of obstructive sleep apnoea and autonomic nervous function in obese patients with obstructive sleep apnoea syndrome

The aim of this study was to examine the effect of a very low-calorie diet (VLCD)-induced weight loss on the severity of obstructive sleep apnoea (OSA), blood pressure and cardiac autonomic regulation in obese patients with obstructive sleep apnoea syndrome (OSAS). A total of 15 overweight patients (14 men and one woman, body weight 114 ± 20 kg, age 52 ± 9 years, range 39–67 years) with OSAS were studied prospectively. They were advised to follow a 2·51–3·35 MJ (600–800 kcal) diet daily for a 3-month period. In the beginning of the study, the patients underwent nocturnal sleep studies, autonomic function tests and 24-h electrocardiograph (ECG) recording. In addition, 15 age-matched, normal-weight subjects were studied. They underwent the Valsalva test, the deep-breathing test and assessment of heart rate variability at rest. The sleep studies and autonomic function tests were repeated after the weight loss period. There was a significant reduction in weight (114 ± 20 kg to 105 ± 21 kg, P<0·001), the weight loss being 9·2 ± 4·0 kg (range 2·3–19·5 kg). This was associated with a significant improvement in the oxygen desaturation index (ODI4) during sleep (31 ± 20–19 ±18, P<0·001). Before the weight loss the OSAS patients had significantly higher blood pressure (150 ± 18 vs. 134 ± 20, P<0·05, for systolic blood pressure, 98 ± 10 vs. 85 ± 13, P<0·05, for diastolic blood pressure) and heart rate (67 ± 10 beats min^?1 vs. 60 ± 13, P<0·05) at rest than the control group. They had also lower baroreflex sensitivity (4·7 ± 2·8 ms mmHg^?1 vs. 10·8 ± 7·1 ms mmHg^?1, P<0·01). During the weight reduction, the blood pressure declined significantly, and the baroreflex sensitivity increased by 49%. In conclusion, our experience shows that weight loss with VLCD is an effective treatment for OSAS. Weight loss improved significantly sleep apnoea and had favourable effects on blood pressure and baroreflex sensitivity that may have prognostic implications.     

Abnormal respiratory-related evoked potentials in untreated awake patients with severe obstructive sleep apnoea syndrome

Aim: Obstructive sleep apnoeas generate an intense afferent traffic leading to arousal and apnoea termination. Yet a decrease in the sensitivity of the afferents has been described in patients with obstructive sleep apnoea, and could be a determinant of disease severity. How mechanical changes within the respiratory system are processed in the brain can be studied through the analysis of airway occlusion‐related respiratory‐related evoked potentials. Respiratory‐related evoked potentials have been found altered during sleep in mild and moderate obstructive sleep apnoea syndrome, with contradictory results during wake. We hypothesized that respiratory‐related evoked potentials’ alterations during wake, if indeed a feature of the obstructive sleep apnoea syndrome, should be present in untreated severe patients. Methods: Ten untreated patients with severe obstructive sleep apnoea syndrome and eight matched controls were studied. Respiratory‐related evoked potentials were recorded in Cz‐C3 and Cz‐C4, and described in terms of the amplitudes and latencies of their components P1, N1, P2 and N2. Results: Components amplitudes were similar in both groups. There was no significant difference in P1 latencies. This was also the case for N1 in Cz‐C3. In contrast, N1 latencies in Cz‐C4 were significantly longer in patients with obstructive sleep apnoea syndrome [median 98 ms (interquartile range 16·00) versus 79·5 ms (5·98), P = 0·015]. P2 and N2 were also significantly delayed, on both sides. Conclusions: The cortical processing of airway occlusion‐related afferents seems abnormal in untreated patients with severe obstructive sleep apnoea syndrome. This could be either a severity marker and/or an aggravating factor.     

Health-related quality of life in patients with obstructive sleep apnoea and chronic obstructive pulmonary disease (overlap syndrome)

The association of obstructive sleep apnoea (OSA) and chronic obstructive pulmonary disease (COPD) is not rare as COPD and OSA are both frequent diseases. The aim of this study was to determine the effect of OSA on quality of life (QOL) in patients with overlap syndrome (OVS). Thirty subjects with OVS and 15 control subjects participated. The St George's Respiratory Questionnaire (SGRQ) was used to determine QOL. The control group included subjects with COPD and no evidence of OSA by overnight polysomnography. All subjects were habitual snorers with normal Epworth Sleepiness Scale scores. Significant differences were found between the groups for the total score and each of the three components of the SGRQ suggesting worse QOL in OVS patients (symptoms 54.9 +/- 18.9 vs. 38.2 +/- 19.3, p = 0.008; activity 59.2 +/- 16.2 vs. 44.4 +/- 11.3, p = 0.003; impacts 35.2 +/- 23 vs. 20.8 +/- 8.7, p = 0.025 and total 45.7 +/- 17.7 vs. 30.9 +/- 8.7, p = 0.004 in OVS patients and control group, respectively). Obstructive sleep apnoea has a major impact on QOL in patients with OVS and can exist in COPD patients with habitual snoring even in the absence of daytime sleepiness. Further studies are needed to determine the impact of OSA treatment on QOL and morbidity in this population.     

Pattern recognition of obstructive sleep apnoea and Cheyne-Stokes respiration

The aim of this study was to assess the validity of an artificial neural network based on flow-related spectral entropy as a diagnostic test for obstructive sleep apnoea and Cheyne-Stokes respiration. A data set of 37 subjects was used for spectral analysis of the airflow by performing a fast Fourier transform. The examined intervals were divided into epochs of 3 min. Spectral entropy S was applied as a measure for the spread of the related power spectrum. The spectrum was divided into several frequency areas with various subsets of spectral entropy. We studied 11 subjects with obstructive apnoeas (n = 267 epochs), 10 subjects with obstructive hypopnoeas (n = 80 epochs), 11 subjects with Cheyne-Stokes respiration (n = 253 epochs) and 5 subjects with normal breathing in non-REM sleep (n = 174 epochs). Based on spectral entropy an artificial neural network was built, and we obtained a sensitivity of 90.2% and a specificity of 90.9% for distinguishing between obstructive apnoeas and Cheyne-Stokes respiration, and a sensitivity of 91.3% and a specificity of 94.6% for discriminating between obstructive hypopnoeas and normal breathing in non-REM sleep. This resulted in an accuracy of 91.5% for identifying flow patterns of obstructive sleep apnoea, Cheyne-Stokes respiration and normal breathing in non-REM sleep. It is concluded that the use of an artificial neural network relying on spectral analysis of the airflow could be a useful method as a diagnostic test for obstructive sleep apnoea and Cheyne-Stokes respiration.     

血管内皮生长因子在阻塞性睡眠呼吸暂停低通气综合征中的意义探讨

目的探讨血管内皮生长因子(VEGF)在阻塞性睡眠呼吸暂停低通气综合征(OSAHS)病理生理过程中的意义。方法①应用酶联免疫吸附法检测40例OSAHS患者(OSAHS合并心脑血管病26例,未合并心脑血管病的单纯OSAHS14例)和30例正常人的血浆VEGF浓度。②将26例OSAHS合并心脑血管病患者分为2组:15例经鼻持续正压通气(nCPAP)治疗(nCPAP治疗组);11例OSAHS合并心脑血管病患者不予任何针对OSAHS的治疗(对照组);比较2组治疗前后的血浆VEGF浓度。结果①OSAHS组血浆VEGF浓度高于正常对照组[(182.5±41.6)ng/L与(117.0±56.2)ng/L,P<0.01],并且与呼吸紊乱指数(r=0.919,P<0.01)、夜间缺氧时间(r=0.945、P<0.01)呈正相关。且OSAHS合并心脑血管病患者VEGF均高于单纯OSAHS患者[(248.4±105.9)ng/L与(161.7±43.2)ng/L,P<0.01]。②经nCPAP治疗半年后,OSAHS合并心脑血管病患者血浆VEGF浓度下降[(252.3±124.9)ng/L与(154.3±50.1)ng/L,P<0.01];对照组观察终点的血浆VEGF浓度较观察起点略有增加[(239.6±101.2)ng/L与(270.0±88.3)ng/L],但差异无显著性(P>0.05)。结论VEGF可能参与了OSAHS相关性心脑血管病的发生发展过程。     

Comparison of invasive intubation and noninvasive mechanical ventilation in patients with chronic obstructive pulmonary disease and obstructive sleep apnoea syndrome

ObjectiveThe concurrence of chronic obstructive pulmonary disease (COPD) and obstructive sleep apnoea syndrome (OSAS) is defined as overlap syndrome (OS), but investigations into predictors of OS in patients with COPD remain limited. Here, potential markers of OS in patients with COPD were investigated, and results of intubation were compared between patients with COPD only or OS.MethodsThis retrospective study included patients with COPD who were divided according to OS diagnosis: COPD only (COPD group) or OS (OS group).ResultsAmong 206 patients with COPD, 120 were diagnosed with OS. Mean body mass index (BMI) was significantly higher in the OS versus COPD group (28.95 ± 2.96 versus 23.84 ± 4.06, respectively). Receiver operating characteristic curve analyses revealed that BMI was associated with OS (area under the curve, 0.835). The rate of invasive intubation within 48 h was lower in the OS versus COPD group (9.2% versus 20.9%, respectively), and the duration of noninvasive ventilation was longer in the OS versus COPD group.ConclusionsBMI may be a predictor of OS in patients with COPD. The duration of noninvasive ventilation was longer in patients with OS than in patients with COPD alone.     

口腔矫治器治疗阻塞性睡眠呼吸暂停综合症

目的 评价口腔矫治器治疗阻塞性睡眠呼吸暂停综合症（OSAS）的临床疗效。方法12例用口腔矫治器治疗的OSAS患者，对其治疗前后多导睡眠监测（PSG）和X射线头影测量所得的气道及呼吸功能改变进行分析。结果 治疗前后呼吸暂停指数（AI）、平均呼吸暂停时间（MAT）、低通气指数（HI）、呼吸紊乱指数（AHI）及血氧饱和度（SaO2）比较，差异有显著性意义（P〈0．05）；下颌平面角（SN—MP），上气道上部前后径（SPAS）、中部前后径（MAS）、软腭长度（SPL）比较，差异有显著性意义（P〈0．05）；SNB，上气道下部前后径（IAS）比较，差异无显著性意义（P〉0．05）。结论 用口腔矫治器可以有效的治疗阻塞性睡眠呼吸暂停综合症，有高效经济、携带方便、无创无风险性及可重复性等优点。     

Oximetry spectral analysis in the diagnosis of obstructive sleep apnoea.

Using spectral analysis of oximetry data, we prospectively evaluated the validity of this methodology in patients clinically suspected of suffering from obstructive sleep apnoea (OSA). A total of 233 outpatients were studied. Nocturnal oximetry was performed simultaneously with conventional polysomnography for all participants. The power density of oxygen saturation was analysed using Fast-Fourier transformation of the oximetric signal. Nocturnal oximetry test results were considered as abnormal (suspicion of OSA) if a peak in the spectrum between the period boundaries 30 and 70 s was observed. A normal test result was defined as the absence of the 30-70 s peak from the spectrum. Single-blind evaluation was performed by three independent observers, and agreement of two or more of these was considered definitive. The peak amplitude and the ratio of the area enclosed in the 30-70 s peak to the total area of the spectrum (r(S)) were measured. The presence of a peak has a sensitivity of 78%, a specificity of 89%, a positive predictive value of 89% and a negative predictive value of 78%. Apnoea-hypopnoea indexes were correlated significantly with peak amplitude (r=0.74; P<0.001) and with r(S) (r=0.69; P<0.001). For a peak amplitude threshold of 0.7%(2), the sensitivity was 94% and the specificity was 65% for OSA diagnosis. Using a threshold for r(S) of 0.15, the sensitivity was 91% and the specificity was 67%. Thus the spectral analysis of nocturnal oximetry and identification of a peak at 30-70 s could be useful as a diagnostic technique for OSA subjects.