Sound speed in pulmonary parenchyma

1983 ◽  
Vol 54 (1) ◽  
pp. 304-308 ◽  
Author(s):  
D. A. Rice
Keyword(s):  
Lung Volume ◽  
Sound Speed ◽  
Sulfur Hexafluoride ◽  
Ambient Pressure ◽  
Linear Regression Analysis ◽  
Free Field ◽  
Average Density ◽  
Sound Waves ◽  
Gas Phases ◽  
Audible Sound

The time it takes audible sound waves to travel across a lobe of excised horse lung was measured. Sound speed, which is the slope in the relationship between transit time and distance across the lobe, was estimated by linear regression analysis. Sound-speed estimates for air-filled lungs varied between 25 and 70 m/s, depending on lung volume. These speeds are less than 5% of sound speed in tissue and less than 20% of sound speed in air. Filling the lung with helium or sulfur hexafluoride, whose free-field sound speeds are 970 and 140 m/s, respectively, changed sound speed +/- 10% relative to air filling. Reducing the ambient pressure to 0.1 atm reduced sound speed to 30% of its 1-atm value. Increasing pressure to 7 atm increased sound speed by a factor of 2.6. These results suggest that 1) translobar sound travels through the bulk of the parenchyma and not along airways or blood vessels, and 2) the parenchyma acts as an elastic continuum to audible sound. The speed of sound is given by c = (B/rho)1/2, where B is composite volumetric stiffness of the medium and rho is average density. In the physiologic state B is affected by ambient pressure and percent gas phase. The average density includes both the tissue and gas phases of the parenchyma, so it is dependent on lung volume. These results may be helpful in the quantification of clinical observations of lung sounds.

scholarly journals IMPACT PRESSURES PRODUCED BY BREAKING WAVES

1974 ◽  
Vol 1 (14) ◽  
pp. 104 ◽  
Author(s):  
Norbert L. Ackerman ◽  
Ping-Ho Chen
Keyword(s):  
Water Surface ◽  
Ambient Pressure ◽  
Pressure Rise ◽  
Breaking Waves ◽  
Absolute Pressure ◽  
Maximum Pressure ◽  
Sound Waves ◽  
The Media ◽  
Entrapped Air ◽  
Entrained Air

Experiments were conducted in a vacuum tank in order to investigate the effect which entrained air has on impact loads which are produced when waves break upon a structure. In these experiments a flat plate was dropped onto a still water surface in an environment where the ambient pressure of the surrounding air could be controlled. Rings of varying height were fixed to the surface of the falling plate in order to trap different volumes of air between the falling plate and the water, Experimentally determined values were obtained of the maximum pressure pmax when the plate struck the water surface for various ring heights 6 and ambient pressures p0 in the vacuum tank. Experimental results indicate that the pressure rise or shock pressure Ps ~ (Pmax~Po) decreased with reductions in the ambient pressure and volume of entrapped air. Even when air was removed such that the absolute pressure in the tank was equal to the vapor pressure of the water, water hammer conditions, where the peak pressures depend upon the celerity of sound waves in the media, were never found to occur.

Effect of increases in lung volume on clearance of aerosolized solute from human lungs

1985 ◽  
Vol 59 (4) ◽  
pp. 1242-1248 ◽  
Author(s):  
J. D. Marks ◽  
J. M. Luce ◽  
N. M. Lazar ◽  
J. N. Wu ◽  
A. Lipavsky ◽  
...  
Keyword(s):  
Lung Volume ◽  
Negative Pressure ◽  
Ambient Pressure ◽  
Pressure Control ◽  
Positive Pressure ◽  
Healthy Humans ◽  
Human Lungs ◽  
Solute Uptake ◽  
Residual Capacity ◽  
Negative Pressure Breathing

To study the effect of increases in lung volume on solute uptake, we measured clearance of 99mTc-diethylenetriaminepentaacetic acid (Tc-DTPA) at different lung volumes in 19 healthy humans. Seven subjects inhaled aerosol (1 micron activity median aerodynamic diam) at ambient pressure; clearance and functional residual capacity (FRC) were measured at ambient pressure (control) and at increased lung volume produced by positive pressure [12 cmH2O continuous positive airway pressure (CPAP)] or negative pressure (voluntary breathing). Six different subjects inhaled aerosol at ambient pressure; clearance and FRC were measured at ambient pressure and CPAP of 6, 12, and 18 cmH2O pressure. Six additional subjects inhaled aerosol at ambient pressure or at CPAP of 12 cmH2O; clearance and FRC were determined at CPAP of 12 cmH2O. According to the results, Tc-DTPA clearance from human lungs is accelerated exponentially by increases in lung volume, this effect occurs whether lung volume is increased by positive or negative pressure breathing, and the effect is the same whether lung volume is increased during or after aerosol administration. The effect of lung volume must be recognized when interpreting the results of this method.

Gas mixing in dog lungs studied by single-breath washout of He and SF6

1983 ◽  
Vol 55 (6) ◽  
pp. 1795-1802 ◽  
Author(s):  
M. Meyer ◽  
C. Hook ◽  
H. Rieke ◽  
J. Piiper
Keyword(s):  
Gas Exchange ◽  
Lung Volume ◽  
Dead Space ◽  
Sulfur Hexafluoride ◽  
Breath Holding ◽  
Concentration Difference ◽  
Alveolar Plateau ◽  
Variable Time ◽  
Single Breath ◽  
Constant Rate

Simultaneously measured helium (He) and sulfur hexafluoride (SF6) single-breath washout was studied in 16 anesthetized paralyzed dogs ventilated with a special hydraulically operated ventilatory servo system. After equilibration of lung gas with 1% He and 1% SF6, the maneuver consisting of inspiration of a test gas-free mixture at constant rate (VI), a variable time of breath holding, and an expiration at constant rate (VE), was performed. Fractional concentrations of He and SF6, recorded against expired volume, were analyzed in terms of slope of the alveolar plateau (S) and series (Fowler) dead space (VD). In control conditions (VI = 0.5 l/s, VE = 0.1 l/s) S was about 10% of alveolar-to-inspired concentration difference per liter expirate both for He and SF6. Both SHe and SSF6 were inversely related to VI and VE, the relative changes being more pronounced with varying VE. SHe/SSF6 was higher or lower than unity depending on VI and VE. Both SHe and SSF6 decreased with increasing preinspiratory lung volume. Breath holding up to 10 s slightly decreased SHe and SSF6 while SHe/SSF6 was unchanged. The contribution of continuing gas exchange to S assessed from comparative measurements using the reversed (single breath washin) technique ranged from 6 to 23% in the various conditions. The VDHe/VDSF6 ratio was 0.84 and was little affected in the various settings. Results indicate that the substantial alveolar gas inhomogeneity in the dog lung and the mechanism accounting for S are little diffusion dependent. By exclusion sequential filling and emptying of lung units is believed to constitute the most important mechanism responsible for the sloping alveolar plateau.

Modification of pulmonary gas mixing by postural changes

1986 ◽  
Vol 61 (1) ◽  
pp. 75-80 ◽  
Author(s):  
H. A. Jones ◽  
E. E. Davies ◽  
J. M. Hughes
Keyword(s):  
Lung Volume ◽  
Sulfur Hexafluoride ◽  
Normal Subjects ◽  
Gas Mixing ◽  
Supine Posture ◽  
Dependent Change ◽  
Postural Changes ◽  
Residual Capacity ◽  
Lateral Decubitus ◽  
The Mean

Mixing for two gases of markedly different gaseous diffusivity, helium (He) (mol wt = 4) and sulfur hexafluoride (SF6) (mol wt = 146) has been studied by a rebreathing method in different postures. In nine normal subjects duplicate measurements were made in the erect (seated), supine, and lateral decubitus posture, at a constant tidal volume (700 ml) and frequency (1 Hz) starting from functional residual capacity (FRC). Additional measurements were made on four of the subjects, rebreathing seated erect at a volume similar to the relaxed FRC supine and supine at a volume similar to the relaxed FRC seated. In the supine posture the mean breath number to reach 99% equilibrium (n99), was not significantly different for the two gases, 8.9 for He and 9.8 for SF6. There was a difference (P less than 0.01) when erect; n99 (He) = 8.2 and n99 (SF6) = 10.9. The greatest He-SF6 difference (P less than 0.001) was in the lateral decubitus position n99 (He) = 10.1 and n99 (SF6) = 15.9. The mean relaxed FRC as percent of seated was 71% supine and 75% in lateral decubitus posture. Rebreathing seated at a lower volume did not abolish the He-SF6 mixing difference nor did rebreathing at a higher volume when supine induce a He-SF6 mixing difference. Thus the effect of posture on gas mixing cannot be due solely to lung volume and must represent a convective and diffusive dependent change in the distribution of ventilation per unit lung volume.

Reflection of sound waves by sound‐speed inhomogeneities

1992 ◽  
Vol 91 (3) ◽  
pp. 1262-1269 ◽  
Author(s):  
Harry Gingold ◽  
Jianming She ◽  
William E. Zorumski
Keyword(s):  
Sound Speed ◽  
Sound Waves

A Numerical Study of Ethanol-Water Droplet Evaporation

2017 ◽  
Author(s):  
Giandomenico Lupo ◽  
Christophe Duwig
Keyword(s):  
Water Droplet ◽  
Composition Range ◽  
Numerical Study ◽  
Ambient Pressure ◽  
Droplet Evaporation ◽  
Droplet Temperature ◽  
Gas Phases ◽  
Initial Droplet ◽  
Liquid Phase Composition ◽  
Evaporation Dynamics

The present effort focuses on detailed numerical modelling of the evaporation of an ethanol-water droplet. The model intends to capture all relevant details of the process: it includes species and heat transport in the liquid and gas phases, and detailed thermo-physical and transport properties, varying with both temperature and composition. Special attention is reserved to the composition range near and below the ethanol/water azeotrope point at ambient pressure. For this case, a significant fraction of the droplet lifetime exhibits evaporation dynamics similar to those of a pure droplet. The results are analysed and model simplifications are examined. In particular, the assumptions of constant liquid properties, homogeneous liquid phase composition and no differential volatility may not be valid depending on the initial droplet temperature.

Use of an acoustic helium analyzer for measuring lung volumes

1981 ◽  
Vol 50 (1) ◽  
pp. 203-209
Author(s):  
P. E. Krumpe ◽  
H. J. MacDannald ◽  
T. N. Finley ◽  
H. E. Schear ◽  
J. Hall ◽  
...  
Keyword(s):  
Lung Volume ◽  
Vital Capacity ◽  
Linear Regression Analysis ◽  
Normal Subjects ◽  
Field Studies ◽  
Chronic Obstructive ◽  
Base Line ◽  
Helium Concentration ◽  
Single Breath ◽  
Wide Range

We have evaluated the use of an acoustic gas analyzer (AGA) for the measurement of total lung capacity (TLC) by single-breath helium dilution. The AGA has a rapid response time (0-90% response = 160 ms for 10% He), is linear for helium concentration of 0.1-10%, is stable over a wide range of ambient temperatures, and is small and portable. We plotted the output of the AGA vs. expired lung volume after a vital capacity breath of 10% He. However, since the AGA is sensitive to changes in speed of sound relative to air, the AGA output signal also reports an artifact due to alveolar gases. We corrected for this artifact by replotting a single-breath expiration after a vital capacity breath of room air. Mean alveolar helium concentration (HeA) was then measured by planimetry, using this alveolar gas curve as the base line. TLC was calculated using the HeA from the corrected AGA output and compared with TLC calculated from HeA simultaneously measured using a mass spectrometer (MS). In 12 normal subjects and 9 patients with chronic obstructive pulmonary disease (COPD) TLC-AGA and TLC-MS were compared by linear regression analysis; correlation coefficient (r) was 0.973 for normals and 0.968 for COPD patients (P less than 0.001). This single-breath; estimation of TLC using the corrected signal of the AGA vs. Expired volume seems ideally suited for the measurement of subdivisions of lung volume in field studies.

Characteristics of the equations of motion of a reacting gas

1958 ◽  
Vol 4 (3) ◽  
pp. 276-282 ◽  
Author(s):  
L. J. F. Broer
Keyword(s):  
Heat Conduction ◽  
High Frequency ◽  
Sound Speed ◽  
Reaction Rate ◽  
Equations Of Motion ◽  
Sound Waves ◽  
Velocity Of Sound ◽  
Frequency Limit ◽  
Chemically Reacting ◽  
Set Up

The equations of motion for a chemically reacting gas in the absence of viscosity and heat conduction are set up. It is shown that the characteristic speed defined by this set of equations is the high-frequency limit of the phase velocity of sound waves as long as the reaction rate is finite. At infinite reaction rate (chemical equilibrium) the characteristics suddenly change to the lowfrequency sound speed. The nature of this transition is discussed in connection with a recent paper of Resler (1957).

A Numerical Study of Ethanol–Water Droplet Evaporation

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Giandomenico Lupo ◽  
Christophe Duwig
Keyword(s):  
Water Droplet ◽  
Composition Range ◽  
Numerical Study ◽  
Ambient Pressure ◽  
Droplet Evaporation ◽  
Droplet Temperature ◽  
Gas Phases ◽  
Initial Droplet ◽  
Liquid Phase Composition ◽  
Evaporation Dynamics

The present effort focuses on detailed numerical modeling of the evaporation of an ethanol–water droplet. The model intends to capture all relevant details of the process: it includes species and heat transport in the liquid and gas phases, and detailed thermophysical and transport properties, varying with both temperature and composition. Special attention is reserved to the composition range near and below the ethanol/water azeotrope point at ambient pressure. For this case, a significant fraction of the droplet lifetime exhibits evaporation dynamics similar to those of a pure droplet. The results are analyzed, and model simplifications are examined. In particular, the assumptions of constant liquid properties, homogeneous liquid phase composition and no differential volatility may not be valid depending on the initial droplet temperature.

scholarly journals Strong Thermal Stratification Reduces Detection Efficiency and Range of Acoustic Telemetry in a Large Freshwater Lake

2021 ◽  
Author(s):  
Yulong Kuai ◽  
Natalie Klinard ◽  
Aaron Fisk ◽  
Timothy Johnson ◽  
Edmund Halfyard ◽  
...  
Keyword(s):  
Great Lakes ◽  
Speed Of Sound ◽  
Sound Speed ◽  
Acoustic Telemetry ◽  
Thermal Stratification ◽  
Detection Efficiency ◽  
Late Summer ◽  
Lake Ontario ◽  
Sound Waves ◽  
Detection Range

Abstract BackgroundThe successful use of acoustic telemetry to detect fish hinges on understanding the factors that control the acoustic range. The speed-of-sound in water is primarily a function of density, and in freshwater lakes density is primarily driven by temperature. The seasonal thermal stratification in the Great Lakes represent the strongest sound speed gradients in any aquatic system. Such speed-of-sound gradients can refract sound waves leading to greater divergence of acoustic signal, and hence more rapid attenuation. The changes in sound attenuation change the detection range of a telemetry array and hence influence the ability to monitor fish. We use three months of data from a sentinel array of V9 and V16 Vemco acoustic fish tags, and a record of temperature profiles to determine how changes in stratification influence acoustic range in eastern Lake Ontario. ResultWe interpret data from an acoustic telemetry array in Lake Ontario to show that changes in acoustic detection efficiency and range correlate strongly with changes in sound speed gradients due to thermal stratification. The strongest sound speed gradients of 10.38 ms-1/m crossing the thermocline occurred in late summer, which caused the sound speed difference between the top and bottom of the water column to be greater than 60 m/s. V9 tags transmitting across the thermocline could have their acoustic range reduced from >650 m to 350 m, while the more powerful V16 tags had their range reduced from >650 m to 450 m. In contrast we found that when the acoustic source and receiver were both transmitting below thermocline there was no change in range, even as the strength of sound speed gradient varied. ConclusionChanges in thermal stratification occur routinely in the Great Lakes, on timescales between months and days. The acoustic range can be reduced by as much as 50% compared to unstratified conditions when fish move across the thermocline. We recommend that researchers consider the influences of thermal stratification to acoustic telemetry when configuring receiver position.

Sign in / Sign up

Export Citation Format

Share Document