Nasal pressure recording in the diagnosis of sleep apnoea hypopnoea syndrome

Nasal cannula use during polysomnography in children aged under three with suspected sleep apnea

OBJECTIVE

Early diagnosis of obstructive sleep apnea (OSA) in children is important. The use of a nasal cannula as an airflow sensor during polysomnography has not been evaluated in younger children. The study aims to evaluate the use of nasal cannula in detecting respiratory events in children under three with suspected OSA during daytime nap studies.

METHODS

A total of 185 patients were prospectively included. Respiratory events were scored using nasal cannula alone, thermistor alone, and both methods simultaneously as the airflow sensor. Agreement and diagnostic accuracy were assessed.

RESULTS

One hundred and seventy-two children were finally analyzed and 110 (64.0%) presented OSA. Total sleep time with an uninterpretable signal was longer with the nasal cannula than with the thermistor (17.8% vs 1.9%; p < 0.001), and was associated with poor sensor tolerance and adenotonsillar hypertrophy. In the estimation of the apnea-hypopnea index, the nasal cannula showed lower agreement than the thermistor with the joint use of the two sensors (intraclass correlation coefficient: 0.79 vs 0.996 with thermistor). Compared with the thermistor, the nasal cannula presented lower sensitivity for detecting OSA (82.7% vs 95.5%) and a lower negative predictive value (76.5% vs 92.4%). Overall, fewer children were diagnosed with severe OSA with the nasal cannula (19.8% vs 30.8% with the thermistor, and 32.6% with both).

CONCLUSIONS

In children under the age of three, the ability of the nasal cannula to detect obstructive events was relatively low. Therefore, other non-invasive measurements for identifying respiratory events during sleep may be of additional value.

Sleep-Disordered Breathing is frequently associated with idiopathic normal pressure hydrocephalus but not other types of hydrocephalus

STUDY OBJECTIVES

Previous studies have shown sleep-disordered breathing (SDB) to be highly prevalent in patients with idiopathic normal pressure hydrocephalus (iNPH). The current study aimed to estimate and compare the prevalence of SDB in patients with different types of hydrocephalus and test if SDB was associated with changed CO2.

METHODS

We investigated the prevalence of SDB in a prospective cohort of 48 hydrocephalus patients with nocturnal polysomnography (PSG). Twenty-three of the patients also had simultaneous CO2 measurements.

RESULTS

The prevalence of SDB was high in patients with iNPH, with moderate-to-severe SDB in 21/22 (96%) of the patients and an apnea-hypopnea index (AHI) of 43.5 (95% CI 33.8-52.2). Patients with pediatric-onset hydrocephalus had moderate-to-severe SDB in 7/16 (44%), with an AHI of 16.1 (95% CI 8.16-23.8). Except for one patient, all patients with adult-onset obstructive hydrocephalus (9/10) had normal respiration or mild SDB with an AHI of 8.4 (95% CI 5.5-10.5). None of the 23 patients measured with CO2 had elevated CO2 associated with SDB and had normal CO2 during sleep, with 40.8 ± 5.5 mmHg, 42.7 ± 4.1 mmHg, 34.5-45.8 mmHg for patients with iNPH, pediatric-onset, and adult-onset, respectively.

CONCLUSION

We found a high prevalence of SDB in patients with iNPH, confirming previous findings. We extended this with the finding that the prevalence of SDB in patients with other types of hydrocephalus is not significantly different from that in the general population. Additionally, we did not find elevations of CO2 associated with SDB or CO2 retention during sleep.

Tidal volume and stroke volume changes caused by respiratory events during sleep and their relationship with OSA severity: a pilot study

PURPOSE

Breath-by-breath tidal volume (TV) and beat-by-beat stroke volume (SV) were continuously measured in patients with OSA undergoing polysomnography (PSG). The objectives were to (1) determine the changes in TV/SV in response to respiratory events and (2) assess the relationship between these changes and the disease severity.

METHODS

From the PSG data of nine patients with OSA, six different types of respiratory events were identified, i.e., flow limitation (FL), respiratory effort related arousal (RERA), hypopnea with arousal only (Ha), hypopnea with desaturation only (Hd), hypopnea with arousal and desaturation (Had), and apnea. The measured TV and SV values during and after each respiratory event were compared with the pre-event baseline values.

RESULTS

The mean TV/SV reductions during all hypopneas and apneas were 38.1%/4.2% and 70.5%/8.8%, respectively. Among three different hypopnea types, the reductions in TV during Hd and Had were significantly greater than those during Ha. The TV reductions during Ha and FL were similar. After RERA, Ha, Had, and apnea, there was an overshoot in TV and SV values, whereas there was no overshoot after FL and Hd. During RERA, there was no reduction in TV/SV.

CONCLUSIONS

The changes in TV during and after each type of respiratory event were significantly different in most cases. The changes in SV between hypopnea and apnea were different with statistical significance. The AHI does not properly account for the ventilation losses caused by respiratory events. Thus, TV measurements might be useful in the future in assessing the OSA severity in conjunction with the AHI.

Deep Recurrent Neural Networks for Automatic Detection of Sleep Apnea from Single Channel Respiration Signals

Sleep apnea is a common sleep disorder that causes repeated breathing interruption during sleep. The performance of automated apnea detection methods based on respiratory signals depend on the signals considered and feature extraction methods. Moreover, feature engineering techniques are highly dependent on the experts’ experience and their prior knowledge about different physiological signals and conditions of the subjects. To overcome these problems, a novel deep recurrent neural network (RNN) framework is developed for automated feature extraction and detection of apnea events from single respiratory channel inputs. Long short-term memory (LSTM) and bidirectional long short-term memory (BiLSTM) are investigated to develop the proposed deep RNN model. The proposed framework is evaluated over three respiration signals: Oronasal thermal airflow (FlowTh), nasal pressure (NPRE), and abdominal respiratory inductance plethysmography (ABD). To demonstrate our results, we use polysomnography (PSG) data of 17 patients with obstructive, central, and mixed apnea events. Our results indicate the effectiveness of the proposed framework in automatic extraction for temporal features and automated detection of apneic events over the different respiratory signals considered in this study. Using a deep BiLSTM-based detection model, the NPRE signal achieved the highest overall detection results with true positive rate (sensitivity) = 90.3%, true negative rate (specificity) = 83.7%, and area under receiver operator characteristic curve = 92.4%. The present results contribute a new deep learning approach for automated detection of sleep apnea events from single channel respiration signals that can potentially serve as a helpful and alternative tool for the traditional PSG method.

The relationship between partial upper-airway obstruction and inter-breath transition period during sleep

Short pauses or "transition-periods" at the end of expiration and prior to subsequent inspiration are commonly observed during sleep in humans. However, the role of transition periods in regulating ventilation during physiological challenges such as partial airway obstruction (PAO) has not been investigated. Twenty-nine obstructive sleep apnea patients and eight controls underwent overnight polysomnography with an epiglottic catheter. Sustained-PAO segments (increased epiglottic pressure over ≥5 breaths without increased peak inspiratory flow) and unobstructed reference segments were manually scored during apnea-free non-REM sleep. Nasal pressure data was computationally segmented into inspiratory (T_I, shortest period achieving 95% inspiratory volume), expiratory (T_E, shortest period achieving 95% expiratory volume), and inter-breath transition period (T_Trans, period between T_E and subsequent T_I). Compared with reference segments, sustained-PAO segments had a mean relative reduction in T_Trans (-24.7±17.6%, P<0.001), elevated T_I (11.8±10.5%, P<0.001), and a small reduction in T_E (-3.9±8.0, P≤0.05). Compensatory increases in inspiratory period during PAO are primarily explained by reduced transition period and not by reduced expiratory period.

An Official American Thoracic Society Research Statement: Impact of Mild Obstructive Sleep Apnea in Adults

BACKGROUND

Mild obstructive sleep apnea (OSA) is a highly prevalent disorder in adults; however, whether mild OSA has significant neurocognitive and cardiovascular complications is uncertain.

OBJECTIVES

The specific goals of this Research Statement are to appraise the evidence regarding whether long-term adverse neurocognitive and cardiovascular outcomes are attributable to mild OSA in adults, evaluate whether or not treatment of mild OSA is effective at preventing or reducing these adverse neurocognitive and cardiovascular outcomes, delineate the key research gaps, and provide direction for future research agendas.

METHODS

Literature searches from multiple reference databases were performed using medical subject headings and text words for OSA in adults as well as by hand searches. Pragmatic systematic reviews of the relevant body of evidence were performed.

RESULTS

Studies were incongruent in their definitions of "mild" OSA. Data were inconsistent regarding the relationship between mild OSA and daytime sleepiness. However, treatment of mild OSA may improve sleepiness in patients who are sleepy at baseline and improve quality of life. There is limited or inconsistent evidence pertaining to the impact of therapy of mild OSA on neurocognition, mood, vehicle accidents, cardiovascular events, stroke, and arrhythmias.

CONCLUSIONS

There is evidence that treatment of mild OSA in individuals who demonstrate subjective sleepiness may be beneficial. Treatment may also improve quality of life. Future research agendas should focus on clarifying the effect of mild OSA and impact of effective treatment on other neurocognitive and cardiovascular endpoints as detailed in the document.

New Rule-Based Algorithm for Real-Time Detecting Sleep Apnea and Hypopnea Events Using a Nasal Pressure Signal

We developed a rule-based algorithm for automatic real-time detection of sleep apnea and hypopnea events using a nasal pressure signal. Our basic premise was that the performance of our new algorithm using the nasal pressure signal would be comparable to that using other sensors as well as manual annotation labeled by a technician on polysomnography study. We investigated fifty patients with sleep apnea-hypopnea syndrome (age: 56.8 ± 10.5 years, apnea-hypopnea index (AHI): 36.2 ± 18.1/h) during full night PSG recordings at the sleep center. The algorithm was comprised of pre-processing with a median filter, amplitude computation and apnea-hypopnea detection parts. We evaluated the performance of the algorithm a confusion matric for each event and statistical analyses for AHI. Our evaluation achieved a good performance, with a sensitivity of 86.4 %, and a positive predictive value of 84.5 % for detection of apnea and hypopnea regardless of AHI severity. Our results indicated a high correlation with the manually labeled apnea-hypopnea events during PSG, with a correlation coefficient of r = 0.94 (p < 0.0001) and a mean difference of -2.9 ± 11.6 per hour. The proposed new algorithm could provide significant clinical and computational insights to design a PSG analysis system and a continuous positive airway pressure (CPAP) device for screening sleep quality related in patients with sleep apnea-hypopnea syndrome.

Nasal pressure recordings for automatic snoring detection

This study presents a rule-based method for automated, real-time snoring detection using nasal pressure recordings during overnight sleep. Although nasal pressure recordings provide information regarding nocturnal breathing abnormalities in a polysomnography (PSG) study or continuous positive airway pressure (CPAP) system, an objective assessment of snoring detection using these nasal pressure recordings has not yet been reported in the literature. Nasal pressure recordings were obtained from 55 patients with obstructive sleep apnea. The PSG data were also recorded simultaneously to evaluate the proposed method. This rule-based method for automatic, real-time snoring detection employed preprocessing, short-time energy and the central difference method. Using this methodology, a sensitivity of 85.4% and a positive predictive value of 92.0% were achieved in all patients. Therefore, we concluded that the proposed method is a simple, portable and cost-effective tool for real-time snoring detection in PSG and CPAP systems that does not require acoustic analysis using a microphone.

Real-time prediction of disordered breathing events in people with obstructive sleep apnea

PURPOSE

Conventional therapies for obstructive sleep apnea (OSA) are effective but suffer from poor patient adherence and may not fully alleviate major OSA-associated cardiovascular risk factors or improve certain aspects of quality of life. Predicting the onset of disordered breathing events in OSA patients may lead to improved strategies for treating OSA and inform our understanding of underlying disease mechanisms. In this work, we describe a deployable system capable of performing real-time predictions of sleep disordered breathing events in patients diagnosed with OSA, providing a novel approach for gaining insight into OSA pathophysiology, discovering population subgroups, and improving therapies.

METHODS

LArge Memory STorage and Retrieval artificial neural networks with 864 different configurations were applied to polysomnogram records from 64 patients. Wavelet transforms, measures of entropy, and other statistics were applied to six physiological signals to provide network inputs. Approximate statistical tests were used to determine the best performing network for each patient. The most important predictors of disordered breathing events in OSA patients were determined by analyzing internal network parameters.

RESULTS

The average optimized individual prediction sensitivity and specificity were 0.81 and 0.77, respectively. Predictions were better than random guessing for all OSA patients. Analysis of internal network parameters revealed a high degree of heterogeneity among disordered breathing event predictors and may reveal patient subgroups.

CONCLUSIONS

We report the first practical system to predict individual disordered breathing events in a heterogeneous group of patients diagnosed with OSA. The pattern of disordered breathing predictors suggests variable underlying pathophysiological mechanisms and highlights the need for an individualized approach to OSA diagnosis, therapy, and management.

Evaluation of candidate measures for home-based screening of sleep disordered breathing in Taiwanese bus drivers

Background: Sleepiness-at-the-wheel has been identified as a major cause of highway accidents. The aim of our study is identifying the candidate measures for home-based screening of sleep disordered breathing in Taiwanese bus drivers, instead of polysomnography. Methods: Overnight polysomnography accompanied with simultaneous measurements of alternative screening devices (pulse oximetry, ApneaLink, and Actigraphy), heart rate variability, wake-up systolic blood pressure and questionnaires were completed by 151 eligible participants who were long-haul bus drivers with a duty period of more than 12 h a day and duty shifting. Results: 63.6% of professional bus drivers were diagnosed as having sleep disordered breathing and had a higher body mass index, neck circumference, systolic blood pressure, arousal index and desaturation index than those professional bus drivers without evidence of sleep disordered breathing. Simple home-based candidate measures: (1) Pulse oximetry, oxygen-desaturation indices by ≥3% and 4% (r = 0.87∼0.92); (2) Pulse oximetry, pulse-rising indices by ≥7% and 8% from a baseline (r = 0.61∼0.89); and (3) ApneaLink airflow detection, apnea-hypopnea indices (r = 0.70∼0.70), based on recording-time or Actigraphy-corrected total sleep time were all significantly correlated with, and had high agreement with, corresponding polysomnographic apnea-hypopnea indices [(1) 94.5%∼96.6%, (2) 93.8%∼97.2%, (3) 91.1%∼91.3%, respectively]. Conversely, no validities of SDB screening were found in the multi-variables apnea prediction questionnaire, Epworth Sleepiness Scale, night-sleep heart rate variability, wake-up systolic blood pressure and anthropometric variables. Conclusions: The indices of pulse oximetry and apnea flow detection are eligible criteria for home-based screening of sleep disordered breathing, specifically for professional drivers.

The prevalence of and risk factors for sleep-disordered breathing in an elderly Korean population

BACKGROUND

There are just a few epidemiological studies on sleep-disordered breathing (SDB) in the elderly, and the results are inconsistent.

STUDY OBJECTIVES

We sought to investigate the prevalence of and risk factors for SDB in a representative elderly population with the use of attended nocturnal polysomnography (NPSG).

METHODS

Among 6,959 individuals aged ≥ 60 years living in Yongin City, Korea, 696 subjects were selected using random sampling. All the subjects were invited to visit a hospital for NPSG, and SDB was defined as an apnea-hypopnea index ≥ 15.

RESULTS

Of the 696 participants investigated, 348 participants completed the sleep study and clinical evaluation. SDB was observed in 127 of the 348 participants, and the prevalence of SDB was 36.5% (52.6% in males and 26.3% in females). A body mass index ≥ 25 was associated with SDB in both male and female subjects, particularly in males, whereas snoring was independently associated with SDB in female participants only. In male participants, SDB was a significant risk factor for hypertension (p = 0.025).

CONCLUSIONS

SDB was found to be common among elderly Koreans, and it was more prevalent and severe in male than in female subjects. Health consequences of SDB in the elderly need to be further explored.

Response characteristics for thermal and pressure devices commonly used for monitoring nasal and oral airflow during sleep studies

We examined thermocouple and pressure cannulae responses to oral and nasal airflow using a polyester model of a human face, with patent nasal and oral orifices instrumented with a dual thermocouple (F-ONT2A, Grass) or a dual cannula (0588, Braebon) pressure transducer (± 10 cm H2O, Celesco) system. Tidal airflow was generated using a dual compartment facemask with pneumotachographs (Fleisch 2) connected to the model orifices. During nasal breathing: thermocouple amplitude = 0.38 Ln [pneumotachograph amplitude] + 1.31 and pressure cannula amplitude = 0.93 [pneumotachograph amplitude](2.15); during oral breathing: thermocouple amplitude = 0.44 Ln [pneumotachograph amplitude] + 1.07 and pressure cannula amplitude = 0.33 [pneumotachograph amplitude](1.72); (all range ∼ 0.1-∼ 4.0 L s(-1); r(2) > 0.7). For pneumotachograph amplitudes <1 L s(-1) (linear model) change in thermocouple amplitude/unit change in pneumotachograph amplitude was similar for nasal and oral airflow, whereas nasal pressure cannula amplitude/unit change in pneumotachograph amplitude was almost four times that for oral. Increasing oral orifice area from 0.33 cm(2) to 2.15 cm(2) increased oral thermocouple amplitude/unit change in pneumotachograph amplitude by ∼ 58% but decreased pressure cannula amplitude/unit change in pneumotachograph amplitude by 49%. For pneumotachograph amplitudes up to 1 L s(-1), alterations in inspiratory/expiratory ratios or total respiratory time did not affect the sensitivity of either nasal or oral pressure cannulae or the nasal thermocouple, but the oral thermocouple sensitivity was influenced by respiratory cycle time. Different nasal and oral responses influence the ability of these systems to quantitatively assess nasal and oral airflow and oro-nasal airflow partitioning.

The effect of respiratory scoring on the diagnosis and classification of sleep disordered breathing in chronic heart failure

STUDY OBJECTIVES

To evaluate the effect of respiratory scoring criteria on diagnosis and classification of sleep disordered breathing (SDB) in chronic heart failure (CHF).

DESIGN

Cross-sectional observational study.

SETTING

Heart failure and general cardiology clinics at two London hospitals.

PATIENTS OR PARTICIPANTS

One hundred eighty stable patients with CHF and a median age of 69.6 y, 86% male.

INTERVENTIONS

SDB was diagnosed by polysomnography. The apnea-hypopnea index (AHI) was initially scored using a conservative hypopnea definition of a ≥ 50% decrease in nasal airflow with a ≥ 4% oxygen desaturation. The AHI was rescored with hypopnea defined according to the American Academy of Sleep Medicine (AASM) alternative scoring rule, requiring an associated ≥ 3% oxygen desaturation or arousal. SDB was defined as AHI ≥ 15/h. Diagnosis and classification of SDB as obstructive sleep apnea (OSA) or central sleep apnea (CSA) with each rule were compared. The effect of mixed apneas on classification of SDB as CSA or OSA was also investigated.

MEASUREMENTS AND RESULTS

Median AHI increased from 9.3/h to 13.8/h (median difference 4.6/h) when the AASM alternative rule was used to score hypopneas. SDB prevalence increased from 29% to 46% with the alternative scoring rule (P < 0.001). Classification of SDB as OSA or CSA was not significantly altered by hypopnea scoring rules or the categorization of mixed apneas.

CONCLUSION

Hypopnea scoring rules can significantly influence the apnea-hypopnea index and diagnosis of sleep disordered breathing in chronic heart failure but do not alter the classification as obstructive sleep apnea or central sleep apnea. Standardization of hypopnea scoring rules is important to ensure consistency in diagnosis of sleep disordered breathing in chronic heart failure patients.

AASM criteria for scoring respiratory events: interaction between apnea sensor and hypopnea definition

STUDY OBJECTIVES

To examine the impact of using a nasal pressure sensor only vs the American Academy of Sleep Medicine (AASM) recommended combination of thermal and nasal pressure sensors on (1) the apnea index (AI), (2) the apnea-hypopnea index (AHI), where the AHI is calculated using both AASM definitions of hypopnea, and (3) the accuracy of a diagnosis of obstructive sleep apnea (OSA).

DESIGN

Retrospective review of previously scored in-laboratory polysomnography.

SETTING

A tertiary-hospital clinical sleep laboratory.

PATIENTS OR PARTICIPANTS

One hundred sixty-four consecutive adult patients with a potential diagnosis of OSA, who were examined during a 3-month period.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Studies were scored with and without the use of the oronasal thermal sensor. AIs and AHIs, using the nasal pressure sensor alone (AI(np) and AHI(np)), were compared with those using both a thermal sensor for the detection of apnea and a nasal pressure transducer for the detection of hypopnea (AI(th) and AHI(th)). Comparisons were repeated using the AASM recommended (AASM(rec)) and alternative (AASM(alt)) hypopnea definitions. AI was significantly different when measured from the different sensors, with AI(np) being 51% higher on average. Using the AASM(rec) hypopnea definition, the mean AHI(np) was 15% larger than the AHI(th); with large interindividual differences and an estimated 9.8% of patients having a false-positive OSA diagnosis at a cutpoint of 15 events and 4.3% at 30 events per hour. Using AASM(alt) hypopnea definition, the mean AHI(np) was 3% larger than the AHI(th), with estimated false-positive rates of 4.6% and 2.4%, respectively. The false-negative rate was negligible at 0.1% for both hypopnea definitions.

CONCLUSIONS

This study demonstrates that using only a nasal pressure sensor for the detection of apnea resulted in higher values of AI and AHI than when the AASM recommended thermal sensor was added to detect apnea. When the AASM(alt) hypopnea definition was used, the differences in AHI and subsequent OSA diagnosis were small and less than when the AASM(rec) hypopnea definition was used. In situations in which a thermal sensor cannot be used, for example, in limited-channel diagnostic devices, the AHI obtained with a nasal pressure sensor alone differs less from the AHI obtained from a polysomnogram that includes a thermal sensor when the AASM(alt) definition rather than the AASM(rec) definition of hypopnea is used. Thus, diagnostic accuracy is impacted both by the absence of the thermal sensor and by the rules used to analyze the polysomnography. Furthermore, where the thermal sensor is unreliable for sections of a study, it is likely that use of the nasal pressure signal to detect apnea will have modest impact.

Does sleep apnea increase the risk of cardiorespiratory complications during endoscopy procedures?

BACKGROUND

Patients with obstructive sleep apnea (OSA) have an increased risk of perioperative complications.

AIM

The purpose of this study is to assess whether OSA increases the risk of cardiorespiratory complications in patients undergoing endoscopic procedures.

METHODS

A retrospective study was performed. We identified all patients who had undergone both an endoscopic procedure under conscious sedation and a sleep study from January 2001 to May 2008. Patients were divided into four groups: OSA negative (apnea-hypopnea index (AHI) < 5/h), OSA positive; mild: AHI 5-15/h, moderate: AHI 15.1-30/h, and severe: AHI > 30/h. Minor and major complications were identified. The minor ones were hypertension, hypotension, bradycardia, tachycardia, oxygen desaturation (<90%), and bradypnea. Major complications included chest pain, respiratory distress, cardiorespiratory arrest, or any minor complication that required intervention.

RESULTS

Procedures were performed in 639 patients: colonoscopies 68.5%, upper endoscopies 20.2%, and combined procedures 11.3%. The mean age was 60.5 years, mean body mass index 33.7, and 93% were males. Sleep study results: 130 negative, 509 positive; 135 mild, 125 moderate, and 249 severe. Of the patients, 19% had minor complications, while 7% had major complications. There was no significant difference between the patients with and without OSA in the rate of minor complications (odds ratio 1.17, 95% confidence interval 0.70-1.92) or major complications (odds ratio 1.19, 95% confidence interval 0.54-2.63). The odds ratio was also not significantly increased when a cutoff value of 10 or 15/h was used to delineate a positive sleep study.

CONCLUSION

For patients undergoing endoscopy procedures under conscious sedation, the presence of OSA does not clearly increase the risk of cardiorespiratory complications.

Obstructive sleep apnoea/hypopnea influences high-density lipoprotein cholesterol in the elderly

BACKGROUND AND PURPOSE

An association between obstructive sleep apnoea/hypopnea (OSAH) and cardiovascular risk factors such as dyslipidemia has been described in adults and high-risk populations.

PATIENTS AND METHODS

We examined this association in a prospective cohort (SYNAPSE study) of 846 elderly (68.5+/-1.1 years) volunteers (41.6% of men). No subject presented with recognized OSAH syndrome, heart disease, or any neurological disorder. Unattended at-home polygraphy was done by all subjects. OSAH severity was defined as moderate (apnoea/hypopnea index: AHI>15/h) or severe (AHI>30/h). High-density lipoprotein cholesterol (HDL-c) was measured by immuno-separation-based homogenous assay.

RESULTS

The prevalence of severe cases reached 21.5% (AHI mean+/-SD: 43.5+/-11.9). Using univariate linear regression analysis, AHI (R=-0.172; p<0.0001), oxyhemoglobin desaturation index (ODI) (R=-0.108; p<0.002), mean SaO(2) (R=0.125; p<0.0003) and Nadir SaO(2) (R=0.094; p<0.007) were significantly associated with HDL-c. Multiple regression analysis demonstrated that male gender, BMI, waist to hip ratio, ODI, and AHI represent independent predictors of HDL-c. Logistic regression analysis showed a significant association between severe OSAH and low HDL-c serum levels (p<0.03) after adjustment for gender, BMI, hypertension, glycaemia, waist to hip ratio, alcohol intake and treated dyslipidemia. The association appears more evident in subjects free of lipid-lowering medications and beta-blockers (p<0.007). There was no independent association of OSAH syndrome with low-density lipoprotein (LDL) cholesterol.

CONCLUSION

Unrecognized moderate to severe apnoea/hypopnea syndrome was independently associated with low HDL-c serum levels in the present cross-sectional based elderly population. This could explain the deleterious effect of OSAH syndrome on cardiovascular risk.

The new AASM criteria for scoring hypopneas: impact on the apnea hypopnea index

STUDY OBJECTIVES

To compare apnea-hypopnea indices (AHIs) derived using 3 standard hypopnea definitions published by the American Academy of Sleep Medicine (AASM); and to examine the impact of hypopnea definition differences on the measured prevalence of obstructive sleep apnea (OSA).

DESIGN

Retrospective review of previously scored in-laboratory polysomnography (PSG).

SETTING

Two tertiary-hospital clinical sleep laboratories.

PATIENTS OR PARTICIPANTS

328 consecutive patients investigated for OSA during a 3-month period.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

AHIs were originally calculated using previous AASM hypopnea scoring criteria (AHI(Chicago)), requiring either >50% airflow reduction or a lesser airflow reduction with associated >3% oxygen desaturation or arousal. AHIs using the "recommended" (AHI(Rec)) and the "alternative" (AHI(Alt)) hypopnea definitions of the AASM Manual for Scoring of Sleep and Associated Events were then derived in separate passes of the previously scored data. In this process, hypopneas that did not satisfy the stricter hypopnea definition criteria were removed. For AHI(Rec), hypopneas were required to have > or =30% airflow reduction and > or =4% desaturation; and for AHI(Alt), hypopneas were required to have > or =50% airflow reduction and > or =3% desaturation or arousal. The median AHI(Rec) was approximately 30% of the median AHI(Chicago), whereas the median AHI(Alt), was approximately 60% of the AHI(Chicago), with large, AHI-dependent, patient-specific differences observed. Equivalent cut-points for AHI(Rec) and AHI(Alt), compared to AHI(Chicago) cut-points of 5, 15, and 30/h were established with receiver operator curves (ROC). These cut-points were also approximately 30% of AHI(Chicago) using AHI(Rec) and 60% of AHI(Chicago) using AHI(Alt). Failure to adjust cut-points for the new criteria would result in approximately 40% of patients previously classifled as positive for OSA using AHI(Chicago) being negative using AHI(Rec) and 25% being negative using AHI(Alt).

CONCLUSIONS

This study demonstrates that using different published standard hypopnea definitions leads to marked differences in AHI. These results provide insight to clinicians and researchers in interpreting results obtained using different published standard hypopnea definitions, and they suggest that consideration should be given to revising the current scoring recommendations to include a single standardized hypopnea definition.

Sleep apnea diagnosis using an ECG Holter device including a nasal pressure (NP) recording: validation of visual and automatic analysis of nasal pressure versus full polysomnography

BACKGROUND

New simplified techniques for diagnosing sleep apnea should be specially tailored for easy use in cardiologic practice.

OBJECTIVES

e dedicated one of the channels of a Holter Electrocardiogram (ECG) device (SpiderView() ELA Medical, France) to nasal pressure (NP) recordings. We also developed an automatic analysis of NP signal providing an apnea-hypopnea index (AHI) for physicians without the know-how in sleep medicine.

METHODS

Thirty-four unselected patients referred for symptoms suggesting sleep apnea underwent a polysomnography (PSG) with simultaneous NP and Holter ECG recordings. An expert blinded to PSG results visually scored the Holter plus NP recordings. The results of the AHI obtained in PSG (AHI-PSG) were compared, respectively, to the AHI-NP obtained by visual analysis and automatic analysis (AHI-NP Auto) of Holter ECG nasal pressure.

RESULTS

In 10 randomly selected subjects (development set), the best cut-off on Holter ECG for diagnosing sleep apnea patients as defined by AHI>20/h in PSG was determined at 35 events/h by a receiver operator curve (ROC) analysis. Prospective testing of this threshold was then performed in 19 subjects (test set). For visually scored recordings of Holter ECG plus NP, we obtained a negative predictive value (NPV) of 80% and a positive predictive value (PPV) of 100% for sleep apnea. The area under the ROC curve was 0.97. For the automatic analysis, the NPV was 86% and the PPV value 100%. The area under the ROC curve was 0.85.

CONCLUSIONS

NP recording using a Holter system is an efficient and easy-to-use tool for screening for sleep-disordered breathing in routine cardiology practice.

Tumor necrosis factor-alpha expression in uvular tissues differs between snorers and apneic patients

BACKGROUND

Inflammatory changes such as subepithelial edema and excessive inflammatory cell infiltration have been observed in uvular tissues of obstructive sleep apnea (OSA) subjects. The levels of proinflammatory cytokines such as tumor necrosis factor (TNF)-alpha and interleukin-6 are elevated in the serum of apneic patients and have been proposed as mediators of muscle weakness. TNF-alpha has been shown to affect diaphragm contractility in mice and rabbit in vivo.

OBJECTIVES

To assess total and compartmental TNF-alpha expression in uvular tissues of apneic and nonapneic patients.

METHODS

Uvular tissues were collected from 14 snorers without sleep disorders breathing, 14 subjects with OSA (OSA 1 group) whose body mass index (BMI) was similar to that of snorers, and 12 additional obese OSA subjects (OSA 2 group) who underwent an uvulopalatopharyngoplasty. Sections were examined using immunohistochemistry and Western blot analysis. TNF-alpha expression was evaluated in the musculus uvulae (MU), epithelial layer, and perimuscular tissues from proximal uvular sections.

RESULTS

TNF-alpha was more highly expressed in whole uvular protein extracts of apneic groups than in snorers ([mean +/- SEM] snorers, 100.5 +/- 3.0%; OSA 1 group, 127.1 +/- 6.9%; OSA 2 group, 140.7 +/- 11.0%; p = 0.01). In the muscular area, TNF-alpha levels were higher in the more obese OSA subjects than in the other two groups (snorers, 100.3 +/- 3%; OSA 1 group, 107.4 +/- 0.7%; OSA 2 group, 124.1 +/- 4.2%; p = 0.007). In the muscular area, TNF-alpha was correlated with BMI, but no relationship was found with the apnea-hypopnea index.

CONCLUSIONS

We conclude that MU is the major TNF-alpha source in uvular tissue and that TNF-alpha is more highly expressed in the heaviest OSA patients compared to less obese OSA patients and nonapneic snorers.

Fasting glycemia in sleep disordered breathing: lowering the threshold on oxyhemoglobin desaturation

STUDY OBJECTIVES

Commonly used definitions of sleep-disordered breathing (SDB) are based on identifying discrete events of breathing abnormalities during sleep that are accompanied by an oxyhemoglobin desaturation (delta SaO2) of at least 4%. However, it is not known whether disordered breathing events with oxyhemoglobin desaturation less than 4% are associated with clinical sequelae such as abnormalities in fasting glycemia.

DESIGN

Cross-sectional study.

SUBJECTS AND SETTING

Participants from the Sleep Heart Health Study (SHHS) with a fasting glucose measurement made within a year of the baseline polysomnogram.

MEASUREMENTS AND RESULTS

SDB severity was defined using the apnea-hypopnea index (AHI) and the hypopnea index (HI) by counting events with different levels of oxyhemoglobin desaturation (0.0%-1.9%, 2.0%-2.9%, 3.0%-3.9%, > or = 4.0%). Fasting glucose levels were used to classify individuals into normal (<100 mg/dL), impaired (100-125 mg/dL), and diabetic (> or = 126 mg/dL) groups. Ordinal logistic regression was used to determine the adjusted relative odds of an abnormal glucose value across quartiles of the hypopnea index, independent of factors such as age, body mass index, waist circumference, and usual sleep duration. The prevalence of impaired and diabetic fasting glucose in the analytical sample was 32.9% and 5.8%, respectively. The covariate-adjusted relative odds of impaired or diabetic fasting glucose in the highest versus the lowest AHI quartile was 1.35 (95% CI: 1.04-1.76) for events with a delta SaO2 > or = 4.0%, 1.72 (95% CI: 1.20-2.48) for events with a delta SaO2 between 3.0%-3.9%, 1.41 (95% CI: 1.07-1.86) for events with a delta SaO2 between 2.0%-2.9%, and 1.07 (95% CI: 0.84-1.37) for events with a delta SaO2 between 0.0%-1.9%. The corresponding odds ratios for the HI were 1.47 (95% CI: 1.13-1.92), 2.25 (95% CI: 1.59-3.19), 1.44 (95% CI: 1.09-1.90), and 1.15 (95% CI: 0.90-1.47), respectively.

CONCLUSIONS

The results of this study indicate that SDB events accompanied by oxyhemoglobin desaturation of between 2% to 4% are associated with fasting hyperglycemia. These findings suggest that milder degrees of SDB may predispose to adverse metabolic outcomes.

Polysomnographic respiratory abnormalities in asymptomatic individuals

STUDY OBJECTIVES

Polysomnographic respiratory abnormalities have been extensively studied in the general population, but studies have not targeted completely healthy individuals. We aimed to (1) define the frequency of respiratory disturbances (RDI: events per hour of sleep) during sleep in healthy individuals using current techniques and criteria and (2) determine how these abnormalities change with age and sex.

DESIGN AND SETTING

Cross-sectional analyses of RDI in healthy volunteers.

PARTICIPANTS

One hundred sixty-three individuals (106 men) were screened for chronic medical illness, as confirmed by extensive questionnaires, physical examination, electrocardiography, and laboratory analysis. Obese subjects (body mass index > 30 kg/m2) and subjects taking medications were excluded. INTERVENTIONS, MEASUREMENTS AND RESULTS: Subjects underwent full polysomnography using current standard recording and scoring techniques. There was a remarkable increase in RDI with age, particularly over 50 years. Ninety-five percent of currently healthy subjects under 50 years of age had an RDI <15, whereas 50% of subjects older than 65 years had an RDI <15. Men had a higher RDI (median 10) than women (median 5). The effect of age on RDI was similar in men and women.

CONCLUSIONS

RDI increases with age even in healthy individuals without symptoms or signs of obstructive sleep apnea syndrome. We do not know whether these individuals will develop pathophysiologic consequences over time or whether this increase with age reflects a normal aging process. If the former, treatment should be considered regardless of symptoms. If the latter, the criteria for treatment should be adjusted by age.

Prolonged spiking in the Emfit sensor in patients with sleep-disordered breathing is characterized by increase in transcutaneous carbon dioxide

A phenomenon of prolonged spiking in movement sensors, such as static-charge-sensitive bed or Emfit (electromechanical film) sensors, has been connected to an increase in carbon dioxide tension in wakefulness. Spiking is also a common finding in sleep studies. This made us hypothesize that carbon dioxide changes might also happen in sleep during prolonged spiking episodes in Emfit sheet. We examined four different kinds of breathing pattern episodes: normal breathing, episodes of repetitive apnea, episodes of repetitive hypopnea and episodes with prolonged spiking lasting at least 3 min. One hundred and fifteen episodes from 19 polysomnograms were finally admitted to the study according to the protocol. The changes in the transcutaneous carbon dioxide tension (TcCO(2)) were defined for different breathing patterns. During prolonged spiking episodes the TcCO(2) increased significantly and differed statistically from the TcCO(2) changes of normal breathing and periodic breathing patterns (episodes of apnea and hypopnea). The rise in TcCO(2) during prolonged spiking episodes might suggest that prolonged spiking is representing another type of breathing disturbance during sleep differing from periodic breathing patterns. The Emfit sensor as a small, flexible and non-invasive sensor might provide useful additional information about breathing during sleep.

Improving diagnostic ability of blood oxygen saturation from overnight pulse oximetry in obstructive sleep apnea detection by means of central tendency measure

OBJECTIVES

Nocturnal pulse oximetry is a widely used alternative to polysomnography (PSG) in screening for obstructive sleep apnea (OSA) syndrome. Several oximetric indexes have been derived from nocturnal blood oxygen saturation (SaO2). However, they suffer from several limitations. The present study is focused on the usefulness of nonlinear methods in deriving new measures from oximetry signals to improve the diagnostic accuracy of classical oximetric indexes. Specifically, we assessed the validity of central tendency measure (CTM) as a screening test for OSA in patients clinically suspected of suffering from this disease.

MATERIALS AND METHODS

We studied 187 subjects suspected of suffering from OSA referred to the sleep unit. A nocturnal pulse oximetry study was applied simultaneously to a conventional PSG. Three different index groups were compared. The first one was composed by classical indexes provided by our oximeter: oxygen desaturation indexes (ODIs) and cumulative time spent below a saturation of 90% (CT90). The second one was formed by indexes derived from a nonlinear method previously studied by our group: approximate entropy (ApEn). The last one was composed by indexes derived from a CTM analysis.

RESULTS

For a radius in the scatter plot equal to 1, CTM values corresponding to OSA positive patients (0.30+/-0.20, mean+/-S.D.) were significantly lower (p<<0.001) than those values from OSA negative subjects (0.71+/-0.18, mean+/-S.D.). CTM was significantly correlated with classical indexes and indexes from ApEn analysis. CTM provided the highest correlation with the apnea-hipopnea index AHI (r=-0.74, p<0.0001). Moreover, it reached the best results from the receiver operating characteristics (ROC) curve analysis, with 90.1% sensitivity, 82.9% specificity, 88.5% positive predictive value, 85.1% negative predictive value, 87.2% accuracy and an area under the ROC curve of 0.924. Finally, the AHI derived from the quadratic regression curve for the CTM showed better agreement with the AHI from PSG than classical and ApEn derived indexes.

CONCLUSION

The results suggest that CTM could improve the diagnostic ability of SaO2 signals recorded from portable monitoring. CTM could be a useful tool for physicians in the diagnosis of OSA syndrome.

Correlation between severity of sleep apnea and upper airway morphology based on advanced anatomical and functional imaging

Determination of the apnea hypopnea index (AHI) as a measure of the severity of obstructive sleep apnea/hypopnea syndrome (OSAHS) is a widely accepted methodology. However, the outcome of such a determination depends on the method used, is time consuming and insufficient for prediction of the effect of all treatment modalities. For these reasons more methods for evaluating the severity of OSAHS, based on different imaging modalities, have been looked into and recent studies have shown that anatomical properties determined from three-dimensional (3D) computed tomography (CT) images are good markers for the severity of the OSAHS. Therefore, we correlated anatomical measurements of a 3D reconstruction of the upper airway together with flow simulation results with the severity of OSAHS in order to find a combination of variables to indicate the severity of OSAHS in patients. The AHI of 20 non-selected, consecutive patients has been determined during a polysomnography. All patients also underwent a CT scan from which a 3D model of the upper airway geometry was reconstructed. This 3D model was used to evaluate the anatomical properties of the upper airway in OSAHS patients as well as to perform computational fluid dynamics (CFD) computations to evaluate the airflow and resistance of this upper airway. It has been shown that a combination of the smallest cross-sectional area and the resistance together with the body mass index (BMI) form a set of markers that predict very well the severity of OSAHS in patients within this study. We believe that these markers can be used to evaluate the outcome of an OSAHS treatment.

Respiratory muscle activity and respiratory obstruction after abdominal surgery

BACKGROUND

Respiratory movements in patients after abdominal surgery are frequently abnormal, with associated disturbances in the pattern of inspiratory pressure generation. The reasons for these abnormalities are not clear and have been attributed to impaired action of the diaphragm. However, an alternative is that partial airway obstruction could trigger reflex activation of the inspiratory ribcage muscles, which would cause a similar pattern of inspiratory pressure change. Direct measurement of electrical activity can indicate if reflex activation of inspiratory muscles occurs when partial airway obstruction is present.

METHODS

In an open study, we implanted electrodes to measure the EMG of scalene, intercostal and external oblique abdominal muscles in patients after lower abdominal surgery. Analgesia was with morphine i.v. by patient control. We used nasal cannulae to measure nasal airflow and compared EMG activity when airway obstruction was present with activity when breathing was not obstructed.

RESULTS

The pattern of activity of the different muscles was distinct. Intercostal activity reached a maximum during inspiration, before the scalene muscles, whereas scalene activity increased in phase with increasing lung volume. Abdominal muscle activity commenced when expiratory flow had ceased and continued until the next inspiration. In all three muscle groups, partial airway obstruction did not alter muscle activity.

CONCLUSIONS

Partial airway obstruction does not activate inspiratory ribcage muscles, in patients receiving morphine for postoperative analgesia after lower abdominal surgery. Changes in respiratory pressures and abnormalities of chest wall movement described in previous studies cannot be attributed to reflex responses and probably result from increased airway resistance and abdominal muscle action.

[Comparison between the 1993 and 2002 Guidelines of the Spanish Society of Pulmonology and Thoracic Surgery (SEPAR) for identifying respiratory events in polysomnography tests]

OBJECTIVE

To compare the results of applying both the 1993 and 2002 guidelines of the Spanish Society of Pulmonology and Thoracic Surgery (SEPAR) to identify respiratory events during nighttime polysomnography tests.

PATIENTS AND METHODS

One hundred twenty consecutive patients with medium to high suspicion of sleep apnea-hypopnea syndrome (SAHS) were included in the study. The 1993 guidelines recommended the use of a thermistor and the evaluation of only apneas and hypopneas. The 2002 guidelines, on the other hand, recommended the use of a thermistor, nasal pressure cannula, and thoracoabdominal bands so that respiratory effort related to arousals could be studied along with apneas and hypopneas. In our study we did not use an esophageal pressure catheter. We calculated the apnea index, hypopnea index, and apnea-hypopnea index (AHI) and determined the number of patients who would be diagnosed with SAHS (AH I > or =10) and the number for whom initiation of continuous positive airway pressure treatment would be recommended (AHI > or =30) according to the 2 sets of guidelines.

RESULTS

Polysomnographic tests were valid for 118 of the 120 patients (80% men). The mean (SD) age was 51 (11.6) years and the mean body mass index 31.2 (4.3). Using the 1993 guidelines, the AHI was less than 10 in 25 patients, between 20 and 29 in 38, and 30 or more in 50. In the group overall, mean apnea and hypopnea indices and AHI were all significantly higher with the 2002 guidelines than with the 1993 criteria. With the 1993 criteria, the mean AHI was 33.16 and with 2002 criteria, 45.02 (P<.05). Sixty-four percent of the studies considered normal according to the 1993 SEPAR guidelines were considered apneic according to the 2002 guidelines. Of the patients considered not to need continuous positive airway pressure according to the 1993 SEPAR guidelines, 47.61% did need therapy according to the 2002 guidelines.

CONCLUSIONS

There are significant differences in AHI, and in both apnea and hypopnea indices depending on whether the 1993 or the 2002 SEPAR guidelines are applied.

Reference values for nocturnal home polysomnography in primary schoolchildren

Abbreviated home polysomnography may be an alternative to laboratory polysomnography in children but is not yet generally accepted, partly due to a lack of reference values. Also, there are no normative data on respiratory events obtained using nasal prongs. We determined the prevalence and frequency of central, obstructive, and mixed apneas and hypopneas in a population-based sample of 50 children (mean age 10.1 years) using abbreviated home polysomnography and nasal prongs. We also determined the frequency of movements/arousals and body position changes. All children had central apneas. Obstructive apneas, mixed apneas, and hypopneas were found in 36%, 6%, and 14% of children, respectively. Average number of central, obstructive, and mixed apneas; hypopneas; movement/arousals; and body position changes per hour of sleep was 1.5, 0.1, 0.01, 0.02, 8.2, and 3.7, respectively. The corresponding cutoff values (mean plus 2 standard deviations or 95th centile) were 3.7, 0.7, 0.1, 0.2, 13.4, and 9.1, respectively. We did not find significant gender differences regarding any sleep variable under study. The presented reference values may help clinicians and researchers to improve the interpretation of abbreviated home polysomnography in school-age children.

Prevalence of Positional Sleep Apnea in Patients Undergoing Polysomnography

STUDY OBJECTIVES

The primary aim of this study was to determine the prevalence of positional obstructive sleep apnea using a functional definition. Positional sleep apnea was defined as a total apnea-hypopnea index (AHI) > or = 5 with a > 50% reduction in the AHI between the supine and nonsupine postures, and an AHI that normalizes (AHI < 5) in the nonsupine posture. A secondary aim was to determine if positional sleep apnea can be diagnosed accurately during a split-night study.

DESIGN

Retrospective chart review.

SETTING

Two sleep centers in Buffalo, NY, one a Veterans Affairs Western New York Healthcare System Sleep Center (VAWNY) and the other a freestanding ambulatory center (Associated Sleep Center [ASC]).

PATIENTS

Three hundred twenty-six patients from the VAWNY, including 57 patients who underwent a split-night study and 242 patients from the ASC who underwent polysomnography.

INTERVENTIONS

None.

MEASUREMENTS

Patient characteristics and sleep study results.

RESULTS

Positional sleep apnea was seen in 49 of 99 patients (49.5%) with mild sleep apnea (AHI, 5 to 15/h), 14 of 72 patients (19.4%) with moderate sleep apnea (AHI, 15 to 30/h), and 5 of 77 patients (6.5%) with severe sleep apnea (AHI > 30/h). Sufficient sleep (> 15 min) in both postures was not seen in 104 of 269 patients (38.7%) and 80 of 242 overnight studies (33.1%) at the VAWNY and ASC, respectively, and was not seen in 47 of 57 split-night studies (82.5%). The percentage of studies with insufficient sleep in both postures was significantly greater for split-night studies (p < 0.0001).

CONCLUSIONS

Positional sleep apnea is common particularly in patients with mild disease. Positional sleep apnea cannot usually be assessed during a split-night study.

Disorders of sleep: an overview

Only recently has the medical profession focused on the importance of sleep and health. There are increasing numbers of studies linking sleep disorders with neurobehavioral and cardiovascular morbidity and possibly mortality. Although sleep disorders are diverse and affect a substantial number of patients, they are often misdiagnosed or underdiagnosed. Common presenting symptoms to physicians include hypersomnia and insomnia. A systematic workup helps to diagnose the underlying cause.

Non-invasive, side-selective nasal airflow monitoring

Nasal obstruction disturbs comfort during daytime, and sleep quality. Convenient objective assessment of nasal ventilation would be desirable. Therefore, we developed a technique for unobtrusive monitoring of bilateral nasal airflow. Nasal cannulae with separated left- and right-sided tubings were connected to two pressure transducers. Calibration tables were obtained by recording left and right nasal pressures during sequential unilateral nasal occlusion over a few breaths along with airflow by a flow meter attached to a mask. Based on these data, nasal pressures subsequently provided side-selective estimates of airflow without need for a mask. Accuracy of left and right nasal pressure derived airflows was evaluated by comparison of their sum to a flow meter in a bench model, in five volunteers at baseline and during unilateral nasal obstruction by histamine and in five patients during overnight sleep. In the model and volunteers, nasal pressure and flow meter derived flow agreed closely at baseline, and during partial nasal obstruction that altered left/right nasal flow ratios. In patients, nasal pressure derived tidal volumes accurately tracked flow meter estimates over >6 h (70 comparisons, bias -1%, limits of agreement +/-19%). The described method allows continuous, side-selective and unobtrusive monitoring of nasal ventilation for diagnostic evaluation and assessment of treatment effects.

Cerebral Structural Changes in Severe Obstructive Sleep Apnea

Obstructive sleep apnea is associated with abnormalities in neuropsychologic function, and defects in respiratory control may contribute to pathogenesis. Abnormalities may be reflected in structural brain changes. Twenty-seven male untreated patients with severe sleep apnea without comorbidities, and 24 age-matched control subjects, had T1-weighted brain imaging in a high-resolution magnetic resonance scanner. Twenty-three patients with sleep apnea had repeat imaging after 6 months of continuous positive airways pressure treatment. No areas of gray matter volume change were found in patients using an optimized voxel-based morphometry technique, at p < 0.05 adjusted for multiple comparisons (despite the method being sensitive to changes in gray matter fraction of 0.17 or less in all voxels). Furthermore, no differences were seen in bilateral hippocampal, temporal lobe, or whole brain volumes, assessed by manual tracing of anatomical borders. No longitudinal changes were seen in gray matter density or regional volumes after treatment, but whole brain volume decreased slightly. We have found no gray matter volume deficits nor focal structural changes in severe obstructive sleep apnea. Whole brain volume decreases without focal changes after 6 months of continuous positive airways pressure treatment.

Pulse transit time improves detection of sleep respiratory events and microarousals in children

OBJECTIVES

To evaluate the additional information provided by pulse transit time (PTT), a noninvasive tool, when using during polysomnography for the diagnosis of sleep breathing disorders in a pediatric population.

MAIN FINDINGS

Respiratory and microarousals events were scored twice. The first scoring was performed using nasal pressure, thermistors, thoracic and abdominal movements, and oxygen saturation. The second scoring, blinded to the first scoring, was performed using PTT in combination with all the other signals. Microarousals were scored once visually on the EEG trace (cortical arousals [CAs]) and once using the PTT signal (autonomic arousals [AAs]) blinded to EEG. For the whole group of 16 children studied (mean age, 9.5 years), there was no significant difference between the respiratory disturbance index (RDI) with or without PTT analysis (22.4 +/- 13.5/h vs 20.4 +/- 14.3/h; not significant [mean +/- SD]). Among the children exhibiting a "without PTT" RDI < 30/h, 5 of 12 children (41.66%) showed a clinically significant >/= 5/h increase in RDI when using PTT. AAs detected by PTT were significantly more frequent than CAs during rapid eye movement (REM) sleep (7.4 +/- 3.9/h vs 3.2 +/- 2.3/h; p < 0.001) and slow wave sleep (SWS) [6.0 +/- 4.3/h vs 0.6 +/- 0.5/h; p < 0.0001].

CONCLUSIONS

The quantification of respiratory effort using PTT improves the detection of respiratory events in children. The detection of microarousals is improved particularly in REM and SWS.

Influence of weight and sleep apnea status on immunologic and structural features of the uvula

We investigated the influence of weight and obstructive sleep apnea status on inflammatory and histologic features of the uvula. Tissue samples resected during uvulopalatopharyngoplasty in 11 snorers without obstructive sleep apnea, 11 subjects with obstructive sleep apnea and of similar body mass index and age, and 8 additional obese subjects with obstructive sleep apnea were examined by immunohistochemistry and histologic staining techniques. The frequency and distribution of immune cells, the amount of collagen, and the integrity of the elastin fiber network were evaluated in proximal and distal uvular sections. T cell (CD4+, CD8+) and macrophage counts were higher in the more obese apneic subjects than in the other two groups. In all patients, T cell counts correlated with body mass index, but there was no relationship with the apnea-hypopnea index. A positive correlation was found between elastin fiber network disorganization score and apnea-hypopnea index. We conclude that (1) the amount of inflammatory markers is linked to obesity rather than to sleep-related breathing disorders, and (2) obstructive sleep apnea is associated with a structural alteration of the extracellular matrix of upper airway tissue.

Sleep . 3: Clinical presentation and diagnosis of the obstructive sleep apnoea hypopnoea syndrome

Patients with OSAHS may present to a sleep clinic or to other specialists with symptoms that are not immediately attributable to the condition. The diagnostic methods available are reviewed.

Evidence-based medicine in sleep apnea surgery

Since the first description of sleep apnea as a clinical entity, the understanding of it within the medical community has increased significantly. Much research has explored the causes, assessment, and treatment of this disease. This research has resulted in a variety of tools for assessment and approaches to treatment. As research progresses, new data have shed light on the strengths of traditional approaches and their limitations. This article gives background for current approaches and charts a potential future course for sleep apnea assessment and treatment.

Monitoring respiration during sleep

The sleep-related breathing disorders have been categorized in various ways. The most basic schema divides them into obstructive or central apneic events. An American Academy of Sleep Medicine (AASM) Task Force Report published in 1999 defined four separate syndromes associated with abnormal respiratory events during sleep among adults, namely, obstructive sleep apnea-hypopnea syndrome (OSAHS), central sleep apnea-hypopnea syndrome, Cheyne-Stokes breathing syndrome, and sleep hypoventilation syndrome. In this classification, the upper airway resistance syndrome was not regarded as a distinct syndrome; instead, respiratory event-related arousals (RERAs) were considered part of the syndrome of OSAHS.

Discriminative power of phrenic twitch-induced dynamic response for diagnosis of sleep apnea during wakefulness

The diagnosis of the obstructive sleep apnea syndrome relies on polysomnography. Bilateral anterior magnetic phrenic stimulation (BAMPS) mimics the dissociation between upper airway (UA) muscles and diaphragm commands that leads to UA closure during sleep. We evaluated BAMPS as a mean to identify obstructive sleep apnea syndrome patients through the characterization of the UA dynamics in 28 consecutive awake patients (18 apneic and 10 nonapneic). Driving pressure (Pd) and instantaneous flow (V) were recorded in response to BAMPS to determine the point of flow limitation (Vimax) and of minimal flow (Vimin) and the flow-pressure relationship [Vi = (k(1) x Pd) + (k(2) x Pd(2))]. Vimax, Vimin, UA resistance at Vi(min), and the coefficient of the flow-pressure relationship (k(1)) were correlated with apnea-hypopnea index (respectively, R = -0.735, P < 0.0001; R = -0.584, P = 0.001; R = 0.474, P = 0.01; and R = -0.567, P < 0.01). Body mass index was also correlated with apnea-hypopnea index (R = 0.500, P < 0.01). Apneic patients had a lower Vimax (Vimax = 678 +/- 386 vs. 1,247 +/- 271 ml/s; P < 0.001), a lower Vimin (Vimin = 460 +/- 313 vs. 822 +/- 393 ml/s; P < 0.05) and a lower k(1) (k(1) = 162 +/- 67 vs. 272 +/- 112 ml x cmH(2)O x s(-1); P < 0.01) than nonapneic ones. Using a classification and regression tree approach, we found that a Vimax of <803 ml/s (n = 12) selected only apneic patients. When Vimax of >803 ml/s (n = 16), a k(1) of >266.7 ml. cmH(2)O x s(-1) identified only nonapneic patients (n = 5). In 11 cases, Vimax > 803 ml/s and k(1) < 266.7 ml. cmH(2)O x s(-1). These included five nonapneic and six apneic patients. We conclude that UA dynamic properties studied with BAMPS during wakefulness significantly differ between nonapneic and apneic patients.

Effects of continuous positive airway pressure on upper airway inspiratory dynamics in awake patients with sleep-disordered breathing

Continuous positive airway pressure (CPAP) is the main treatment of the obstructive sleep apnoea syndrome (OSAS). We assessed its effects on the upper airway (UA) dynamics in response to bilateral anterior magnetic phrenic nerve stimulation (BAMPS) in 17 awake untreated OSAS patients (15 males; 52 +/- 7 years) whose effective CPAP (P(eff)) had been determined beforehand by a conventional titration sleep study. All twitch-related inspirations were flow-limited, flow first rising to a maximum (V(Imax)), then decreasing to a minimum (V(Imin)), and then increasing again (M-shaped pattern). Up to V(Imin), the relationship between driving pressure (P(d)) and flow (V) could adequately be fitted to a polynomial regression model (V = k(1)P(d) + k(2)P(d)(2); r(2) = 0.71-0.98, P < 0.0001). At atmospheric pressure V(Imax) was 700 +/- 377 ml s(-1), V(Imin) was 458 +/- 306 ml s(-1), k(1) was 154.5 +/- 63.9 ml s(-1) (cmH(2)O)(-1), and k(2) was 10.7 +/- 7.3 ml s(-1) (cmH(2)O)(-1). CPAP significantly increased V(Imax) and V(Imin) (peak values 1007 +/- 332 ml and 837 +/- 264 ml s(-1), respectively) as well as k(1) and k(2) (peak values 300.9 +/- 178.2 ml s(-1) (cmH(2)O)(-1) and 55.2 +/- 65.3 ml s(-1) (cmH(2)O)(-1), respectively). With increasing CPAP, k(1)/k(2) increased up to a peak value before decreasing. We defined as P(eff,stim) the CPAP value corresponding to the highest k(1)/k(2) value. P(eff,stim) was correlated with P(eff) (P(eff) = 7.0 +/- 2.0; P(eff,stim) = 6.4 +/- 2.6 cmH(2)O; r = 0.886; 95 % CI 0.696-0.960, P < 0.001). We conclude that CPAP improves UA dynamics in OSAS and that the therapeutic CPAP to apply can be predicted during wakefulness using BAMPS.