Relationship of arousals from sleep to sympathetic nervous system activity and BP in obstructive sleep apnea.

STUDY OBJECTIVE: Obstructive sleep apnea (OSA) patients have a high frequency of arousals. We hypothesized that arousals significantly influence tonic sympathetic nervous system function. DESIGN: We examined the association of 11 variables measuring sympathetic activity, including plasma norepinephrine (NE), urinary NE, and BP measurements, with movement and cortical arousals. PATIENTS: Sixty-seven subjects with various degrees of hypertension and OSA were evaluated. All patients were free from antihypertensive medications. RESULTS: The age (range, 35 to 60 years), weight (range, 100 to 150% of ideal body weight), and diet of the subjects were similar. The movement arousal index was correlated with daytime baseline plasma NE (BNE), daytime urine NE, mean daytime diastolic BP, and systolic BP during rapid eye movement sleep (r = 0.39 to 0.53; p < or = 0.002). Cortical arousals did not correlate with any of the variables. A multiple regression procedure was performed to examine how well movement arousals predicted those variables with significant correlations. The respiratory disturbance index (RDI) and nighttime pulse oxyhemoglobin saturation were included in the regression equation due to their close association with movement arousals. Movement arousals independently predicted BNE (t [48] = 2.06; p < 0.05). No other variable independently predicted any of the measurements of sympathetic activity. CONCLUSIONS: These findings suggest that movement arousals may influence daytime sympathetic tone independently of RDI and nighttime saturation.     

Inhibition of awake sympathetic nerve activity of heart failure patients with obstructive sleep apnea by nocturnal continuous positive airway pressure

OBJECTIVES: This study was designed to determine whether reductions in morning systolic blood pressure (BP) elicited by treatment of moderate to severe obstructive sleep apnea (OSA) in heart failure (HF) patients are associated with a reduction in sympathetic vasoconstrictor tone. BACKGROUND: Daytime muscle sympathetic nerve activity (MSNA) is elevated in HF patients with coexisting OSA. In our recent randomized trial in HF, abolition of OSA by continuous positive airway pressure (CPAP) increased left ventricular ejection fraction (LVEF) and lowered morning systolic BP. METHODS: Muscle sympathetic nerve activity, BP, and heart rate (HR) of medically treated HF patients (EF <45%) and OSA (apnea-hypopnea index > or =20/h of sleep) were recorded on the morning after overnight polysomnography, and again one month after patients were randomly allocated nocturnal CPAP treatment or no CPAP (control). RESULTS: In nine control patients, there were no significant changes in the severity of OSA, MSNA, systolic BP, or HR. In contrast, in the 8 CPAP-treated patients, OSA was attenuated, and there were significant reductions in daytime MSNA (from 58 +/- 4 bursts/min to 48 +/- 5 bursts/min; 84 +/- 4 bursts/100 heart beats to 72 +/- 5 bursts/100 heart beats; p < 0.001 and p = 0.003, respectively), systolic BP (from 135 +/- 5 mm Hg to 120 +/- 6 mm Hg, p = 0.03), and HR (from 69 +/- 2 min(-1) to 66 +/- 2 min(-1); p = 0.013). CONCLUSIONS: Treatment of coexisting OSA by CPAP in HF patients lowers daytime MSNA, systolic BP, and HR. Inhibition of increased central sympathetic vasoconstrictor outflow is one mechanism by which nocturnal CPAP reduces awake BP in HF patients with moderate to severe OSA.     

The sleep supine position has a major effect on optimal nasal continuous positive airway pressure : relationship with rapid eye movements and non-rapid eye movements sleep, body mass index, respiratory disturbance index, and age.

STUDY OBJECTIVES: To evaluate the impact of sleep position on optimal nasal continuous positive airway pressure (nCPAP [op-nCPAP]) in obstructive sleep apnea (OSA) patients and to investigate how rapid eye movements (REM) and Non-REM (NREM) sleep, body mass index (BMI), respiratory disturbance index (RDI), and age are related to this effect. DESIGN: Retrospective analysis. Setting: Sleep Disorders Unit at Loewenstein Hospital Rehabilitation Center. PATIENTS: Eighty-three consecutive adult OSA patients who underwent a complete nCPAP titration. From this group, 60 patients who spent at least 30 min in both the supine (Sup) and lateral (Lat) positions and 46 patients who had data on both positions during REM and NREM sleep were included in the analysis. RESULTS: In most OSA patients (52; 86.7%), the recommended op-nCPAP was obtained when the patients slept in the Sup posture. The mean op-nCPAP was significantly higher in the Sup posture (10.00 +/- 2.20 cm H(2)O) than it was in the Lat posture (7.61 +/- 2.69 cm H(2)O). The op-nCPAP was significantly higher in the Sup position than it was in the Lat position in both REM and NREM sleep, as well as in the severe BMI group (BMI >/= 30) and in the less obese group (BMI < 30). Similarly, in the severe (RDI >/= 40) and less severe groups (RDI < 40), as well as in both age groups (< and > 60 years of age), the op-nCPAP was significantly higher in the Sup posture than it was in the Lat posture. Irrespective of the four parameters mentioned, the actual differences in op-nCPAP between the two body postures were almost identical, ranging between 2.31 and 2.66 cm H(2)O. CONCLUSIONS: For most OSA patients, the op-nCPAP level is significantly higher in the Sup position than it is in the Lat position. This is true for REM and NREM sleep, for obese and nonobese patients, for patients with different degrees of severity, and for young and old OSA patients. Since the op-nCPAP was highest in the Sup posture during REM sleep, no nCPAP titration should be considered complete without the patient having slept in the Sup posture during REM sleep.     

Clinical and polysomnographic data of positional sleep apnea and its predictors

Introduction

In Asian population, facial structure may contribute to the primary pathophysiology of obstructive sleep apnea (OSA). We hypothesized that sleep position may have more effect on OSA in Asians compared to the Western population. If this hypothesis is accurate, positional therapy will have a major impact on treatment of OSA among Asians.

Patients/methods

We reviewed 263 polysomnographic studies from our laboratory from January 1, 2010 to June 30, 2010. Criteria for positional and non-positional OSA were (1) supine respiratory disturbance index (RDI)/non-supine RDI ??2 and total RDI ??5 and (2) supine RDI/non-supine RDI <2 and total RDI ??5, respectively. We aimed to determine the difference in baseline characteristics, polysomnographic findings, and predictors for positional OSA.

Results

We found 144 patients diagnosed with OSA (RDI ??5), and 96 patients met the criteria for positional OSA (67%), in which in almost half of these patients (47%), RDI was normalized (RDI?<?5) in non-supine position. Snoring frequency were significantly lower among positional OSA and OSA was less severe indicated by lower RDI and arousal index, higher mean and nadir oxygen saturation, and higher %NREM3. We also found that low snoring frequency (less than 20% of total sleep time) was a significant predictor for positional OSA (odd ratio of 3.27; p?=?0.011), contrarily to low mean oxygen saturation (<95%) which was found to be a negative predictor (odd ratio of 0.31; p?=?0.009). Among OSA patients, low RDI (<15) was a significant predictor for normalization of RDI in non-supine position (odd ratio of 8.77; p?=?<?0.001), contrarily to low mean oxygen saturation (<95%) which was also found to be a negative predictor (odd ratio of 0.13; p?=?0.001).

Conclusion

Positional OSA is very prevalent and noted in almost 70% of our patients. Low snoring frequency was noted to be a positive predictor for positional OSA, contrarily to low mean oxygen saturation which was found to be a negative predictor. These findings are encouraging that positional therapy can be very beneficial as the treatment modality for OSA among Asians.     

Difficult-to-control asthma and obstructive sleep apnea.

This study tested the hypothesis that asthma can promote obstructive sleep apnea (OSA) by looking at the prevalence of OSA among patients with difficult-to-control asthma receiving long-term oral corticosteroid (CS) therapy and examined some possible etiological factors. The study design was a prospective cohort study and was conducted in the pulmonary outpatient clinic of a tertiary care center in Haifa, Israel. Twenty-two consecutive patients with severe unstable asthma, 14 on continuous and 8 on bursts of oral CS, in addition to their standard therapy for a mean of 8.9 +/- 3.3 years, underwent a night polysomnography in a sleep laboratory regardless of sleep complaints. A standard questionnaire was completed upon attending the sleep laboratory. The OSA was defined as respiratory disturbance index (RDI) of > or = 5 and typical complaints. The correlation between RDI to asthma and morphometric parameters was tested. All but one patient had OSA [95.5% prevalence], with mean RDI of 17.7 +/- 2.5. The RDI values were significantly higher in the continuous CS therapy subgroup (21.4 +/- 3.4 vs. 11.1 +/- 1.6, p < 0.05]. The study group had above normal neck circumferences and body mass index. The former increased by 12.1% +/- 3.1% % to 29.8% +/- 1% during the oral CS therapy interval but had no significant effect on RDI as a covariant. This study showed an unexpectedly high prevalence of OSA among patients with unstable asthma receiving long-term chronic or frequent burst of oral CS therapy. It may be assumed that prolonged and especially continuous oral CS therapy in asthma increases airway collapsibility.     

The effect of nightly nasal CPAP treatment on nocturnal hypoxemia and sleep disorders in mustard gas-injured patients

Introduction

Sleep-related breathing disorders are associated with unusual respiratory pattern or an abnormal reduction in gas exchange during sleep that is common in sulfur mustard (SM) exposure.

Methods

We compared 57 Iranian male patients injured with SM and had any complaints of sleep problems with an age-matched group of 21 Iranian male patients who had complaints of sleep problems and were not chemically injured; this group had Epworth Sleepiness Scale (ESS) above 10 and whom referred for polysomnography. Split-night studies were performed for patients with diagnostic polysomnography for obstructive sleep apnea (OSA) and respiratory events. We then studied respiratory events including episodes of OSA, apnea–hypopnea index (AHI) and respiratory disturbance index (RDI).

Results

The mean age in mustard-exposed patients was 48.14?±?8.04 years and in age-matched group, 48.19?±?8.39 years. In mustard exposed patients, there were statistical differences for the episodes of OSA (p?=?0.001), AHI (p?=?0.001), and RDI (p?=?0.001) between two segments of split-night studies. In the age-matched group, there were statistically differences for each parameter (episodes of OSA (p?=?0.001), AHI (p?=?0.001), and RDI (p?=?0.001)). There were no significant differences between two groups.

Conclusion

This study indicated that the incidence of respiratory events and nocturnal hypoxemia during sleep in mustard-exposed patients were high and treatment with CPAP significantly reduced all these events.     

Blood pressure variability in obstructive sleep apnea: role of sympathetic nervous activity and effect of continuous positive airway pressure

BACKGROUND: Many studies support a link between obstructive sleep apnea (OSA), increased blood pressure (BP) and/or BP variability, and sympathetic nervous system (SNS) activity. We assessed the relationship between SNS activity and 24-h BP variability in patients with OSA, and the effect of continuous positive airway pressure (CPAP) on BP variability. DESIGN: Forty-one patients with a respiratory disturbance index (RDI) > 15 were randomized into CPAP or CPAP placebo groups for a 1-week trial. METHODS: Ambulatory BP, 24-h urine norepinephrine (NE) and polysomnography were measured prior to treatment and after 1 and 7 days of treatment. RESULTS: Neither RDI nor 24-h urine NE levels were related to 24-h mean BP levels. While RDI was associated only with night-time BP variability, daytime urine NE levels were associated with both night-time and daytime BP variability. After treatment, the BP variability decreased significantly but equally in both active and placebo CPAP groups. CONCLUSIONS: Obstructive sleep apnea is more related to BP variability than BP. Sympathetic nervous activity, as inferred from daytime urine NE, is related to changes in BP variability in OSA patients. BP variability is not specifically affected by CPAP.     

Insulin and obstructive sleep apnea in obese Chinese children

OBJECTIVE: In adults, obstructive sleep apnea (OSA) is associated with insulin resistance and dyslipidemia. We aimed to establish correlation between OSA, serum lipid profile, and insulin levels in obese snoring children. METHODS: Consecutive obese children with habitual snoring were recruited. They underwent physical examination, overnight polysomnography (PSG), and metabolic studies. OSA was diagnosed if apnea hypopnea index (AHI) > 1.0, and cases were considered to have moderate to severe OSA if AHI > 10. RESULTS: Ninety-four obese subjects with habitual snoring were studied. Seventy-three subjects were male and the median age of the studied group was 12.0 years (IQR 9.7-13.9). None of the subjects had active cardiopulmonary disease, and the BMI values of our subjects were >95th percentile using local reference charts. Sixty subjects had OSA, 47 being mild, and 13 being moderate to severe OSA. Multiple logistic regression analysis revealed that saturation nadir and insulin levels were significantly associated with OSA. CONCLUSION: OSA is prevalent among obese children with habitual snoring and insulin is independently associated with the condition. Its role in the cardiovascular complications of childhood sleep apnea is worthy of further exploration.     

Contributions of hypoxia and respiratory disturbance index to sympathetic activation and blood pressure in obstructive sleep apnea syndrome

Hypertension is a common finding among obstructive sleep apnea (OSA) patients, and is thought to be caused by sympathetic hyperactivity. The present study compares the contributions of the respiratory disturbance index (RDI) as a reflection of sleep fragmentation, and the magnitude of oxygen desaturation, to sympathetic activation as indexed by urinary norepinephrine concentrations, as well as to morning and evening blood pressure in sleep apnea syndrome patients. Data (polysomnography, blood pressure [BP], and urine catecholamines) of 38 consecutive OSA patients (age, 46 ± 14.5 years) were analyzed. Stepwise logistic regression analysis revealed that minimal oxygen saturation level (SaO₂min) was a significant predictor of both morning and evening norepinephrine levels, and that 37% of morning systolic BP variance could be accounted for by a combination of age and norepinephrine, while 20% of the diastolic BP variance was accounted for by SaO₂min alone. In contrast, RDI entered the prediction equation only when minimal oxygen saturation was rejected first. Our results indicate that the degree of nocturnal hypoxia is more closely associated with the level of sympathetic activation and with daytime level of blood pressure than with sleep fragmentation.     

Cardiovascular function alterations induced by acute paradoxical sleep deprivation in rats

Sleep loss has been implicated in triggering the hypertension. The goal of the present study was investigated the possible mechanisms underlying cardiovascular alterations after acute paradoxical sleep deprivation (PSD). Male Wistar rats were assigned in two experimental groups: (1) control and (2) PSD for 24?h using the modified single platform method. Paradoxical sleep deprived rats exhibited higher blood pressure, heart rate (HR) and impaired baroreceptor sensitivity. After pharmacological autonomic double blockade (propranolol and methylatropine administration), intrinsic heart rate was decreased after PSD. The PSD rats showed a reduction in the vagal tone without affecting sympathetic tone. Isoproterenol administration (0.001, 0.01 and 1?µg/kg) induced an increase in ΔHR responses in PSD group. Electrocardiographic analysis in response to β-adrenergic stimulation indicated that PSD contributed to ventricular cardiac arrhythmias. Our findings suggest that acute paradoxical sleep loss induce cardiovascular alterations, autonomic imbalance accompanied by impaired baroreflex sensitivity and increased arrhythmia susceptibility.     

Nasal pressure recordings to detect obstructive sleep apnea

Obstructive sleep apnea (OSA) is a common disease. Given the costs of in-laboratory polysomnography (PSG), alternative ambulatory methods for accurate diagnosis are desirable. The objective of this study was to evaluate the performance of a simple device (SleepCheck) to identify patients with sleep apnea. A total of 30 consecutive patients with suspected OSA syndrome referred to the sleep clinic were prospectively evaluated with standard PSG and SleepCheck simultaneously during an in-laboratory, supervised full-night diagnostic study. The PSG apnea and hypopnea index (AHI) was evaluated according to standard criteria, and SleepCheck assessed the respiratory disturbance index (RDI) based on nasal cannula pressure fluctuations. Compared to the full-night PSG, SleepCheck systematically overscored respiratory events (the mean difference between SleepCheck RDI and PSG AHI was 27.4±13.3 events per hour). This overscoring was in part related to normal physiologic decreases in flow during rapid eye movement sleep or after an arousal. However, there was reasonable correlation between AHI and RDI (r=0.805). Receiver operating characteristic curves with threshold values of AHI of 10 and 20/h demonstrated areas under the curves (AUCs) of 0.915 and 0.910, respectively. Optimum combinations of sensitivity and specificity for these thresholds were calculated as 86.4/75.0 and 88.9/81.0, respectively. Overall, the SleepCheck substantially overscored apneas and hypopneas in patients with suspected OSA. However, after correction of the bias, the SleepCheck had reasonable accuracy with an AUC, sensitivity, and specificity similar to other ambulatory type 4 devices currently available.This study was conducted at the Sleep Laboratory and Division of Orthodontics, The University of British Columbia, Canada     

Fibrinogen levels and obstructive sleep apnea in ischemic stroke

The plasma level of fibrinogen is felt to be an independent risk factor for vascular events. Obstructive sleep apnea (OSA) has a high prevalence in patients with stroke and may also be an independent risk factor. The aim of our study was to determine the association between OSA and plasma levels of fibrinogen in patients with stroke. Polysomnography was performed during neurological rehabilitation in 113 patients (82 men, 31 women, age 58 +/- 11.1 yr, mean +/- SD) with ischemic stroke. OSA was absent (RDI < 5) in 44 patients, 42 had mild OSA (5 < or = RDI < 20), and 27 had moderate to severe OSA (RDI > or = 20). Parameters of OSA (respiratory disturbance index [RDI], oxygen indices) were correlated to plasma levels of fibrinogen, measured in the morning after admission to rehabilitation. Fibrinogen was positively correlated with RDI (r = 0.24, p = 0.007), duration of the longest apnea (r = 0.18, p = 0.049), and negatively correlated with several oxygen indices including average minimal oxygen saturation (r = -0.41, p < 0.001). Correlation coefficients were slightly higher when excluding patients with stroke of presumed cardiac origin. Multiple linear regression identified minimal mean oxygen saturation and sex as independent predictors of fibrinogen level. The correlation between severity of coexisting OSA and fibrinogen level in patients with stroke suggests a possible pathophysiological mechanism for an increased risk of stroke in patients with OSA.     

The effect of sibutramine-assisted weight loss in men with obstructive sleep apnoea

OBJECTIVE: Obstructive sleep apnoea (OSA) occurs frequently in obese patients and may be reversible with weight loss. Obstructive sleep apnoea and obesity are both independent risk factors for hypertension and increased sympathetic activity. Sibutramine has been increasingly used in the management of obesity, but is relatively contraindicated in patients with hypertension. No studies have investigated the effect of sibutramine on OSA, blood pressure and heart rate. We aimed to assess the changes in OSA and cardiovascular parameters in obese men with OSA enrolled in a sibutramine-assisted weight loss programme (SIB-WL). DESIGN: Open uncontrolled cohort study of obese male subjects with OSA in an SIB-WL. SUBJECTS: Eighty-seven obese (body mass index =34.2+/-2.8 kg/m(2)) middle-aged (46.3+/-9.3 years) male subjects with symptomatic OSA (Epworth score 13.4+/-3.6; respiratory disturbance index (RDI) 46.0+/-23.1 events/h) completed the study. RESULTS: At 6 months, there was significant weight loss (8.3+/-4.7 kg, P<0.0001), as well as a reduction in waist and neck circumference and sagittal height (all P<0.0001). These changes were accompanied by a reduction in OSA severity (RDI fell by 16.3+/-19.4 events/h and Epworth score by 4.5+/-4.6), both P<0.0001). There was no significant change to systolic (P=0.07) or diastolic blood pressure (P=0.87); however, there was a mild rise in resting heart rate (P<0.0001). CONCLUSION: Moderate (approximately 10%) weight loss with SIB-WL results in improvement in OSA severity without increase in blood pressure in closely monitored OSA subjects.     

Effect of nasal-valve dilation on obstructive sleep apnea

OBJECTIVE: Nasal-valve dilation reduces nasal resistance and increases air flow. It is possible that this mechanism prevents hypopharyngeal collapse and sleep apneas. We investigated the effect of a plastic device (Nozovent; Prevancure AB; V?stra Fr?lunda, Sweden)-which dilates the nasal valve-on patients with obstructive sleep apnea (OSA). DESIGN: Prospective interventional study. SUBJECTS: Twenty-six consecutive patients with OSA were included (22 men; mean +/- SD age, 54.8+/-11.3 years; respiratory disturbance index [RDI], 34.4+/-18.5 events/h; body mass index, 31.6+/-5.7 kg/m(2)). INTERVENTION: The nasal dilator was inserted during sleep into the nares and fitted to exert a dilating force on the nasal valves by means of its elasticity. MEASUREMENTS: Polysomnographic studies were performed before and after 1 month of treatment. A responder is defined as one with a reduction in RDI to < 50% of the baseline value and RDI of < or =10 events/h during treatment. RESULTS: Five patients dropped out. As a result, only 21 patients were analyzed. Four patients responded, and 17 patients were nonresponders. In the whole population, neither the mean values for respiration during sleep nor sleep staging changed significantly with the device. CONCLUSIONS: The investigated nasal dilator had no effect on sleep-related breathing disorders in patients with moderate to severe OSA. The reduction in nasal resistance does not prevent hypopharyngeal obstruction.     

Influence of gender and anthropometric measures on severity of obstructive sleep apnea

Purpose

Gender differences influence upper airway anatomy and physiology. The purpose of our study was to evaluate the influence of gender as well as anthropometric measures on severity of obstructive sleep apnea (OSA).

Methods

A retrospective review of patients referred to our sleep laboratory for evaluation of OSA was done. Patients with a diagnosis of OSA (Respiratory Disturbance Index (RDI) >?5) were included in the study. Anthropometric measurements were available for all the patients included in the study. Measurements of subjects?? height, weight, neck size, and waist and hip sizes were used in the study; waist?Chip ratio and neck-to-height ratio were calculated.

Results

Three hundred eighty-six females and 661 males were included. Women were older than men and had a higher body mass index (BMI) and waist-to-hip ratio; men had a thicker neck circumference and a higher neck-to-height ratio. The severity of OSA was significantly higher in males (RDI 41.2?±?27.9 in men vs. 30.0?±?26.7 in women, p?<?0.0001) despite a lower BMI and age in the men. Severity of OSA, as measured by RDI, varied significantly with changes in anthropometric measures such as neck circumference, and waist and hip sizes in both genders. Waist-to-hip ratio was associated with severity of OSA in men but not in women (p?=?0.19 and 0.0001 in women and men, respectively). However, no single anthropometric value was found to be strongly predictive of OSA severity.

Conclusion

Despite having a higher mean BMI and age, women have lower RDI compared with men. Waist-to-hip ratio is more predictive of severity of OSA in men than in women. However, the correlation of anthropometric measures with severity of OSA was weak in our subjects.     

Prevalence of left ventricular hypertrophy in persons with and without obstructive sleep apnea

We investigated the prevalence of left ventricular hypertrophy (LVH) in persons with and without obstructive sleep apnea (OSA). Fifty-three persons had a nocturnal polysomnogram to diagnose OSA and 2-dimensional echocardiograms to measure left ventricular mass. OSA was considered mild if the respiratory disturbance index (RDI) was 5 to 15, moderate if the RDI was 15 to 30, and severe if the RDI was >30. LVH was diagnosed if the left ventricular mass index was >110 g/m in women and >134 g/m in men. LVH was present in 21 of 27 persons (78%) with moderate or severe OSA, in 6 of 13 persons (46%) with mild OSA, and in 3 of 13 persons (23%) with no OSA (P < 0.001 comparing moderate or severe OSA with no OSA and P < 0.05 comparing moderate or severe OSA with mild OSA). OSA was a significant independent predictor of LVH after controlling the confounding effects of hypertension with an odds ratio of 3.579 (95% confidence interval, 1.589-8.058).     

Evaluation and validation of four translated Chinese questionnaires for obstructive sleep apnea patients in Hong Kong

Background

The present study validates and evaluates the sensitivity and specificity of four internationally popular questionnaires, translated into Chinese, for assessing suspected obstructive sleep apnea (OSA) patients, namely, the Berlin questionnaire, the ASA checklist, the STOP questionnaire and the STOP–BANG questionnaire. Their predictive values in OSA risks in patients presenting with OSA symptoms are examined. Questionnaires may be helpful in prioritizing polysomnography (PSG) and in treatment for the more severe cases.

Methods

All patients attending our sleep laboratory for overnight PSG were recruited. They were asked to complete three questionnaires (Berlin, ASA checklist and STOP) 2 weeks before and on the same night as the PSG. STOP–BANG questionnaire, an extended STOP with demographic data, ‘B’-body mass index (BMI), ‘A’-age, ‘N’-neck circumference and ‘G’-gender was completed by our technologists using the patient’s completed STOP.

Results

A number of 141 patients were recruited. The sensitivities and specificities for STOP–BANG with cutoffs at PSG’s RDI?=?5, RDI?=?15 and RDI?=?30 were 81 % to 86 % and 34 % to 57 %, respectively. The high-risk group patients identified by STOP–BANG had significantly higher respiratory disturbance index and lower minimum oxygen saturation than the low-risk group patients.

Conclusion

Among the four questionnaires studied, STOP–BANG, with only eight questions and the highest sensitivity, is the best questionnaire of the four for OSA screening. This can potentially assist in prioritizing PSG and can be helpful in clinical or self-evaluation by the general public.     

Selective potentiation of peripheral chemoreflex sensitivity in obstructive sleep apnea

BACKGROUND: The chemoreflexes are an important mechanism for regulation of both breathing and autonomic cardiovascular function. Abnormalities in chemoreflex mechanisms may be implicated in increased cardiovascular stress in patients with obstructive sleep apnea (OSA). We tested the hypothesis that chemoreflex function is altered in patients with OSA. METHODS AND RESULTS: We compared ventilatory, sympathetic, heart rate, and blood pressure responses to hypoxia, hypercapnia, and the cold pressor test in 16 untreated normotensive patients with OSA and 12 normal control subjects matched for age and body mass index. Baseline muscle sympathetic nerve activity (MSNA) was higher in the patients with OSA than in the control subjects (43+/-4 versus 21+/-3 bursts per minute; P<0. 001). During hypoxia, patients with OSA had greater increases in minute ventilation (5.8+/-0.8 versus 3.2+/-0.7 L/min; P=0.02), heart rate (10+/-1 versus 7+/-1 bpm; P=0.03), and mean arterial pressure (7+/-2 versus 0+/-2 mm Hg; P=0.001) than control subjects. Despite higher ventilation and blood pressure (both of which inhibit sympathetic activity) in OSA patients, the MSNA increase during hypoxia was similar in OSA patients and control subjects. When the sympathetic-inhibitory influence of breathing was eliminated by apnea during hypoxia, the increase in MSNA in OSA patients (106+/-20%) was greater than in control subjects (52+/-23%; P=0.04). Prolongation of R-R interval with apnea during hypoxia was also greater in OSA patients (24+/-6%) than in control subjects (7+/-5%) (P=0.04). Autonomic, ventilatory, and blood pressure responses to hypercapnia and the cold pressor test in OSA patients were not different from those observed in control subjects. CONCLUSIONS: OSA is associated with a selective potentiation of autonomic, hemodynamic, and ventilatory responses to peripheral chemoreceptor activation by hypoxia.     

Is there a chronic sleep stage-dependent linear and nonlinear cardiac autonomic impairment in obstructive sleep apnea?

Rationale

Obstructive sleep apnea (OSA) is a respiratory disorder that has the potential to negatively impact heart rate variability (HRV) during the sleep cycle. However, it is uncertain whether there is a chronic sleep stage-dependent linear and nonlinear cardiac autonomic impairment in OSA. The aim of this study was to perform HRV analysis in apnea-free samples as well as during stage 2 and rapid eye movement (REM) sleep in mild and moderate OSA (MiOSA and MOSA, respectively) subjects as well as health controls (NonOSA).

Methods

This study included 20 MiOSA (37?±?14 years), 20 MOSA (39?±?8 years), and 18 NonOSA (36?±?8 years) subjects. Subjects underwent in-laboratory overnight polysomnography with electrocardiography recording. HRV indices were obtained by analyzing the R–R intervals (RRis) in 5-min apnea-free samples by the linear frequency domain [low frequency (LF), high frequency (HF) and LF/HF], Poincaré plot [standard deviation (SD1) and (SD2)], recurrence plot [mean line length (Lmean)], recurrence rate (REC), determinism (DET), and Shannon entropy (ShanEn).

Results

The MOSA group presented with higher LF, LF/HF, and DET indices compared to NonOSA as well as a lower parasympathetic index (HF), suggesting sympathetic hyperactivity in MOSA subjects. Interestingly, MiOSA subjects failed to show the expected linear HRV difference between sleep stages, as observed in NonOSA, which may represent an early onset of autonomic impairment at this stage of OSA.

Conclusion

In OSA patients, there is a chronic sleep stage-dependent impairment of linear and nonlinear cardiac autonomic modulation. Interestingly, this impairment may be identifiable during the early stages of the disease.     

Effects of tonsillectomy on sleep study parameters in adult patients with obstructive sleep apnea—a prospective study

Objective

The objective of this study is to evaluate the efficacy of tonsillectomy in reduction of respiratory disturbance index (RDI) and other sleep study parameters in patients with obstructive sleep apnea (OSA).

Methods

This study involves 34 adults with OSA and Friedman grade 3 or 4 tonsils. All 34 patients were treated with tonsillectomy, as the only surgical treatment for OSA from 2007 to 2011. Pre- and postoperative polysomnography were performed in all these patients.

Results

Prior to tonsillectomy, 21 patients had severe, 9 had moderate, and 4 had mild OSA. Surgical response rate (defined as 50 % or more reduction in apnea–hypopnea index (AHI) and a postoperative AHI of less than 20) was 71.4 % among patients with severe OSA, 77.7 % among patients with moderate, and 75 % among patients with mild. Among all the 34 patients, there was a reduction of 24.6 (p?=?0.000) in the RDI postoperatively. In our sub-analysis, we arbitrarily divided the patients into three groups: patients with RDI less than 30, patients with RDI between 30 and 60, and patients with RDI above 60. It showed that, in the group with RDI >60, an average reduction of RDI by 57.6 (p?=?0.000) was achieved and was the greatest reduction in RDI.

Conclusions

Tonsillectomy alone may be considered as an effective first line surgical procedure in the treatment of OSA in selected patients. Patients with Friedman grade 3 or 4 tonsils may be considered for tonsillectomy as the initial surgical procedure, reserving other upper airway procedures at a later stage if necessary.