Respiratory mechanics in the normal dog determined by expiratory flow interruption

1989 ◽  
Vol 67 (6) ◽  
pp. 2276-2285 ◽  
Author(s):  
J. H. Bates ◽  
K. A. Brown ◽  
T. Kochi
Keyword(s):  
Mechanical Behavior ◽  
Chest Wall ◽  
Lung Tissue ◽  
Respiratory System ◽  
Viscoelastic Properties ◽  
Respiratory Mechanics ◽  
Frequency Dependent ◽  
Low Frequencies ◽  
Flow Interruption ◽  
Airways Resistance

We recently proposed an eight-parameter model of the respiratory system to account for its mechanical behavior when flow is interrupted during passive expiration. The model consists of two four-parameter submodels representing the lungs and the chest wall, respectively. The lung submodel consists of an airways resistance together with elements embodying the viscoelastic properties of the lung tissues. The chest wall submodel has similar structure. We estimated the parameters of the model from data obtained in four normal, anesthetized, paralyzed, tracheostomized mongrel dogs. This model explains why lung tissue and chest wall resistances should be markedly frequency dependent at low frequencies and also permits a physiological interpretation of resistance measurements provided by the flow interruption method.

Chest wall impedance partitioned into rib cage and diaphragm-abdominal pathways

1989 ◽  
Vol 66 (1) ◽  
pp. 350-359 ◽  
Author(s):  
G. M. Barnas ◽  
K. Yoshino ◽  
D. Stamenovic ◽  
Y. Kikuchi ◽  
S. H. Loring ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Chest Wall ◽  
Viscoelastic Properties ◽  
Vital Capacity ◽  
Wall Surface ◽  
Body Plethysmography ◽  
Frequency Range ◽  
Entire Frequency Range ◽  
Rib Cage ◽  
Pressure Changes

We measured chest wall "pathway impedances" (ratios of pressure changes to rates of volume displacement at the surface) with esophageal and gastric balloons and inductance plethysmographic belts around the rib cage and abdomen during forced volume oscillations (5% vital capacity, 0.5–4 Hz) at the mouth of five relaxed, seated subjects. Volume displacements of the total chest wall surface, measured by summing the rib cage and abdominal signals, approximated measurements using volume-displacement, body plethysmography over the entire frequency range. Resistance (R) and elastance (E) of the diaphragm-abdomen pathway were several times greater than those of the rib cage pathway, except at the highest frequencies where diaphragm-abdominal E was small. R and E of the diaphragm-abdomen pathway and of the rib cage pathway showed the same frequency dependencies as that of the total chest wall: R decreased markedly as frequency increased, and E (especially in the diaphragm-abdomen) decreased at the highest frequencies. These results suggest that the chest wall can be reasonably modeled, over the frequency range studied, as a system with two major pathways for displacement. Each pathway seems to exhibit behavior that reflects nonlinear, rate-independent dissipation as well as viscoelastic properties. Impedances of these pathways are useful indexes of changes in chest wall mechanical behavior in different situations.

Nonlinear and Frequency-Dependent Mechanical Behavior of the Mouse Respiratory System

2003 ◽  
Vol 31 (3) ◽  
pp. 318-326 ◽  
Author(s):  
Henrique T. Moriya ◽  
José Carlos T. B. Moraes ◽  
Jason H. T. Bates
Keyword(s):  
Mechanical Behavior ◽  
Respiratory System ◽  
Frequency Dependent

Techniques for measuring respiratory mechanics: an analytic approach with a viscoelastic model

1993 ◽  
Vol 74 (5) ◽  
pp. 2373-2379 ◽  
Author(s):  
A. M. Lorino ◽  
A. Harf
Keyword(s):  
Mechanical Ventilation ◽  
Mechanical Behavior ◽  
Respiratory System ◽  
Respiratory Mechanics ◽  
Homogeneous Model ◽  
Viscoelastic Model ◽  
Normal Subjects ◽  
Inspiratory Time ◽  
Airway Occlusion ◽  
Analytic Expressions

A homogeneous model with stress relaxation that is described by a pure viscoelastic component was recently proposed to describe the mechanical behavior of the respiratory system during mechanical ventilation (Bates et al. J. Appl. Physiol. 67: 2276–2285, 1989). With the use of this model, analytic expressions of the pressure in response to typical volume inputs are developed, and the recently published studies relating to the influence of the ventilatory pattern on respiratory mechanics are reviewed and analyzed. The analytic expression of pressure responses to rapid airway occlusion following constant-flow inflation and to sinusoidal volume oscillations allows prediction of most of the reported results. The theoretical analysis suggests that in normal subjects the observed flow and volume dependencies of respiratory mechanics are, in fact, illustrations of the dependence of the viscoelastic resistance on inspiratory time and respiratory frequency. Thus the homogeneous viscoelastic model appears suitable to describe respiratory system mechanical behavior under mechanical ventilation.

Respiratory system compliance and resistance in the critically ill

2016 ◽  
Author(s):  
Ricardo Luiz Cordioli ◽  
Laurent Brochard
Keyword(s):  
Chest Wall ◽  
Respiratory System ◽  
Gas Flow ◽  
Respiratory Mechanics ◽  
Volume Ratio ◽  
Plateau Pressure ◽  
Volume Controlled Ventilation ◽  
Ventilation Monitoring ◽  
Resistive Forces ◽  
Pressure Resistance

Under mechanical ventilation, monitoring of respiratory mechanics is fundamental, especially in patients with abnormal mechanics. In order to appropriately set the ventilator, clinicians need to understand the relationship between pressure, volume and flow. To move air in and out the thorax, energy must be dissipated against elastic and resistive forces. Elastance is the pressure to volume ratio and necessitates an end inspiratory occlusion to measure the so-called plateau pressure. Resistance is the ratio between pressure dissipated and mean gas flow. Finally, the total positive end expiratory pressure must be measured with an end expiratory occlusion. Volume-controlled ventilation is the recommended mode to assess respiratory mechanics of a passive patient. Clinicians must be aware that both chest wall and lung participate in forces imposed by the respiratory system. An oesophageal catheter can estimate pleural pressure, and used to partition the respective role of the lung and the chest wall.

Effects of vagotomy on respiratory mechanics in newborn and adult pigs

1986 ◽  
Vol 60 (6) ◽  
pp. 1992-1999 ◽  
Author(s):  
M. G. Clement ◽  
J. P. Mortola ◽  
M. Albertini ◽  
G. Aguggini
Keyword(s):  
Chest Wall ◽  
Respiratory System ◽  
Respiratory Mechanics ◽  
Breathing Patterns ◽  
External Work ◽  
Vagal Control ◽  
Before And After ◽  
Wall Compliance ◽  
Bilateral Vagotomy ◽  
System Time

We have examined breathing patterns and respiratory mechanics in anesthetized tracheostomized newborn piglets and adult pigs and the changes determined by cervical bilateral vagotomy. Piglets had a respiratory system compliance and resistance, on a per kilogram basis, respectively, higher and smaller than the adults. After vagotomy neither variable changed in the newborn, but resistance dropped in the adult. This may suggest that efferent vagal control of bronchomotor tone is more pronounced in the adult. Respiratory system time constant was longer in newborns both before and after vagotomy. The distortion of the chest wall, examined as the ratio between the volume inhaled spontaneously and the passive volume for the same abdominal motion, was more marked in newborns, reflecting their higher chest wall compliance. The work per minute, computed from the pressure and volume changes, was larger in piglets. After vagotomy the external work per minute was not different; however, the larger tidal volumes were accompanied by a larger chest distortion. This may indicate that vagal control of the breathing pattern, by limiting the depth of inspiration and hence the amount of chest distortion, has implications on the energetics of breathing.

A comparison of interrupter and forced oscillation measurements of respiratory resistance in the dog

1992 ◽  
Vol 72 (1) ◽  
pp. 46-52 ◽  
Author(s):  
J. H. Bates ◽  
B. Daroczy ◽  
Z. Hantos
Keyword(s):  
Respiratory System ◽  
High Frequency ◽  
Forced Oscillation ◽  
Forced Oscillation Technique ◽  
Respiratory Resistance ◽  
Modest Contribution ◽  
Flow Interruption ◽  
Tracheal Pressure ◽  
Airways Resistance ◽  
Respiratory System Resistance

We compared the values of resistance produced by the forced oscillation technique (FOT) and the flow interruption technique (IT) when applied to six anesthetized paralyzed tracheostomized dogs. The FOT returned values of respiratory system resistance as a function of frequency [Re(f)] between 0.25 and 20 Hz. The IT returned a single value of resistance (Rinit) calculated by dividing the immediate change in tracheal pressure occurring upon interruption by the preinterruption flow. We found Rinit to coincide closely with Re(f) in the frequency range 5–20 Hz. Rinit has previously been interpreted as the high-frequency resistance of a resistance-elastance model of the respiratory system airways and tissues. It has also been shown previously, by direct measurement of alveolar pressure in dogs, that Rinit from the lungs alone is an accurate measure of airways resistance while Rinit obtained from the total respiratory system equals airways resistance plus a modest contribution from the chest wall. Re(f) at a frequency of approximately 10 Hz thus appears to be a useful quantity to measure as an index of airways resistance in the dog.

Lung and chest wall impedances in the dog: effects of frequency and tidal volume

1992 ◽  
Vol 72 (1) ◽  
pp. 87-93 ◽  
Author(s):  
G. M. Barnas ◽  
D. Stamenovic ◽  
K. R. Lutchen ◽  
C. F. Mackenzie
Keyword(s):  
Tidal Volume ◽  
Chest Wall ◽  
Respiratory System ◽  
Peak Flow ◽  
Data Capture ◽  
Normal Range ◽  
Flow Dependence ◽  
Normal Ranges ◽  
Airways Resistance

Dependences of the mechanical properties of the respiratory system on frequency (f) and tidal volume (VT) in the normal ranges of breathing are not clear. We measured, simultaneously and in vivo, resistance and elastance of the total respiratory system (Rrs and Ers), lungs (RL and EL), and chest wall (Rcw and Ecw) of five healthy anesthetized paralyzed dogs during sinusoidal volume oscillations at the trachea (50–300 ml, 0.2–2 Hz) delivered at a constant mean lung volume. Each dog showed the same f and VT dependences. The Ers and Ecw increased with increasing f to 1 Hz and decreased with increasing VT up to 200 ml. Although EL increased slightly with increasing f, it was independent of VT. The Rcw decreased from 0.2 to 2 Hz at all VT and decreased with increasing VT. Although the RL decreased from 0.2 to 0.6 Hz and was independent of VT, at higher f RL tended to increase with increasing f and VT (i.e., as peak flow increased). Finally, the f and VT dependences of Rrs were similar to those of Rcw below 0.6 Hz but mirrored RL at higher f. These data capture the competing influences of airflow nonlinearities vs. tissue nonlinearities on f and VT dependence of the lung, chest wall, and total respiratory system. More specifically, we conclude that 1) VT dependences in Ers and Rrs below 0.6 Hz are due to nonlinearities in chest wall properties, 2) above 0.6 Hz, the flow dependence of airways resistance dominates RL and Rrs, and 3) lung tissue behavior is linear in the normal range of breathing.

Effect of PEEP on respiratory mechanics in anesthetized paralyzed humans

1992 ◽  
Vol 73 (5) ◽  
pp. 1736-1742 ◽  
Author(s):  
E. D′Angelo ◽  
E. Calderini ◽  
M. Tavola ◽  
D. Bono ◽  
J. Milic-Emili
Keyword(s):  
Chest Wall ◽  
Lung Volume ◽  
Respiratory Mechanics ◽  
Viscoelastic Model ◽  
Esophageal Pressure ◽  
Airway Occlusion ◽  
Flow Interruption ◽  
Peep Ventilation ◽  
Overall Resistance ◽  
Viscoelastic Constants

With the use of the technique of rapid airway occlusion during constant flow inflation, respiratory mechanics were studied in eight anesthetized paralyzed supine normal humans during zero (ZEEP) and positive end-expiratory pressure (PEEP) ventilation. PEEP increased the end-expiratory lung volume by 0.49 liter. The changes in transpulmonary and esophageal pressure after flow interruption were analyzed in terms of a seven-parameter “viscoelastic” model. This allowed assessment of static lung and chest wall elastance (Est,L and Est,W), partitioning of overall resistance into airway interrupter (Rint,L) and tissue resistances (delta RL and delta RW), and computation of lung and chest wall “viscoelastic constants.” With increasing flow, Rint,L increased, whereas delta RL and delta RW decreased, as predicted by the model. Est,L, Est,W, and Rint,L decreased significantly with PEEP because of increased lung volume, whereas delta R and viscoelastic constants of lung and chest wall were independent of PEEP. The results indicate that PEEP caused a significant decrease in Rint,L, Est,L, and Est,W, whereas the dynamic tissue behavior, as reflected by delta RL and delta RW, did not change.

Effect of pulmonary blood flow on measurements of respiratory mechanics using the interrupter technique

1993 ◽  
Vol 74 (3) ◽  
pp. 1083-1088 ◽  
Author(s):  
N. J. Freezer ◽  
C. J. Lanteri ◽  
P. D. Sly
Keyword(s):  
Blood Flow ◽  
Chest Wall ◽  
Respiratory System ◽  
Left Atrial ◽  
Pulmonary Blood Flow ◽  
Respiratory Mechanics ◽  
Dynamic Compliance ◽  
Left Atrial Pressure ◽  
Conducting Airways ◽  
The Relationship

The relationship between respiratory mechanics, changes in pulmonary blood flow (PBF), pulmonary arterial pressure, and left atrial pressure is unclear. Conventional methods for the measurement of respiratory mechanics model the respiratory system as a single compartment, which may not adequately represent the respiratory system in a diseased state. The interrupter technique models the respiratory system as two compartments, with the "flow resistance" of the conducting airways and chest wall (Raw) considered separately from Pdif, a measure of the viscoelastic properties of the lung and chest wall, together with any pendelluft present. The respiratory mechanics of 15 infants in the first year of life were studied during cardiac catheterization with the use of conventional methods and the interrupter technique. The infants had a PBF-to-systemic blood flow ratio ranging from 0.6 to 4.0:1. The specific dynamic compliance of the respiratory system was not related to the PBF; however, there was a significant relationship between PBF and the total resistance of the respiratory system (Rrs) [analysis of variance (ANOVA) F = 5.69, P < 0.05], Raw (ANOVA, F = 12.30, P < 0.01), and Pdif (ANOVA, F = 3.79, P < 0.05). Rrs increased significantly with an increase in mean left atrial pressure (ANOVA, F = 6.92, P < 0.05); however, dynamic compliance, Raw, and Pdif did not. These results suggest that the relationship between Rrs and PBF is due an increase in the resistive properties of the conducting airways and tissue components.

Viscoplasticity of respiratory tissues

1990 ◽  
Vol 69 (3) ◽  
pp. 973-988 ◽  
Author(s):  
D. Stamenovic ◽  
G. M. Glass ◽  
G. M. Barnas ◽  
J. J. Fredberg
Keyword(s):  
Stress Relaxation ◽  
Mechanical Behavior ◽  
Chest Wall ◽  
Low Frequency ◽  
Low Frequencies ◽  
Rate Dependent ◽  
Independent Verification ◽  
Calculated Stress ◽  
In Series

Low-frequency mechanical behavior of various respiratory tissues shows certain similarities. In this study we test the hypothesis that rate-independent plastic processes along with rate-dependent viscoelastic processes are responsible. We considered oscillatory responses of several respiratory tissues measured over prescribed ranges of frequency (up to 6 Hz) and amplitude of forcing. These included the excised cat lung, the human chest wall in vivo, and two components of the chest wall: the excised dog rib cage and the excised rabbit abdominal viscera; some data were previously reported and some are new. We analyzed these data using the viscoplastic model of Hildebrandt (J. Appl. Physiol. 28: 365-372, 1970). It consists of three compartments: a plastoelastic compartment mechanically in parallel with a viscoelastic compartment, both in series with a lumped inertia. We fitted oscillatory data of the above respiratory tissues to the model by a least-squares technique. The fit was qualitatively consistent with the observations and exhibited moderately good to very good quantitative correspondence. As an independent verification of this approach, we obtained the stress relaxation after a step-volume change. Based on the oscillatory response of cat lungs, the calculated stress relaxation function was found to be generally consistent with corresponding observations. This study indicates that both plasticity and viscoelasticity appear to be important determinants of mechanical behavior of respiratory tissues at low frequencies and that inertial effects are negligible.

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