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[Changes of sleep architecture in children with obstructive sleep apnea syndrome].

OBJECTIVE: To explore how obstructive sleep apnea syndrome (OSAS) affects children's sleep architecture. METHODS: Eighty-three children with OSAS were reviewed; every patient was monitored with polysommography for 7 hours at night for 11 parameters, including the number of arousal, snoring index, nadir O(2) desaturation, stage I %, stage II %, show wave sleep (SWS)% and rapid eye movement (REM)%. The basis for diagnosis of OSAS was the widely accepted pediatric diagnostic criteria of apnea/hypopnea index, apnea/ hypopnea index of > 1 episode/hour, nadir O(2) desaturation < 92%. Sleep was scored manually according to the standard set by Rechtschaffen. RESULTS: In OSAS group, the number of arousal was 22.5 +/- 1.4, snoring index was 70.6 +/- 16.5, and/or SaO(2) was (73.8 +/- 1.9)%. OSAS group had increased stage I : (45.8 +/- 2.0)% vs. (2.3 +/- 1.1)%, t = 22.46, P < 0.01 and decreased stage II : (23.9 = 1.7)% vs (47.9 = 4.4)%, t = - 14.18, P < 0.01, SWS (15.6 +/- 1.8)% vs. (21.1 +/- 5.0)%, t = - 3.123, P < 0.01, REM (14.7 +/- 1.5)% VS. (28.2 +/- 4.1)%, T = -8.923, p < 0.01. CONCLUSION: The severity of OSAS relates to changes of sleep architecture in children. Intermittent nocturnal hypoxia secondary to apnea/hypopnea, and frequent electroencephalogram arousals from sleep may result in significant sleep fragmentation. Children with OSAS had learning problems and failure to thrive.

Child↗

[Study on the levels of C-reactive protein and fibrinolytic activity in patients with obstructive sleep apnea syndrome].

OBJECTIVE: To study the changes of plasm CRP levels and the fibrinolytic activity in patients with obstructive sleep apnea syndrome (OSAS). METHOD: Thirty-two patients with OSAS, who were free of other diseases and had never been treated for OSAS, were as test group, 30 adults without OSAS were as control group. Plasma high-sensitivity CRP (hsCRP) levels and tissue-type plasminogen activator (t-PA) activity, plasminogen activator inhibitor-1 (PAI-1) activity were measured in two groups. RESULT: In OSAS group the levels of CRP and the activity of PAI-1 were increased, the activity of t-PA were decreased as compared with control group (P < 0.01). CONCLUSION: The OSAS patients are associated with elevated plasma CRP level and decreased fibrinolytic activity. The severity of OSAS is proportional to the CRP level.

Adult↗

[The obstructive sleep apnoea syndrome in obesity: a conspirator in the shadow].

The obstructive sleep apnoea syndrome (OSAS) is caused by upper airway collapse during sleep. These episodes are associated with recurrent oxyhaemoglobin desaturations and arousals which lead to disruption of the sleep pattern and cognitive deterioration. Factors such as age, male sex, menopause, tobacco and alcohol consumption and anatomic abnormalities are demonstrated risk factors for OSAS development. Obesity, specially of abdominal type, is also a very strong predictor of OSAS, increasing the risk of apnoea by ten times. OSAS prevalence may reach 80% and 50% en males and females with morbid obesity respectively. OSAS induces sympathoexcitation, insulin resistance, renin-angiotensin system activation, oxidative stress, endothelial dysfunction, hypercoagulability and reduction of fibrinolysis leading to hypertension and increased cardiovascular risk. The best diagnostic procedure is polysomnography. Obesity treatment is followed by a dramatic improvement in OSAS. Weight loss of 10% results in reductions of apnoea index by 26%. Application of a positive pressure system is a very effective treatment for OSAS which reduces the apnoea index and improves cardiovascular risk and cognitive impairment.

Cardiovascular Diseases↗

[Influence of nocturnal hypoxemia on the function of the visual tract in the course of the obstructive sleep apnea syndrome].

BACKGROUND AND PURPOSE: In patients with obstructive sleep apnea (OSA) syndrome the episodes of upper airway obstruction lead to hypoxemia during sleep. The aim of the study was to establish the influence of sleep hypoxemia on the function of the visual tract in OSA patients. MATERIAL AND METHODS: The latency and amplitude of wave P100 of visual evoked potentials have been studied in 35 patients with OSA syndrome (mean apnea index 48+/-19). The diagnosis of OSA was established on the basis of continuous recordings of the respiratory function during sleep with additional full polysomnography in 17 patients. RESULTS: Mean absolute latency of P100 was longer in OSA patients than in healthy controls (117.0+/-8.8 ms vs. 104.3+/-4.6 ms, p<0.001). The differences in the amplitude of P100 were not significant (5.9+/-2.6 mV in OSA patients and 7.62+/-3.04 mV in healthy persons). In 60% of patients the latency of P100 exceeded 118 ms; in this group of patients the mean SaO2 during sleep apneas was lower than in patients with normal P100 latency (46+/-15% vs. 69+/-10%, p<0.05). Full polysomnographic studies revealed that in patients with prolonged latencies as compared with patients with normal P100 latencies there were lower: minimal SaO2 during NREM sleep (63+/-12% vs. 78+/-8%, p<0.05), as well as mean and minimal SaO2 during REM sleep (53+/-15% vs. 80+/-5% and 46+/-15% vs. 69+/-10%, p<0.05), without differences in apnea index or apnea duration. CONCLUSIONS: In patients with OSA syndrome the electrophysiological abnormalities suggesting damage of the optical tract may develop probably as a consequence of profound sleep hypoxemia.

Adult↗

Validity of tidal breathing flow volume loops in diagnosing obstructive sleep apnea in young children with adenotonsillar hypertrophy: a preliminary study.

Tidal breathing flow volume loops (TBFVL) can indicate the site/severity of upper airway obstruction (UAO). The authors did a pilot study to determine 1) the correlation between TBFVL and obstructive sleep apnea (OSA) as well as its severity and 2) the validity of TBFVL in determining OSA and desaturation during sleep in young children with a denotonsillar hypertrophy (ATH). A cross sectional analytical study was performed in 10 patients with ATH (age 4.2 +/- 0.4 yrs; 40% female) at King Chulalongkorn Memorial Hospital during January-June 2004. All had polysomnography and TBFVL performed during sleep. Median apnea/hypopnea index (AHI) was 3.4/hr. Eight (80%) patients had OSA. The TBFVL was normal in 2, variable UAO in 3, and fixed UAO in 5 patients. Among these 3 groups, the number of OSA patients (2, 3 and 3, respectively; ns) and the number of those who had desaturation (2, 3 and 3, respectively; ns) were not different. There was no correlation between mid tidal expiratory flow rate/mid tidal inspiratory flow rate (Me/Mi) ratio and AHI (r=0.5; ns) or lowest arterial oxygen saturation during sleep (r=-0.4; ns). The accuracy of Me/Mi > 1.5 for diagnosing OSA and desaturation was 50% and 60%, respectively. The abnormal TBFVL also had the same accuracy in defining these 2 conditions. In conclusion, TBFVL did not correlate with OSA and its severity and had low accuracy in determining either OSA or desaturation in young children with ATH.

Adenoids↗

[Serum leptin concentration and sympathetic activation estimated on the adrenaline and noradrenaline serum concentration in patients with obstructive sleep apnea].

UNLABELLED: Hypertension, coronary heart diseases, obesity, diabetes mellitus are often present in patients with obstructive sleep apnea (OSA). The aim of the study was to estimate the serum leptin concentration and sympathetic activity in patients with obstructive sleep apnea and in control group. INVESTIGATED GROUP: 51 persons (F6, M45) were included into the study. The control group (GK) consisted of 15 snoring person (15 M) in the age x = 44.19 +/- 14.60, study group (GB) consisted of 36 patients with OSA (6F, 30M) in the age 5 1.47 +/- 8.95 years. METHODS: Leptin was measured by RIA methods using the HUMAN LEPTIN RIA KIT (LINCO Research, Inc).: adrenaline and noradrenaline were measured in the serum by HPLC methods (BIO-RAD). RESULTS: The serum concentrations of leptin (ng/mL), adrenaline and noradrenaline (pg/mL) in patients with OSA compared with control group were respectively 15.55 +/- 11.26 : 61.2 +/- 27.4: 523.2 +/- 165.1 vs 10.34+/- 6.86 : 47.7 +/- 27.3: 447.9 +/- 102.6. There was positive significant correlation between leptin concentration and BMI (r = 0,34) and serum leptin and adrenalin concentration (r = 0,34). The serum leptin concentration was significantly higher in the female group. In the male group there was tendency to increase leptin concentration together with degree of OSA grade estimated by AHI and AHI <50 leptin concentration 12.23+/- 6.96 ng/mL vs AHI>50 and leptin concentration 13.35 +/- 3.54ng/ml. CONCLUSIONS: 1. In the group of patients with OSA the serum concentrations of leptin, adrenaline and noradrenaline were higher then in control group. 2. There are positive statistical significant correlation between serum leptin levels and BMI and serum adrenaline concentration in the study group. 3. The serum leptin concentration was higher in the female group. 4. There was tendency to increased leptin concentration in the study group together with degree of OSA grade estimated by AHI. 5. Our results confirm correlation between leptin and sympathetic activity and their influences on obesity and degree of OSA grade in studied group.

Adult↗

Comparison of tongue volume/oral cavity volume ratio between obstructive sleep apnea syndrome patients and normal adults using magnetic resonance imaging.

Obstructive sleep apnea syndrome (OSAS) is a group of disorders in which breathing stops intermittently and repeatedly for 10 seconds or more during sleep. The causal site of the disorders is thought to be in the upper airway above the glottis. In order to understand the three-dimensional features of the oral and peripharyngeal structures involved in the disorders, we calculated the tongue volume/oral cavity volume ratio (TV/OCV ratio) in the oral cavity using magnetic resonance imaging (MRI) for both OSAS patients and normal controls. The study subjects comprised 20 male patients with OSAS (apnea-hypopnea index [AHI] > or = 5.0, with a diagnosis of OSAS) and 20 normal male adults (AHI<5.0, with no history of OSAS) as the controls. We performed MRI to acquire T1- and T2-weighted images. We estimated tongue volumes on the basis of the cross-sectional area of each image, then using the tongue volume data, we calculated TV/OCV ratios. In the normal control group, mean (+/- SD) body mass index (BMI) was 21.68 +/- 1.73 and the mean TV/OCV ratio was 86.98 +/- 3.16%, whereas these values were 25.0 +/- 15.94 and 90.56 +/- 2.15%, respectively, in the OSAS patient group. The TV/OCV ratio of the OSAS patient group was significantly higher than that of the normal control group (p<0.01).

Adult↗

Obstructive sleep apnea and hypertension: epidemiology, mechanisms and treatment effects.

Obstructive sleep apnea (OSA) is a highly prevalent disorder of breathing during sleep. A growing body of evidence suggests that OSA is independently associated with an increased risk of cardiovascular disease, although the extent of this risk and underlying mechanisms remain to be elucidated. However, there is clearer evidence from epidemiological and pathophysiological research of a causal link between OSA and hypertension. The acute hemodynamic and autonomic perturbations that accompany obstructive apneas during sleep, with associated repeated arousals and intermittent hypoxemia, appear to result in sustained hypertension. In addition to the metabolic and humoral effects from obesity, OSA appears to predispose individuals to autonomic imbalance characterized by sympathetic overactivity and altered baroreflex mechanisms as well as alterations to vascular function. Treatment of OSA restores normal sleep architecture and generally mitigates the acute hemodynamic effects of OSA. Treatment of symptomatic OSA, particular at the severe end of the spectrum, appears to be associated with improvements in blood pressure, both during sleep and wakefulness, and there may also be additional gains in subjects who are hypertensive and/or resistant to antihypertensive medications. The severe group appears to be particularly at risk for developing fatal and non-fatal cardiovascular events and treatment with continuous positive airway pressure appears to markedly reduce that risk. Future treatment studies will need to be extended for greater than the current average of 1-2 months in order to more fully evaluate any time dependent improvements in blood pressure, and consequent cardiovascular risk.

Adult↗

Cardiovascular diseases in obstructive sleep apnea.

Obstructive sleep apnea (OSA) affects approximately 5% of women and 15% of men in the middle-aged adults, and associated with adverse health outcomes. Cardiovascular disturbances are the most serious complications of OSA. These complications include heart failure, left/right ventricular dysfunction, acute myocardial infarction, arrhythmias, stroke, systemic and pulmonary hypertension. All these cardiovascular complications increase morbidity and mortality of OSA. Several epidemiologic studies have demonstrated that sleep related breathing disorders are an independent risk factor for hypertension, probably resulting from a combination of intermittent hypoxia and hypercapnia, arousals, increased sympathetic activity, and altered baroreflex control during sleep. Arterial hypertension, obesity, diabetes mellitus and coronary artery disease (CAD) which are independent predictors of left ventricular dysfunction, often have co-existence with OSA. Especially severe OSA patients having diastolic dysfunction might have an increased risk of heart failure, since diastolic dysfunction might be combined with systolic dysfunction. Early recognition and appropriate therapy of ventricular dysfunction is advisable to prevent further progression to heart failure and death. Patients with acute myocardial infarction, especially if they had apneas and hypoxemia without evident heart failure should be evaluated for sleep disorders. So, patients with CAD should be evaluated for OSA and vice versa. Early recognition and treatment of OSA may improve cardiovascular functions. Continuous positive airway pressure (CPAP) applied by nasal mask, is still the gold standard method for treatment of the disease and prevention of complications.

Cardiovascular Diseases↗

Obstructive sleep apnoea in Asia.

Obstructive sleep apnoea (OSA) syndrome is the commonest sleep-related breathing disorder worldwide. In Asia, the prevalence of symptomatic OSA in middle-aged men and women is 4.1-7.5% and 2.1-3.2%, respectively. These prevalence rates are similar to those reported in Caucasian populations. Obesity, an established major risk factor for OSA, is less common among Asians, and the reported values of body mass indices (BMIs) of Asians with OSA are lower than in their Caucasian counterparts. However, these population-based studies have consistently demonstrated that obesity is still the major risk factor for OSA in Asians, while other studies have suggested that craniofacial structural factors may make a greater contribution towards development of OSA in Asians than in Caucasians. Sleep medicine is in a developmental stage in many Asian countries, and the condition is likely under-recognised. Although sleep laboratories have been set up in various countries in Asia, the availability of this service is very limited. Continuous positive airway pressure is available in most parts of Asia, but financial constraints may limit its utility. Oral appliances have been postulated to have a greater role in the management of OSA in Asian patients, as they are likely to have more modifiable factors in their craniofacial structures, but this is yet to be proven. There is a great need for research and health care development on sleep disordered breathing in Asia, and the solution will only come with efforts towards promotion of awareness of this condition in both professional and lay communities.

Asia↗

Peripheral chemoreceptor reflex in obstructive sleep apnea patients; a relationship between ventilatory response to hypoxia and nocturnal bradycardia during apnea events.

15 patients with obstructive sleep apnea syndrome and arterial hypertension (H-OSAS), 25 normotensive patients with sleep apnea syndrome (N-OSAS) and 20 healthy age-matched controls (C) were included in this study. Ventilatory responses to activation (hypoxia) and inactivation (hyperoxia) of carotid chemoreceptors were studied in all subjects. Relationship between hypoxic ventilatory reactivity and nocturnal bradycardia during apnea-phases was analysed in both groups of patients. Results and conclusions. 1. We found an impairment of ventilatory response to hypoxia in H-OSAS and N-OSAS patients. However, the increase in ventilation in response to hypoxia was significantly greater in H-OSAS as compared to N-OSAS patients. 2. An augmented ventilatory response to inactivation of carotid chemoreceptors (the decrease in ventilation), observed in H-OSAS patients, indicates an increase in resting peripheral chemoreceptors drive in this group of patients. 3. The relationship between ventilatory response to hypoxia and nocturnal bradycaria in obstructive sleep apnea patients suggests, that hypoxic reactivity of arterial chemoreceptors might be involved in the origin of bradycardia during apnea events.

Bradycardia↗

[Anamnestic and polygraphic parameters in obstructive sleep apnea syndrome patients with reduced nasal respiration during the day in comparison with obstructive sleep apnea patients with normal nasal respiration].

Nasal obstruction is a predictive factor for snoring and may contribute to the development of an obstructive sleep apnea syndrome (OSAS). The aim of this study was to further evaluate the impact of nasal obstruction in OSAS. Therefore, we investigated 2 groups of OSAS-patients, matched pairs concerning gender, age, and BMI: OSAS-patients with nasal obstruction (N, n = 28), total nasal airflow < 500 ccm/s (referred to 150 pa pressure of difference or unilateral nasal resistance > 1 pa/ccm/s), and 28 OSAS-patients without nasal obstruction (control-group K, total nasal airflow > 700 ccm/s [referred to 150 pa pressure of difference or unilateral nasal resistance > 1 pa/ccm/s]). We performed anterior rhinomanometry, lung-function testing, cardio-respiratory polygraphy, and patients answered a standardized questionnaire. We found the following significant differences: 1) N complained more often (n = 17) about dyspnea at night than K (n = 7, p < 0.05, Chi2-test). 2) N had a higher apnea index (20.4 +/- 19.0/h) than K (9.6 +/- 10.0/h, p < 0.05, Student's t-test). There were, however, no significant differences concerning lung function, number of nocturnal hypopneas, nocturnal SaO2 and heart rate. Our results underline the importance of nasal ventilation in the pathogenesis of OSAS. At least in moderate cases of OSAS a therapy of nasal obstruction might be of success in order to abolish nCPAP-therapy or might reduce nasal problems during nCPAP-therapy and thus ameliorate patient's therapy compliance.

Airway Resistance↗

Adenotonsillar hypertrophy and skeletal morphology of children with obstructive sleep apnea syndrome.

To define the role of adenotonsillar hypertrophy and facial morphology in obstructive sleep apnea (OSA) in children we performed a cephalometric analysis of an OSA group and an age-matched control group. Adenotonsillar hypertrophy was remarkable in OSA children at every age level. Maxillary protrusion expressed by SNA was significantly smaller in the OSA group than in the control group for elderly children (5-9 years old). Mandibul protrusion expressed by SNB was significantly smaller in the OSA group even at younger ages (1-2 years). The hyoid bone was significantly lower in the OSA group than in the control group who were from 3 to 6 years. Environmental factors due to upper airway obstruction as well as genetic factors are suspected to cause abnormal facial morphology in OSA children.

Adenoids↗

Clinical diagnosis and assessment of obstructive sleep apnoea syndrome.

Obstructive sleep apnoea (OSA) syndrome is very common, affecting up to 4% of adult males. The pathophysiology of OSA is complex and incompletely understood, but upper airway (UA) obstruction appears to be the net result of an inability of the UA dilating muscles to maintain a patent oropharyngeal airway during sleep. A narrowed UA is common among OSA patients, and in adults this is usually due to nonspecific factors, such as fat deposition in the neck, or abnormal bony morphology of the UA. The present criteria for the diagnosis of OSA are not well-defined, and different centres use different thresholds of apnoea and hypopnoea frequency during sleep to diagnose the clinical syndrome. The advent of many simplified diagnostic systems, some of which are portable and suitable for use in the patient's home, represents a major advance, but many of these systems are poorly validated, and there is no uniformity of measured variables among the various systems, apart from arterial oxygen saturation (Sa,O2). The established prevalence of OSA among the general population implies that most patients with suspected OSA should be initially assessed outside major sleep laboratories, in many cases by clinicians who may not have as detailed an understanding of the syndrome as clinicians who have undertaken specific training in sleep medicine. It is important, therefore, that clear-cut guidelines and criteria be established for the assessment and management of patients with suspected OSA.

Adult↗

[Indications in sleep-apnea syndrome. When and why is further assessment meaningful?].

Forms of sleep apnea syndrome: Interrupted breathing and hypoventilation during sleep lead to sleep disorders and to cardiovascular sequelae. In the common obstructive sleep apnea syndrome (OSAS) apneas are related to intermittent obstruction of the upper airways. In the rarer central sleep apnea syndrome certain cardiovascular or central nervous system disorders lead to disturbed regulation of respiration connected with periodic breathing. Signs indicating OSAS: Loud, cyclic snoring, interrupted by cessation of breathing during sleep observed by relatives and excessive daytime to diurnal sleepiness indicate OSAS. Furthermore alteration of personality, headache in the morning, non-refreshing sleep and nocturnal choking sensations may indicate OSAS. When is evaluation necessary? Patients with complaints possibly induced by OSAS should be further evaluated since nocturnal application of continuous positive airway pressure (CPAP) by means of a nose mask and other treatment forms often lead to significant improvement of OSAS. In addition patients with untreated OSAS have an increased risk for car accidents and premature death as consequence of cardiovascular diseases. The type and extent of a supposed respiratory disorder is evaluated by means of a sleep study.

Airway Obstruction↗

[Changes in regional CNS perfusion in obstructive sleep apnea syndrome: initial SPECT studies with injected nocturnal 99mTc-HMPAO].

Some of the clinical features of obstructive sleep apnoea syndrome (OSA) are suggestive of impaired cerebral blood flow. Cerebral blood flow alterations might, for example, be responsible for headaches, which are frequent complaints in patients with OSA. Even the high frequency of ischaemic cerebral complications in patients with OSA might be caused in part by sleep apnoea-associated impairment of cerebral perfusion. Previous studies have demonstrated reduced total cerebral blood flow in patients with OSA, but regional changes of cerebral perfusion have not been studied up to now. We performed SPECT studies using 99mTc-(d,l)-hexamethyl-propylenaminoxim (HMPAO) as a tracer in 14 adult patients with moderate to severe OSA (AHI > 30/h; mean AHI 59.2 +/- 4.3). The injection of the tracer took place between 2:00 and 4:00 a.m. while repeated episodes of obstructive apnoea were detected by polysomnography during stage II sleep. Data acquisition took place at 7:30 a.m. All measurements were repeated some nights later under effective treatment with nCPAP. Visual analysis showed marked frontal hyperperfusion in 5 patients. When regional perfusion indices were calculated for 32 regions of interest statistical analysis showed reduced perfusion of the left parietal region. These changes were completely reversed by effective nCPAP therapy. These data suggest that OSA is associated with reversible changes of regional cerebral perfusion. The underlying pathophysiologic mechanisms are matter of speculation so far. There might be an apnoea-associated effect of local vascular autoregulation mechanisms acting to compensate systemic blood flow alterations or blood gas changes in OSA. The observed frontal hyperperfusion might be caused by activation of the frontal lobe by repetitive cortical arousals.

Adult↗

[The detection of the sleep apnea syndrome in a population of professional drivers].

The aim of this study was to reduce the risk of traffic accidents related to obstructive sleep apnea syndrome (OSAS) by means its detection and treatment in a group of 100 commercial drivers from Seville. Besides, to analyze which clinical findings could suggest OSAS. By means a questionnaire we selected subjects without (questionnaire score < 10 points) and with (questionnaire score > or = 10) clinical history of OSAS. In cases with score > or = 10, an overnight home polygraphy was carried out (Apnoescreen II, Jaeger), with measurement of oronasal airflow, chest and abdominal movements, oxygen saturation, electrocardiogram, body position and actimetry. We performed a manual analysis of recordings, and polygraphy was considered to be positive for OSAS if both AHI (respiratory events Index) or DI (desaturation Index) were > or = 10. In these positive cases, overnight conventional polysomnography was carried out (SleepLab, Jaeger), with therapeutic tests with CPAP if OSAS was diagnosed (AHI > or = 10). Average age and BMI (Body Mass Index) were 41.5 +/- 0.9 years and 28.2 +/- 0.4 kg/m2. Questionnaire was positive in 59 subjects, in 35 of whom home polysomnography was done. We did not find differences in age, BMI, neck circumference or symptomatology among these 35 drivers and the 24 remaining subjects in whom home polygraphy was not performed. Home polygraphy was positive in 10 subjects and negative In 25. Drivers in first group were older, heavier and complaint more frequently about snoring, sleep apnea and daytime sleepiness. We did not find differences in neck circumference, waist/hip ratio nor alcohol consumption between both groups. From the group with positive polygraphy, we performed conventional polysomnography in 8 cases and OSAS was diagnosed in 5 (in all cases, treatment with CPAP was started). This study does not provide data about prevalence, but it seems that the percentage of our drivers with OSAS could be lightly higher than the prevalence in general population. These subjects seem to be older, heavier and complaint more frequently about snoring, sleep apnea and daytime sleepiness.

Adult↗

Autonomic dysfunction in normotensive awake subjects with obstructive sleep apnoea syndrome.

Obstructive sleep apnoea syndrome (OSAS) is associated with systemic arterial hypertension and cardiac arrhythmias and may lead to cardiovascular complications. Dysfunction of the autonomic nervous system (ANS) may play a role in the development of cardiovascular complications. The aim of this work was to study the ANS by spectral analysis of the heart rate variability (HRV) at rest and after stress (head-up tilt test) in a group of normotensive awake OSAS subjects. We studied 22 males with OSAS, aged 47.6 +/- 13.1 yrs, with a body mass index (BMI) 35.6 +/- 7.7 kg.m-2 and blood systolic and diastolic pressure (BSP and BDP, respectively) of 128 +/- 16 and 80 +/- 9 mmHg. Nineteen healthy males were studied as controls. Autonomic investigations were performed using the computerized power spectral analysis of HRV with autoregressive modelling which identifies low frequency (LF), as a marker of sympathetic activity and high frequency (HF), as a marker of vagal activity. OSAS patients showed greater sympathetic activity (LF) at rest than normal subjects, and an abnormal response to the head-up tilt test compared to control subjects. Five OSAS patients behaved like control subjects. Comparison of the functional parameters between these five OSAS patients and the other 17 OSAS patients showed a statistically significant difference for only basal arterial carbon dioxide tension (Pa,CO2) and minimal nocturnal oxyhaemoglobin (HbO2) saturation (NADIR). Our study shows autonomic nervous system dysfunction in patients with obstructive sleep apnoea syndrome, which may have facilitated a pathophysiological link with the cardiovascular complications observed in these patients.

Autonomic Nervous System Diseases↗