Steve Kraman | University of Kentucky (original) (raw)
Papers by Steve Kraman
Respiratory Care, Mar 1, 2003
American Review of Respiratory Disease, 1981
Within the last 5 yr, several studies have suggested that if the lung sound intensity at the ches... more 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.
The American review of respiratory disease
The site of origin of the vesicular lung sound has long been in question. A technique (subtractio... more The site of origin of the vesicular lung sound has long been in question. A technique (subtraction phonopneumography) is described here for determining the relative distance of a sound source from the chest wall. This technique involves the simultaneous recording of lung sounds from two different sites on the chest wall, phase inversion of one of the signals, and then mixing the signals in a summing amplifier. The degree of cancellation that results is inversely proportional to the number of sources and the degree to which each source is detected by both microphones simultaneously. A study of six normal subjects revealed little or no cancellation of inspiratory vesicular sounds with microphones separated by 10 cm. During expiration, cancellation did occur at distances well beyond 10 cm and was detectable over several homologous segments of opposite lungs. This finding is consistent with an intrapulmonic and probably intralobar source for the inspiratory component and an upper airway source for at least some of the expiratory component.
Respiration
When a subject exhales forcefully, a wheeze is usually heard during the latter part of the maneuv... more When a subject exhales forcefully, a wheeze is usually heard during the latter part of the maneuver. The origin and mechanism of this wheeze has been the subject of speculation but this has never been approached experimentally. In this study, a computerized frequency analysis technique was used to count the number of discrete frequency components making up the forced expiratory wheeze (FEW) in 10 normal subjects. The number varied from 1 to 5 implying a source in the larger airways. The supports previous theoretical considerations that relate the FEW to the so-called "equal pressure point" (EPP) in the larger airways. Since the EPP is thought to be determined principally by lung static recoil pressure, it can be surmised that this also determines (roughly) the number of wheeze components in the FEW.
The American review of respiratory disease
The precise sound sources that contribute to the vesicular lung sound heard on the chest wall hav... more The precise sound sources that contribute to the vesicular lung sound heard on the chest wall have never been accurately determined. Current thinking favors the mainstem, lobar, and segmental airways as the principal sources contributing to the sound. The larynx has occasionally been said to be responsible for some or all of the vesicular sound, but its actual contribution has never been determined in humans. This study was designed around the hypothesis that, were the laryngeal noise to form an audible part of the vesicular sound heard on the chest wall during quiet breathing, the vesicular sound should get louder during voluntarily produced noisy breathing provided that the sounds are compared at approximately equal flow rates and lung volumes. In this study, sounds from the larynx and 4 sites on the chest wall were simultaneously recorded and displayed along with flow volume loops during quiet breathing and voluntarily produced noisy breathing without actual phonation in 3 healthy subjects. Although increases in amplitude of the laryngeal noise of severalfold were observed in both inspiration and expiration, the amplitude of the simultaneously recorded vesicular sound correlated only with flow rates and were completely unaffected by changes in laryngeal sound amplitude. This demonstrates that during quiet breathing in healthy subjects no detectable component of the laryngeal noise reaches the periphery.
Journal of applied physiology: respiratory, environmental and exercise physiology
A recently developed automated apparatus capable of determining vesicular lung sound amplitude ra... more 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.
The American review of respiratory disease
Considerable confusion exists regarding the frequency spectrum of the normal lung sound, especial... more Considerable confusion exists regarding the frequency spectrum of the normal lung sound, especially the components in the lower frequency range. Frequencies of peak intensity varying from 10 to 200 Hz have been reported by different laboratories. A component of musculoskeletal sound could contribute to the inspiratory lung sound, but this has never been assessed. This study attempted to separate the sound made by the lung from that of muscular contraction by frequency analysis of the sounds occurring during inspiration and preinspiration and postinspiration open-glottis breath-holds in 4 normal subjects. The data showed that at frequencies below 200 Hz, the musculoskeletal component increased as the lung sound component decreased. At 50 Hz and below, the sounds of inspiration and postinspiratory breath-holding were almost indistinguishable. It is concluded that musculoskeletal noise seriously contaminates what is usually considered to be lung sound.
European Respiratory Journal
Auscultatory percussion is a technique that is potentially useful to study the acoustic behaviour... more Auscultatory percussion is a technique that is potentially useful to study the acoustic behaviour of the chest. However, finger percussion, as used in this technique, has not been previously assessed for consistency. We calculated the intrasubject variability and short-term reproducibility of this technique in 10 healthy subjects. We examined several indices of the output sound of two series of sternal percussion manoeuvres performed one hour apart by the same examiner. The results were compared to those obtained during sternal percussion performed by a mechanical thumper. Consistency for both finger and thumper percussion varied from 4.8-20.6 (coefficients of variation) for various acoustic indices. For thumper percussion, the average results were not significantly different from those of finger percussion. We conclude that finger percussion of the sternum is sufficiently consistent to be used as a tool to investigate the acoustic behaviour of the chest.
Journal of Applied Physiology
We examined the transmission to the chest wall of white noise and 25-Hz square-wave-generated noi... more 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.
Journal of Applied Physiology
We indirectly determined the transmission path of sound generated by sternal percussion in five h... more We indirectly determined the transmission path of sound generated by sternal percussion in five healthy subjects. We percussed the sternum of each subject while recording the output audio signal at the posterior left and right upper and lower lung zones. Sound measurements were done during apnea at functional residual capacity, total lung capacity, and residual volume both with the lungs filled with air and with an 80% He-20% O2 (heliox) gas mixture. Three acoustic indexes were calculated from the output sound pulse: the peak-to-peak amplitude, the peak frequency, and the mid-power frequency. We found that the average values of all indexes tended to be greater in the upper than in the ipsilateral lower lung zones. In the upper zones, peak-to-peak amplitude was greater at total lung capacity and residual volume than at functional residual capacity. Replacing air with heliox did not change these results. These experiments, together with others performed during Mueller and Valsalva maneuvers, suggest that resonance of the chest cage is the predominant factor determining the transmission of sternal percussion sounds to the posterior chest wall. The transmission seems to be only minimally affected by the acoustic characteristics of the lung parenchyma.
MedEdPORTAL Publications, 2007
Journal of Applied Physiology
If the lung is an elastic continuum, both longitudinal and transverse stress waves should be prop... more If the lung is an elastic continuum, both longitudinal and transverse stress waves should be propagated in the medium with distinct velocities. In five isolated sheep lungs, we investigated the propagation of stress waves. The lungs were degassed and then inflated to a constant transpulmonary pressure (Ptp). We measured signals transmitted at locations approximately 1.5, 6, and 11 cm from an impulse surface distortion with the use of small microphones embedded in the pleural surface. Two transit times were computed from the first two significant peaks of the cross-correlation of microphone signal pairs. The "fast" wave velocities averaged 301 +/- 92, 445 +/- 80, and 577 +/- 211 (SD) cm/s for Ptp values of 5, 10, and 15 cmH2O, respectively. Corresponding "slow" wave velocities averaged 139 +/- 22, 217 +/- 36, and 255 +/- 89 cm/s. The fast waves were consistent with longitudinal waves of velocity [(K + 4G/3)/p]1/2, where bulk modulus K = 4 Ptp and shear modulus G = 0.7 Ptp. The slow waves were consistent with transverse (and/or Rayleigh) waves of velocity (G/p)1/2, with a G value of 0.9 Ptp. Measured values of K were 5 Ptp and values of G measured by indentation tests were 0.7 Ptp. Thus, stress wave velocities measured on pleural surface of isolated lungs correlated well with elastic moduli of lung parenchyma.
Journal of applied physiology: respiratory, environmental and exercise physiology
The speed of propagation of vesicular lung sound through the lung has not been clearly establishe... more 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.
Respiratory care
Spirometry is the most useful and commonly available tests of pulmonary function. It is a physiol... more Spirometry is the most useful and commonly available tests of pulmonary function. It is a physiological test that measures individual inhalation and exhalation volumes of air as a function of time. Pulmonologists and general-practice physicians commonly use spirometry in their offices in the assessment and management of lung disease. Spirometric indices are well validated and easily interpreted by comparison with established normal values. The remarkable reproducibility of spirometry results from the presence of compliant intrathoracic airways that act as air flow regulators during forced expiration. Because of this anatomic arrangement, expiratory flow becomes dependent solely on the elasticity of the lungs and airway resistance once a certain degree of expiratory force is exerted. Insight into this aspect of respiratory physiology can help in the interpretation of spirometry.
COPD, 2007
The measurements of lung compliance, airway resistance and respiratory dead space as clinical tes... more The measurements of lung compliance, airway resistance and respiratory dead space as clinical tests have gradually fallen into disuse as the standard pulmonary function testing procedures; spirometry, lung volume and diffusing capacity measurement, followed, if necessary, by imaging have become the norm for diagnosis of COPD and other lung diseases. To have a real understanding of what spirometry and lung volume tests measure requires some knowledge of compliance and airway resistance. The respiratory dead space is an important global indicator of ventilation/perfusion relationships that remains of interest in the early detection of pulmonary emboli. There are other situations as well where it is clinically useful to perform the measurements described here, so these techniques, although generally set aside from the commonly used tests, should not be forgotten.
Respiratory care, 2009
Spirometry is the most useful and commonly available tests of pulmonary function. It is a physiol... more Spirometry is the most useful and commonly available tests of pulmonary function. It is a physiological test that measures individual inhalation and exhalation volumes of air as a function of time. Pulmonologists and general-practice physicians commonly use spirometry in their offices in the assessment and management of lung disease. Spirometric indices are well validated and easily interpreted by comparison with established normal values. The remarkable reproducibility of spirometry results from the presence of compliant intrathoracic airways that act as air flow regulators during forced expiration. Because of this anatomic arrangement, expiratory flow becomes dependent solely on the elasticity of the lungs and airway resistance once a certain degree of expiratory force is exerted. Insight into this aspect of respiratory physiology can help in the interpretation of spirometry.
Journal of Patient Safety, 2015
Respiration physiology, 1985
Turbulent airflow (largely gas density dependent) in larger airways is believed by many lung soun... more Turbulent airflow (largely gas density dependent) in larger airways is believed by many lung sound researchers to be the mechanism responsible for the generation of vesicular lung sounds. To test the validity of this concept, we measured the amplitude of lung and tracheal sounds of 6 subjects alternately breathing air and a low density gas mixture (80% helium, 20% oxygen: He-O2). Lung sounds were recorded from 3 chest wall sites: Anterior right upper lobe (RUL), posterior and posterolateral right lower lobe (RLL), and a site over the proximal trachea below the larynx. The subjects rebreathed into an electronic spirometer filled with the test gas, and achieved a peak inspiratory and expiratory airflow of 2-2.5 L/sec. Lung sound amplitude was determined by an automated, flow-corrected measurement procedure. The mean decrease in sound amplitude when breathing He-O2 compared to air was: trachea, inspiration 44%; trachea, expiration 45%; RUL, inspiration 13%; RUL, expiration 25%; RLL, in...
Respiratory Care, Mar 1, 2003
American Review of Respiratory Disease, 1981
Within the last 5 yr, several studies have suggested that if the lung sound intensity at the ches... more 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.
The American review of respiratory disease
The site of origin of the vesicular lung sound has long been in question. A technique (subtractio... more The site of origin of the vesicular lung sound has long been in question. A technique (subtraction phonopneumography) is described here for determining the relative distance of a sound source from the chest wall. This technique involves the simultaneous recording of lung sounds from two different sites on the chest wall, phase inversion of one of the signals, and then mixing the signals in a summing amplifier. The degree of cancellation that results is inversely proportional to the number of sources and the degree to which each source is detected by both microphones simultaneously. A study of six normal subjects revealed little or no cancellation of inspiratory vesicular sounds with microphones separated by 10 cm. During expiration, cancellation did occur at distances well beyond 10 cm and was detectable over several homologous segments of opposite lungs. This finding is consistent with an intrapulmonic and probably intralobar source for the inspiratory component and an upper airway source for at least some of the expiratory component.
Respiration
When a subject exhales forcefully, a wheeze is usually heard during the latter part of the maneuv... more When a subject exhales forcefully, a wheeze is usually heard during the latter part of the maneuver. The origin and mechanism of this wheeze has been the subject of speculation but this has never been approached experimentally. In this study, a computerized frequency analysis technique was used to count the number of discrete frequency components making up the forced expiratory wheeze (FEW) in 10 normal subjects. The number varied from 1 to 5 implying a source in the larger airways. The supports previous theoretical considerations that relate the FEW to the so-called "equal pressure point" (EPP) in the larger airways. Since the EPP is thought to be determined principally by lung static recoil pressure, it can be surmised that this also determines (roughly) the number of wheeze components in the FEW.
The American review of respiratory disease
The precise sound sources that contribute to the vesicular lung sound heard on the chest wall hav... more The precise sound sources that contribute to the vesicular lung sound heard on the chest wall have never been accurately determined. Current thinking favors the mainstem, lobar, and segmental airways as the principal sources contributing to the sound. The larynx has occasionally been said to be responsible for some or all of the vesicular sound, but its actual contribution has never been determined in humans. This study was designed around the hypothesis that, were the laryngeal noise to form an audible part of the vesicular sound heard on the chest wall during quiet breathing, the vesicular sound should get louder during voluntarily produced noisy breathing provided that the sounds are compared at approximately equal flow rates and lung volumes. In this study, sounds from the larynx and 4 sites on the chest wall were simultaneously recorded and displayed along with flow volume loops during quiet breathing and voluntarily produced noisy breathing without actual phonation in 3 healthy subjects. Although increases in amplitude of the laryngeal noise of severalfold were observed in both inspiration and expiration, the amplitude of the simultaneously recorded vesicular sound correlated only with flow rates and were completely unaffected by changes in laryngeal sound amplitude. This demonstrates that during quiet breathing in healthy subjects no detectable component of the laryngeal noise reaches the periphery.
Journal of applied physiology: respiratory, environmental and exercise physiology
A recently developed automated apparatus capable of determining vesicular lung sound amplitude ra... more 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.
The American review of respiratory disease
Considerable confusion exists regarding the frequency spectrum of the normal lung sound, especial... more Considerable confusion exists regarding the frequency spectrum of the normal lung sound, especially the components in the lower frequency range. Frequencies of peak intensity varying from 10 to 200 Hz have been reported by different laboratories. A component of musculoskeletal sound could contribute to the inspiratory lung sound, but this has never been assessed. This study attempted to separate the sound made by the lung from that of muscular contraction by frequency analysis of the sounds occurring during inspiration and preinspiration and postinspiration open-glottis breath-holds in 4 normal subjects. The data showed that at frequencies below 200 Hz, the musculoskeletal component increased as the lung sound component decreased. At 50 Hz and below, the sounds of inspiration and postinspiratory breath-holding were almost indistinguishable. It is concluded that musculoskeletal noise seriously contaminates what is usually considered to be lung sound.
European Respiratory Journal
Auscultatory percussion is a technique that is potentially useful to study the acoustic behaviour... more Auscultatory percussion is a technique that is potentially useful to study the acoustic behaviour of the chest. However, finger percussion, as used in this technique, has not been previously assessed for consistency. We calculated the intrasubject variability and short-term reproducibility of this technique in 10 healthy subjects. We examined several indices of the output sound of two series of sternal percussion manoeuvres performed one hour apart by the same examiner. The results were compared to those obtained during sternal percussion performed by a mechanical thumper. Consistency for both finger and thumper percussion varied from 4.8-20.6 (coefficients of variation) for various acoustic indices. For thumper percussion, the average results were not significantly different from those of finger percussion. We conclude that finger percussion of the sternum is sufficiently consistent to be used as a tool to investigate the acoustic behaviour of the chest.
Journal of Applied Physiology
We examined the transmission to the chest wall of white noise and 25-Hz square-wave-generated noi... more 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.
Journal of Applied Physiology
We indirectly determined the transmission path of sound generated by sternal percussion in five h... more We indirectly determined the transmission path of sound generated by sternal percussion in five healthy subjects. We percussed the sternum of each subject while recording the output audio signal at the posterior left and right upper and lower lung zones. Sound measurements were done during apnea at functional residual capacity, total lung capacity, and residual volume both with the lungs filled with air and with an 80% He-20% O2 (heliox) gas mixture. Three acoustic indexes were calculated from the output sound pulse: the peak-to-peak amplitude, the peak frequency, and the mid-power frequency. We found that the average values of all indexes tended to be greater in the upper than in the ipsilateral lower lung zones. In the upper zones, peak-to-peak amplitude was greater at total lung capacity and residual volume than at functional residual capacity. Replacing air with heliox did not change these results. These experiments, together with others performed during Mueller and Valsalva maneuvers, suggest that resonance of the chest cage is the predominant factor determining the transmission of sternal percussion sounds to the posterior chest wall. The transmission seems to be only minimally affected by the acoustic characteristics of the lung parenchyma.
MedEdPORTAL Publications, 2007
Journal of Applied Physiology
If the lung is an elastic continuum, both longitudinal and transverse stress waves should be prop... more If the lung is an elastic continuum, both longitudinal and transverse stress waves should be propagated in the medium with distinct velocities. In five isolated sheep lungs, we investigated the propagation of stress waves. The lungs were degassed and then inflated to a constant transpulmonary pressure (Ptp). We measured signals transmitted at locations approximately 1.5, 6, and 11 cm from an impulse surface distortion with the use of small microphones embedded in the pleural surface. Two transit times were computed from the first two significant peaks of the cross-correlation of microphone signal pairs. The "fast" wave velocities averaged 301 +/- 92, 445 +/- 80, and 577 +/- 211 (SD) cm/s for Ptp values of 5, 10, and 15 cmH2O, respectively. Corresponding "slow" wave velocities averaged 139 +/- 22, 217 +/- 36, and 255 +/- 89 cm/s. The fast waves were consistent with longitudinal waves of velocity [(K + 4G/3)/p]1/2, where bulk modulus K = 4 Ptp and shear modulus G = 0.7 Ptp. The slow waves were consistent with transverse (and/or Rayleigh) waves of velocity (G/p)1/2, with a G value of 0.9 Ptp. Measured values of K were 5 Ptp and values of G measured by indentation tests were 0.7 Ptp. Thus, stress wave velocities measured on pleural surface of isolated lungs correlated well with elastic moduli of lung parenchyma.
Journal of applied physiology: respiratory, environmental and exercise physiology
The speed of propagation of vesicular lung sound through the lung has not been clearly establishe... more 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.
Respiratory care
Spirometry is the most useful and commonly available tests of pulmonary function. It is a physiol... more Spirometry is the most useful and commonly available tests of pulmonary function. It is a physiological test that measures individual inhalation and exhalation volumes of air as a function of time. Pulmonologists and general-practice physicians commonly use spirometry in their offices in the assessment and management of lung disease. Spirometric indices are well validated and easily interpreted by comparison with established normal values. The remarkable reproducibility of spirometry results from the presence of compliant intrathoracic airways that act as air flow regulators during forced expiration. Because of this anatomic arrangement, expiratory flow becomes dependent solely on the elasticity of the lungs and airway resistance once a certain degree of expiratory force is exerted. Insight into this aspect of respiratory physiology can help in the interpretation of spirometry.
COPD, 2007
The measurements of lung compliance, airway resistance and respiratory dead space as clinical tes... more The measurements of lung compliance, airway resistance and respiratory dead space as clinical tests have gradually fallen into disuse as the standard pulmonary function testing procedures; spirometry, lung volume and diffusing capacity measurement, followed, if necessary, by imaging have become the norm for diagnosis of COPD and other lung diseases. To have a real understanding of what spirometry and lung volume tests measure requires some knowledge of compliance and airway resistance. The respiratory dead space is an important global indicator of ventilation/perfusion relationships that remains of interest in the early detection of pulmonary emboli. There are other situations as well where it is clinically useful to perform the measurements described here, so these techniques, although generally set aside from the commonly used tests, should not be forgotten.
Respiratory care, 2009
Spirometry is the most useful and commonly available tests of pulmonary function. It is a physiol... more Spirometry is the most useful and commonly available tests of pulmonary function. It is a physiological test that measures individual inhalation and exhalation volumes of air as a function of time. Pulmonologists and general-practice physicians commonly use spirometry in their offices in the assessment and management of lung disease. Spirometric indices are well validated and easily interpreted by comparison with established normal values. The remarkable reproducibility of spirometry results from the presence of compliant intrathoracic airways that act as air flow regulators during forced expiration. Because of this anatomic arrangement, expiratory flow becomes dependent solely on the elasticity of the lungs and airway resistance once a certain degree of expiratory force is exerted. Insight into this aspect of respiratory physiology can help in the interpretation of spirometry.
Journal of Patient Safety, 2015
Respiration physiology, 1985
Turbulent airflow (largely gas density dependent) in larger airways is believed by many lung soun... more Turbulent airflow (largely gas density dependent) in larger airways is believed by many lung sound researchers to be the mechanism responsible for the generation of vesicular lung sounds. To test the validity of this concept, we measured the amplitude of lung and tracheal sounds of 6 subjects alternately breathing air and a low density gas mixture (80% helium, 20% oxygen: He-O2). Lung sounds were recorded from 3 chest wall sites: Anterior right upper lobe (RUL), posterior and posterolateral right lower lobe (RLL), and a site over the proximal trachea below the larynx. The subjects rebreathed into an electronic spirometer filled with the test gas, and achieved a peak inspiratory and expiratory airflow of 2-2.5 L/sec. Lung sound amplitude was determined by an automated, flow-corrected measurement procedure. The mean decrease in sound amplitude when breathing He-O2 compared to air was: trachea, inspiration 44%; trachea, expiration 45%; RUL, inspiration 13%; RUL, expiration 25%; RLL, in...