Bilateral asymmetry of respiratory acoustic transmission (original) (raw)
Related papers
Transmission to the chest of sound introduced at the mouth
Journal of Applied Physiology
We examined the transmission to the chest wall of white noise and 25-Hz square-wave-generated noise introduced at the mouth of five healthy subjects. The output audio signals were recorded over the left and right upper and lower lung zones, posteriorly. Sound measurements were made during apnea at functional residual capacity, total lung capacity, and residual volume both after breathing air and an 80% He-20% O2 (heliox) gas mixture. We calculated the peak-to-peak amplitude, the peak frequency, and the midpower frequency of the output sound. We found no consistent variations in the values of these indexes due to lung volume or resident gas density. In all cases, the transmitted sound was most intense at the right upper zone. This could not be explained on the basis of technical factors but was probably the result of normal asymmetry of the mediastinal anatomy. These data suggest that sound introduced through the mouth of healthy individuals excites intrathoracic structures but is transmitted through the parenchyma in such a manner that it is not markedly affected by familiar physiological variables. This must be taken into account if objective acoustical tests of lung physiology are to be developed.
Resonances and wave propagation velocity in the subglottal airways
Journal of The Acoustical Society of America, 2011
Previous studies of subglottal resonances have reported findings based on relatively few subjects, and the relations between these resonances, subglottal anatomy, and models of subglottal acoustics are not well understood. In this study, accelerometer signals of subglottal acoustics recorded during sustained [a:] vowels of 50 adult native speakers (25 males, 25 females) of American English were analyzed. The study confirms that a simple uniform tube model of subglottal airways, closed at the glottis and open at the inferior end, is appropriate for describing subglottal resonances. The main findings of the study are: 1) whereas the walls may be considered rigid in the frequency range of Sg2 and Sg3, they are yielding and resonant in the frequency range of Sg1, with a resulting ∼ 4/3 increase in wave propagation velocity and, consequently, in the frequency of Sg1; 2) the 'acoustic length' of the equivalent uniform tube varies between 18 cm and 23.5 cm, and is approximately equal to the height of the speaker divided by an empirically determined scaling factor; 3) trachea length can also be predicted by dividing height by another empirically determined scaling factor; and 4) differences between the subglottal resonances of males and females can be accounted for by height-related differences.
An acoustic model of the respiratory tract
IEEE Transactions on Biomedical Engineering, 2001
With the emerging use of tracheal sound analysis to detect and monitor respiratory tract changes such as those found in asthma and obstructive sleep apnea, there is a need to link the attributes of these easily measured sounds first to the underlying anatomy, and then to specific pathophysiology. To begin this process, we have developed a model of the acoustic properties of the entire respiratory tract (supraglottal plus subglottal airways) over the frequency range of tracheal sound measurements, 100 to 3000 Hz. The respiratory tract is represented by a transmission line acoustical analogy with varying cross sectional area, yielding walls, and dichotomous branching in the subglottal component. The model predicts the location in frequency of the natural acoustic resonances of components or the entire tract. Individually, the supra and subglottal portions of the model predict well the distinct locations of the spectral peaks (formants) from speech sounds such as /a/ as measured at the mouth and the trachea, respectively, in healthy subjects. When combining the supraglottic and subglottic portions to form a complete tract model, the predicted peak locations compare favorably with those of tracheal sounds measured during normal breathing. This modeling effort provides the first insights into the complex relationships between the spectral peaks of tracheal sounds and the underlying anatomy of the respiratory tract.
Phase delay of pulmonary acoustic transmission from trachea to chest wall
IEEE Transactions on Biomedical Engineering, 1992
The frequency-dependent propagation time, or phase delay T (f), of sonic noise transmission from the trachea to the chest wall was estimated over the 100-600 Hz frequency range using a phase estimation technique from measurements performed on eight healthy subjects. Since 7 (f) can be greater than one period of the input signal at frequencies greater than 100 Hz, the unambiguous phase estimate at 100 Hz was used as a starting-point to determine the phase + H ( f ) and ~( f ) at higher frequencies under the constraint that the spectra did not exhibit large point-to-point discontinuities. The resulting 7 (f) range of 0.9-4.1 ms is consistent with sound propagation to the chest wall through both airways and surrounding parenchyma.
Comparison of Lung Sound and Transmitted Sound Amplitude in Normal Men 1, 2
American Review of Respiratory Disease, 1981
Within the last 5 yr, several studies have suggested that if the lung sound intensity at the chest wall is compared with the intensity of white noise transmitted from the mouth to the same site, the acoustic transmitting properties of the thorax can be assessed and separated from the properties of the lung sound generator. In this study, we used a computer-aided rapid amplitude measuring technique to study this question over a much greater area on the chest wall in 7 subjects. Study locations were at 2cm intervals, apex to base, over both hemithoraxes, anteriorly and posteriorly. Lung sound intensity (LS) was measured by an air-flow-corrected technique. Colored noise (50 to 500 Hz) introduced at the mouth (TRANS) was measured on the chest wall and adjusted for glottic aperture by comparison with the signal from a reference microphone at a fixed location on the chest. The LS amplitude patterns that we observed were similar to those previously determined in this laboratory and were bilaterally equal for the group. The TRANS sound patterns were always of greater intensity near the apex and, over the right hemithorax, were approximately twice the amplitude of those over the left. Similar LS and TRANS maps performed at locations completely encircling the upper thorax in one upright subject revealed wide intensity variations in each that appeared unrelated to each other or to the presumed distribution of ventilation. The transmission of sounds introduced at the mouth appears to be influenced by factors other than simple propagation down airways in certain lung regions. Therefore, the use of such transmitted sounds may not be an appropriate way to correct for transmission characteristics affecting normal lung sounds in these regions.
Speed of low-frequency sound through lungs of normal men
Journal of applied physiology: respiratory, environmental and exercise physiology
The speed of propagation of vesicular lung sound through the lung has not been clearly established. In a recent study (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 54: 304-308, 1983), Rice measured the speed of sound through the parenchyma of excised horse lungs and found it to be 25-70 m/s (less than 20% the speed of sound in air). Filling the lung with helium or sulfur hexafluoride changed the speed of transmission by less than 10%, indicating nongas propagation. The present study was designed to measure the speed of sound through human lungs in vivo. Five healthy, nonsmoking males (aged 27-38 yr) were studied. A microphone was placed on the neck beneath the larynx and another at each of eight locations on the chest wall. Measurements were made at functional residual capacity. White noise was band-pass filtered between 125 and 500 Hz, amplified, and delivered to a loudspeaker connected to a mouthpiece. The speed of sound was measured by cross-correlation analysis of the signals simultaneously detected by the tracheal and chest microphones. This was done after breathing both air and a mixture of 80% He in 20% O2 (He-O2). With air, the mean sound-transit time (trachea to chest wall) ranged from 2 ms at the upper chest to 5 ms at the lower chest (speed of approximately 30 m/s). With He-O2 the mean speed increased by only 10%, whereas the predicted increase of sound speed through gas alone would be greater than 100%. These results are consistent with the in vitro findings of Rice and suggest that within the frequency range of vesicular lung sounds transmission of sound introduced at the mouth is predominantly through the lung parenchyma, not through the airways.
Sound transmission in porcine thorax through airway insonification
Medical & Biological Engineering & Computing, 2015
Many pulmonary injuries and pathologies may lead to structural and functional changes in the lungs resulting in measurable sound transmission changes on the chest surface. Additionally, noninvasive imaging of externally driven mechanical wave motion in the chest (e.g., using magnetic resonance elastography) can provide information about lung structural property changes and, hence, may be of diagnostic value. In the present study, a comprehensive computational simulation (in silico) model was developed to simulate sound wave propagation in the airways, lung, and chest wall under normal and pneumothorax conditions. Experiments were carried out to validate the model. Here, sound waves with frequency content from 50 to 700 Hz were introduced into airways of five porcine subjects via an endotracheal tube, and transmitted waves were measured by scanning laser Doppler vibrometry at the chest wall surface. The computational model predictions of decreased sound transmission with pneumothorax were consistent with experimental measurements. The in silico model can also be used to visualize wave propagation inside and on the chest wall surface for other pulmonary pathologies, which may help in developing and interpreting diagnostic procedures that utilize sound and vibration.
Effects of breathing pathways on tracheal sound spectral features
Respiration physiology, 1998
The spectra of sounds recorded over the trachea of adults typically reveal peaks near 700 and 1500 Hz. We assessed the anatomical determinants of these peaks and the conditions contributing to their presence. We studied five adult subjects with normal lung function, measuring sounds at the suprasternal notch and on the right cheek. The subjects breathed at target airflows of 15 and at 30 ml sec(-1) kg(-1) both through the mouth with nose clips and then through the mouth and nose using a cushioned face mask. The mouth breathing maneuvers were performed with three lengths (3.6, 21.1 and 38.6 cm) of 2.6 cm diameter tubing between the mouth and the pneumotachograph. The nose breathing maneuver was performed with the longest tube (between the mask and pneumotachograph). The signals occurring at the target flows +/- 20% were used to create averaged, spectral estimates. We found that all subjects had two predominant spectral peaks; a approximately 700 Hz peak loudest over the cheek and a a...
The relationship between airflow and lung sound amplitude in normal subjects
CHEST Journal, 1984
Few investigators have examined the relationship between airflow and lung sound amplitude; the available data are contradictory. I measured airflow at the mouth and compared the peak flow (Vmax) to mean and peak lung sound amplitude (mean AMP and peak AMP) at four sites on the chest wall (right and left anterior apices and posterior bases) in four healthy young adults. At each site, the sounds produced by 20 breaths at Vmax ranging between 1.5 and 4 L/s (Vvar) were measured by an automated technique. Ten breaths during nearly constant Vmax breathing (Vcon) also were measured at each site. The lung sound amplitudes at the four sites in each subject were grouped and compared to Vmax by linear regression analysis. The same sounds were also submitted to an automated V-correction procedure to evaluate its adequacy in automatically adjusting for the effect of variations in Vmax on lung sound amplitude. The data showed that lung sound amplitude (mean or peak) was linearly related to V in all subjects (r for mean AMP vs Vmax:0.77, 0.85, 0.69, 0.89; r for peak AMP vs Vmax:0.80, 0.83, 0.79, 0.88), p less than 1 X 10(-7) in all cases. The average mean AMP vs Vmax regression line slope was 0.42, and the average peak AMP vs Vmax regression line slope was 0.45. V-correction decreased the coefficient of variation of the Vvar sounds by 61 percent and flattened the average regression line slopes to 0.128. For the Vcon series, V-correction diminished the coefficient of variation from 12.2 to 10.0 percent. The relationship between lung sound amplitude and airflow appears to be substantially linear and this relationship can be used to adjust effectively for variations in airflow.
The Journal of the Acoustical Society of America, 2002
A theoretical and experimental study was undertaken to examine the feasibility of using audible-frequency vibro-acoustic waves for diagnosis of pneumothorax, a collapsed lung. The hypothesis was that the acoustic response of the chest to external excitation would change with this condition. In experimental canine studies, external acoustic energy was introduced into the trachea via an endotracheal tube. For the control ͑nonpneumothorax͒ state, it is hypothesized that sound waves primarily travel through the airways, couple to the lung parenchyma, and then are transmitted directly to the chest wall. In contradistinction, when a pneumothorax is present the intervening air presents an added barrier to efficient acoustic energy transfer. Theoretical models of sound transmission through the pulmonary system and chest region to the chest wall surface are developed to more clearly understand the mechanisms of intensity loss when a pneumothorax is present, relative to a baseline case. These models predict significant decreases in acoustic transmission strength when a pneumothorax is present, in qualitative agreement with experimental measurements. Development of the models, their extension via finite element analysis, and comparisons with experimental canine studies are reviewed.