Inverse relationship of subjective daytime sleepiness to mortality in heart failure patients with sleep apnoea.

AIMS: Patients with sleep apnoea (SA) and heart failure (HF) are less sleepy than SA patients without HF. HF and SA both increase sympathetic nervous system activity (SNA). SNA can augment alertness. We previously showed that in HF patients, the degree of daytime sleepiness was not related to the severity of SA but was inversely related to SNA. Elevated SNA is associated with increased mortality in HF. Therefore, we hypothesized that in HF patients with SA, the degree of daytime sleepiness will be inversely related to mortality. METHODS AND RESULTS: In a prospective cohort study, 218 consecutive patients with systolic HF had overnight polysomnography. Among them, 80 subjects with SA (apnoea-hypopnoea index ≥15) were followed for a mean of 28 months to determine all-cause mortality rate. Subjective daytime sleepiness was assessed by the Epworth Sleepiness Scale (ESS). During follow-up, 20 patients died. The 5 year death rate in patients with ESS less than 6 (i.e. less sleepy) was significantly higher than in patients with an ESS at or above the median of 6 (i.e. sleepier) [21.3 deaths/100 patient-years vs. 6.2 deaths/100 patient-years, unadjusted hazard ratio (HR) 2.94, 95% confidence interval (CI) 1.20 to 7.20, P = 0.018]. After adjusting for confounding factors that included sex, history of hypertension, and mean arterial oxyhaemoglobin saturation, compared with the sleepier patients, less sleepy patients had greater risk of mortality (HR 2.56, 95% CI 1.01 to 6.47, P = 0.047). As a continuous variable, ESS scores were inversely related to mortality risk (HR 0.86, 95% CI 0.75 to 0.98, P = 0.022). CONCLUSIONS: In patients with HF and SA, the degree of subjective daytime sleepiness is inversely related to the mortality risk, suggesting that among HF patients with SA, those with the least daytime sleepiness are at greater risk of death. They may therefore have greater potential for mortality benefit from therapy of SA than those with greater daytime sleepiness.

The Prioritization of Clinical Risk Factors of Obstructive Sleep Apnea Severity Using Fuzzy Analytic Hierarchy Process.

Recently, there has been a problem of shortage of sleep laboratories that can accommodate the patients in a timely manner. Delayed diagnosis and treatment may lead to worse outcomes particularly in patients with severe obstructive sleep apnea (OSA). For this reason, the prioritization in polysomnography (PSG) queueing should be endorsed based on disease severity. To date, there have been conflicting data whether clinical information can predict OSA severity. The 1,042 suspected OSA patients underwent diagnostic PSG study at Siriraj Sleep Center during 2010-2011. A total of 113 variables were obtained from sleep questionnaires and anthropometric measurements. The 19 groups of clinical risk factors consisting of 42 variables were categorized into each OSA severity. This study aimed to array these factors by employing Fuzzy Analytic Hierarchy Process approach based on normalized weight vector. The results revealed that the first rank of clinical risk factors in Severe, Moderate, Mild, and No OSA was nighttime symptoms. The overall sensitivity/specificity of the approach to these groups was 92.32%/91.76%, 89.52%/88.18%, 91.08%/84.58%, and 96.49%/81.23%, respectively. We propose that the urgent PSG appointment should include clinical risk factors of Severe OSA group. In addition, the screening for Mild from No OSA patients in sleep center setting using symptoms during sleep is also recommended (sensitivity = 87.12% and specificity = 72.22%).

Overnight Effects of Obstructive Sleep Apnea and Its Treatment on Stroke Volume in Patients With Heart Failure.

BACKGROUND: We previously showed in heart failure (HF) patients that obstructive respiratory events during sleep and generation of negative intrathoracic pressure during Mueller manoeuvres, mimicking obstructive apneas, acutely reduced stroke volume (SV). We also showed that treating obstructive sleep apnea (OSA) with continuous positive airway pressure (CPAP) increased left ventricular ejection fraction over a 1-month period. We therefore hypothesized that, in HF patients, those with OSA would have greater overnight declines in SV and cardiac output (CO) than in those without sleep apnea, and that therapy of OSA using CPAP would prevent these declines. METHODS: We examined overnight percent change in SV and CO in 32 HF patients with and 28 without OSA using digital photoplethysmography. Among patients with OSA, we also examined changes in SV and CO during a CPAP titration study. RESULTS: During the baseline polysomnogram SV and CO decreased more overnight in those with OSA than in those without sleep apnea (-12.6 ± 7.7% vs -3.2 ± 6.8%; P < 0.001 and -16.2 ± 9.9% vs -3.7 ± 8.3%; P < 0.001, respectively). Overnight changes in SV and CO correlated inversely with total apnea-hypopnea index (r = -0.551; P < 0.001 and r = -0.522; P < 0.001, respectively). In 21 patients with OSA, CPAP reduced the total apnea-hypopnea index from 37.7 ± 21.4 to 15.0 ± 16.0 (P < 0.001) in association with attenuation of the overnight reduction of SV (from -14.0 ± 7.9% to -3.4 ± 9.8%; P = 0.002) and CO (from -17.2 ± 9.0% to -9.7 ± 10.7%; P = 0.042). CONCLUSIONS: In patients with HF, coexisting OSA causes overnight declines in SV and CO that are prevented through reversal of OSA by CPAP.

Reliability and validity of the Thai version of the Pittsburgh Sleep Quality Index.

OBJECTIVE: To assess the internal consistency, test-retest reliability, and validity of the Thai version of the Pittsburgh Sleep Quality Index (Thai-PSQI), which was recently translated using a standardized method, in Thai patients with major sleep disorders. MATERIAL AND METHOD: The Thai-PSQI was developed under a standard translation protocol and administered to "bad" sleepers (i.e. patients with suspected obstructive sleep apnea [OSA], depression, or insomnia) and "good" sleepers in an academic tertiary care setting. All participants were asked to complete the same questionnaire after 2-4 weeks. RESULTS: A total of 138 participants consisting of 69 patients with OSA, 28 with major depression, 11 with primary insomnia, and 30 controls completed the questionnaire. The global scores of the Thai-PSQI revealed that it had excellent internal consistency (Cronbach's alpha = 0.837) and test-retest reliability (intraclass correlation coefficient = 0.89). An analysis of covariance demonstrated a significant difference in Thai-PSQI global score between good sleepers and bad sleepers (p < 0.001). A cut-off point of 5 out of 6 on the global score resulted in a sensitivity of 77.78% and specificity of 93.33%. CONCLUSION: The Thai-PSQI is a valid and reliable tool for screening and identifying the presence of significant sleep disturbances, and is comparable to the original English version.

Relation of periodic leg movements during sleep and mortality in patients with systolic heart failure.

Periodic leg movements during sleep (PLMs) are a disorder characterized by regularly recurring movements of the legs during sleep. Although PLMs are common in patients with heart failure (HF), their clinical significance is unknown. The aim of this study was to determine whether, in patients with HF, PLMs are associated with increased mortality risk. In a prospective cohort study, 218 consecutive patients with systolic HF newly referred to an HF clinic from 1997 to 2004 who underwent overnight polysomnography, regardless of symptoms or signs of sleep disorders, were enrolled. The frequency of PLMs per hour of sleep was quantified as the PLM index (PLMI). Patients were classified as either normal (PLMI <5) or abnormal (PLMI ≥5). Eighty-one of the patients (37%) had PLMIs ≥5. During a mean follow-up period of 32.9 months, complete follow-up data were obtained in 95%. Patients with PLMIs ≥5 were older and had lower left ventricular ejection fractions and higher New York Heart Association classes than patients with PLMIs <5. The mortality rate was significantly higher in patients with PLMIs ≥5 than those with PMLIs <5 (10.4 vs 3.4 deaths/100 patient-years, p = 0.002). After adjusting for significant confounding factors, the presence of PLMI ≥5 remained a significant independent risk for death (hazard ratio 2.42, 95% confidence interval 1.16 to 5.02, p = 0.018). In conclusion, in patients with systolic HF, the presence of PLMI ≥5 is associated with an increased mortality risk, but these findings do not establish a cause-effect relation.

Severe obesity is a risk factor for severe obstructive sleep apnea in obese children.

OBJECTIVE: To determine the association between degree of obesity and severity of OSA in Thai children MATERIAL AND METHOD: The present retrospective study recruited obese children aged 3 to 15 years who had habitual snoring and underwent polysomnography (PSG) between January 2009 and June 2010. Obesity was defined as percentage of ideal weight for height (%W/H) > or = 120 and was classified as mild (%W/H of 120-139), moderate (140-159), severe (160-199) and morbid (> or = 200). OSA was classified as severe (AHI > or = 10) and non-severe (AHI < 10). RESULTS: Of 73 obese children, the mean age was 9.92 +/- 3.42 years of which 60.3% were boys. The mean +/- SD of BMI was 28.38 +/- 5.99 kg/m2 and %W/H +/- SD was 162.63 +/- 26 26. Gender age, height, weight and BMI were not significantly different between severe and non-severe OSA groups. However, the %W/H of the severe OSA group (171.38% +/- 29.54%) was significantly greater than the non-severe group (157.19% +/- 22.68%) (p = 0.02). Severe to morbid obesity (OR 2.80, 95% CI 1.06-7.42; p = 0.038) and enlarged tonsils at least 3+ (OR 3.28, 95% CI 1.22-8.81; p = 0.018) were the risk factors for severe OSA. CONCLUSION: Severe to morbid obesity was a predicting factor for severe OSA. These results suggested that severely obese children with snoring should have early recognition for severe OSA, which is highly contributing to multiple sequalae.

Nocturnal rostral fluid shift: a unifying concept for the pathogenesis of obstructive and central sleep apnea in men with heart failure.

BACKGROUND: Obstructive sleep apnea (OSA) and central sleep apnea are common in patients with heart failure. We hypothesized that in such patients, severity of OSA is related to overnight rostral leg fluid displacement and increase in neck circumference, severity of central sleep apnea is related to overnight rostral fluid displacement and to sleep Pco(2), and continuous positive airway pressure alleviates OSA in association with prevention of fluid accumulation in the neck. METHODS AND RESULTS: In 57 patients with heart failure (ejection fraction or=50% of apneas and hypopneas obstructive) and a central-dominant group (>50% of events central). Patients with OSA received continuous positive airway pressure. In obstructive-dominant patients, there were inverse relationships between overnight change in leg fluid volume and both the overnight change in neck circumference (r=-0.780, P<0.001) and the apnea-hypopnea index (r=-0.881, P<0.001) but not transcutaneous Pco(2). In central-dominant patients, the overnight reduction in leg fluid volume correlated inversely with the apnea-hypopnea index (r=-0.919, P<0.001) and the overnight change in neck circumference (r=-0.568, P=0.013) and directly with transcutaneous Pco(2) (r=0.569, P=0.009). Continuous positive airway pressure alleviated OSA in association with prevention of the overnight increase in neck circumference (P<0.001). CONCLUSIONS: Our findings suggest that nocturnal rostral fluid shift is a unifying concept contributing to the pathogenesis of both OSA and central sleep apnea in patients with heart failure.

Independent association of drug-resistant hypertension to reduced sleep duration and efficiency.

BACKGROUND: Experimentally induced sleep deprivation can raise blood pressure (BP) and worsen hypertension. We recently reported a significantly higher prevalence of obstructive sleep apnea (OSA) and reduced rapid eye movement (REM) sleep time in drug-resistant hypertensives compared to controlled hypertensives. The objective of this study was to test the hypothesis that short sleep duration is associated with resistant hypertension (RH) independently of OSA, which can itself disrupt and shorten sleep. METHODS: In a case-control study, overnight polysomnographic results of subjects with OSA and RH (n = 62) were compared to those with OSA of equal severity and either controlled hypertension (CH) (n = 49) or normotension (n = 40). RESULTS: Subjects with RH slept 33.8 min (P = 0.02) and 37.2 min (P = 0.02) less than those with CH and normotension, respectively. Consequently, sleep efficiency was reduced by 7.9% (P = 0.007) and 10.2% (P = 0.002), respectively. They also spent 9.7 min (P = 0.06) and 11.6 min (P = 0.04) less time in REM sleep compared to those with CH and normotension, respectively. Older age, greater body mass index (BMI) and greater apnea-hypopnea index (AHI) were also associated with shorter sleep time (P = 0.02, P = 0.001, and P = 0.03, respectively) and reduced sleep efficiency (P = 0.0003, P = 0.03, and P = 0.01, respectively). CONCLUSIONS: Our study demonstrates that, compared to subjects with CH or normotension, those with RH have shorter total and REM sleep times and lower sleep efficiency independently of OSA. These data suggest that reduced sleep time may contribute to the severity of hypertension.

Association between refractory hypertension and obstructive sleep apnea.

BACKGROUND: Obstructive sleep apnea (OSA) increases the risk for mild hypertension, but its relationship to refractory hypertension (RHT) has not been systematically examined. We previously reported a high prevalence of OSA in patients with RHT, but did not have a control group with which to compare. Rapid eye movement (REM) sleep deprivation can raise blood pressure in animals. However, a potential relationship of OSA and REM sleep time with RHT has not been examined. OBJECTIVE: To determine whether, compared with patients with well controlled hypertension, those with RHT have a higher prevalence of OSA (apnea-hypopnea index > or = 10 per hour of sleep) and shorter REM sleep time. METHODS: We compared the prevalence of OSA and sleep structure in 42 patients with RHT with 22 patients with controlled hypertension, matched for age, sex and BMI. RESULTS: Compared with the controlled hypertension group, the RHT group had a significantly higher prevalence of OSA (81 versus 55%, P = 0.03) and less REM sleep time (47.0 +/- 4.5 versus 63.2 +/- 4.9 min, P = 0.02). Multivariate analysis revealed significantly increased odds of having RHT associated with OSA independent of other risk factors (adjusted odds ratio, 3.994; 95% confidence interval, 1.191-13.388). Reduced REM sleep time was also independently associated with the presence of RHT (adjusted odds ratio, 1.025; 95% confidence interval, 1.002-1.049). CONCLUSION: OSA and reduced REM sleep time are associated with increased odds of having RHT and, therefore, may play roles in its pathogenesis.

Prevalence and physiological predictors of sleep apnea in patients with heart failure and systolic dysfunction.

BACKGROUND: Previous studies reported high prevalences of obstructive and central sleep apnea (OSA and CSA, respectively) in patients with heart failure (HF). However, these preceded widespread use of beta-blockers and spironolactone that might have reduced their prevalences. We therefore determined, in patients with HF, prevalences and predictors of OSA and CSA and the influence of changes in HF therapy on prevalences. METHODS AND RESULTS: A total of 218 HF patients with left ventricular ejection fraction (LVEF) or=15 hours of sleep, either OSA or CSA), or mild to no sleep apnea. The prevalence of moderate to severe OSA was 26% and of CSA was 21%. Predictors of OSA were older age, male sex, and greater body mass index, and of CSA were older age, male sex, atrial fibrillation, hypocapnia, and diuretic use. Between 1997 and 2004, the prevalences of OSA and CSA did not change significantly (P(trend) =.460, P(trend) =.211, respectively) despite increased use of beta-blockers and spironolactone (P(trend) < .001, P(trend) < .001, respectively), and an increase in LVEF (P(trend)=.005). CONCLUSIONS: OSA and CSA remain common in patients with HF, despite increases in beta-blocker and spironolactone use.

Effect of continuous positive airway pressure on sleep structure in heart failure patients with central sleep apnea.

STUDY OBJECTIVES: At termination of obstructive apneas, arousal is a protective mechanism that facilitates restoration of upper airway patency and airflow. Treating obstructive sleep apnea (OSA) by continuous positive airway pressure (CPAP) reduces arousal frequency indicating that such arousals are caused by OSA. In heart failure (HF) patients with central sleep apnea (CSA), however, arousals frequently occur several breaths after apnea termination, and there is uncertainty as to whether arousals from sleep are a consequence of CSA. If so, they should diminish in frequency when CSA is attenuated. We therefore sought to determine whether attenuation of CSA by CPAP reduces arousal frequency. DESIGN: Randomized controlled clinical trial. PATIENTS AND SETTING: We examined data from 205 HF patients with CSA (apnea-hypopnea index [AHI] > or =15, > 50% were central) randomized to CPAP or control who had polysomnograms performed at baseline and 3 months later. MEASUREMENTS AND RESULTS: In the control group, there was no change in AHI or frequency of arousals. In the CPAP-treated group, the AHI decreased significantly (from [mean +/- SD] 38.9 +/- 15.0 to 17.6 +/- 16.3, P < 0.001) but neither the frequency of arousals nor sleep structure changed significantly. CONCLUSION: These data suggest that attenuation of CSA by CPAP does not reduce arousal frequency in HF patients. We conclude that arousals were not mainly a consequence of CSA, and may not have been acting as a defense mechanism to terminate apneas in the same way they do in OSA.

Difference in upper airway collapsibility during wakefulness between men and women in response to lower-body positive pressure.

Fluid shift from the legs to the neck induced by LBPP (lower-body positive pressure) increases UA (upper airway) collapsibility in healthy men. Rostral fluid displacement during recumbency may therefore contribute to the pathogenesis of OSA (obstructive sleep apnoea). There is a higher prevalence of OSA in men than in women. We therefore hypothesized that UA collapsibility increases more in men in response to rostral fluid displacement than in women. UA collapsibility was assessed in healthy, non-obese men and women while awake by determining UA Pcrit (critical closing pressure) during application of different suction pressures to the UA. Subjects were randomized to 5 min control or LBPP arms after which they crossed-over into the other arm following a 30 min washout. LBPP was applied by inflating anti-shock trousers wrapped around both legs to 40 mmHg. Pcrit, leg fluid volume and neck circumference were measured at baseline and after 5 min of both control and LBPP periods. LBPP caused a decrease in leg fluid volume and an increase in neck circumference that did not differ between men and women. However, compared with the control period, LBPP induced a much greater increase in Pcrit in men than in women (7.2+/-1.8 compared with 2.0+/-1.5 cm H2O, P=0.035). We conclude that rostral fluid displacement by LBPP increases UA collapsibility more in healthy, non-obese men than in women. This may be one mechanism contributing to the higher prevalence of OSA in men than in women.

Relationship between overnight rostral fluid shift and Obstructive Sleep Apnea in nonobese men.

RATIONALE: The cause of increased pharyngeal collapsibility in patients with obstructive sleep apnea is incompletely understood. In awake healthy subjects, we showed that fluid displacement from the legs into the neck induced by lower body positive pressure reduces upper airway size and increases its collapsibility. Prolonged sitting leads to dependent fluid accumulation in the legs. OBJECTIVES: To test the hypotheses that the apnea-hypopnea index (AHI) during sleep will be related to the amount of fluid spontaneously displaced from the legs overnight, and that this will, in turn, be related to the time spent sitting the previous day. METHODS: In 23 nonobese healthy men referred for sleep studies for suspected obstructive sleep apnea, we assessed the changes in leg fluid volume and in neck circumference from the beginning to the end of the night, and the time spent sitting during the previous day. MEASUREMENTS AND MAIN RESULTS: The overnight change in leg fluid volume correlated strongly with the AHI (r = -0.773, P < 0.001), the change in neck circumference (r = -0.792, P < 0.001), and the time spent sitting (r = -0.588, P = 0.003). Multivariate analysis showed that the only significant independent correlates of the AHI were the overnight changes in leg fluid volume and neck circumference, which together explained 68% of the variability in the AHI among subjects. CONCLUSIONS: These novel findings suggest that overnight rostral fluid displacement from the legs, related to prolonged sitting, may play a previously unrecognized role in the pathogenesis of obstructive sleep apnea in nonobese men that is independent of body weight.

Sustained effect of continuous positive airway pressure on baroreflex sensitivity in congestive heart failure patients with obstructive sleep apnea.

BACKGROUND: Patients with either heart failure or obstructive sleep apnea have a reduced baroreflex sensitivity for heart rate, a sign of poor prognosis. We previously demonstrated that nocturnal application of continuous positive airway pressure to heart failure patients with obstructive sleep apnea increased baroreflex sensitivity acutely, but it is not known whether these effects persist into wakefulness. OBJECTIVE: To determine whether treating obstructive sleep apnea in heart failure patients with continuous positive airway pressure improves baroreflex sensitivity during wakefulness. METHODS: Spontaneous baroreflex sensitivity was assessed during wakefulness in 33 heart failure patients (left ventricular ejection fraction < or = 45%) with obstructive sleep apnea (apnea-hypopnea index > or = 20). Subsequently, baroreflex sensitivity was reassessed 1 month after patients were randomly allocated to nocturnal continuous positive airway pressure treatment or no treatment (control). RESULTS: Compared with the 14 control patients, the 19 continuous positive airway pressure-treated patients experienced a greater increase in baroreflex sensitivity [median, (25%, 75%)] [from 5.4 (2.2, 8.3) to 7.9 (4.4, 9.4) ms/mmHg; P = 0.01] and left ventricular ejection fraction (P < 0.001). In addition, daytime systolic blood pressure and heart rate decreased more in the continuous positive airway pressure group (from 122 +/- 15 to 113 +/- 12 mmHg; P = 0.02, and from 66 +/- 8 to 62 +/- 8 bpm; P < 0.001, respectively) than in the control group. CONCLUSION: Treatment of coexisting obstructive sleep apnea by continuous positive airway pressure in heart failure patients improves baroreflex sensitivity during wakefulness in addition to improving left ventricular ejection fraction and lowering blood pressure and heart rate. These data indicate that the improved autonomic regulation of heart rate in heart failure patients treated for obstructive sleep apnea during sleep persists into wakefulness.

Lower body positive pressure increases upper airway collapsibility in healthy subjects.

We previously showed that rostral fluid displacement by lower body positive pressure (LBPP) narrows the upper airway (UA) and increases UA resistance, but effects on UA collapsibility remained unknown. To test if LBPP increases UA collapsibility, 13 healthy men were randomized into a control or LBPP arm then crossed over into the other arm with a 30-min washout in between. LBPP was applied by inflating anti-shock trousers wrapped around both legs to 40 mmHg. UA collapsibility was assessed by determining UA critical closing pressure (P crit) during application of different negative airway pressures. P crit and leg fluid volume were measured at baseline and after 5 min during both periods. LBPP caused a significant increase in P crit associated with a reduction in leg fluid volume. We conclude that rostral fluid displacement by LBPP increases UA collapsibility in healthy men, suggesting that fluid shift into the neck could increase UA collapsibility during sleep and thereby predispose patients with fluid overload states to obstructive sleep apnea.

Influence of obstructive sleep apnea on mortality in patients with heart failure.

OBJECTIVES: This study sought to determine, in patients with heart failure (HF), whether untreated moderate to severe obstructive sleep apnea (OSA) is associated with a higher mortality rate than in patients with mild to no sleep apnea (M-NSA). BACKGROUND: Obstructive sleep apnea is common in patients with HF and exposes the heart and circulation to adverse mechanical and autonomic effects. However, its effect on mortality rates of patients with HF has not been reported. METHODS: In a prospective study involving 164 HF patients with left ventricular ejection fractions (LVEFs) < or =45%, we performed polysomnography and compared death rates between those with M-NSA (apnea-hypopnea index [AHI] <15/h of sleep) and those with untreated OSA (AHI > or =15/h of sleep). RESULTS: During a mean (+/- SD) of 2.9 +/- 2.2 and a maximum of 7.3 years of follow-up, the death rate was significantly greater in the 37 untreated OSA patients than in the 113 M-NSA patients after controlling for confounding factors (8.7 vs. 4.2 deaths per 100 patient-years, p = 0.029). Although there were no deaths among the 14 patients whose OSA was treated by continuous positive airway pressure (CPAP), the mortality rate was not significantly different from the untreated OSA patients (p = 0.070). CONCLUSIONS: In patients with HF, untreated OSA is associated with an increased risk of death independently of confounding factors.

Alterations in upper airway cross-sectional area in response to lower body positive pressure in healthy subjects.

BACKGROUND: Fluid accumulation in the neck during recumbency might narrow the upper airway (UA) and thereby contribute to its collapse in patients with obstructive sleep apnoea (OSA). It is hypothesised that acute fluid shifts from the legs to the upper body in healthy subjects would increase neck circumference and reduce the cross-sectional area of the UA (UA-XSA). METHODS: In 27 healthy non-obese subjects of mean (SE) age 39 (3) years and body mass index 23.2 (0.6) kg/m2 studied while supine, leg fluid volume was measured using bioelectrical impedance, neck circumference using a mercury strain gauge and mean UA-XSA between the velum and the glottis using acoustic pharyngometry at end expiration. Measurements were made at baseline after which subjects were randomly assigned to a 5 min time control period or to a 5 min application of lower body positive pressure (LBPP) at 40 mm Hg by anti-shock trousers, separated by a 15 min washout period. Subjects then crossed over to the opposite arm of the study. RESULTS: Compared with control, application of LBPP significantly reduced leg fluid volume (p<0.001) and increased neck circumference (p<0.001), both at 1 min and 5 min, and reduced UA-XSA after both 1 min (-0.15 cm2; 95% CI -0.23 to -0.09, p<0.001) and 5 min (-0.20 cm2; 95% CI -0.33 to -0.09, p<0.001). CONCLUSION: In healthy subjects, displacement of fluid from the legs by LBPP causes distension of the neck and narrowing of the UA lumen. Fluid displacement from the lower to the upper body while recumbent may contribute to pharyngeal narrowing and obstruction to airflow in patients with OSA. This may have particular pathological significance in oedematous states such as heart and renal failure.

Comparison of clinical and polysomnographic characteristics of non-obese and obese patients with obstructive sleep apnea.

OBJECTIVE: To compare the clinical features, anthropometric indices, and polysomnographic data between different body mass index (BMI) subgroups of obstructive sleep apnea (OSA) patients. MATERIAL AND METHOD: The authors reviewed the data from OSA patients in Siriraj Sleep Clinic from April 2005 to September 2006. Objective measurement for sleepiness (Epworth Sleepiness Scale, ESS), anthropometric measurements [body mass index (BMI), neck circumference, thyromental distance, Mallampati S score, and occlusion pattern] and polysomnographic recordings [apnea/hypopnea index (AHI) during REM and NREM periods, respiratory arousal index, periodic leg movement index, minimal oxygen saturation, total sleep time with oxygen saturation <90%, and desaturation index] were collected. The patients were stratified into the non-obese group and obese group if their BMI was <27 or > or =27 kg/m2 respectively. RESULTS: Of the total 158 patients, 71 were non-obese and 87 were obese, no difference in mean age and sex was observed, but more patients with hypertension and coronary artery disease were noted in the obese group. Mean ESS was not different between the 2 groups. In anthropometric measurements, the obese group had statistically significant large neck circumference (41.6 +/- 3.5 cm vs. 37.0 +/- 2.9 cm, p<0.001), but the nonobese group had a shorter thyromental distance (56.4 +/- 11.7 mm vs. 61.4 +/- 11.2 mm, p=0.006), with no significant difference in Mallampatis score and occlusion pattern. In polysomnographic data, the obese group had statistical significantly more severity of various indices except for AHI during the REM period and the periodic limb movement index. CONCLUSION: Non-obese obstructive sleep apnea patients have more bony structural change than the obese ones as demonstrated by shorter thyromental distance. But degree of abnormalities during sleep was less severe in nearly all aspects.

Fluid shift by lower body positive pressure increases pharyngeal resistance in healthy subjects.

INTRODUCTION: Fluid displacement into nuchal and peripharyngeal soft tissues while recumbent may contribute to narrowing and increased airflow resistance of the pharynx (Rph), and predispose to pharyngeal collapse in patients at risk for obstructive sleep apnea. OBJECTIVES: To determine whether displacement of fluid from the lower body to the neck will increase both neck circumference and Rph in healthy subjects. METHODS: In 11 healthy, nonobese subjects, studied while awake and supine, leg fluid volume, neck circumference, and Rph were measured at baseline. Subjects were then randomized to a control period or to application of lower body positive pressure (LBPP) of 40 mm Hg via antishock trousers to displace fluid from the legs, after which they crossed over to the other arm. Baseline measurements were repeated at 1 and 5 min during the control and LBPP periods. RESULTS: Compared with the control period, application of LBPP caused a significant reduction in leg fluid volume (p < 0.001) and a significant increase in neck circumference (p = 0.004). Rph remained stable during the control period, but increased significantly from baseline after 1 and 5 min of LBPP (from 0.43 +/- 0.10 to 0.60 +/- 0.11 cm H(2)O/L/s, p = 0.034, and to 0.87 +/- 0.19 cm H(2)O/L/s, p < 0.001, compared with baseline, respectively). CONCLUSIONS: Fluid displacement from the legs by LBPP increases neck circumference and Rph in healthy subjects. These findings suggest the hypothesis that fluid displacement to the upper body during recumbency may predispose to pharyngeal obstruction during sleep, especially in fluid overload states, such as heart and renal failure.

Prevalence of bronchial hyperresponsiveness and asthma in the adult population in Thailand.

OBJECTIVES: We conducted a nationwide cross-sectional survey of respiratory health in adults aged 20 to 44 years during 2001 to 2002 to determine the prevalence of bronchial hyperresponsiveness (BHR) and asthma in the adult Thai population. DESIGN: Subjects were selected by a multistage stratified random sampling. The stratification was done on geographic area, age group, and sex. Subjects were interviewed with questionnaires and underwent spirometric testing. Methacholine challenge tests were performed on all subjects without contraindication to determine BHR defined as the provocative concentration of methacholine producing a 20% fall in FEV(1) < or = 8 mg/mL. Definite asthma was defined as BHR present with any asthma symptom within the past 12 months or demonstrated reversible airflow obstruction. Current diagnosed asthma was defined as previous physician-diagnosed asthma and any asthma symptom within the past 12 months or currently receiving asthma medication. RESULTS: The study population was from 20 provinces of five geographic regions of Thailand and included 1,882 women and 1,572 men. The prevalence of BHR was 3.31% (95% confidence interval [CI], 2.68 to 3.94). However, if subjects with positive reversibility test results were included, the prevalence increased to 3.98% (95% CI, 3.30 to 4.67). The prevalence of definite asthma was 2.91% (95% CI, 2.32 to 3.50), whereas the prevalence of current diagnosed asthma by the questionnaire interview was 2.15% (95% CI, 1.66 to 2.63). The kappa index of the agreement between both definitions of asthma was 0.40, indicating poor to fair agreement. CONCLUSION: The prevalence of BHR and asthma in the adult Thai population is relatively low as compared with western countries.