Active and passive respiratory mechanics in anesthetized dogs

1986 ◽  
Vol 61 (5) ◽  
pp. 1647-1655 ◽  
Author(s):  
W. A. Zin ◽  
A. Boddener ◽  
P. R. Silva ◽  
T. M. Pinto ◽  
J. Milic-Emili
Keyword(s):  
Chest Wall ◽  
Respiratory System ◽  
Power Functions ◽  
Intrinsic Resistance ◽  
Pressure Losses ◽  
Inspiratory Muscles ◽  
Anesthetized Dogs ◽  
Force Velocity ◽  
Spontaneously Breathing ◽  
Active Impedance

In six spontaneously breathing anesthetized dogs (pentobarbital sodium, 30 mg/kg) airflow, volume, and tracheal and esophageal pressures were measured. The active and passive mechanical properties of the total respiratory system, lung, and chest wall were calculated. The average passive values of respiratory system, lung, and chest wall elastances amounted to, respectively, 50.1, 32.3, and 17.7 cmH2O X l-1. Resistive pressure-vs.-flow relationships for the relaxed respiratory system, lung, and chest wall were also determined; a linear relationship was found for the former (the total passive intrinsic resistance averaged 4.1 cmH2O X l-1 X s), whereas power functions best described the others: the pulmonary pressure-flow relationship exhibited an upward concavity, which for the chest wall presented an upward convexity. The average active elastance and resistance of the respiratory system were, respectively, 64.0 cmH2O X l-1 and 5.4 cmH2O X l-1 X s. The greater active impedance reflects pressure losses due to force-length and force-velocity properties of the inspiratory muscles and those due to distortion of the respiratory system from its relaxed configuration.

Interrupter technique for measurement of respiratory mechanics in anesthetized cats

1984 ◽  
Vol 56 (3) ◽  
pp. 681-690 ◽  
Author(s):  
S. B. Gottfried ◽  
A. Rossi ◽  
P. M. Calverley ◽  
L. Zocchi ◽  
J. Milic-Emili
Keyword(s):  
Chest Wall ◽  
Respiratory System ◽  
Flow Resistance ◽  
Muscle Relaxation ◽  
Esophageal Pressure ◽  
Inspiratory Muscles ◽  
Tracheal Pressure ◽  
Force Velocity ◽  
Spontaneously Breathing

In six spontaneously breathing anesthetized cats (pentobarbital sodium, 35 mg/kg ip), airflow, changes in lung volume, and tracheal and esophageal pressures were measured. Airflow was interrupted by brief airway occlusions during relaxed expirations (elicited via the Breuer-Hering inflation reflex) and throughout spontaneous breaths. A plateau in tracheal pressure occurred throughout relaxed expirations and the latter part of spontaneous expirations indicating respiratory muscle relaxation. Measurement of tracheal pressure, immediately preceding airflow, and corresponding volume enabled determination of respiratory system elastance and flow resistance. These were partitioned into lung and chest wall components using esophageal pressure. Respiratory system elastance was constant over the tidal volume range, divided approximately equally between the lung and chest wall. While the passive pressure-flow relationship for the respiratory system was linear, those for the lung and chest wall were curvilinear. Volume dependence of chest wall flow resistance was demonstrated. During inspiratory interruptions, tracheal pressure increased progressively; initial tracheal pressure was estimated by backward extrapolation. Inspiratory flow resistance of the lung and total respiratory system were constant. Force-velocity properties of the contracting inspiratory muscles contributed little to overall active resistance.

Chest wall and respiratory system mechanics in cats: effects of flow and volume

1988 ◽  
Vol 64 (6) ◽  
pp. 2636-2646 ◽  
Author(s):  
T. Kochi ◽  
S. Okubo ◽  
W. A. Zin ◽  
J. Milic-Emili
Keyword(s):  
Chest Wall ◽  
Time Constant ◽  
Flow Rate ◽  
Respiratory System ◽  
Flow Resistance ◽  
Stress Adaptation ◽  
Inspiratory Flow Rate ◽  
Intrinsic Resistance ◽  
Pressure Losses ◽  
Airway Occlusion

The effects of inspiratory flow rate and inflation volume on the resistive properties of the chest wall were investigated in six anesthetized paralyzed cats by use of the technique of rapid airway occlusion during constant flow inflation. This allowed measurement of the intrinsic resistance (Rw,min) and overall dynamic inspiratory impedance (Rw,max), which includes the additional pressure losses due to time constant inequalities within the chest wall tissues and/or stress adaptation. These results, together with our previous data pertaining to the lung (Kochi et al., J. Appl. Physiol. 64: 441–450, 1988), allowed us to determine Rmin and Rmax of the total respiratory system (rs). We observed that 1) Rw,max and Rrs,max exhibited marked frequency dependence; 2) Rw,min was independent of flow (V) and inspired volume (delta V), whereas Rrs,min increased linearly with V and decreased with increasing delta V; 3) Rw,max decreased with increasing V, whereas Rrs,max exhibited a minimum value at a flow rate substantially higher than the resting range of V; 4) both Rw,max and Rrs,max increased with increasing delta V. We conclude that during resting breathing, flow resistance of the chest wall and total respiratory system, as conventionally measured, includes a significant component reflecting time constant inequalities and/or stress adaptation phenomena.

Hydraulic conductivity of canine parietal pleura in vivo

1990 ◽  
Vol 69 (2) ◽  
pp. 438-442 ◽  
Author(s):  
D. Negrini ◽  
M. I. Townsley ◽  
A. E. Taylor
Keyword(s):  
Hydraulic Conductivity ◽  
Chest Wall ◽  
Body Position ◽  
Linear Regression Analysis ◽  
Isotonic Saline ◽  
Parietal Pleura ◽  
Autologous Plasma ◽  
Anesthetized Dogs ◽  
Spontaneously Breathing

The hydraulic conductivity (Lp) of the parietal pleura was measured in vivo in spontaneously breathing anesthetized dogs in either the supine (n = 8) or the prone (n = 7) position and in an excised portion of the chest wall in which the pleura and its adjacent tissue were intact (n = 3). A capsule was glued to the exposed parietal pleura after the intercostal muscles were removed. The capsule was filled with either autologous plasma or isotonic saline. Transpleural fluid flow (V) was measured at several transpleural hydrostatic pressures (delta P) from the rate of meniscus movement within a graduated pipette connected to the capsule. Delta P was defined as the measured difference between capsule and pleural liquid pressures. The Lp of the parietal pleura was calculated from the slope of the line relating V to delta P by use of linear regression analysis. Lp in vivo averaged 1.36 X 10(-3) +/- 0.45 X 10(-3) (SD) ml.h-1.cmH2O-1.cm-2, regardless of whether the capsule was filled with plasma or saline and irrespective of body position. This value was not significantly different from that measured in the excised chest wall preparation (1.43 X 10(-3) +/- 1.1 X 10(-3) ml.h-1.cmH2O-1.cm-2). The parietal pleura offers little resistance to transpleural protein movement, because there was no observed difference between plasma and saline. We conclude that because the Lp for intact parietal pleura and extrapleural interstitium is approximately 100 times smaller than that previously measured in isolated stripped pleural preparations, removal of parietal pleural results in a damaged preparation.

Decay of inspiratory muscle pressure during expiration in anesthetized cats

1983 ◽  
Vol 54 (2) ◽  
pp. 408-413 ◽  
Author(s):  
W. A. Zin ◽  
L. D. Pengelly ◽  
J. Milic-Emili
Keyword(s):  
Respiratory System ◽  
Time Course ◽  
Pentobarbital Sodium ◽  
Airway Occlusion ◽  
Inspiratory Muscles ◽  
Tracheal Pressure ◽  
Resistive Loads ◽  
The Moment ◽  
Spontaneously Breathing

In six spontaneously breathing anesthetized cats (pentobarbital sodium, 35 mg/kg) we studied the antagonistic pressure developed by the inspiratory muscles during expiration (PmusI). This was accomplished in two ways: 1) with our previously reported method (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 52: 1266–1271, 1982) based on the measurement of changes in lung volume and airflow during spontaneous expiration, together with determination of the total passive respiratory system elastance and resistance; and 2) measurement of the time course of changes in tracheal/pressure after airway occlusion at end inspiration, up to the moment when the inspiratory muscles become completely relaxed. The agreement between the two methods is generally good, both in the amplitude of PmusI and in its time course. We also applied the first method to spontaneous expirations through added linear resistive loads. These did not alter the relative decay of PmusI. Thus in anesthetized cats the braking action of the inspiratory muscles does not decrease when expiratory resistive loads are added, i.e., when such braking is clearly not required.

Pliometric activity of inspiratory muscles: maximal pressure-flow curves

1987 ◽  
Vol 62 (1) ◽  
pp. 322-327 ◽  
Author(s):  
G. P. Topulos ◽  
M. B. Reid ◽  
D. E. Leith
Keyword(s):  
Respiratory System ◽  
Flow Characteristics ◽  
Esophageal Pressure ◽  
Flow Curves ◽  
Reduced Pressure ◽  
Pressure Flow ◽  
Inspiratory Muscles ◽  
Airway Opening ◽  
Maximal Pressure ◽  
Force Velocity

We tested the hypothesis that inspiratory muscles, like other skeletal muscles, would exert greater force under pliometric conditions (being lengthened while active) than under isometric or miometric (active shortening) conditions. Maximal inspiratory pressure-flow curves of the respiratory system are analogous to the force-velocity curves for isolated muscle (Agostoni and Fenn, J. Appl. Physiol. 15:349–353, 1960). We measured esophageal pressure (Pes) and plethysmographic flow (V) at relaxation volume of the respiratory system in six trained subjects inspiring maximally through graded resistors (miometric), against a closed airway (isometric), and while constant expiratory flows were forced by a reduced pressure source at the airway opening (pliometric). Pes varied inversely with V and this trend continued into the pliometric range. In addition we found that the pressure-flow characteristics of the rib cage and of the abdomen are similar to those for the chest wall as a whole. The mechanical and energetic advantages of muscle activity under pliometric conditions may be available to some inspiratory muscles in both normal and pathological situations.

scholarly journals Effects of Pleural Effusion on Respiratory Function

2004 ◽  
Vol 11 (7) ◽  
pp. 499-503 ◽  
Author(s):  
I Mitrouska ◽  
M Klimathianaki ◽  
NM Siafakas
Keyword(s):  
Pleural Effusion ◽  
Pleural Fluid ◽  
Chest Wall ◽  
Respiratory System ◽  
Lung Volume ◽  
Respiratory Function ◽  
Elastic Equilibrium ◽  
Underlying Disease ◽  
Inspiratory Muscles ◽  
Ventilatory Effect

The accumulation of pleural effusion has important effects on respiratory system function. It changes the elastic equilibrium volumes of the lung and chest wall, resulting in a restrictive ventilatory effect, chest wall expansion and reduced efficiency of the inspiratory muscles. The magnitude of these alterations depends on the pleural fluid volume and the underlying disease of the respiratory system. The decrease in lung volume is associated with hypoxemia mainly due to an increase in right to left shunt. The drainage of pleural fluid results in an increase in lung volume that is considerably less than the amount of aspirated fluid, while hypoxemia is not readily reversible upon fluid aspiration.

Decay of inspiratory muscle pressure during expiration in conscious humans

1985 ◽  
Vol 58 (6) ◽  
pp. 1859-1865 ◽  
Author(s):  
C. D. Shee ◽  
Y. Ploy-Song-Sang ◽  
J. Milic-Emili
Keyword(s):  
Respiratory System ◽  
Elastic Energy ◽  
Relaxation Method ◽  
Inspiratory Muscle ◽  
Expiratory Time ◽  
Negative Work ◽  
Inspiratory Muscles ◽  
The Mean ◽  
Spontaneously Breathing ◽  
Mean Time

In eight conscious spontaneously breathing adults we studied the decay of pressure developed by the inspiratory muscles during expiration (PmusI). PmusI was obtained according to the following equation: PmusI(t) = Ers X V(t) - Rrs X V(t), where V is volume and V is flow at any instant t during spontaneous expiration, and Ers and Rrs are, respectively, the passive elastance and resistance of the total respiratory system. Ers was determined with the relaxation method, and resistance with the interrupter method. All subjects showed marked braking of expiratory flow by PmusI. The mean time for PmusI to reduce to 50 and 0% amounted, respectively, to 23 and 79% of expiratory time. During expiration, 24–55% of the elastic energy stored during inspiration was used as resistive work and the remainder (45–76%) as negative work.

Respiratory system, lung, and chest wall impedances in anesthetized dogs

1984 ◽  
Vol 57 (1) ◽  
pp. 34-39 ◽  
Author(s):  
A. C. Jackson ◽  
J. W. Watson ◽  
M. I. Kotlikoff
Keyword(s):  
Chest Wall ◽  
Respiratory System ◽  
Anesthetized Dogs

Stress relaxation of the respiratory system in developing piglets

1992 ◽  
Vol 73 (4) ◽  
pp. 1297-1309 ◽  
Author(s):  
J. J. Perez Fontan ◽  
A. O. Ray ◽  
T. R. Oxland
Keyword(s):  
Stress Relaxation ◽  
Chest Wall ◽  
Respiratory System ◽  
Time Course ◽  
Structural Changes ◽  
Somatic Growth ◽  
Viscoelastic Behavior ◽  
Elastic Recoil ◽  
Pressure Losses ◽  
Double Exponential

To characterize the effect of postnatal development on the viscoelastic behavior of the respiratory system, we quantified the amplitude and time course of stress relaxation in the lungs and chest wall of seven newborn and eight 8-wk-old anesthetized piglets. Stress relaxation was distinguished from other dissipative pressure losses by performing airway occlusions at various constant inspiratory flows and fitting the pressure decays that ensue during the occlusions to a double-exponential function. We found that the amplitude of stress relaxation related linearly to the increase in elastic recoil (and, by extension, in the volume) of the lungs, chest wall, and respiratory system during the inflations preceding the occlusions. On the average, the slope of this relationship was 38–44% lower in the 8-wk-old than in the newborn piglets for the lungs and was not different for the chest wall. The time course of stress relaxation, expressed as a time constant, was not influenced by age. Our results indicate that respiratory system viscoelasticity is sensitive to the geometric and structural changes experienced by the lungs during the period of rapid somatic growth that follow birth in most mammals.

Mechanics in rats by end-inflation occlusion and single-breath methods

1987 ◽  
Vol 63 (5) ◽  
pp. 1711-1718 ◽  
Author(s):  
P. H. Saldiva ◽  
W. V. Cardoso ◽  
M. P. Caldeira ◽  
W. A. Zin
Keyword(s):  
Chest Wall ◽  
Respiratory System ◽  
Constant Flow ◽  
Power Functions ◽  
Pressure Flow ◽  
Mean Values ◽  
Mechanically Ventilated ◽  
Pentobarbital Sodium ◽  
Single Breath ◽  
Wall Components

In six mechanically ventilated anesthetized (pentobarbital sodium, 30 mg/kg) paralyzed rats (187–253 g body wt) volume, airflow, and tracheal, esophageal, and transpulmonary pressures were measured. Respiratory system elastic and resistive properties were partitioned into their lung and chest wall components after end-inflation occlusion of the airways subsequent to constant-flow inspirations and during relaxed expiration ensuing release of occlusion. The values provided by both methods were similar. Mean respiratory system, lung, and chest wall elastances amounted to, respectively, 5.536, 3.440, and 2.097 cmH2O.ml-1. Mean values of intrinsic respiratory system, pulmonary, and chest wall resistances (at flows of 3.5 ml.s-1) were 0.235, 0.144, and 0.091 cmH2O.ml-1.s, respectively. Resistive pressure-flow relationships for the respiratory system, lung, and chest wall were also determined during the entire tidal expiration. A linear relationship was found for the former, whereas power functions best described the others: the pulmonary pressure-flow relationship exhibited an upward concavity and that for the chest wall presented an upward convexity.

Sign in / Sign up

Export Citation Format

Share Document