Tracheal sounds for the scoring of sleep respiratory events in children

Quantitative validation of the suprasternal pressure signal to assess respiratory effort during sleep

Objective.Intra-esophageal pressure (Pes) measurement is the recommended gold standard to quantify respiratory effort during sleep, but used to limited extent in clinical practice due to multiple practical drawbacks. Respiratory inductance plethysmography belts (RIP) in conjunction with oronasal airflow are the accepted substitute in polysomnographic systems (PSG) thanks to a better usability, although they are partial views on tidal volume and flow rather than true respiratory effort and are often used without calibration. In their place, the pressure variations measured non-invasively at the suprasternal notch (SSP) may provide a better measure of effort. However, this type of sensor has been validated only for respiratory events in the context of obstructive sleep apnea syndrome (OSA). We aim to provide an extensive verification of the suprasternal pressure signal against RIP belts and Pes, covering both normal breathing and respiratory events.Approach.We simultaneously acquired suprasternal (207) and esophageal pressure (20) signals along with RIP belts during a clinical PSG of 207 participants. In each signal, we detected breaths with a custom algorithm, and evaluated the SSP in terms of detection quality, breathing rate estimation, and similarity of breathing patterns against RIP and Pes. Additionally, we examined how the SSP signal may diverge from RIP and Pes in presence of respiratory events scored by a sleep technician.Main results.The SSP signal proved to be a reliable substitute for both esophageal pressure (Pes) and respiratory inductance plethysmography (RIP) in terms of breath detection, with sensitivity and positive predictive value exceeding 75%, and low error in breathing rate estimation. The SSP was also consistent with Pes (correlation of 0.72, similarity 80.8%) in patterns of increasing pressure amplitude that are common in OSA.Significance.This work provides a quantitative analysis of suprasternal pressure sensors for respiratory effort measurements.

Alternatives to Polysomnography for the Diagnosis of Pediatric Obstructive Sleep Apnea

Diagnosis of obstructive sleep apnea (OSA) in children with sleep-disordered breathing (SDB) requires hospital-based, overnight level I polysomnography (PSG). Obtaining a level I PSG can be challenging for children and their caregivers due to the costs, barriers to access, and associated discomfort. Less burdensome methods that approximate pediatric PSG data are needed. The goal of this review is to evaluate and discuss alternatives for evaluating pediatric SDB. To date, wearable devices, single-channel recordings, and home-based PSG have not been validated as suitable replacements for PSG. However, they may play a role in risk stratification or as screening tools for pediatric OSA. Further studies are needed to determine if the combined use of these metrics could predict OSA.

Validity and reliability of the Japanese version of the severity hierarchy score for pediatric obstructive sleep apnea screening

OBJECTIVE

This study aimed to evaluate the validity and reliability of the Japanese version of the severity hierarchy score (J-SHS) in the screening of pediatric obstructive sleep apnea (OSA) among Japanese community children.

METHODS

A total of 922 children from elementary schools in Tokyo were recruited. Their parents completed the J-SHS questionnaire, and the children underwent an overnight Tracheal Sound (TS) recording. The reliability of the J-SHS was assessed by Cronbach's alpha coefficients and Spearman's correlation. Construct validity was determined by factor analysis. The discriminative ability to diagnose OSA was evaluated by constructing ROC curves.

RESULTS

Five hundred and seventeen children (51.8% male, mean age 7.1 ± 0.7 years) were included. Cronbach's alpha coefficient was 0.80. Factor analysis resulted in a two-factor structure, with factor loadings all above 0.4. A J-SHS score of >1.88 exhibited a 60% sensitivity, 93% specificity, and an area under the curve (AUC) of 0.78 for detecting an apnea-hypopnea index (AHI) of ≥5/h; a J-SHS score of >2.06 exhibited a 75% sensitivity, 84% specificity and AUC of 0.84 for detecting an AHI of ≥3/h among the children with a snoring frequency above two nights/wk.

CONCLUSION

The J-SHS exhibits good performance as a screening tool providing a quick and straightforward approach for identifying Japanese children at risk for OSA.

Recent advances in paediatric sleep disordered breathing

This article reviews the latest evidence pertaining to childhood sleep disordered breathing (SDB), which is associated with negative neurobehavioural, cardiovascular and growth outcomes. Polysomnography is the accepted gold standard for diagnosing SDB but is expensive and limited to specialist centres. Simpler tests such as cardiorespiratory polygraphy and pulse oximetry are probably sufficient for diagnosing obstructive sleep apnoea (OSA) in typically developing children, and new data-processing techniques may improve their accuracy. Adenotonsillectomy is the first-line treatment for OSA, with recent evidence showing that intracapsular tonsillectomy results in lower rates of adverse events than traditional techniques. Anti-inflammatory medication and positive airway pressure respiratory support are not always suitable or successful, although weight loss and hypoglossal nerve stimulation may help in select comorbid conditions.

Educational aims

To understand the clinical impact of childhood sleep disordered breathing (SDB).To understand that, while sleep laboratory polysomnography has been the gold standard for diagnosis of SDB, other diagnostic techniques exist with their own benefits and limitations.To recognise that adenotonsillectomy and positive pressure respiratory support are the mainstays of treating childhood SDB, but different approaches may be indicated in certain patient groups.

Tracheal Sound Analysis

Tracheal sound sensors provide multiple respiratory signals that are valuable for studying upper airway characteristics. This chapter reviews the original work and ongoing research on tracheal sound analysis in relation to upper airway obstruction during sleep. Past and current research suggest that being associated with other sleep study recording sensors and advanced signal processing techniques, tracheal sound analysis can extensively contribute to the diagnosis and assessment of sleep-disordered breathing.

Quality of poly(somno)graphy recordings in children

The aim of the study was to assess the scorability of the signals of four poly(somno)graphy devices and transcutaneous carbon dioxide tracings (PtcCO₂ ) of one device in children. The presence (0%, < 25%, 25%-50%, 50%-75%, 75%-99%, 100% of recording time) and quality (bad, average, good) of the signal of each sensor were analysed. During a 5-month period, 364 poly(somno)graphies were performed in 12 different hospital units. Forty-one children had poor/bad cooperation, and 13 severe behaviour disorders. Seventy-one and 293 poly(somno)graphies were performed in children aged ≤ 2 and > 2 years, respectively; nine poly(somno)graphies failed. For the four poly(somno)graphy devices, the signal was present during 99% of recording time for the electroencephalogram, 99% for thoracic belt, 97% for abdominal belt, 97% for body position, 95% for the microphone, 92% for pulse oximetry, 87% for tracheal sound, 71% for oronasal thermistor, 52% (41% for ≤ 2 years, 55% for > 2 years old) for nasal pressure and 86% for PtcCO₂ . The signal was of good quality in 98% of poly(somno)graphies for body position, 96% for microphone, 96% for thoracic belt, 95% for pulse oximetry, 91% for abdominal belt, 91% for tracheal sound, 82% for oronasal thermistor, 78% for electroencephalogram, 73% for nasal pressure and 46% of PtcCO₂ recordings. The scorability was comparable between devices. Nasal pressure and oronasal thermistor had the lowest scorability, especially in children aged ≤ 2 years. This underlines the necessity of the development or improvement of alternative, ideally face-free, sensors, or miniaturized devices adapted for infants and children.

Estimation of heart rate from tracheal sounds recorded for the sleep apnea syndrome diagnosis

Obstructive sleep apnea is a common sleep disorder with a high prevalence and often accompanied by significant snoring activity. To diagnose this condition, polysomnography is the standard method, where a neck microphone could be added to record tracheal sounds. These can then be used to study the characteristics of breathing, snoring or apnea. In addition cardiac sounds, also present in the acquired data, could be exploited to extract heart rate. The paper presents new algorithms for estimating heart rate from tracheal sounds, especially in very loud snoring environment. The advantage is that it is possible to reduce the number of diagnostic devices, especially for compact home applications. Three algorithms are proposed, based on optimal filtering and cross-correlation. They are tested firstly on one patient presenting significant pathology of apnea syndrome, with a recording of 509 min. Secondly, an extension to a database of 16 patients is proposed (16 hours of recording). When compared to a reference ECG signal, the final results obtained from tracheal sounds reach an accuracy of 81% to 98% and an RMS error from 1.3 to 4.2 bpm, according to the level of snoring and to the considered algorithm.

Diagnosis of sleep apnea without sensors on the patient's face

STUDY OBJECTIVES

Thermistors, nasal cannulas, and respiratory inductance plethysmography (RIP) are the recommended reference sensors of the American Academy of Sleep Medicine (AASM) for the detection and characterization of apneas and hypopneas; however, these sensors are not well tolerated by patients and have poor scorability. We evaluated the performance of an alternative method using a combination of tracheal sounds (TSs) and RIP signals.

METHODS

Consecutive recordings of 70 adult patients from the Pays de la Loire Sleep Cohort were manually scored in random order using the AASM standard signals and the combination TS and RIP signals, without respiratory sensors placed on the patient's face. The TS-RIP scoring used the TS and RIP-flow signals for detection of apneas and hypopneas, respectively, and the suprasternal pressure and RIP belt signals for the characterization of apneas.

RESULTS

Sensitivity and specificity of the TS-RIP combination were 96.21% and 91.34% for apnea detection and 89.94% and 93.25% for detecting hypopneas, respectively, with a kappa coefficient of 0.87. For the characterization of apneas, sensitivity and specificity were 98.67% and 96.17% for obstructive apneas, 92.66% and 99.36% for mixed apneas, and 96.14% and 98.89% for central apneas, respectively, with a kappa coefficient of 0.94. The TS-RIP scoring revealed a high agreement for classifying obstructive sleep apnea into severity classes (none, mild, moderate, and severe obstructive sleep apnea) with a Cohen's kappa coefficient of 0.96.

CONCLUSIONS

Compared with the AASM reference sensors, the TS-RIP combination allows reliable noninvasive detection and characterization of respiratory events with a high degree of sensitivity and specificity. TS-RIP combination could be used for diagnosis of obstructive sleep apnea in adults, either as an alternative to the AASM sensors or in combination with the recommended AASM sensors.