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.

Proportionality between chest wall resistance and elastance

1991 ◽  
Vol 70 (2) ◽  
pp. 511-515 ◽  
Author(s):  
G. M. Barnas ◽  
D. Stamenovic ◽  
J. J. Fredberg
Keyword(s):  
Tidal Volume ◽  
Chest Wall ◽  
Narrow Range ◽  
Respiratory Muscles ◽  
External Forcing ◽  
Breathing Frequency ◽  
Normal Range ◽  
Normal Ranges ◽  
Wide Range ◽  
The Relationship

Fredberg and Stamenovic (J. Appl. Physiol. 67: 2408-2419, 1989) demonstrated a relatively robust phenomenological relationship between resistance (R) and elastance (E) of lung tissue during external forcing. The relationship can be expressed as omega R = eta E, where omega = 2 pi times forcing frequency and eta is hysteresivity; they found eta to be remarkably invariant under a wide range of circumstances. From data gathered in previous experiments, we have tested the adequacy and utility of this phenomenological description for the chest wall (eta w) and its major compartments, the rib cage (eta rc), diaphragm-abdomen (eta d-a), and belly wall (eta bw+). For forcing frequencies and tidal volumes within the normal range of breathing, we found that eta w remained in a relatively narrow range (0.27-0.37) and that neither eta w nor the compartmental eta's changed much with frequency or tidal volume. Compared with eta w, eta rc tended to be slightly low, whereas eta d-a tended to be slightly higher than eta w. However, at higher frequencies (greater than 1 Hz) all eta's increased appreciably with frequency. During various static nonrespiratory maneuvers involving use of respiratory muscles, eta w increased up to twofold. We conclude that in the normal ranges of breathing frequency and tidal volume 1) elastic and dissipative processes within the chest wall appear to be coupled, 2) eta's of the various component parts of the chest wall are well matched, 3) respiratory muscle contraction increases the ratio of cyclic dissipative losses to energy storage, and 4) R of the relaxed chest wall can be estimated from E.(ABSTRACT TRUNCATED AT 250 WORDS)

Lung and chest wall impedances in the dog in normal range of breathing: effects of pulmonary edema

1992 ◽  
Vol 73 (3) ◽  
pp. 1040-1046 ◽  
Author(s):  
G. M. Barnas ◽  
D. Stamenovic ◽  
K. R. Lutchen
Keyword(s):  
Oleic Acid ◽  
Pulmonary Edema ◽  
Chest Wall ◽  
Mean Airway Pressure ◽  
Normal Range ◽  
Normal Ranges ◽  
Before And After ◽  
Measured Resistance ◽  
The Right ◽  
Severe Pulmonary Edema

We evaluated the effect of pulmonary edema on the frequency (f) and tidal volume (VT) dependences of respiratory system mechanical properties in the normal ranges of breathing. We measured resistance and elastance of the lungs (RL and EL) and chest wall of four anesthetized-paralyzed dogs during sinusoidal volume oscillations at the trachea (50–300 ml, 0.2–2 Hz), delivered at a constant mean airway pressure. Measurements were made before and after severe pulmonary edema was produced by injection of 0.06 ml/kg oleic acid into the right atrium. Chest wall properties were not changed by the injection. Before oleic acid, EL increased slightly with increasing f in each dog but was independent of VT. RL decreased slightly and was independent of VT from 0.2 to 0.4 Hz, but above 0.4 Hz it tended to increase with increasing flow, presumably due to the airway contribution. After oleic acid injection, EL and RL increased greatly. Large negative dependences of EL on VT and of RL on f were also evident, so that EL and RL after oleic acid changed two- and fivefold, respectively, within the ranges of f and VT studied. We conclude that severe pulmonary edema changes lung properties so as to make behavior VT dependent (i.e., nonlinear) and very frequency dependent in the normal range of breathing.

Effects of mean airway pressure and tidal volume on lung and chest wall mechanics in the dog

1993 ◽  
Vol 74 (5) ◽  
pp. 2286-2293 ◽  
Author(s):  
G. M. Barnas ◽  
J. Sprung
Keyword(s):  
Mechanical Properties ◽  
Tidal Volume ◽  
Chest Wall ◽  
Respiratory System ◽  
Lung Volume ◽  
Airway Pressure ◽  
Dynamic Mechanical Properties ◽  
Mean Airway Pressure ◽  
Residual Capacity ◽  
Normal Mean

Dependencies of the dynamic mechanical properties of the respiratory system on mean airway pressure (Paw) and the effects of tidal volume (VT) are not completely clear. We measured resistance and dynamic elastance of the total respiratory system (Rrs and Ers), lungs (RL and EL), and chest wall (Rcw and Ecw) in six healthy anesthetized paralyzed dogs during sinusoidal volume oscillations at the trachea (50–300 ml; 0.4 Hz) delivered at mean Paw from -9 to +23 cmH2O. Changes in end-expiratory lung volume, estimated with inductance plethysmographic belts, showed a typical sigmoidal relationship to mean Paw. Each dog showed the same dependencies of mechanical properties on mean Paw and VT. All elastances and resistances were minimal between 5 and 10 cmH2O mean Paw. All elastances, Rrs, and RL increased greatly with decreasing Paw below 5 cmH2O. Ers and EL increased above 10 cmH2O. Ecw, Ers, Rcw, and Rrs decreased slightly with increasing VT, but RL and EL were independent of VT. We conclude that 1) respiratory system impedance is minimal at the normal mean lung volume of supine anesthetized paralyzed dogs; 2) the dependency of RL on lung volume above functional residual capacity is dependent on VT and respiratory frequency; and 3) chest wall, but not lung, mechanical behavior is nonlinear (i.e., VT dependent) at any given lung volume.

Lung, Chest Wall, and Total Respiratory System Resistances and Elastances in the Normal Range of Breathing

1992 ◽  
Vol 145 (1) ◽  
pp. 110-113 ◽  
Author(s):  
G. M. Barnas ◽  
D. N. Campbell ◽  
C. F. Mackenzie ◽  
J. E. Mendham ◽  
B. G. Fahy ◽  
...  
Keyword(s):  
Chest Wall ◽  
Respiratory System ◽  
Normal Range

Quasi-static pressure-volume hysteresis in the canine respiratory system in vivo

1990 ◽  
Vol 68 (5) ◽  
pp. 2230-2236 ◽  
Author(s):  
F. R. Shardonofsky ◽  
J. Sato ◽  
J. H. Bates
Keyword(s):  
Gas Exchange ◽  
Chest Wall ◽  
Respiratory System ◽  
Static Pressure ◽  
Transpulmonary Pressure ◽  
Mechanically Ventilated ◽  
Loop Area ◽  
Hysteresis Loop Area ◽  
Isolated Lungs

We investigated the quasi-static pressure-volume (P-V) hysteresis of the normal canine lung in vivo by performing 15-s flow interruptions at various points throughout the breathing cycle in mechanically ventilated anesthetized paralyzed dogs. By measuring the transpulmonary pressure (Ptp) at 5 s after each interruption, we built up a quasi-static P-V loop of the lungs. We found, however, that the area of the loop was significantly smaller (by a factor of 4-6) than has been reported by others for the isolated canine lung. We also found the hysteresis loop area of the chest wall to be of similar magnitude. If we measured Ptp 10-15 s after interruption, we found it always decreased at a rate expected to result from continuing gas exchange in the lungs. We conclude that 1) the areas of the quasi-static P-V loop in vivo for the total respiratory system, as well as the lungs and chest wall separately, are significantly smaller than has been reported previously for isolated lungs and 2) continuing gas exchange in the lungs places a lower limit on the frequencies (equivalent to flow interruptions of greater than 5- to 7-s duration) at which the P-flow-V behavior of the lungs in vivo can be considered in purely mechanical terms.

Absolute intraesophageal pressure at functional residual capacity in frequency

1981 ◽  
Vol 51 (2) ◽  
pp. 270-275 ◽  
Author(s):  
P. Helms ◽  
C. S. Beardsmore ◽  
J. Stocks
Keyword(s):  
Chest Wall ◽  
Wall Thickness ◽  
Respiratory System ◽  
Functional Residual Capacity ◽  
Esophageal Pressure ◽  
Elastic Recoil ◽  
Residual Capacity ◽  
The Mean ◽  
Intraesophageal Pressure

Absolute intraesophageal pressure at functional residual capacity (FRC) has been estimated in 15 infants (age 1-30 wk) by the extrapolation of the esophageal pressure-volume relationships to zero balloon volume by use of air-filled balloons in their ranges of infinite compliance. The pressure-volume relationships of the esophageal balloons (length 3.5-5.0 cm, perimeter 1.7-2.5 cm, wall thickness 0.045-0.075 mm) were determined in air and in erect and horizontal positions under water, the behavior of the balloons placed horizontally under water closely approximated that of the balloons in vivo. The mean absolute intraesophageal pressure at FRC was -1.44 cmH2O in eight normal infants and -1.56 cmH2O in seven convalescent infants with a variety of cardiorespiratory disorders. The less negative absolute end-expiratory esophageal pressure in infants when compared with that in adults can be explained by changes in lung elastic recoil, chest wall recoil, or a combination of these factors during the development and growth of the respiratory system from birth to adulthood.

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.

Lung and chest wall mechanical properties before and after cardiac surgery with cardiopulmonary bypass

1994 ◽  
Vol 76 (1) ◽  
pp. 166-175 ◽  
Author(s):  
G. M. Barnas ◽  
R. J. Watson ◽  
M. D. Green ◽  
A. J. Sequeira ◽  
T. B. Gilbert ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Cardiac Surgery ◽  
Cardiopulmonary Bypass ◽  
Tidal Volume ◽  
Chest Wall ◽  
Respiratory System ◽  
Supine Posture ◽  
Duration Of Surgery ◽  
Before And After ◽  
System Properties

From measurements of airway and esophageal pressures and flow, we calculated the elastance and resistance of the total respiratory system (Ers and Rrs), chest wall (Ecw and Rcw), and lungs (EL and RL) in 11 anesthetized-paralyzed patients immediately before cardiac surgery with cardiopulmonary bypass and immediately after chest closure at the end of surgery. Measurements were made during mechanical ventilation in the frequency and tidal volume ranges of normal breathing. Before surgery, frequency and tidal volume dependences of the elastances and resistances were similar to those previously measured in awake seated subjects (Am. Rev. Respir. Dis. 145: 110–113, 1992). After surgery, Ers and Rrs increased as a result of increases in EL and RL (P < 0.05), whereas Ecw and Rcw did not change (P > 0.05). EL and RL exhibited nonlinearities (i.e., decreases with increasing tidal volume) that were not seen before surgery, and RL showed a greater dependence on frequency than before surgery. The changes in RL or EL after surgery were not correlated with the duration of surgery or cardiopulmonary bypass time (P > 0.05). We conclude that 1) frequency and tidal volume dependences of respiratory system properties are not affected by anesthesia, paralysis, and the supine posture, 2) open-chest surgery with cardiopulmonary bypass does not affect the mechanical properties of the chest, and 3) cardiac surgery involving cardiopulmonary bypass causes changes in the mechanical behavior of the lung that are generally consistent with those caused by pulmonary edema induced by oleic acid (J. Appl. Physiol. 73: 1040–1046, 1992) and decreases in lung volume.

Comparison of Immunological and Functional Assays for Measurement of Soluble Fibrin

1995 ◽  
Vol 74 (02) ◽  
pp. 673-679 ◽  
Author(s):  
C E Dempfle ◽  
S A Pfitzner ◽  
M Dollman ◽  
K Huck ◽  
G Stehle ◽  
...  
Keyword(s):  
Venous Thrombosis ◽  
Low Grade ◽  
Plasma Samples ◽  
Normal Range ◽  
Soluble Fibrin ◽  
Discriminating Power ◽  
Fibrin Monomer ◽  
Cerebral Ischemic

SummaryVarious assays have been developed for quantitation of soluble fibrin or fibrin monomer in clinical plasma samples, since this parameter directly reflects in vivo thrombin action on fibrinogen. Using plasma samples from healthy blood donors, patients with cerebral ischemic insult, patients with septicemia, and patients with venous thrombosis, we compared two immunologic tests using monoclonal antibodies against fibrin-specific neo-epitopes, and two functional tests based on the cofactor activity of soluble fibrin complexes in tPA-induced plasminogen activation. Test A (Enzymun®-Test FM) showed the best discriminating power among normal range and pathological samples. Test B (Fibrinostika® soluble fibrin) clearly separated normal range from pathological samples, but failed to discriminate among samples from patients with low grade coagulation activation in septicemia, and massive activation in venous thrombosis. Functional test C (Fibrin monomer test Behring) displayed good discriminating power between normal and pathological range samples, and correlated with test A (r = 0.61), whereas assay D (Coa-Set® Fibrin monomer) showed little discriminating power at values below 10 μg/ml and little correlation with other assays. Standardization of assays will require further characterization of analytes detected.

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