Респіраторна акустика та її клінічна інтерпретація в педіатрії

На сьогодні респіраторна акустика – це сформований науковий напрямок, основними завданнями якого є розробка теорії розповсюдження і генерації звуку в легенях та створення інформативних акустичних методів діагностики легеневих захворювань. В області респіраторної акустики опубліковано багато робіт, але зовсім недостатньо робіт з педіатричних позицій. Тому конкретизація окремих питань, на наш погляд, буде цінним матеріалом для трактовки різноманітних легеневих звуків у пульмонологічній практиці педіатра. Фізіологічні пояснення аускультативних явищ до цього часу представляли собою важко розв’язувану проблему. Зміна структури та перебігу захворювань органів дихання у дітей в сучасних умовах вимагає перегляду існуючих трактувань аускультативної симптоматики та їх інтерпретації. Базуючись на аускультативних даних, лікар-педіатр, в першу чергу, складає для себе алгоритм інтерпретації звукових явищ, а потім аналізує їх зв’язок з тим чи іншим патологічним процессом, клінічними та інструментальними даними. Формулювання діагнозу прямо пов’язано з аускультативним феноменом, який лікар має визначити та відобразити в діагнозі. Колектив авторів має надію, що приведені в монографії матеріли допоможуть практикуючим лікарям визначитись в правильному формулюванні звукових явищ, одержаних при аускультації дітей з патологією дихальної системи

A Morphological Approach To Identify Respiratory Phases Of Seismocardiogram

Respiration affects the cardiovascular system significantly and the morphology of signals relevant to the heart changes with respiration. Such changes have been used to extract respiration signal from electrocardiogram (ECG). It is also shown that accelerometers placed on the body can be used to extract respiration signals. It has been demonstrated that the signal morphology for seismocardiogram, the lower frequency band of chest accelerations, is different between inhale and exhale. For instance, systolic time intervals (STI), which provide a quantitative estimation of left ventricular performance, vary between inhale and exhale phases. In other words, heart beats happening in exhale phase are different compared to those in inhale phase. Thus, our main goal in this thesis is investigating feasibility of finding an automatic morphological based method to identify respiratory phases of heart cycles. In this thesis, forty signal recordings from twenty subjects were used. In each recording, the reference respiratory belt signal, three dimensional (3D) chest acceleration signals, and electrocardiogram signals were recorded. The first stage was is choosing a proper estimated respiratory signal. The second stage, was the automatic respiratory phase detection of heart cycles using the selected estimated respiratory signal. The result shows that among estimated respiratory signals, accelerometer-derived respiration (ADR), in z-direction, has a potential m to identify respiratory phase of heart cycles with total accuracy of about 77%

Testing procedures and acquisition systems for contact sensor¿based vocal monitoring devices

L'abstract è presente nell'allegato / the abstract is in the attachmen

Measurement and analysis of breath sounds

Existing breath sound measurement systems and possible new methods have been critically investigated. The frequency response of each part of the measurement system has been studied. Emphasis has been placed on frequency response of acoustic sensors; especially, a method to study a diaphragm type air-coupler in contact use has been proposed. Two new methods of breath sounds measurement have been studied: laser Doppler vibrometer and mobile phones. It has been shown that these two methods can find applications in breath sounds measurement, however there are some restrictions. A reliable automatic wheeze detection algorithm based on auditory modelling has been developed. That is the human’s auditory system is modelled as a bank of band pass filters, in which the bandwidths are frequency dependent. Wheezes are treated as signals additive to normal breath sounds (masker). Thus wheeze is detectable when it is above the masking threshold. This new algorithm has been validated using simulated and real data. It is superior to previous algorithms, being more reliable to detect wheezes and less prone to mistakes. Simulation of cardiorespiratory sounds and wheeze audibility tests have been developed. Simulated breath sounds can be used as a training tool, as well as an evaluation method. These simulations have shown that, under certain circumstance, there are wheezes but they are inaudible. It is postulated that this could also happen in real measurements. It has been shown that simulated sounds with predefined characteristics can be used as an objective method to evaluate automatic algorithms. Finally, the efficiency and necessity of heart sounds reduction procedures has been investigated. Based on wavelet decomposition and selective synthesis, heart sounds can be reduced with a cost of unnatural breath sounds. Heart sound reduction is shown not to be necessary if a time-frequency representation is used, as heart sounds have a fixed pattern in the time-frequency plane

Fractional order models of the human respiratory system

The fractional calculus is a generalization of classical integer-order integration and derivation to fractional (non-integer) order operators. Fractional order (FO) models are those models which contain such fractional order operators. A common representation of these models is in frequency domain, due to its simplicity. The dynamical systems whose model can be approximated in a natural way using FO terms, exhibit specific features, such as viscoelasticity, diffusion and a fractal structure; hence the respiratory system is an ideal application for FO models. Although viscoelastic and diffusive properties were intensively investigated in the respiratory system, the fractal structure was ignored. Probably one of the reasons is that the respiratory system does not pose a perfect symmetry, hence failing to satisfy one of the conditions for being a typical fractal structure. In the 70s, the respiratory impedance determined by the ratio of air-pressure and air-flow, has been introduced in a model structure containing a FO term. It has also been shown that the fractional order models outperform integer-order models on input impedance measurements. However, there was a lack of underpinning theory to clarify the appearance of the fractional order in the FO model structure. The thesis describes a physiologically consistent approach to reach twofold objectives: 1. to provide a physiologically-based mathematical explanation for the necessity of fractional order models for the input impedance, and 2. to determine the capability of the best fractional order model to classify between healthy and pathological cases. Rather than dealing with a specific case study, the modelling approach presents a general method which can be used not only in the respiratory system application, but also in other similar systems (e.g. leaves, circulatory system, liver, intestines). Furthermore, we consider also the case when symmetry is not present (e.g. deformations in the thorax - kyphoscoliose) as well as various pathologies. We provide a proof-of-concept for the appearance of the FO model from the intrinsic structure of the respiratory tree. Several clinical studies are then conducted to validate the sensitivity and specificity of the FO model in healthy groups and in various pathological groups

The role of lower airway resonances in defining vowel feature contrasts.

Thesis (Ph. D.)—Harvard University--MIT Division of Health Sciences and Technology, 2006.Includes bibliographical references (p. 139-145).This electronic version was prepared by the author. The certified thesis is available in the Institute Archives and Special Collections.Ph. D

Acoustic articulatory evidence for quantal vowel categories : the features [low] and [back]

Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, 2009.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (p. 139-142).In recent years, research in human speech communication suggested that the inventory of sound units that are observed in vowels across languages is strongly influenced by the acoustic properties of the human subglottal system. That is, there is a discrete set of possible vowel features that are constrained by the interaction of the acoustic/articulatory properties of the vowels and a small set of attributes that are observed in the subglottal region. This thesis tests the hypothesis that subglottal resonances govern vowel feature boundaries for three populations: adult speakers of English; adult speakers of Korean; and children learning English. First, we explored the relations among F1 of vowels, the first subglottal resonances (SubF1) and the feature [low] in English. For the diphthong [??], F1 peaks for vowels showed an acoustic irregularity near the speaker' s SubF1. For monophthongs, analysis of F1 frequency distributions shows a boundary between [+low] and [-low] vowels at the speakers' SubF1. Second, we studied the relations among F2 of Korean vowels, SubF2 and the feature [back], to test whether the relation between subglottal resonances and the feature boundary, demonstrated earlier for English, also can be applied to other languages. Results show that the F2 boundary between [back] and [front] vowels was placed near SubF2 in Korean, as in English. Third, we explored the development of vowel formants in relation to subglottal resonances for 10 children in the age range of 2;6-3;9 years using the database of Imbrie (2005). Results show that at the earlier ages, formant values deviated from the expected relations, but during the six month period in which the measurements were made, there was considerable movement toward the expected values.(cont.)The transition to the expected relations appeared to occur by the age of 3 years for most of these children, in a developmental pattern that was inconsistent with an account in terms of simple anatomical increase. These three sets of observations provide evidence that subglottal resonances play a role in defining vowel feature boundaries, as predicted by Stevens' (1972) hypothesis that contrastive phonological features in human languages have arisen from quantal discontinuities in articulatory-acoustic space.by Youngsook Jung.Ph.D