An article recently published in the journal Scientific Reports introduced a novel method for assessing the severity of pediatric sleep apnea. This method uses deep learning (DL) models to analyze blood oxygen saturation (SpO2) signals. The researchers from Iran and the USA aimed to offer a less invasive and more child-friendly alternative to the traditional polysomnography (PSG) test, which can be distressing or uncomfortable for children.
Study: Deep learning approaches for assessing pediatric sleep apnea severity through SpO2 signals. Image Credit: Natalya Bardushka/Shutterstock.com
Pediatric Sleep Apnea and Diagnostic Challenges
Pediatric Sleep Apnea-Hypopnea (SAH) is a serious sleep disorder in children, characterized by breathing disruptions during sleep. These disruptions can reduce airflow (hypopnea) or complete airflow cessation (apnea). Such issues can negatively impact sleep quality, leading to daytime drowsiness, difficulty concentrating, and long-term health problems, including cognitive, behavioral, and cardiovascular issues.
The conventional diagnostic technique for pediatric SAH is the overnight PSG test, which monitors various physiological signals. Although PSG is effective, it is complex, costly, and uncomfortable for children, highlighting the need for simple diagnostic methods.
Deep Learning for SpO2 Signal Analysis
In this paper, the authors explored DL techniques to analyze SpO2 signals. These signals can be easily recorded with pulse oximeters. SpO2 indicates the oxygen content in blood hemoglobin and is convenient for portable monitoring.
Previous studies have utilized machine learning (ML) methods to analyze airflow (AF) and SpO2 signals for detecting pediatric obstructive sleep apnea (OSA). However, DL algorithms offer advantages over traditional ML methods. They automatically extract complex features from raw data, which improves diagnostic accuracy and robustness.
The study employed two advanced DL architectures, including residual network (ResNet), and attention-augmented hybrid convolutional neural network bidirectional gated recurrent unit (CNN-BiGRU) model. These models were employed to process SpO2 signals to estimate the Apnea-Hypopnea Index (AHI) in pediatric subjects.
Methodology and Model Development
The researchers utilized the Childhood Adenotonsillectomy Trial (CHAT) dataset, including 844 SpO2 signals from pediatric subjects aged 5 to 9.9 years. The data was divided into training (60%), validation (10%), and testing (30%) sets. Furthermore, a threefold cross-validation approach was employed to ensure model robustness.
The ResNet-based model was adapted to a one-dimensional (1D) format suitable for analyzing SpO2 signals. In contrast, the CNN-BiGRU-Attention model combined convolutional neural networks (CNNs) with bidirectional gated recurrent units (BiGRUs) and an attention mechanism to improve feature extraction and temporal processing.
The methodology involved several key stages. First, signal segmentation and preprocessing were performed. Then, SpO2 signal segments were labeled, followed by model training and optimization, and finally AHI estimation. The SpO2 signals were re-sampled to a unified rate of 1 Hz and divided into non-overlapping 20-minute segments.
Motion and zero-level artifacts were addressed, and a 3-second moving average filter was applied to smooth the signals. The labeling algorithm identified desaturation events associated with apneic episodes. The models were trained using the Adam optimizer and Huber loss function.
Key Findings and Insights
The comparative analysis showed that the CNN-BiGRU-Attention model outperformed the ResNet model, achieving an average accuracy of 75.95% and a kappa score of 0.63. In contrast, the ResNet model had an accuracy of 72.9% and a kappa score of 0.57. Additionally, the CNN-BiGRU-Attention model demonstrated superior performance in estimating the AHI and categorizing SAH severity levels.
The models were evaluated using standard AHI thresholds of 1, 5, and 10 events per hour during each test fold, which confirmed their ability to detect pediatric SAH accurately. The authors used various regression metrics to evaluate the models’ proficiency in AHI estimation, including mean absolute error (MAE), root mean squared error (RMSE), and R-squared (R²).
The CNN-BiGRU-Attention model showed better agreement between actual and estimated AHI, with narrower limits of agreement (LoA) and reduced variability compared to the ResNet model. Furthermore, confusion matrices and diagnostic metrics such as sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were employed to assess the models’ diagnostic capabilities.
Potential Applications
This research has significant implications for diagnosing and managing pediatric SAH. The proposed technique is a non-invasive and child-friendly alternative to the conventional PSG test. This could improve accessibility and comfort for children undergoing SAH diagnosis.
Additionally, this method can be integrated into portable monitoring devices, making SAH diagnosis more accessible and less distressing. It may also reduce the costs and complexities associated with traditional diagnostic methods. By accurately estimating the AHI and categorizing SAH severity levels using SpO2 signals, this approach could lead to more efficient and effective diagnostic processes.
Conclusion and Future Scope
In summary, the novel approach proved effective for diagnosing pediatric SAH. By leveraging DL techniques to analyze SpO2 signals, this study offered a promising alternative to the conventional PSG test. The superior performance of the CNN-BiGRU-Attention model highlights the potential of DL models to enhance diagnostic accuracy and robustness.
Future work could focus on refining these models further and exploring their application in broader clinical settings to improve the diagnosis and management of pediatric SAH. Overall, the presented approach can potentially enhance early detection and management of pediatric SAH, ultimately benefiting children's health and well-being.
Journal Reference
Mortazavi, E., Tarvirdizadeh, B., Alipour, K. et al. Deep learning approaches for assessing pediatric sleep apnea severity through SpO2 signals. Sci Rep 14, 22696 (2024). DOI: 10.1038/s41598-024-67729-9, https://link.springer.com/article/10.1038/s41598-024-67729-9
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