Comparison of the shear modulus of mature and immature rabbit lungs

1999 ◽  
Vol 87 (2) ◽  
pp. 711-714 ◽  
Author(s):  
Robert S. Tepper ◽  
Barry Wiggs ◽  
Susan J. Gunst ◽  
Peter D. Paré
Keyword(s):  
Shear Modulus ◽  
Bulk Modulus ◽  
Transpulmonary Pressure ◽  
Lung Parenchyma ◽  
Local Deformation ◽  
Mean Value ◽  
Airway Narrowing ◽  
Significant Difference ◽  
Muscle Shortening ◽  
Immature Lung

Maximal airway narrowing during bronchoconstriction is greater in immature than in mature rabbits. At a given transpulmonary pressure (Pl), the lung parenchyma surrounding the airway resists local deformation and provides a load that opposes airway smooth muscle shortening. We hypothesized that the force required to produce lung parenchymal deformation, quantified by the shear modulus, is lower in immature rabbit lungs. The shear modulus and the bulk modulus were measured in isolated mature ( n = 8; 6 mo) and immature ( n = 9; 3 wk) rabbit lungs at Pl of 2, 4, 6, 8, and 10 cmH2O. The bulk modulus increased with increasing Pl for mature and immature lungs; however, there was no significant difference between the groups. The shear modulus was lower for the immature than the mature lungs ( P < 0.025), progressively increasing with increasing Pl( P < 0.001) for both groups, and there was no difference between the slopes for shear modulus vs. Pl for the mature and the immature lungs. The mean value of the shear modulus for mature and immature rabbit lungs at Pl = 6 cmH2O was 4.5 vs. 3.8 cmH2O. We conclude that the shear modulus is less in immature than mature rabbit lungs. This small maturational difference in the shear modulus probably does not account for the greater airway narrowing in the immature lung, unless its effect is coupled with a relatively thicker and more compliant airway wall in the immature animal.

scholarly journals Lung parenchymal shear modulus, airway wall remodeling, and bronchial hyperresponsiveness

1997 ◽  
Vol 83 (1) ◽  
pp. 140-147 ◽  
Author(s):  
Rodney K. Lambert ◽  
Peter D. Paré
Keyword(s):  
Smooth Muscle ◽  
Shear Modulus ◽  
Airway Remodeling ◽  
Bronchial Hyperresponsiveness ◽  
Lung Parenchyma ◽  
Wall Thickening ◽  
Forced Expiration ◽  
Airway Wall ◽  
Airway Narrowing ◽  
Muscle Shortening

Lambert, Rodney K., and Peter D. Paré. Lung parenchymal shear modulus, airway wall remodeling, and bronchial hyperresponsiveness. J. Appl. Physiol.83(1): 140–147, 1997.—When airways narrow, either through the action of smooth muscle shortening or during forced expiration, the lung parenchyma is locally distorted and provides an increased peribronchial stress that resists the narrowing. Although this interdependence has been well studied, the quantitative significance of airway remodeling to interdependence has not been elucidated. We have used an improved computational model of the bronchial response to smooth muscle agonists to investigate the relationships between airway narrowing (as indicated by airway resistance), parenchymal shear modulus, adventitial thickening, and inner wall thickening at lung recoil pressures of 4, 5, and 8 cmH2O. We have found that, at low recoil pressures, decreases in parenchymal shear modulus have a significant effect that is comparable to that of moderate thickening of the airway wall. At higher lung recoil pressures, the effect is negligible.

Surface forces in lungs. III. Alveolar surface tension and elastic properties of lung parenchyma

1986 ◽  
Vol 60 (4) ◽  
pp. 1358-1362 ◽  
Author(s):  
D. Stamenovic ◽  
J. C. Smith
Keyword(s):  
Surface Tension ◽  
Shear Modulus ◽  
Bulk Modulus ◽  
Qualitative Difference ◽  
Transpulmonary Pressure ◽  
Lung Parenchyma ◽  
Shear Moduli ◽  
Wide Range ◽  
Physiological Values ◽  
Alveolar Surface

The bulk modulus and the shear modulus describe the capacity of material to resist a change in volume and a change of shape, respectively. The values of these elastic coefficients for air-filled lung parenchyma suggest that there is a qualitative difference between the mechanisms by which the parenchyma resists expansion and shear deformation; the bulk modulus changes roughly exponentially with the transpulmonary pressure, whereas the shear modulus is nearly a constant fraction of the transpulmonary pressure for a wide range of volumes. The bulk modulus is approximately 6.5 times as large as the shear modulus. In recent microstructural modeling of lung parenchyma, these mechanisms have been pictured as being similar to the mechanisms by which an open cell liquid foam resists deformations. In this paper, we report values for the bulk moduli and the shear moduli of normal air-filled rabbit lungs and of air-filled lungs in which alveolar surface tension is maintained constant at 16 dyn/cm. Elevating surface tension above normal physiological values causes the bulk modulus to decrease and the shear modulus to increase. Furthermore, the bulk modulus is found to be sensitive to a dependence of surface tension on surface area, but the shear modulus is not. These results agree qualitatively with the predictions of the model, but there are quantitative differences between the data and the model.

Comparison of elastic properties and contractile responses of isolated airway segments from mature and immature rabbits

2003 ◽  
Vol 95 (1) ◽  
pp. 265-271 ◽  
Author(s):  
R. Ramchandani ◽  
X. Shen ◽  
S. J. Gunst ◽  
R. S. Tepper
Keyword(s):  
Mechanical Properties ◽  
Shear Modulus ◽  
Elastic Properties ◽  
Lung Parenchyma ◽  
Structure And Function ◽  
Airway Narrowing ◽  
Lower Shear ◽  
And Function ◽  
Immature Lung

Immature rabbits have greater maximal airway narrowing with bronchoconstriction in vivo compared with mature animals. As isolated immature lungs have a lower shear modulus, it is unclear whether the greater airway narrowing in the immature lung is secondary to less tethering between the airways and the lung parenchyma or to differences in the mechanical properties of the mature and immature airways. In the present study, we compared the mechanical properties of fluid-filled, isolated, intraparenchymal airway segments of the same generation from mature and immature rabbits. Stimulation with ACh resulted in greater airway narrowing in immature than mature bronchi. The immature bronchi were more compliant, had a lower resting airway volume, and were more collapsible compared with the mature bronchi. When the airways were contracted with ACh under isovolume conditions, the immature bronchi generated greater active pressure, and they were more sensitive to ACh than were mature bronchi. Our results suggest that maturational differences in the structure and function of the airways in the absence of the lung parenchyma can account for the greater maximal narrowing of immature than mature airways in vivo.

Strain-induced growth of the immature lung

1996 ◽  
Vol 81 (4) ◽  
pp. 1471-1476 ◽  
Author(s):  
Shaoping Zhang ◽  
Vicki Garbutt ◽  
John T. McBride
Keyword(s):  
Total Lung Capacity ◽  
Mechanical Strain ◽  
Lung Parenchyma ◽  
Control Group ◽  
Study Group ◽  
Lung Growth ◽  
Lung Weight ◽  
Lung Capacity ◽  
Significant Difference ◽  
Immature Lung

Zhang, Shaoping, Vicki Garbutt, and John T. McBride.Strain-induced growth of the immature lung. J. Appl. Physiol. 81(4): 1471–1476, 1996.—To investigate the relationship between strain and postnatal lung growth, two groups of weanling ferrets were tracheotomized: the study group was exposed for 2 wk to a continuous positive airway pressure (CPAP) of 6 cmH2O and the other group was exposed to atmospheric pressure (control). Total lung capacity after 2 wk was ∼40% higher in the CPAP-exposed animals than in the control animals ( n = 19 for the control group and 18 for the study group; P < 0.01). CPAP exposure was also associated with increases in lung weight and total lung protein and DNA contents. Lung recoil, measured in a subgroup of animals, was characterized by air-filled and saline-filled static expiratory pressure-volume curves. Neither in the air-filled lungs nor in the saline-filled lungs was there a significant difference between CPAP-exposed and control animals in lung recoil at equal fractions of total lung capacity. These data indicate that mechanical strain was associated with an acceleration of lung growth in immature ferrets. The preservation of volume-corrected lung recoil and the expected contribution of surface forces and tissue forces to lung recoil in CPAP-exposed animals suggest that this response did not involve simple lung distension but included a remodeling of the lung parenchyma.

Placental elastography in second trimester preeclampsia prediction: A prospective study

Ultrasound ◽  
2021 ◽  
pp. 1742271X2110405
Author(s):  
Rajkumar Meena ◽  
Amita Malik ◽  
Swarna Jain ◽  
Achla Batra
Keyword(s):  
Shear Modulus ◽  
Shear Wave ◽  
Predictive Value ◽  
Shear Wave Elastography ◽  
Mean Value ◽  
Diagnostic Potential ◽  
Significant Difference ◽  
Group A ◽  
The Mean ◽  
Group B

Objective The aim of the study was to evaluate the diagnostic potential of placental shear wave elastography in predicting preeclampsia at 16 to 20 weeks of gestation. Materials and methods A total of 230 pregnant women between 16 and 20 weeks of gestation were observed for the study. These women underwent shear wave elastography ElastPQ (Philips Healthcare, Bothell, Washington, USA) of the placenta. The mean value of placental shear modulus was obtained for each participant. These participants were followed up for the development of preeclampsia and were divided into two groups; group A included those who developed preeclampsia and group B included those who remained normotensive until delivery. The elasticity values of the two groups were compared, and the ROC curve was drawn to obtain the best cut-off value that would predict the onset of preeclampsia. Results Placental shear modulus varied from 1.03 kPa to 7.4 kPa at 16 to 20 weeks of gestation with an average of 2.74 ± 0.87 kPa. There was a statistically significant difference in the mean value of elasticity between two groups, being 4.61 kPa in group A and 2.51 kPa in group B. Maximum diagnostic accuracy was obtained at 2.9667 kPa with area under the curve 0.970, sensitivity 92%, specificity 91.71%, positive predictive value 57.5% and negative predictive value 98.9%. Conclusion Stiffness of placenta, quantitatively measured by SWE at 16 to 20 weeks of gestation, is higher in the women who develop preeclampsia and hence may be used for predicting preeclampsia.

Airway wall dimensions during carbachol-induced bronchoconstriction in rabbits

1996 ◽  
Vol 81 (4) ◽  
pp. 1578-1583 ◽  
Author(s):  
F. Sasaki ◽  
Y. Saitoh ◽  
L. Verburgt ◽  
M. Okazawa
Keyword(s):  
Smooth Muscle ◽  
Freeze Substitution ◽  
Transpulmonary Pressure ◽  
Muscle Layer ◽  
Airway Wall ◽  
En Bloc ◽  
Airway Narrowing ◽  
Wall Area ◽  
Peripheral Airways ◽  
Muscle Shortening

Sasaki, F., Y. Saitoh, L. Verburgt, and M. Okazawa.Airway wall dimensions during carbachol-induced bronchoconstriction in rabbits. J. Appl. Physiol. 81(4): 1578–1583, 1996.—Airway wall area is an important determinant of airway narrowing. We hypothesized that in cross-sectioned peripheral airways, the wall area internal to the outer smooth muscle border (inner wall area) would decrease and the airway wall area external to the outer smooth the muscle layer (adventitial area) would increase during bronchoconstriction because of the relocation of blood and/or fluid between these compartments. To test this hypothesis, we used anesthetized open-chest rabbits and measured airway wall dimensions and smooth muscle shortening of membranous airways after carbachol-induced bronchoconstriction using morphometric techniques. Acute (3-min) and sustained (40-min) bronchoconstriction was induced by aerosol nebulization of carbachol and compared with saline treatment. After physiological measurements, the heart base was snared, and the lung and heart were excised en bloc and frozen by using liquid nitrogen while a transpulmonary pressure of 2 cmH2O was maintained. The lung was processed for light-microscopic examination by using a freeze substitution technique. Results show that adventitial area was significantly decreased after sustained but not acute bronchoconstriction. The mechanism of this change, which contradicts our hypothesis, is unclear. However, the decrease of adventitial area could increase rather than decrease the effect of lung parenchymal tethering and attenuate airway narrowing.

Behavior of artificially produced holes in lung parenchyma

1977 ◽  
Vol 43 (4) ◽  
pp. 648-655 ◽  
Author(s):  
S. J. Lai-Fook ◽  
R. E. Hyatt ◽  
J. R. Rodarte ◽  
T. A. Wilson
Keyword(s):  
Shear Modulus ◽  
Continuum Mechanics ◽  
Transpulmonary Pressure ◽  
Lung Parenchyma ◽  
Volume Curve ◽  
Pressure Volume Curve ◽  
Mechanics Analysis ◽  
Cylindrical Holes ◽  
Hole Boundary ◽  
Lung Lobes

Spherical and cylindrical holes were cut in the parenchyma of isolated dog lung lobes. The holes were insufflated with tantalum dust and the hole diameters were measured along the deflation limb of the lobe pressure-volume curve from transpulmonary pressures of 20 to 0 cmH2O. Hole volume as a fraction of lobe volume was found to be independent of transpulmonary pressure. The hole volume relative to the amount of tissue removed was used to determine the displacement at the hole boundary. A comparison of this displacement with the displacement predicted by a continuum mechanics analysis provides evidence for the applicability of the methods of continuum mechanics and further evidence that the shear modulus of the parenchyma is relatively small.

Detection of Circulating Tissue Factor and Factor VII in a Normal Population

1996 ◽  
Vol 75 (05) ◽  
pp. 772-777 ◽  
Author(s):  
Sybille Albrecht ◽  
Matthias Kotzsch ◽  
Gabriele Siegert ◽  
Thomas Luther ◽  
Heinz Großmann ◽  
...  
Keyword(s):  
Tissue Factor ◽  
Normal Population ◽  
Mean Value ◽  
Factor Vii ◽  
Significant Difference ◽  
Age Dependent ◽  
The Mean ◽  
Highly Correlated ◽  
And Gender

SummaryThe plasma tissue factor (TF) concentration was correlated to factor VII concentration (FVIIag) and factor VII activity (FVIIc) in 498 healthy volunteers ranging in age from 17 to 64 years. Immunoassays using monoclonal antibodies (mAbs) were developed for the determination of TF and FVIIag in plasma. The mAbs and the test systems were characterized. The mean value of the TF concentration was 172 ± 135 pg/ml. TF showed no age- and gender-related differences. For the total population, FVIIc, determined by a clotting test, was 110 ± 15% and the factor VIlag was 0.77 ± 0.19 μg/ml. FVII activity was significantly increased with age, whereas the concentration demonstrated no correlation to age in this population. FVII concentration is highly correlated with the activity as measured by clotting assay using rabbit thromboplastin. The ratio between FVIIc and FVIIag was not age-dependent, but demonstrated a significant difference between men and women. Between TF and FVII we could not detect a correlation.

Risk Factors in Diabetes and Pregnant Women with Urinary Tract Infections Compared to Younger Aged Female.

2018 ◽  
Vol 1 (3) ◽  
pp. 26-38
Author(s):  
Abdulghani Mohamed Alsamarai ◽  
Shler Ali Khorshed
Keyword(s):  
Risk Factors ◽  
Urinary Tract Infection ◽  
Urinary Tract ◽  
Tract Infection ◽  
Pregnant Women ◽  
Female Student ◽  
Mean Value ◽  
Infected Female ◽  
Significant Difference ◽  
Tract Infections

Background: Urinary tract infection is common with health impact in women and characterised by failure to treatment and recurrent episodes. Aim: This study was conducted to determine the risk factors for the development of urinary tract infection in diabetic and pregnant women in comparison to student female. Materials and methods: A prospective cross-sectional study conducted during the period from 1st of June 2015 to the end of January 2016. The population included in the study are 563 women, of them 425 were outpatients, and 138 were inpatients. Their age range between 18 and 80 years, with a mean age of 33.59±15.29 years. Urine samples collected and cultured on blood agar and MacConkey agar by spread plate technique. Bacterial colonies with different morphology were selected, purified and identified according to their biochemical characteristics using conventional standard methods. Results: In diabetic women, there were no significant difference in mean age and BMI values between culture positive and culture negative groups. However, pus cell mean scale was significantly higher [P=0.000] in women with urinary tract infection [1.76±1.25] than in those with negative culture [0.69±1.00]. In pregnant women, BMI mean value was significantly [P=0.013] lower in pregnant women with UTI [26.14] as compared to those without infection [26.99]. Pus cell scale mean value was significantly [P=0.000] higher in pregnant women with UTI [1.55] than women with negative UTI [0.85]. While there was no significant difference in mean age between UTI positive and negative pregnant women. In female student, there was a significant difference between UTI infected and non-infected in mean age [P=0.041] and pus cell scale [P=0.000]. However, BMI was not significantly different between infected and non-infected female student. Other risk factors association are variables in the 3 groups when analysed using X2, while AUC and OR show different trends of association between risk factors and UTI. Conclusion: BMI, pus cell scale, child number, delivery method, operation history and hospital setting were significantly associated with culture positivity in the 3 studied groups as determined by AUC. While OR confirmed association with pus sale scale in the 3 groups.

A new simpler approach to measure the strength of toe plantar flexion requiring no mechanical restraint with a light-weight device

2021 ◽  
pp. 095441192110029
Author(s):  
Yuko Komuro ◽  
Yuji Ohta
Keyword(s):  
Plantar Flexion ◽  
Mean Value ◽  
Simple Approach ◽  
Light Weight ◽  
New Approach ◽  
Mean Values ◽  
Mechanical Restraint ◽  
Significant Difference ◽  
Ankle Joints ◽  
The Mean

Conventionally, the strength of toe plantar flexion (STPF) is measured in a seated position, in which not only the target toe joints but also the knee and particularly ankle joints, are usually restrained. We have developed an approach for the measurement of STPF which does not involve restraint and considers the interactions of adjacent joints of the lower extremities. This study aimed to evaluate this new approach and comparing with the seated approach. A thin, light-weight, rigid plate was attached to the sole of the foot in order to immobilize the toe area. Participants were 13 healthy young women (mean age: 24 ± 4 years). For measurement of STPF with the new approach, participants were instructed to stand, raise the device-wearing leg slightly, plantar flex the ankle, and push the sensor sheet with the toes to exert STPF. The sensor sheet of the F-scan II system was inserted between the foot sole and the plate. For measurement with the seated approach, participants were instructed to sit and push the sensor with the toes. They were required to maintain the hip, knee, and ankle joints at 90°. The mean values of maximum STPF of the 13 participants obtained with each approach were compared. There was no significant difference in mean value of maximum STPF when the two approaches were compared (new: 59 ± 23 N, seated: 47 ± 33 N). The coefficient of variation of maximum STPF was smaller for data obtained with the new approach (new: 39%, seated: 70%). Our simple approach enables measurement of STPF without the need for the restraints that are required for the conventional seated approach. These results suggest that the new approach is a valid method for measurement of STPF.

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