T model partition of lung and respiratory system impedances

1995 ◽  
Vol 78 (3) ◽  
pp. 938-947 ◽  
Author(s):  
M. Rotger ◽  
R. Farre ◽  
R. Peslin ◽  
D. Navajas
Keyword(s):  
Respiratory System ◽  
Frequency Range ◽  
Tissue Impedance ◽  
Gas Compression ◽  
Thoracic Gas Volume ◽  
The Mean ◽  
Gas Volume ◽  
Mean Compliance ◽  
Gas Compressibility ◽  
Shunt Impedance

The aim of this work was to demonstrate that the three compartments of the lung T network and the chest wall impedance (Zcw) can be identified from input and transfer impedances of the respiratory system if the pleural pressure is recorded during the measurements. The method was tested in six healthy volunteers in the range of 8–32 Hz. The impedances resulting from the decomposition confirm the adequacy of the monoalveolar structure commonly used in healthy subjects. Indeed, the T shunt impedance is well modeled by a purely compliant element, the mean compliance [0.038 +/- 0.081 (SD) l/kPa], which coincides within 9.5 +/- 6.3% of the alveolar gas compressibility derived from thoracic gas volume (0.036 +/- 0.011 l/kPa). The results obtained provide experimental evidence that the alveolar gas compression is predominantly isothermal and that lung tissue impedance is negligible throughout the whole frequency range. The shape of Zcw is consistent with a low compliance-low inertance pathway in parallel with a high compliance-high inertance pathway. We conclude that the proposed method is able to reliably identify the T network featuring the lung and Zcw.

Modeling of respiratory system impedances in dogs

1987 ◽  
Vol 62 (2) ◽  
pp. 414-420 ◽  
Author(s):  
A. C. Jackson ◽  
K. R. Lutchen
Keyword(s):  
Respiratory System ◽  
Element Model ◽  
Parameter Estimates ◽  
Frequency Range ◽  
Nonlinear Regression Analysis ◽  
Entire Frequency Range ◽  
Frequency Dependent ◽  
Impedance Data ◽  
Parameter Values ◽  
Gas Compressibility

Mechanical impedances between 4 and 64 Hz of the respiratory system in dogs have been reported (A.C. Jackson et al. J. Appl. Physiol. 57: 34–39, 1984) previously by this laboratory. It was observed that resistance (the real part of impedance) decreased slightly with frequency between 4 and 22 Hz then increased considerably with frequency above 22 Hz. In the current study, these impedance data were analyzed using nonlinear regression analysis incorporating several different lumped linear element models. The five-element model of Eyles and Pimmel (IEEE Trans. Biomed. Eng. 28: 313–317, 1981) could only fit data where resistance decreased with frequency. However, when the model was applied to these data the returned parameter estimates were not physiologically realistic. Over the entire frequency range, a significantly improved fit was obtained with the six-element model of DuBois et al. (J. Appl. Physiol. 8: 587–594, 1956), since it could follow the predominate frequency-dependent characteristic that was the increase in resistance. The resulting parameter estimates suggested that the shunt compliance represents alveolar gas compressibility, the central branch represents airways, and the peripheral branch represents lung and chest wall tissues. This six-element model could not fit, with the same set of parameter values, both the frequency-dependent decrease in Rrs and the frequency-dependent increase in resistance. A nine-element model recently proposed by Peslin et al. (J. Appl. Physiol. 39: 523–534, 1975) was capable of fitting both the frequency-dependent decrease and the frequency-dependent increase in resistance. However, the data only between 4 and 64 Hz was not sufficient to consistently determine unique values for all nine parameters.

Partitioning of airway and respiratory tissue mechanical impedances by body plethysmography

1998 ◽  
Vol 84 (2) ◽  
pp. 553-561 ◽  
Author(s):  
R. Peslin ◽  
C. Duvivier
Keyword(s):  
Body Plethysmography ◽  
Tissue Resistance ◽  
Gas Compression ◽  
Thoracic Gas Volume ◽  
Airway Opening ◽  
Elastic Loading ◽  
Gas Volume ◽  
The Relationship ◽  
Respiratory Tissue ◽  
Good Agreement

Peslin, R., and C. Duvivier. Partitioning of airway and respiratory tissue mechanical impedances by body plethysmography. J. Appl. Physiol. 84(2): 553–561, 1998.—We have tested the feasibility of separating the airway (Zaw) and tissue (Zti) components of total respiratory input impedance (Zrs,in) in healthy subjects by measuring alveolar gas compression by body plethysmography (Vpl) during pressure oscillations at the airway opening. The forced oscillation setup was placed inside a body plethysmograph, and the subjects rebreathedbtps gas. Zrs,in and the relationship between Vpl and airway flow (Hpl) were measured from 4 to 29 Hz. Zaw and Zti were computed from Zrs,in and Hpl by using the monoalveolar T-network model and alveolar gas compliance derived from thoracic gas volume. The data were in good agreement with previous observations: airway and tissue resistance exhibited some positive and negative frequency dependences, respectively; airway reactance was consistent with an inertance of 0.015 ± 0.003 hPa ⋅ s2 ⋅ l−1and tissue reactance with an elastance of 36 ± 8 hPa/l. The changes seen with varying lung volume, during elastic loading of the chest and during bronchoconstriction, were mostly in agreement with the expected effects. The data, as well as computer simulation, suggest that the partitioning is unaffected by mechanical inhomogeneity and only moderately affected by airway wall shunting.

Frequency dependence of plethysmographic measurement of thoracic gas volume

1984 ◽  
Vol 57 (6) ◽  
pp. 1865-1871 ◽  
Author(s):  
R. Brown ◽  
A. S. Slutsky
Keyword(s):  
Frequency Dependence ◽  
Normal Subjects ◽  
Lung Capacity ◽  
Airways Obstruction ◽  
Gas Compression ◽  
Thoracic Gas Volume ◽  
Mouth Pressure ◽  
Extrathoracic Airway ◽  
Shunt Capacitor ◽  
Gas Volume

With airways obstruction, panting frequency affects plethysmographically determined thoracic gas volume (Vtg) because the extrathoracic airway acts as a shunt capacitor. Stanescu et al. (19) suggested that in the calculation of Vtg, use of esophageal (delta Pes) rather than mouth pressure (delta Pm) swings might eliminate the problem. We measured total lung capacity (TLC) plethysmographically in 10 subjects with chronic airways obstruction (CAO) and in four normal subjects. TLC (using delta Pm) was derived from Vtg obtained from slow-(approximately 1 Hz) and fast- (approximately 4 Hz) panting frequencies. In the normal subjects and four subjects with CAO, TLC was also obtained using delta Pes. In these subjects abdominal gas compression and decompression did not contribute significantly to the frequency dependence of TLC. In CAO, TLC was frequency dependent in direct proportion to the severity of obstruction. Although the frequency dependence was greater using delta Pm to calculate Vtg, it also occurred using delta Pes. Thus it could not be explained entirely by the shunt capacitor effect of the extrathoracic airways. The residual and significant overestimations of TLC (reflected by frequency dependency of TLC derived from Vtg calculated from delta Pes) may be explained by interregional nonhomogeneities during the panting maneuver.

Computer determination of thoracic gas volume using plethysmographic "thoracic flow"

1980 ◽  
Vol 48 (5) ◽  
pp. 911-916 ◽  
Author(s):  
H. Lorino ◽  
A. Harf ◽  
G. Atlan ◽  
Y. Brault ◽  
A. M. Lorino ◽  
...  
Keyword(s):  
Regression Line ◽  
Time Derivative ◽  
Thoracic Gas Volume ◽  
Mouth Pressure ◽  
Computer Determination ◽  
The Subject ◽  
The Mean ◽  
Gas Volume ◽  
Very High

Plotting a line to the variables obtained during a panting maneuver, i.e. thoracic volume and mouth pressure, is the conventional way of computing plethysmographic thoracic gas volume (TGV). This procedure is reliable if the magnitude of the thoracic volume changes is large compared to the drift on the signal; this is one of the major problems in volumetric plethysmography. We propose replacing the thoracic volume signal (Vt) by its time derivative (Vt) and similarly mouth pressure (Pm) with its time derivative (Pm). Drift is thus ruled out, and the magnitude of Vt is preserved when the subject fails to carry out noticeable changes in thoracic volume during the panting, since even then the speed of these changes in thoracic volume remains high. The use of Vt and Pm appeared to be necessary when a minicomputer was connected to a pressure-compensated flow plethysmograph to obtain an automatic calculation of TGV. A regression-line technique applied to signals obtained during the panting was used to find the slope of the relation and thus TGV. However, this slope can only be predicted with less than 5% error if the correlation coefficient is very high (i.e., above 0.99). The analysis of 121 recordings from patients showed that the mean r was only 0.954 when Vt and Pm were used. It increased to 0.993 with Vt and Pm. For the same recordings the comparison of hand-calculated TGV and computer-derived TGV showed a much better agreement for the Vt-Pm method (standard error of the estimate (SEE) = 0.14 liter) than for the Vt-Pm method (SEE = 0.34 liter). These results emphasize that, in contrast to the manual technique, the computer does not adequately handle even a small drift of the thoracic signal. The proposed time-derivative method is therefore useful for a hand calculation, but essential to a reliable computer determination of thoracic gas volume.

Respiratory tissue properties derived from flow transfer function in healthy humans

1997 ◽  
Vol 82 (4) ◽  
pp. 1098-1106 ◽  
Author(s):  
W. Tomalak ◽  
R. Peslin ◽  
C. Duvivier
Keyword(s):  
Transfer Function ◽  
Upper Airway ◽  
Tissue Impedance ◽  
Tissue Properties ◽  
Healthy Humans ◽  
Volume Curve ◽  
Thoracic Gas Volume ◽  
Gas Volume ◽  
Flow Transfer ◽  
Respiratory Tissue

Tomalak, W., R. Peslin, and C. Duvivier. Respiratory tissue properties derived from flow transfer function in healthy humans. J. Appl. Physiol. 82(4): 1098–1106, 1997.—Assuming homogeneity of alveolar pressure, the relationship between airway flow and flow at the chest during forced oscillation at the airway opening [flow transfer function (FTF)] is related to lung and chest wall tissue impedance (Zti): FTF = 1 + Zti/Zg, where Zg is alveolar gas impedance, which is inversely proportional to thoracic gas volume. By using a flow-type body plethysmograph to obtain flow rate at body surface, FTF has been measured at oscillation frequencies ( f os) of 10, 20, 30 and 40 Hz in eight healthy subjects during both quiet and deep breathing. The data were corrected for the flow shunted through upper airway walls and analyzed in terms of tissue resistance (Rti) and effective elastance (Eti,eff) by using plethysmographically measured thoracic gas volume values. In most subjects, Rti was seen to decrease with increasing f os and Eti,eff to vary curvilinearly with f os 2, which is suggestive of mechanical inhomogeneity. Rti presented a weak volume dependence during breathing, variable in sign according to f os and among subjects. In contrast, Eti,eff usually exhibited a U-shaped pattern with a minimum located a little above or below functional residual capacity and a steep increase with decreasing or increasing volume (30–80 hPa/l2) on either side. These variations are in excess of those expected from the sigmoid shape of the static pressure-volume curve and may reflect the effect of respiratory muscle activity. We conclude that FTF measurement is an interesting tool to study Rti and Eti,eff and that these parameters have probably different physiological determinants.

Influence of panting frequency on plethysmographic measurements of thoracic gas volume

1982 ◽  
Vol 52 (3) ◽  
pp. 739-747 ◽  
Author(s):  
A. B. Bohadana ◽  
R. Peslin ◽  
B. Hannhart ◽  
D. Teculescu
Keyword(s):  
High Frequency ◽  
Healthy Subjects ◽  
Airflow Obstruction ◽  
Gastric Balloon ◽  
Gas Compression ◽  
Thoracic Gas Volume ◽  
Mouth Pressure ◽  
Before And After ◽  
Flow Pressure ◽  
Gas Volume

Using an integrated flow pressure-corrected body plethysmograph we obtained total lung capacities (TLC) derived from thoracic gas volumes measured at low, medium, and high panting frequencies in 10 healthy men and in 13 patients with chronic airflow obstruction before and after an aerosol of albuterol. Using a gastric balloon we also assessed gastric-to-mouth pressure ratios (delta Pga/delta Pm). In patients before albuterol, estimated TLC remained unchanged from low to medium and increased (not significantly) from medium to high frequency. Healthy subjects and patients after albuterol showed a significant decrease in TLC from low to medium panting frequencies, which persisted after correcting the data for abdominal gas compression using observed delta Pga/delta Pm. In patients after albuterol the results may be explained, at least in part, by intrathoracic airway compliance and mechanical inhomogeneity of the lung. In healthy subjects a remote possibility is the association of mechanical inhomogeneity and nonuniform pleural pressure.

Inability to separate airway from tissue properties by use of human respiratory input impedance

1990 ◽  
Vol 68 (6) ◽  
pp. 2403-2412 ◽  
Author(s):  
K. R. Lutchen ◽  
C. A. Giurdanella ◽  
A. C. Jackson
Keyword(s):  
Input Impedance ◽  
Acoustic Resonance ◽  
Element Model ◽  
Tissue Properties ◽  
Rigid Tube ◽  
Gas Compression ◽  
Thoracic Gas Volume ◽  
Alveolar Tissue ◽  
High Frequency Resonance ◽  
Gas Volume

Respiratory input impedance (Zrs) from 2.5 to 320 Hz displays a high-frequency resonance, the location of which depends on the density of the resident gas in the lungs (J. Appl. Physiol. 67: 2323-2330, 1989). A previously used six-element model has suggested that the resonance is due to alveolar gas compression (Cg) resonating with tissue inertance (Iti). However, the density dependence of the resonance indicates that is associated with the first airway acoustic resonance. The goal of this study was to determine whether unique properties for tissues and airways can be extracted from Zrs data by use of models that incorporate airway acoustic phenomena. We applied several models incorporating airway acoustics to the 2.5- to 320-Hz data from nine healthy adult humans during room air (RA) and 20% He-80% O2 (HeO2) breathing. A model consisting of a single open-ended rigid tube produced a resonance far sharper than that seen in the data. To dampen the resonance features, we used a model of multiple open-ended rigid tubes in parallel. This model fit the data very well for both RA and HeO2 but required fewer and longer tubes with HeO2. Another way to dampen the resonance was to use a single rigid tube terminated with an alveolar-tissue unit. This model also fit the data well, but the alveolar Cg estimates were far smaller than those expected based on the subject's thoracic gas volume. If Cg was fixed based on the thoracic gas volume, a large number of tubes were again required. These results along with additional simulations show that from input Zrs alone one cannot uniquely identify features indigenous to alveolar Cg or to the respiratory tissues.

Gas compression in lungs decreases peak expiratory flow depending on resistance of peak flowmeter

1997 ◽  
Vol 83 (5) ◽  
pp. 1517-1521 ◽  
Author(s):  
O. F. Pedersen ◽  
T. F. Pedersen ◽  
M. R. Miller
Keyword(s):  
Peak Expiratory Flow ◽  
Wave Speed ◽  
Vital Capacity ◽  
Added Resistance ◽  
Alveolar Pressure ◽  
Healthy Men ◽  
Gas Compression ◽  
Thoracic Gas Volume ◽  
Expiratory Flow ◽  
Gas Volume

Pedersen, O. F., T. F. Pedersen, and M. R. Miller. Gas compression in lungs decreases peak expiratory flow depending on resistance of peak flowmeter. J. Appl. Physiol. 83(5): 1517–1521, 1997.—It has recently been shown (O. F. Pedersen T. R. Rasmussen, Ø. Omland, T. Sigsgaard, P. H. Quanjer, and M. R. Miller. Eur. Respir. J. 9: 828–833, 1996) that the added resistance of a mini-Wright peak flowmeter decreases peak expiratory flow (PEF) by ∼8% compared with PEF measured by a pneumotachograph. To explore the reason for this, 10 healthy men (mean age 43 yr, range 33–58 yr) were examined in a body plethysmograph with facilities to measure mouth flow vs. expired volume as well as the change in thoracic gas volume (Vb) and alveolar pressure (Pa). The subjects performed forced vital capacity maneuvers through orifices of different sizes and also a mini-Wright peak flowmeter. PEF with the meter and other added resistances were achieved when flow reached the perimeter of the flow-Vb curves. The mini-Wright PEF meter decreased PEF from 11.4 ± 1.5 to 10.3 ± 1.4 (SD) l/s ( P < 0.001), Pa increased from 6.7 ± 1.9 to 9.3 ± 2.7 kPa ( P < 0.001), an increase equal to the pressure drop across the meter, and caused Vb at PEF to decrease by 0.24 ± 0.09 liter ( P < 0.001). We conclude that PEF obtained with an added resistance like a mini-Wright PEF meter is a wave-speed-determined maximal flow, but the added resistance causes gas compression because of increased Pa at PEF. Therefore, Vb at PEF and, accordingly, PEF decrease.

Thoracoabdominal blood volume change and its effect on lung and chest wall volumes

1986 ◽  
Vol 61 (3) ◽  
pp. 953-959 ◽  
Author(s):  
W. R. Kimball ◽  
K. B. Kelly ◽  
J. Mead
Keyword(s):  
Chest Wall ◽  
Blood Volume ◽  
Respiratory System ◽  
Volume Change ◽  
Volume Increase ◽  
Rib Cage ◽  
Thoracic Gas Volume ◽  
Gas Volume ◽  
Male Subjects ◽  
Boyle’S Law

The effects of changing blood volume within the thoracoabdominal cavity (Vtab) have been studied in four male subjects trained in respiratory maneuvers. Subjects were studied lying supine in a pressure plethysmograph with inflatable fracture splints placed around both arms and legs. Changes in Vtab were produced by inflating the splints to 30 cmH2O. Thoracic gas volume (Vtg) measured by Boyle's law, and the change in chest wall volume (delta Vw), measured by anteroposterior magnetometers on rib cage and abdomen, were measured almost simultaneously and at two respiratory system volumes. The quantity of blood moved by splint inflation was estimated for each subject at both respiratory system volumes and varied between 215 and 752 ml. The chest wall increased 64 +/- 11.8% (mean +/- SD) of the increase in Vtab. Thus increases in thoracoabdominal blood volume increase Vw about twice the decrease in Vtg.

Concurrent measurements of functional residual capacity by three methods

1962 ◽  
Vol 17 (6) ◽  
pp. 871-873 ◽  
Author(s):  
Donald F. Tierney ◽  
Jay A. Nadel
Keyword(s):  
Functional Residual Capacity ◽  
Total Lung Capacity ◽  
Open Circuit ◽  
The Body ◽  
Lung Capacity ◽  
Thoracic Gas Volume ◽  
Nitrogen Dilution ◽  
Residual Capacity ◽  
The Mean ◽  
Gas Volume

We made concurrent measurements of the functional residual capacity (FRC) with the body plethysmograph (thoracic gas volume) and by 7-min and prolonged open-circuit nitrogen dilution methods (communicating gas volume). The mean difference between the 7-min communicating gas volume and the thoracic gas volume in 13 healthy subjects was only 0.13 liters. The thoracic gas volume averaged 0.99 liters larger than the communicating gas volume after 7 min of O2 breathing in 13 patients with emphysema. The communicating gas volume at 12–18 min was the same as the thoracic gas volume in 11 of 13 patients but was smaller in the other 2. When the thoracic gas volume was used to measure FRC, the total lung capacity averaged 142% of predicted normal in 13 patients with emphysema. Submitted on January 4, 1962

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