Impact of Airflow Rate on Amplitude and Regional Distribution of Normal Lung Sounds (original) (raw)
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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.
2020 42nd Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC), 2020
Respiratory sounds yield pertinent information about respiratory function in both health and disease. Normal lung sound intensity is a characteristic that correlates well with airflow and it can therefore be used to quantify the airflow changes and limitations imposed by respiratory diseases. The dual aims of this study are firstly to establish whether previously reported asymmetries in normal lung sound intensity are affected by varying the inspiratory threshold load or the airflow of respiration, and secondly to investigate whether fixed sample entropy can be used as a valid measure of lung sound intensity. Respiratory sounds were acquired from twelve healthy individuals using four contact microphones on the posterior skin surface during an inspiratory threshold loading protocol and a varying airflow protocol. The spatial distribution of the normal lung sounds intensity was examined. During the protocols explored here the normal lung sound intensity in the left and right lungs in healthy populations was found to be similar, with asymmetries of less than 3 dB. This agrees with values reported in other studies. The fixed sample entropy of the respiratory sound signal was also calculated and compared with the gold standard root mean square representation of lung sound intensity showing good agreement. Clinical Relevance-This study provides information on the spatial distribution of normal lung sound intensity in a healthy population during two separate protocols and presents a novel representation of lung sound intensity. The results obtained here in a healthy population may be used for comparison with respiratory sounds recorded in a patient population using similar protocols.
Lung sounds: Relative sites of origin and comparative amplitudes in normal subjects
Lung, 1983
Little is known about the comparative amplitude of the vesicular lung sounds heard over the tung apices and bases. Neither is the site of origin of these sounds known. Recent studies suggest that differences in amplitude between the left and right sides of the chest may be considerable. In order to better assess these differences, and to determine the relative sites of origin of these sounds, a new computerized tung sound measurement technique was employed to study the lung sound amplitude and phase relationships over the left and right posterior lung bases and anterior apices in 9 healthy volunteers. Twenty-four inspiratory breath sounds were recorded simultaneously using 2 microphones at 8 different intermicrophone separations (1 to 8 cm) at those locations. The mean amplitude of the lung sounds so recorded at each location was determined by automated flow-gated measurement at an inspirato~ air flow rate of 1.3 l/s. Simultaneously, the degree of similarity of phase between the sounds from both microphones (Subtraction intensity index -SII) was determined. In addition, 3 inspirations were recorded simultaneously by 1 microphone on either side of the sternum in the second intercostal space in order to assess the phase similarity of the lung sounds at these positions. The results showed that the sound intensity at one base (left or right) was significantly greater than at the opposite base in 7 of the 9 subjects. The sound intensity at the left apex was always louder than or equal to that at the right. The subtraction patterns suggested that the sound sources at the apex were more central than at the bases but that additional phase shifting may have occurred during transmission to the chest wall. The sounds recorded from opposite sides of the sternum showed little or no similarity indicating that the sound at this location, though bronchial in character, was not transmitted from the trachea. It is concluded that significant inequality in lung sound amplitude between homologous areas on opposite sides of the chest is a corn-* Supported in part by NHLBI Grant HL 26334 mon finding and that the vesicular sounds over the lung apices are possibly produced more centrally than those at the bases but that the trachea is not the source of these sounds.
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.
Effects of lung volume and airflow on the frequency spectrum of vesicular lung sounds
Respiration physiology, 1986
The purpose of this study was to determine whether the vesicular lung sound frequency spectrum is affected by changes in lung volume and airflow. Nine healthy young nonsmokers were studied. The dependent variables were the points that divide the power spectrum of the vesicular lung sound into quarters (1st, 2nd and 3rd quartiles (Q1, Q2 and Q3]. Recording sites were the right upper anterior (RUL) and lower posterior (RLL) chest wall. Lung sounds were high-pass filtered at 100 Hz. To evaluate the effect of volume, lung sounds were recorded during an inspiratory vital capacity (VC) maneuver at near constant airflow rates. The spectral parameters were determined at each sixth of the VC. To assess the effects of airflow, 5 of the subjects breathed from resting lung volume at peak inspiratory airflows of between 1 and 3.0 L/sec for a total of 16 breaths each and the frequency parameters of the lung sounds occurring during peak inspiratory airflows were determined. Volume effects: only at...
Changes in regional distribution of lung sounds as a function of positive end-expiratory pressure
Critical Care, 2009
Introduction Automated mapping of lung sound distribution is a novel area of interest currently investigated in mechanically ventilated, critically ill patients. The objective of the present study was to assess changes in thoracic sound distribution resulting from changes in positive end-expiratory pressure (PEEP). Repeatability of automated lung sound measurements was also evaluated.
Vesicular lung sound amplitude mapping by automated flow-gated phonopneumography
Journal of applied physiology: respiratory, environmental and exercise physiology
A recently developed automated apparatus capable of determining vesicular lung sound amplitude rapidly and accurately was used to construct detailed inspiratory vesicular sound amplitude maps in eight healthy male subjects to determine the normal amplitude patterns on the chest wall. The sounds were recorded in 2-cm steps along the following lines bilaterally: A, vertically, clavicle to abdomen, 6 cm from the sternal border; B, vertically, from the level of T1 to the lung bases, 6 cm from the spine; and C, horizontally, from the sternal border to the spine at the level of the nipple. Sound amplitude was measured at an airflow rate of 1.3 l/s. The resulting amplitude maps revealed considerable intra- and intersubject variation with frequent amplitude heterophony. Th patterns for the subjects as a group were as follows: series A, amplitude decreasing with distance from the clavicle; series B, amplitude increasing with distance from T1 with a peak at the bases; and series C, approximately equal amplitude at all positions. The findings in series B and C are, in general, consistent with an explanation of ventilation following hydrostatic gradients. The series A pattern and the intersubject variability in amplitude are inconsistent with this explanation and suggest that the inspiratory vesicular sound amplitude is not simply a result of ventilation distribution but involves other as yet undefined factors.
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.