Abstract

Breathing Rate (BR), an important deterioration indicator, has been widely neglected in hospitals due to the requirement of invasive procedures and the need for skilled nurses to be measured. On the other hand, biomedical signals such as Seismocardiography (SCG), which measures heart vibrations transmitted to the chest-wall, can be used as a non-invasive technique to estimate the BR. This makes SCG signals a highly appealing way for estimating the BR. As such, this work proposes three novel methods for extracting the BR from SCG signals. The first method is based on extracting respiration-dependent features such as the fundamental heart sound components, S1 and S2 from the SCG signal. The second novel method investigates for the first time the use of data driven methods such as the Empirical Mode Decomposition (EMD) method to identify the respiratory component from an SCG signal. Finally, the third advanced method is based on fusing frequency information from the respiration signals that result from the aforementioned proposed methods and other standard methods. The developed methods in this paper are then evaluated on adult recordings from the combined measurement of ECG, the Breathing and Seismocardiograms database. Both fusion and EMD filter-based methods outperformed the individual methods, giving a mean absolute error of 1.5 breaths per minute, using a one-minute window of data.

Highlights

  • The Breathing Rate (BR) plays a key role in patient monitoring as it describes the air in and out of lungs, which can be an indicator of deterioration as the body attempts to maintain oxygen delivery to the tissues [1]

  • The majority of studies decide the model order experimentally by testing orders ranging from 6 to 20 [23]. This approach of order selection is lurking risks as it is referring to a specific age and type of patients, it may deteriorate the BR estimation accuracy for subjects with different characteristics. This drawback is addressed in our suggested enhanced fusion method by introducing a model order selection criterion which is based on the partial autocorrelation function (PACF) of the respiration signal

  • The aforementioned features (S1-S1 interval, S1 and S2 intensity) create discrete non-uniform time series which are sampled at the heart rate (HR) frequency because their location depends on the R-peaks in the ECG signal

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Summary

Introduction

The Breathing Rate (BR) plays a key role in patient monitoring as it describes the air in and out of lungs, which can be an indicator of deterioration as the body attempts to maintain oxygen delivery to the tissues [1]. The majority of studies decide the model order experimentally by testing orders ranging from 6 to 20 [23] This approach of order selection is lurking risks as it is referring to a specific age and type of patients, it may deteriorate the BR estimation accuracy for subjects with different characteristics. This drawback is addressed in our suggested enhanced fusion method by introducing a model order selection criterion which is based on the partial autocorrelation function (PACF) of the respiration signal.

Database Used
Standard Methods
S1-S1 Interval Derived Respiratory Signal
SCG-Derived Respiratory Signal
S1 Peak Amplitude Modulation Derived Respiratory Signal
Empirical Mode Decomposition Derived Respiratory Signal
Time and Frequency Domain Analysis of Respiration Signals
Frequency Domain Analysis
Time Domain Analysis
Evaluation
S1-S1 Interval Derived BR
S1 Intensity and S2 Intensity Derived BR
S1 Peak Amplitude Modulation Derived BR
Empirical Mode Decomposition Derived BR
Proposed Method Fusion and Results
Errors Associated with Gender and Differences in Lifestyle
Errors Associated with Different Respiratory Rates
10. Discussion
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