scholarly journals Evaluation of a forced oscillation method to measure thoracic gas volume

1998 ◽  
Vol 84 (3) ◽  
pp. 862-867 ◽  
Author(s):  
R. Peslin ◽  
C. Duvivier
Keyword(s):  
Forced Oscillation ◽  
Forced Oscillations ◽  
Strongly Correlated ◽  
Thoracic Gas Volume ◽  
Peripheral Airway ◽  
Multiple Frequencies ◽  
Gas Conditioning ◽  
Gas Volume ◽  
The Relationship

The purpose of this study was to test a plethysmographic method of measuring thoracic gas volume (TGV) that, contrary to the usual panting method, would not require any active cooperation from the subject. It is based on the assumption that the out-of-phase component of airway impedance varies linearly with frequency. By using that assumption, TGV may be computed by combining measurements of total respiratory impedance (Zrs) and of the relationship between the plethysmographic signal (Vpl) and airway flow (V˙) during forced oscillations at several frequencies. Zrs and Vpl/V˙were measured at 10 noninteger multiple frequencies ranging from 4 to 29 Hz in 15 subjects breathing gas in nearlybtps conditions. Forced oscillation measurements were immediately followed by determination of TGV by the standard method. The data were analyzed on different frequency ranges, and the best agreement was seen in the 6- to 29-Hz range. Within that range, forced oscillation TGV and standard TGV differed little (3.92 ± 0.66 vs. 3.83 ± 0.73 liters, n = 77, P < 0.05) and were strongly correlated ( r = 0.875); the differences were not correlated to the mean of the two estimates, and their SD was 0.35 liter. In seven subjects the differences were significantly different from zero, which may, in part, be due to imperfect gas conditioning. We conclude that the method is not highly accurate but could prove useful when, for lack of sufficient cooperation, the panting method cannot be used. The results of computer simulation, however, suggest that the method would be unreliable in the presence of severe airway inhomogeneity or peripheral airway obstruction.

Human respiratory input impedance from 4 to 200 Hz: physiological and modeling considerations

1988 ◽  
Vol 64 (2) ◽  
pp. 823-831 ◽  
Author(s):  
H. L. Dorkin ◽  
K. R. Lutchen ◽  
A. C. Jackson
Keyword(s):  
Input Impedance ◽  
Element Model ◽  
Forced Oscillations ◽  
Parameter Estimates ◽  
Tissue Resistance ◽  
Thoracic Gas Volume ◽  
Reliable Parameter ◽  
Quarter Wave ◽  
Lumped Element Model ◽  
Gas Volume

Recent studies on respiratory impedance (Zrs) have predicted that at frequencies greater than 64 Hz a second resonance will occur. Furthermore, if one intends to fit a model more complicated than the simple series combination of a resistance, inertance, and compliance to Zrs data, the only way to ensure statistically reliable parameter estimates is to include data surrounding this second resonance. An additional question, however, is whether the resulting parameters are physiologically meaningful. We obtained input impedance data from eight healthy adult humans using discrete frequency forced oscillations from 4 to 200 Hz. Three resonant frequencies were seen: 8 +/- 2, 151 +/- 10, and 182 +/- 16 Hz. A seven-parameter lumped element model provided an excellent fit to the data in all subjects. This model consists of an airway resistance (Raw), which is linearly dependent on frequency, and airway inertance separated from a tissue resistance, inertance, and compliance by a shunt compliance (Cg) thought to represent gas compressibility. Model estimates of Raw and Cg were compared with those suggested by measurement of Raw and thoracic gas volume using a plethysmograph. In all subjects the model Raw and Cg were significantly lower than and not correlated with the corresponding plethysmographic measurement. We hypothesize that the statistically reliable but physiologically inconsistent parameters are a consequence of the distorting influence of airway wall compliance and/or airway quarter-wave resonance. Such factors are not inherent to the seven-parameter model.

scholarly journals Lung volumes and respiratory mechanics in elastase-induced emphysema in mice

2008 ◽  
Vol 105 (6) ◽  
pp. 1864-1872 ◽  
Author(s):  
Z. Hantos ◽  
Á. Adamicza ◽  
T. Z. Jánosi ◽  
M. V. Szabari ◽  
J. Tolnai ◽  
...  
Keyword(s):  
Mouse Model ◽  
Low Frequency ◽  
Forced Oscillations ◽  
Mechanical Parameters ◽  
Tissue Destruction ◽  
Lung Volumes ◽  
Lung Capacity ◽  
Thoracic Gas Volume ◽  
Residual Capacity ◽  
Gas Volume

Absolute lung volumes such as functional residual capacity, residual volume (RV), and total lung capacity (TLC) are used to characterize emphysema in patients, whereas in animal models of emphysema, the mechanical parameters are invariably obtained as a function of transrespiratory pressure (Prs). The aim of the present study was to establish a link between the mechanical parameters including tissue elastance (H) and airway resistance (Raw), and thoracic gas volume (TGV) in addition to Prs in a mouse model of emphysema. Using low-frequency forced oscillations during slow deep inflation, we tracked H and Raw as functions of TGV and Prs in normal mice and mice treated with porcine pancreatic elastase. The presence of emphysema was confirmed by morphometric analysis of histological slices. The treatment resulted in an increase in TGV by 51 and 44% and a decrease in H by 57 and 27%, respectively, at 0 and 20 cmH2O of Prs. The Raw did not differ between the groups at any value of Prs, but it was significantly higher in the treated mice at comparable TGV values. In further groups of mice, tracheal sounds were recorded during inflations from RV to TLC. All lung volumes but RV were significantly elevated in the treated mice, whereas the numbers and size distributions of inspiratory crackles were not different, suggesting that the airways were not affected by the elastase treatment. These findings emphasize the importance of absolute lung volumes and indicate that tissue destruction was not associated with airway dysfunction in this mouse model of emphysema.

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.

Quiet-breathing vs. panting methods for determination of specific airway conductance

1984 ◽  
Vol 57 (6) ◽  
pp. 1917-1922 ◽  
Author(s):  
W. S. Krell ◽  
K. P. Agrawal ◽  
R. E. Hyatt
Keyword(s):  
Interobserver Variability ◽  
Direct Method ◽  
Normal Subjects ◽  
Intrasubject Variability ◽  
Quiet Breathing ◽  
Thoracic Gas Volume ◽  
Coefficients Of Variation ◽  
Gas Volume ◽  
Airway Conductance

Specific airway conductance (sGaw) was measured during quiet breathing and during panting in 21 normal subjects and 10 patients with obstructive lung disease. The direct method used does not require measuring thoracic gas volume (TGV). Coefficients of variation were 5.5% for panting and 5.1% for quiet breathing. Interobserver variability was 4.7% in the quiet-breathing method and 6.3% in the panting method. The two methods gave equivalent results for sGaw. A slightly greater sGaw was found by the panting method in normal subjects with the highest sGaw values, probably due to widening of the oropharynx-glottis during panting. In six normal subjects studied for intrasubject variability over time, no significant diurnal or day-to-day variability was seen by either method. We conclude that the quiet-breathing method is a simple valid means of determining sGaw and utilizes a physiological respiratory maneuver. Obviation of the need to measure TGV is advantageous. Results are equivalent to those of the panting method and variability is similar.

Improved method in the computer determination of plethysmographic thoracic gas volume

1982 ◽  
Vol 52 (3) ◽  
pp. 798-801 ◽  
Author(s):  
A. Harf ◽  
H. Lorino ◽  
G. Atlan ◽  
A. M. Lorino ◽  
D. Laurent
Keyword(s):  
Data Analysis ◽  
Improved Method ◽  
New Approaches ◽  
Thoracic Gas Volume ◽  
Mouth Pressure ◽  
Computer Determination ◽  
Pressure Changes ◽  
Gas Volume ◽  
Boyle’S Law

To improve the computer determination of thoracic gas volume (TGV), two new approaches were worked out. 1) A new program was designed, which overcomes the difficulties encountered in the time recognition of the panting maneuver and rules out the artifacts. Such a procedure is based on the data analysis in the pressure-volume time derivatives plane. 2) A hyperbolic fitting of the signals recorded during the panting maneuver was introduced. This last procedure, lying on Boyle's law, has proved to be useful in case of large mouth pressure changes. In fact the error induced by the conventional linear fitting may reach 500 ml (9% of the TGV value).

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.

Influence of abdominal gas on the Boyle's law determination of thoracic gas volume

1978 ◽  
Vol 44 (3) ◽  
pp. 469-473 ◽  
Author(s):  
R. Brown ◽  
F. G. Hoppin ◽  
R. H. Ingram ◽  
N. A. Saunders ◽  
E. R. McFadden
Keyword(s):  
Vital Capacity ◽  
Relative Magnitude ◽  
Lung Capacity ◽  
Thoracic Gas Volume ◽  
Residual Capacity ◽  
Almost All ◽  
Gas Volume ◽  
Boyle’S Law ◽  
Different Levels

In a body plethysmograph we have demonstrated differences in total lung capacity (TLC) derived from panting maneuvers performed at different levels in the vital capacity. In almost all cases, the discrepancies were due to the magnitude of the abdominal gas volume (AGV) and the relative magnitude of abdominal and thoracic pressure swings during the panting mandeuver. When panting was performed at functional residual capacity (FRC), the effect of AGV compression on the determination of thoracid gas volume (TGV) was small. Of 11 individuals studied 2 were known to have mild asthma. Compression and decompression of AGV appeared to be an insufficient explanation for discrepancies in derived TLC's in these two, suggesting that other as yet unidentified factors may influence the plethysmographic determination of TGV.

Shunt effect of gas compression inside pneumotachographs during forced oscillations

1991 ◽  
Vol 70 (1) ◽  
pp. 143-151 ◽  
Author(s):  
B. Louis ◽  
A. Harf ◽  
H. Lorino ◽  
D. Isabey
Keyword(s):  
Frequency Response ◽  
High Frequency ◽  
Forced Oscillation ◽  
Series Resistance ◽  
Forced Oscillations ◽  
Respiratory Impedance ◽  
Gas Compression ◽  
Normal Humans ◽  
Oscillation Method

Determination of the frequency response of pneumotachographs is needed whenever they are used to measure high-frequency flows, such as in the forced oscillation method. When screen and capillary pneumotachographs are calibrated using an adiabatic compression in a closed box as a reference impedance, they can be adequately described by a series of inertial-resistive elements. However, this type of reference impedance strongly differs from the actual respiratory impedance (ZL). We studied the frequency response of pneumotachographs up to 250 Hz in reference to the impedance of a compressible gas oscillating in a long tube, taken as a more generalizable model of actual ZL. We found that, with this device, the series resistance-inertance models fail to describe the frequency response of the pneumotachograph. However, when compressible effects in the pneumotachograph are taken into account by adding to the resistive models a compliance (Cpn) corresponding to the compression in half of the inner volume of the pneumotachograph, the agreement with experiments becomes satisfactory. Gas compression-related phenomena were demonstrated to be negligible only when the parameter omega Cpn magnitude of ZL is much smaller than 1 (omega pulsation). Results obtained in normal humans have shown that such a correction is required above 100 Hz. Similar correction at lower frequency might also be necessary in cases of large respiratory impedance (e.g., babies, subjects with pathological lungs, and intubated subjects).

Nonhomogeneous alveolar pressure swings in the presence of airway closure

1980 ◽  
Vol 49 (3) ◽  
pp. 398-402 ◽  
Author(s):  
R. Brown ◽  
S. Scharf ◽  
R. H. Ingram
Keyword(s):  
Lower Lobe ◽  
Chronic Obstructive ◽  
Airway Closure ◽  
Alveolar Pressure ◽  
Obstructive Pulmonary Disease ◽  
Thoracic Gas Volume ◽  
Airway Opening ◽  
The Right ◽  
Gas Volume

When thoracic gas volume (TGV) is determined plethysmographically, it is assumed that the alveolar pressure swings are homogeneous and are appropriately represented by pressure swings at the mouth. However, recent studies have demonstrated differences in total lung capacities derived from TGV measurements made at different levels in the vital capacity. These differences suggested that, in the presence of airway closure, alveolar pressure swings may be nonhomogeneous during a TGV determination. This possibility was tested in six dogs. Pressure at the airway opening (ao) was measured from an endotracheal catheter. A balloon-tipped catheter was passed into the right lower lobe (RLL) bronchus for measurement of RLL pressure. delta PRLL -- delta Pao was monitored during inspiratory efforts with the airway opening occluded. With the RLL balloon inflated, delta PRLL always exceeded delta Pao by an amount averaging 8.2%. Induction of a pneumothorax eliminated all differences between delta PRLL and delta Pao. Thus, during a TGV measurement, the chest wall may apply to the lungs nonhomogeneous forces that, in the presence of airway closure (e.g., chronic obstructive pulmonary disease and asthma) would result in nonhomogeneous alveolar pressure swings and potentially significant errors in the plethysmographic determination of TGV.

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