Computer-aided auscultation
Encyclopedia
Computer-aided auscultation (CAA) is a clinical decision support system
, which is designed to assist physicians and other health professionals with decision making
tasks when assessing a heart murmur
. The need for computer-aided auscultation is increasing as the auscultation
skills of physicians are declining. More than half of the number of babies with undiagnosed congenital heart defect
s, which comes to light in infancy, are missed by routine neonatal examination and more than one third by the 6 week examination. In many cases the referral of paediatric patients to paediatric cardiologist are subjective and more than 60% of the referrals are due to an innocent or functional murmur.
A computer-aided auscultation clinical decision support uses a electronic stethoscope to record the acoustic heart sound, acoustic signal processing algorithms, a computer analyzes the recording to identify specific heart sounds that may be present, including S1, S2 and suspected murmurs. A graphic user interface displays the results.
in the mid nineties. Studies focusing on CAA really only become popular when laptop computers and specialized digital stethoscopes started being used more commonly. The early 1990s and 2000 studies focused on the use of frequency domain Fourier
analysis of heart sounds. Whereas, newer Time–frequency analysis like, Wavelet
and Wigner distribution function
showed enhanced detail when investigating murmurs. Further classification techniques has evolved from the Decision tree
methods to more complex methods such as Artificial neural network
and Hidden Markov model
.
Today, powerful personal computers are available and large medical manufactures are offering very good digital stethoscopes. Capturing heart sounds have become simple enough to become part of everyday auscultation use. Analyses of these recordings can be done quickly enough to act as an aid in diagnostic decision making.
file format. Other formats where lossy
compression techniques are used are not recommended such as MP3
.
are a non-Stationary process
making it difficult to use some Digital signal processing
techniques. Background noises and noisy sounds made by the lungs and bowls can also affect the analysis. Some specialized software tools exist that can automatically detect S1-S2 components in a heart beat and even detect S3 and S4 sounds. The real value of a CAA system is when irregular heart sound and heart murmurs can be detected.
Clinical decision support system
Clinical decision support system is an interactive decision support system Computer Software, which is designed to assist physicians and other health professionals with decision making tasks, as determining diagnosis of patient data. A working definition has been proposed by Dr...
, which is designed to assist physicians and other health professionals with decision making
Decision making
Decision making can be regarded as the mental processes resulting in the selection of a course of action among several alternative scenarios. Every decision making process produces a final choice. The output can be an action or an opinion of choice.- Overview :Human performance in decision terms...
tasks when assessing a heart murmur
Heart murmur
Murmurs are extra heart sounds that are produced as a result of turbulent blood flow that is sufficient to produce audible noise. Most murmurs can only be heard with the assistance of a stethoscope ....
. The need for computer-aided auscultation is increasing as the auscultation
Auscultation
Auscultation is the term for listening to the internal sounds of the body, usually using a stethoscope...
skills of physicians are declining. More than half of the number of babies with undiagnosed congenital heart defect
Congenital heart defect
A congenital heart defect is a defect in the structure of the heart and great vessels which is present at birth. Many types of heart defects exist, most of which either obstruct blood flow in the heart or vessels near it, or cause blood to flow through the heart in an abnormal pattern. Other...
s, which comes to light in infancy, are missed by routine neonatal examination and more than one third by the 6 week examination. In many cases the referral of paediatric patients to paediatric cardiologist are subjective and more than 60% of the referrals are due to an innocent or functional murmur.
A computer-aided auscultation clinical decision support uses a electronic stethoscope to record the acoustic heart sound, acoustic signal processing algorithms, a computer analyzes the recording to identify specific heart sounds that may be present, including S1, S2 and suspected murmurs. A graphic user interface displays the results.
Auscultation and heart defects
Heart defects are a major cause of worldwide morbidity and mortality. Properly performed, the cardiac auscultatory examination is an inexpensive, widely available tool in the detection and management of heart disease. Unfortunately, accurate interpretation of heart sounds by primary care providers is fraught with error, leading to missed diagnosis of disease and/or excessive costs associated with evaluation of normal variants. Thus, automated heart sound analysis, also known as computer aided auscultation (CAA), has the potential to become a cost-effective screening and diagnostic tool in the primary care setting.History of CAA
CAA started when heart sounds could be captured for analysis and further study. The digitizing of heart sounds using simple microphones where first captured on a Tape recorderTape recorder
An audio tape recorder, tape deck, reel-to-reel tape deck, cassette deck or tape machine is an audio storage device that records and plays back sounds, including articulated voices, usually using magnetic tape, either wound on a reel or in a cassette, for storage...
in the mid nineties. Studies focusing on CAA really only become popular when laptop computers and specialized digital stethoscopes started being used more commonly. The early 1990s and 2000 studies focused on the use of frequency domain Fourier
Fourier
Fourier most commonly refers to Joseph Fourier , French mathematician and physicist, or the mathematics, physics, and engineering terms named in his honor for his work on the concepts underlying them:In mathematics:...
analysis of heart sounds. Whereas, newer Time–frequency analysis like, Wavelet
Wavelet
A wavelet is a wave-like oscillation with an amplitude that starts out at zero, increases, and then decreases back to zero. It can typically be visualized as a "brief oscillation" like one might see recorded by a seismograph or heart monitor. Generally, wavelets are purposefully crafted to have...
and Wigner distribution function
Wigner distribution function
The Wigner distribution function was first proposed to account for quantum corrections to classical statistical mechanics in 1932 by Eugene Wigner, cf. Wigner quasi-probability distribution....
showed enhanced detail when investigating murmurs. Further classification techniques has evolved from the Decision tree
Decision tree
A decision tree is a decision support tool that uses a tree-like graph or model of decisions and their possible consequences, including chance event outcomes, resource costs, and utility. It is one way to display an algorithm. Decision trees are commonly used in operations research, specifically...
methods to more complex methods such as Artificial neural network
Artificial neural network
An artificial neural network , usually called neural network , is a mathematical model or computational model that is inspired by the structure and/or functional aspects of biological neural networks. A neural network consists of an interconnected group of artificial neurons, and it processes...
and Hidden Markov model
Hidden Markov model
A hidden Markov model is a statistical Markov model in which the system being modeled is assumed to be a Markov process with unobserved states. An HMM can be considered as the simplest dynamic Bayesian network. The mathematics behind the HMM was developed by L. E...
.
Today, powerful personal computers are available and large medical manufactures are offering very good digital stethoscopes. Capturing heart sounds have become simple enough to become part of everyday auscultation use. Analyses of these recordings can be done quickly enough to act as an aid in diagnostic decision making.
Components in a CAA system
The main components in a CAA systems involves the hardware; computer and stethoscope, and a software solution for analysis.Acquisition and storage
Data acquisition is done by capturing the input from the stethoscope and recording that data. The data is usually saved in a loss less WAVWAV
Waveform Audio File Format , is a Microsoft and IBM audio file format standard for storing an audio bitstream on PCs...
file format. Other formats where lossy
compression techniques are used are not recommended such as MP3
MP3
MPEG-1 or MPEG-2 Audio Layer III, more commonly referred to as MP3, is a patented digital audio encoding format using a form of lossy data compression...
.
Analysis
Tools to analyse sound are widely used in the sound engineering field. To analyse heart sounds specialized software is however required. Heart soundsHeart sounds
Heart sounds, or heartbeats, are the noises generated by the beating heart and the resultant flow of blood through it...
are a non-Stationary process
Stationary process
In the mathematical sciences, a stationary process is a stochastic process whose joint probability distribution does not change when shifted in time or space...
making it difficult to use some Digital signal processing
Digital signal processing
Digital signal processing is concerned with the representation of discrete time signals by a sequence of numbers or symbols and the processing of these signals. Digital signal processing and analog signal processing are subfields of signal processing...
techniques. Background noises and noisy sounds made by the lungs and bowls can also affect the analysis. Some specialized software tools exist that can automatically detect S1-S2 components in a heart beat and even detect S3 and S4 sounds. The real value of a CAA system is when irregular heart sound and heart murmurs can be detected.
Classification
Detecting irregular heart sounds is only the beginning. Once these irregularities are detected they can be classified into groups. These classifications can be as simple as differentiating between physiological heart sounds and pathological heart sounds. More complex classification might be to specify the condition which caused the murmur.See also
- BallistocardiographyBallistocardiographyThe ballistocardiograph is a measure of ballistic forces on the heart. Ballistocardiography is a technique for producing a graphical representation of repetitive motions of the human body arising from the sudden ejection of blood into the great vessels with each heart beat...
- Benign paediatric heart murmurBenign paediatric heart murmurA functional murmur is a heart murmur that is primarily due to physiologic conditions outside the heart, as opposed to structural defects in the heart itself....
- Heart soundsHeart soundsHeart sounds, or heartbeats, are the noises generated by the beating heart and the resultant flow of blood through it...
- Precordial examinationPrecordial examinationIn medicine, the precordial exam, also cardiac exam, is performed as part of a physical examination, or when a patient presents with chest pain suggestive of a cardiovascular pathology. In reality it's unlikely that this examination would be performed in isolation or in its entirety outside of a...