Effect of forced expiration on thoracic gas volume in wheezy infants

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.

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Pulmonary response to threshold levels of sulfur dioxide (1.0 ppm) and ozone (0.3 ppm)

Journal of Applied Physiology ◽

10.1152/jappl.1985.58.6.1783 ◽

1985 ◽

Vol 58 (6) ◽

pp. 1783-1787 ◽

Cited By ~ 16

Author(s):

L. J. Folinsbee ◽

J. F. Bedi ◽

S. M. Horvath

Keyword(s):

Sulfur Dioxide ◽

Pulmonary Response ◽

Rest Periods ◽

Pollutant Concentrations ◽

Thoracic Gas Volume ◽

Exercise Ventilation ◽

Before And After ◽

Residual Capacity ◽

Gas Volume ◽

Male Subjects

We exposed 22 healthy adult nonsmoking male subjects for 2 h to filtered air, 1.0 ppm sulfur dioxide (SO2), 0.3 ppm ozone (O3), or the combination of 1.0 ppm SO2 + 0.3 ppm O3. We hypothesized that exposure to near-threshold concentrations of these pollutants would allow us to observe any interaction between the two pollutants that might have been masked by the more obvious response to the higher concentrations of O3 used in previous studies. Each subject alternated 30-min treadmill exercise with 10-min rest periods for the 2 h. The average exercise ventilation measured during the last 5 min of exercise was 38 1/min (BTPS). Forced expiratory maneuvers were performed before exposure and 5 min after each of the three exercise periods. Maximum voluntary ventilation, He dilution functional residual capacity, thoracic gas volume, and airway resistance were measured before and after the exposure. After O3 exposure alone, forced expiratory measurements (FVC, FEV1.0, and FEF25–75%) were significantly decreased. The combined exposure to SO2 + O3 produced similar but smaller decreases in these measures. There were small but significant differences between the O3 and the O3 + SO2 exposure for FVC, FEV1.0, FEV2.0, FEV3.0, and FEF25–75% at the end of the 2-h exposure. We conclude that, with these pollutant concentrations, there is no additive or synergistic effect of the two pollutants on pulmonary function.

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

Journal of Applied Physiology ◽

10.1152/japplphysiol.90924.2008 ◽

2008 ◽

Vol 105 (6) ◽

pp. 1864-1872 ◽

Cited By ~ 38

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.

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ALVEOLAR-ARTERIAL O2 AND CO2 DIFFERENCES AND THEIR RELATION TO LUNG VOLUME IN THE NEWBORN

PEDIATRICS ◽

10.1542/peds.41.3.574 ◽

1968 ◽

Vol 41 (3) ◽

pp. 574-587 ◽

Cited By ~ 1

Author(s):

D. W. Thibeault ◽

E. Poblete ◽

P. A. M. Auld

Keyword(s):

Carbon Dioxide ◽

Premature Infants ◽

Lung Volume ◽

Term Infant ◽

Full Term ◽

Arterial Oxygen ◽

Term Infants ◽

Oxygen Gradient ◽

Thoracic Gas Volume ◽

Gas Volume

Twenty-six premature and five full-term infants, ranging in birth weight from 860 to 4,040 gm and in age from 3 hours to 98 days, were the subjects of this study. Measurements of thoracic gas volume and determination of alveolar-arterial oxygen gradient and arterial-alveolar carbon dioxide gradient were performed. All infants showed a decrease in thoracic gas volume in the first days of life. The initial high thoracic gas volume is thought to be due to trapped gas. The ability to trap gas was demonstrated in a number of infants. In the full-term infant the decrease in thoracic gas volume is associated with improvement in lung function. In the premature infants the decrease in lung volume is associated with a persistently elevated alveolar-arterial oxygen gradient and in an inequality of perfusion and ventilation, as evidenced by the large arterial-alveolar carbon dioxide gradient. In a small group of infants increase in functional residual capacity produced by negative pressure around the chest resulted in a decrease in the carbon dioxide and oxygen gradients, indicating that the infant's lung volume is less than optimum. These observations characterize in physiological terms some of the respiratory difficulties in small premature infants.

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Determinants of forced expiratory flows in newborn infants

Journal of Applied Physiology ◽

10.1152/jappl.1982.53.5.1220 ◽

1982 ◽

Vol 53 (5) ◽

pp. 1220-1227 ◽

Cited By ~ 139

Author(s):

L. M. Taussig ◽

L. I. Landau ◽

S. Godfrey ◽

I. Arad

Keyword(s):

Newborn Infants ◽

Cross Sectional Area ◽

Physiological Data ◽

Sectional Area ◽

Older Children ◽

Cross Sectional ◽

Thoracic Gas Volume ◽

Residual Capacity ◽

The Cross ◽

Gas Volume

Maximal flows at functional residual capacity (VmaxFRC) from partial expiratory flow-volume (PEFV) curves (achieved with rapid compression of the chest) were obtained on 11 healthy newborn babies. Mean VmaxFRC, size corrected by dividing absolute values by measured thoracic gas volume, was 1.90 TGV's/s. Specific upstream conductances were high, and the cross-sectional area of the flow-limiting segment was estimated to be approximately 0.30 cm2 in the three infants on whom recoil pressures at FRC were also measured. The cross-sectional area of the major bronchi in the neonate is approximately 0.26–0.30 cm2. PEFV curves were convex to the volume axis. Many of the neonates increased their flows while breathing a helium-oxygen gas mixture. These results suggest 1) size-corrected flows are higher in the neonate than in older children or adults; 2) the site of the flow-limiting segment at FRC during maximal expiratory maneuvers is in large proximal airways, similar to the adult; and 3) the relationship of airway size to parenchymal size may be similar in neonates and adults or, in fact, airways may be larger, relative to parenchyma, in neonates. These physiological data do not support the hypothesis, based on pathological studies, that peripheral airways are disproportionately smaller (when compared with central airways) in infants than in adults.

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T model partition of lung and respiratory system impedances

Journal of Applied Physiology ◽

10.1152/jappl.1995.78.3.938 ◽

1995 ◽

Vol 78 (3) ◽

pp. 938-947 ◽

Cited By ~ 5

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.

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Body composition by air-displacement plethysmography by using predicted and measured thoracic gas volumes

Journal of Applied Physiology ◽

10.1152/jappl.1998.84.4.1475 ◽

1998 ◽

Vol 84 (4) ◽

pp. 1475-1479 ◽

Cited By ~ 93

Author(s):

Megan A. McCrory ◽

Paul A. Molé ◽

Terri D. Gomez ◽

Kathryn G. Dewey ◽

Edmund M. Bernauer

Keyword(s):

Body Composition ◽

Body Volume ◽

Air Displacement Plethysmography ◽

Bod Pod ◽

Individual Basis ◽

Thoracic Gas Volume ◽

Significant Difference ◽

Hydrostatic Weighing ◽

Gas Volume ◽

Boyle’S Law

The BOD POD, a new air-displacement plethysmograph for measuring human body composition, utilizes the inverse relationship between pressure and volume (Boyle’s law) to measure body volume directly. The quantity of air in the lungs during tidal breathing, the average thoracic gas volume (Vtg), is also measured by the BOD POD by using a standard plethysmographic technique. Alternatively, the BOD POD provides the use of a predicted Vtg (Vtgpred). The validity of using Vtgpred in place of measured Vtg (Vtgmeas) to determine the percentage of body fat (%BF) was evaluated in 50 subjects (36 women, 14 men; ages 18–56 yr). There was no significant difference between Vtgmeas and Vtgpred (mean difference ± SE, 53.5 ± 63.3 ml) nor in %BF by using Vtgmeas vs. Vtgpred (0.2 ± 0.2 %BF). On an individual basis, %BF measured by using Vtgmeas vs. Vtgpred differed within ±2.0% BF for 82% of the subjects; maximum differences were −2.9 to +3.0% BF. For comparison, data from 24 subjects who had undergone hydrostatic weighing were evaluated for the validity of using predicted vs. measured residual lung volume (Vr pred vs. Vr meas, respectively). Differences between Vr meas and Vr pred and in %BF calculated by using Vr meas vs. Vr pred were significant (187 ± 46 ml and 1.4 ± 0.3% BF, respectively; P < 0.001). On an individual basis, %BF determined by using Vr meas vs. Vr preddiffered within ±2.0% BF for 46% of the subjects; maximum differences were −2.9 to +3.8% BF. With respect to %BF measured by air displacement, our findings support the use of Vtgpred for group mean comparisons and for purposes such as screening in young to middle-aged individuals. This contrasts with the use of Vr pred in hydrostatic weighing, which leads to significant errors in the estimation of %BF. Furthermore, although the use of Vtgpred has some application, determining Vtgmeas is relatively simple in most cases. Therefore, we recommend that the use of Vtgmeas remain as standard experimental and clinical practice.

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Partitioning of airway and respiratory tissue mechanical impedances by body plethysmography

Journal of Applied Physiology ◽

10.1152/jappl.1998.84.2.553 ◽

1998 ◽

Vol 84 (2) ◽

pp. 553-561 ◽

Cited By ~ 11

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.

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

Journal of Applied Physiology ◽

10.1152/jappl.1984.57.6.1917 ◽

1984 ◽

Vol 57 (6) ◽

pp. 1917-1922 ◽

Cited By ~ 21

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.

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