A Deep-Learning Framework for Detecting and Predicting Clinical Events Using Continuous, Multimodal Physiological Signals
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Date
2024-02-20
Authors
Ross-Howe, Sara Anne
Advisor
Tizhoosh, Hamid
Journal Title
Journal ISSN
Volume Title
Publisher
University of Waterloo
Abstract
There are an estimated 313 million surgeries performed worldwide each year. Even
with significant clinical and technical advances in perioperative research, many patients
experience a major complication during the first 30 days following surgery. In recent
years, there has been significant advancement in wearable technology and digital health
platforms to support remote patient monitoring. Research into machine learning models for
predicting adverse clinical events have predominantly focused on utilizing static, derived
vital metrics extracted from Electronic Health Record (EHR) systems. However, many
limitations have been identified with developing machine learning models from EHR data.
Deep learning offers a solution to these challenges by analyzing the physiological signals
directly to organize and automatically extract progressive layers of features. Preliminary
research in deep learning has just begun for biomedical signal analysis and has been
predominately limited to processing individual biometric channels and signal modalities.
This dissertation presents a novel deep learning framework, called the BiometricNet, for
processing continuous, multimodal physiological signals for the detection and prediction of
adverse clinical events. In the initial signal pre-processing stage of the BiometricNet,
an integrated Generative Multiscale Wavelet De-Noising Autoencoder (Ψ-GANDAE)
is utilized to remove common noise patterns encountered during ambulatory signal
collection. Signal segmentation and feature extraction is performed in the second
processing phase of the BiometricNet, where ResNet and BiLSTM architectures leverage
post-processing attention layers (RBLAN) to support multiple signal sensor formats (e.g.,
electrocardiograms, photoplethysmograms, respiration, temperature, and arterial blood
pressure), and collation of multiple synchronized channels. In the final stage of the
BiometricNet, detection and prediction of adverse health events is achieved by a Siamese
Neural Network (SNN), which produces a risk score based on the comparison of a baseline
signal with samples taken through the patient event timeline.
Important considerations addressed in the proposed framework include optimizing
the use of available data, given the lack of large publicly available labelled datasets
in healthcare, and addressing the imbalanced nature of clinical data, where there is a
chronic scarcity representing target adverse event conditions. The BiometricNet is flexible
and adaptive to support application to a wide array of adverse clinical events, and it is
demonstrated on continuous non-invasive blood pressure estimations from synchronized
ECG and PPG signals, and myocardial infarction predication from ECG Lead I, II, and
III channels. Lastly, this research honours important considerations regarding AI ethics
and network interpretability and transparency to facilitate regulatory approval processes
and garner confidence from clinical practitioners.
Description
Keywords
Deep Learning, Biomedical Signal Analysis, Digital Signal Processing, De-Noising Autoencoder, Siamese Neural Network, Predictive Modelling, Residual Neural Network, Attention-based Network, Generative Adversarial Network, Remote Automated Monitoring, Convolutional Neural Network, Long Short-Term Memory