Effect of lung lavage on the stress relaxation of the respiratory system

1993 ◽  
Vol 75 (4) ◽  
pp. 1536-1544 ◽  
Author(s):  
J. J. Perez Fontan
Keyword(s):  
Stress Relaxation ◽  
Respiratory System ◽  
Time Course ◽  
Lung Lavage ◽  
Elastic Recoil ◽  
Lung Inflation ◽  
Pressure Losses ◽  
Elastic Stresses ◽  
Double Exponential ◽  
Before And After

To test the hypothesis that lowering the concentrations of surfactant molecules at the gas-liquid interface increases viscoelastic dissipation in the lungs, the amplitude and time course of stress relaxation were quantified before and after lavage of the lungs with warm saline in five newborn and five 8-wk-old anesthetized piglets. Stress relaxation was separated from other dissipative pressure losses by fitting the pressure decays that follow airway occlusions performed during a period of constant inspiratory flow to a double-exponential regression. The amplitude of stress relaxation (defined by the term of the regression with the longest time constant) related linearly to the changes in respiratory system volume and elastic recoil preceding the occlusions both before and after the lavage. Lung lavage increased the slope of both relationships without altering the time course of the relaxations. In addition to being consistent with the proposed hypothesis, these results suggest that viscoelastic pressure losses remain linked to the elastic stresses generated during lung inflation, as proposed by Fredberg and Stamenovic's structural dumping theory (J. Appl. Physiol. 67: 2408#x2013;2419, 1989).

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.

scholarly journals Lung elastic recoil during breathing at increased lung volume

1999 ◽  
Vol 87 (4) ◽  
pp. 1491-1495 ◽  
Author(s):  
Joseph R. Rodarte ◽  
Gassan Noredin ◽  
Charles Miller ◽  
Vito Brusasco ◽  
Riccardo Pellegrino ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Tidal Volume ◽  
Lung Volume ◽  
Normal Subjects ◽  
Dynamic Hyperinflation ◽  
Airway Closure ◽  
Elastic Recoil ◽  
Volume Increase ◽  
Before And After ◽  
Residual Capacity

During dynamic hyperinflation with induced bronchoconstriction, there is a reduction in lung elastic recoil at constant lung volume (R. Pellegrino, O. Wilson, G. Jenouri, and J. R. Rodarte. J. Appl. Physiol. 81: 964–975, 1996). In the present study, lung elastic recoil at control end inspiration was measured in normal subjects in a volume displacement plethysmograph before and after voluntary increases in mean lung volume, which were achieved by one tidal volume increase in functional residual capacity (FRC) with constant tidal volume and by doubling tidal volume with constant FRC. Lung elastic recoil at control end inspiration was significantly decreased by ∼10% within four breaths of increasing FRC. When tidal volume was doubled, the decrease in computed lung recoil at control end inspiration was not significant. Because voluntary increases of lung volume should not produce airway closure, we conclude that stress relaxation was responsible for the decrease in lung recoil.

Changes in regional lung impedance after intravenous histamine bolus in dogs: effects of lung volume

1995 ◽  
Vol 78 (3) ◽  
pp. 875-880 ◽  
Author(s):  
Z. Balassy ◽  
M. Mishima ◽  
J. H. Bates
Keyword(s):  
Lung Volume ◽  
Time Course ◽  
Lung Inflation ◽  
Lung Elastance ◽  
Airway Narrowing ◽  
Tracheal Pressure ◽  
Lung Resistance ◽  
Regional Lung ◽  
Before And After ◽  
Induced Changes

We measured the effect of lung volume on the time course of regional lung input impedance (ZA) after bolus intravenous administration of 2 mg of histamine in seven open-chest dogs using alveolar capsule oscillators. ZA (24–200 Hz) was obtained during apnea at constant lung volume every 2 s for 80 s at lung inflation pressures of 0.1, 0.2, 0.3, 0.5, 0.7, and 1.0 kPa. Local airway resistance (RA) and elastance of the local lung region were calculated by fitting a four-parameter model to the measured ZA. Total lung resistance and lung elastance were also calculated from tracheal pressure and flow measured during mechanical ventilation (0.3 Hz) just before and after each set of ZA measurements. We found the histamine-induced changes in both lung resistance and lung elastance to decrease with increasing lung volume. RA also showed a large negative dependency on lung volume, and the variation between different RA measurements became markedly increased as lung volume decreased. In contrast, local airway elastance was essentially unaffected by lung volume. These results support the idea that parenchymal tethering of the very distal airways impedes their narrowing during bronchoconstriction. They also indicate that reduced parenchymal tethering causes airway narrowing to become markedly more inhomogeneous.

Volume-time profile during relaxed expiration in the normal dog

1985 ◽  
Vol 59 (3) ◽  
pp. 732-737 ◽  
Author(s):  
J. H. Bates ◽  
M. Decramer ◽  
D. Chartrand ◽  
W. A. Zin ◽  
A. Boddener ◽  
...  
Keyword(s):  
Respiratory System ◽  
Time Course ◽  
Elastic Equilibrium ◽  
Esophageal Pressure ◽  
Time Profile ◽  
Time Interval ◽  
Opening Pressure ◽  
Lung Inflation ◽  
Volume Comparison ◽  
Airway Opening

Airway opening pressure, esophageal pressure, and flow were obtained during relaxed expirations in two normal anesthetized paralyzed dogs. The signal-to-noise ratio in the flow signals was greatly increased by averaging 10 different signals obtained with the same lung inflation volume. Numerical integration of an averaged flow signal then yielded the time course of the volume of the respiratory system above functional residual capacity (the elastic equilibrium volume). Comparison of volume signals obtained with different inflation volumes suggests that the resistance of the respiratory system increases with flow. The flow-volume and semilog volume curves show that expiration is induced by two apparently separate mechanisms: one causes emptying of most of the expired volume over a time interval of much less than 1 s, whereas the other contributes a relatively small amount to the expired volume over a significantly longer time (greater than or equal to 1 s). We postulate the first mechanism to be due to that of the respiratory system behaving like a single unit, with an elastance that is slightly volume dependent, emptying through a single airway which has a resistance that increases with flow. From the nature of airway opening pressure and esophageal pressure measured after occlusion in midexpiration, we conclude that the second mechanism is due to the viscoelastic properties (i.e., creep) of the respiratory system. The properties are manifest mainly in the chest wall.

Preliminary Evaluation of a Weibull Function for Fitting Slow-Component Eye Velocity over the Time Course of Caloric-Induced Nystagmus

1989 ◽  
Vol 32 (3) ◽  
pp. 681-687 ◽  
Author(s):  
C. Formby ◽  
B. Albritton ◽  
I. M. Rivera
Keyword(s):  
Time Course ◽  
Slow Component ◽  
Weibull Function ◽  
Preliminary Evaluation ◽  
Mathematical Function ◽  
Before And After ◽  
Best Fitting ◽  
Eye Velocity ◽  
Fitting Parameters ◽  
Weibull Equation

We describe preliminary attempts to fit a mathematical function to the slow-component eye velocity (SCV) over the time course of caloric-induced nystagmus. Initially, we consider a Weibull equation with three parameters. These parameters are estimated by a least-squares procedure to fit digitized SCV data. We present examples of SCV data and fitted curves to show how adjustments in the parameters of the model affect the fitted curve. The best fitting parameters are presented for curves fit to 120 warm caloric responses. The fitting parameters and the efficacy of the fitted curves are compared before and after the SCV data were smoothed to reduce response variability. We also consider a more flexible four-parameter Weibull equation that, for 98% of the smoothed caloric responses, yields fits that describe the data more precisely than a line through the mean. Finally, we consider advantages and problems in fitting the Weibull function to caloric data.

scholarly journals Measuring phenotypic flexibility by transcriptome time‐course analyses during challenge tests before and after energy restriction

2019 ◽  
Vol 33 (9) ◽  
pp. 10280-10290 ◽  
Author(s):  
Inge P. G. Bussel ◽  
Parastoo Fazelzadeh ◽  
Gary S. Frost ◽  
Milena Rundle ◽  
Lydia A. Afman
Keyword(s):  
Time Course ◽  
Energy Restriction ◽  
Phenotypic Flexibility ◽  
Before And After ◽  
Challenge Tests

scholarly journals Performance of a capnodynamic method estimating cardiac output during respiratory failure - before and after lung recruitment

2019 ◽  
Vol 34 (6) ◽  
pp. 1199-1207
Author(s):  
Thorir Svavar Sigmundsson ◽  
Tomas Öhman ◽  
Magnus Hallbäck ◽  
Eider Redondo ◽  
Fernando Suarez Sipmann ◽  
...  
Keyword(s):  
Cardiac Output ◽  
Respiratory Failure ◽  
Reference Method ◽  
Hemodynamic Instability ◽  
Lung Lavage ◽  
Lung Recruitment ◽  
Recruitment Manoeuvre ◽  
Percentage Error ◽  
Before And After ◽  
The Right

AbstractRespiratory failure may cause hemodynamic instability with strain on the right ventricle. The capnodynamic method continuously calculates cardiac output (CO) based on effective pulmonary blood flow (COEPBF) and could provide CO monitoring complementary to mechanical ventilation during surgery and intensive care. The aim of the current study was to evaluate the ability of a revised capnodynamic method, based on short expiratory holds (COEPBFexp), to estimate CO during acute respiratory failure (LI) with high shunt fractions before and after compliance-based lung recruitment. Ten pigs were submitted to lung lavage and subsequent ventilator-induced lung injury. COEPBFexp, without any shunt correction, was compared to a reference method for CO, an ultrasonic flow probe placed around the pulmonary artery trunk (COTS) at (1) baseline in healthy lungs with PEEP 5 cmH2O (HLP5), (2) LI with PEEP 5 cmH2O (LIP5) and (3) LI after lung recruitment and PEEP adjustment (LIPadj). CO changes were enforced during LIP5 and LIPadj to estimate trending. LI resulted in changes in shunt fraction from 0.1 (0.03) to 0.36 (0.1) and restored to 0.09 (0.04) after recruitment manoeuvre. Bias (levels of agreement) and percentage error between COEPBFexp and COTS changed from 0.5 (− 0.5 to 1.5) L/min and 30% at HLP5 to − 0.6 (− 2.3 to 1.1) L/min and 39% during LIP5 and finally 1.1 (− 0.3 to 2.5) L/min and 38% at LIPadj. Concordance during CO changes improved from 87 to 100% after lung recruitment and PEEP adjustment. COEPBFexp could possibly be used for continuous CO monitoring and trending in hemodynamically unstable patients with increased shunt and after recruitment manoeuvre.

Preoperative and postoperative cognitive functioning in patients with frontal meningiomas

2003 ◽  
Vol 98 (1) ◽  
pp. 21-31 ◽  
Author(s):  
Oliver Tucha ◽  
Christian Smely ◽  
Michael Preier ◽  
Georg Becker ◽  
Geraldine M. Paul ◽  
...  
Keyword(s):  
Executive Functions ◽  
Cognitive Functioning ◽  
Time Course ◽  
Lesion Size ◽  
Test Battery ◽  
Surgical Removal ◽  
Specific Information ◽  
Content Type ◽  
Before And After ◽  
Fine Print

Object. There is presently no specific information available concerning the nature and course of cognitive deficits caused by intracranial meningiomas. In this prospective study the authors examined the cognitive functioning of patients with frontal meningiomas. Methods. Fifty-four patients with frontal meningiomas were examined neuropsychologically before and after neurosurgery. The test battery consisted of standardized instruments including those assessing memory, attention, visuoconstructive abilities, and executive functions. The time period between pre-and postoperative assessment ranged from 4 to 9 months. The patients' performance was compared with the results in 54 healthy adults who were also assessed twice by using the same test battery in a period ranging from 4 to 9 months. In addition, the effect on cognition of meningioma lateralization, localization, lesion size, edema, brain compression, time course, and the occurrence of preoperative seizures was analyzed. Conclusions. Except in the case of working memory, comparisons of pre- and postoperative assessments of cognition revealed no differences in memory, visuoconstructive abilities, or executive functions, although a postoperative improvement in attentional functions was observed. The results of this study indicate that the surgical removal of frontal meningiomas does not impair patients' cognitive functioning. Furthermore, improvements in attentional functions may occur in these patients.

Mechanics of respiratory system in healthy anesthetized humans with emphasis on viscoelastic properties

1993 ◽  
Vol 75 (1) ◽  
pp. 132-140 ◽  
Author(s):  
B. Jonson ◽  
L. Beydon ◽  
K. Brauer ◽  
C. Mansson ◽  
S. Valind ◽  
...  
Keyword(s):  
Respiratory System ◽  
Driving Force ◽  
Viscoelastic Behavior ◽  
Elastic Recoil ◽  
Inspiratory Flow Rate ◽  
Static Compliance ◽  
Viscoelastic System ◽  
Flow Interruption ◽  
In Series ◽  
Flow Dependency

The classic model of the respiratory system (RS) is comprised of a Newtonian resistor in series with a capacitor and a viscoelastic unit including a resistor and a capacitor. The flow interruption technique has often been used to study the viscoelastic behavior under constant inspiratory flow rate. To study the viscoelastic behavior of the RS during complete respiratory cycles and to quantify viscoelastic resistance (Rve) and compliance (Cve) under unrestrained conditions, we developed an iterative technique based on a differential equation. We, as others, assumed Rve and Cve to be constant, which concords with volume and flow dependency of model behavior. During inspiration Newtonian resistance (R) was independent of flow and volume. During expiration R increased. Static elastic recoil showed no significant hysteresis. The viscoelastic behavior of the RS was in accordance with the model. The magnitude of Rve was 3.7 +/- 0.7 cmH2O.l-1 x s, i.e., two times R. Cve was 0.23 +/- 0.051 l/cmH2O, i.e., four times static compliance. The viscoelastic time constant, i.e., Cve.Rve, was 0.82 +/- 0.11s. The work dissipated against the viscoelastic system was 0.62 +/- 0.13 cmH2O x 1 for a breath of 0.56 liter, corresponding to 32% of the total energy loss within the RS. Viscoelastic recoil contributed as a driving force during the initial part of expiration.

Respiratory mechanics in supine subjects during progressive partial curarization

1982 ◽  
Vol 52 (1) ◽  
pp. 57-63 ◽  
Author(s):  
T. J. Gal ◽  
N. S. Arora
Keyword(s):  
Muscle Strength ◽  
Muscle Weakness ◽  
Respiratory Mechanics ◽  
Handgrip Strength ◽  
Elastic Recoil ◽  
Lung Inflation ◽  
Progressive Muscle Weakness ◽  
Inspiratory Resistance ◽  
Residual Capacity ◽  
Partial Curarization

Respiratory mechanics were studied in six supine conscious volunteers during progressive muscle weakness produced by infusion of d-tubocurarine. Partial curarization was carried out to the point of abolishing head lift ability and handgrip strength. At all levels of partial paralysis, expiratory muscle strength was significantly more impaired than inspiratory strength. Despite this, subjects maintained relatively normal maximal expiratory flow rates, whereas inspiratory flows decreased significantly. The diminished inspiratory flows are not fully explained by decreased driving pressures during force inspiration, since inspiratory resistance increased significantly with the decreased flow. Inspiratory flow patterns suggest a variable extrathoracic obstruction most likely due to the absence of normal airway abductor activity during inspiration. Maximal respiratory muscle weakness decreased forced vital capacity by 29% and total lung capacity by 15%. The decreased level of lung inflation did not alter lung elastic recoil. Functional residual capacity was unchanged, but inspiratory capacity decreased by 25% and residual volume increased by 38%. These changes are in accord with predictions based on the decreased muscle strength and normal respiratory system recoil.

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