Trapped air in ventilated excised rat lungs

1976 ◽  
Vol 40 (6) ◽  
pp. 915-922 ◽  
Author(s):  
D. G. Frazer ◽  
K. C. Weber
Keyword(s):  
Stress Relaxation ◽  
Flow Rate ◽  
Lung Volume ◽  
Transpulmonary Pressure ◽  
Maximum Pressure ◽  
Lung Inflation ◽  
Minimum Pressure ◽  
Trapped Air ◽  
Rat Lungs ◽  
Reference Pressure

Degassed excised rat lungs were ventilated in a water-filled plethysmograph with the carina as the zero pressure reference. Pressure-volume curves were recorded from a minimum transpulmonary pressure (Pmin) of -5 cmH2O to a maximum pressure (Pmin) of 30 cmH2O. An index of the minimun volume for the lung (Vm) divided by the maximum lung volume for the same cycle (Vmax) was used as an index of the amount of air trapped within the lung. As the flow rate was decreased from 38.2 to 1.9 ml/min, there were significant increases in the amount of air trapped in the lung. As the maximum pressure was decreased to 25 and 20 cmH2O, or the minimum pressure was increased to 6 and 11 cmH2O, the amount of trapped air in the lung significantly decreased. The rate of lung inflation had a much greater influence on the amount of trapped air than either the deflation rate or stress relaxation. The results are consistent with the theory that bubbles are formed during inflation and are the main cause of air trapped in the excised lung.

High lung volume increases stress failure in pulmonary capillaries

1992 ◽  
Vol 73 (1) ◽  
pp. 123-133 ◽  
Author(s):  
Z. Fu ◽  
M. L. Costello ◽  
K. Tsukimoto ◽  
R. Prediletto ◽  
A. R. Elliott ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Lung Volume ◽  
Autologous Blood ◽  
Physiological Mechanism ◽  
Transpulmonary Pressure ◽  
Lung Volumes ◽  
Lung Inflation ◽  
Pulmonary Capillaries ◽  
Scanning Electron

We previously showed that when pulmonary capillaries in anesthetized rabbits are exposed to a transmural pressure (Ptm) of approximately 40 mmHg, stress failure of the walls occurs with disruption of the capillary endothelium, alveolar epithelium, or sometimes all layers. The present study was designed to test whether stress failure occurred more frequently at high than at low lung volumes for the same Ptm. Lungs of anesthetized rabbits were inflated to a transpulmonary pressure of 20 cmH2O, perfused with autologous blood at 32.5 or 2.5 cmH2O Ptm, and fixed by intravascular perfusion. Samples were examined by both transmission and scanning electron microscopy. The results were compared with those of a previous study in which the lung was inflated to a transpulmonary pressure of 5 cmH2O. There was a large increase in the frequency of stress failure of the capillary walls at the higher lung volume. For example, at 32.5 cmH2O Ptm, the number of endothelial breaks per millimeter cell lining was 7.1 +/- 2.2 at the high lung volume compared with 0.7 +/- 0.4 at the low lung volume. The corresponding values for epithelium were 8.5 +/- 1.6 and 0.9 +/- 0.6. Both differences were significant (P less than 0.05). At 52.5 cmH2O Ptm, the results for endothelium were 20.7 +/- 7.6 (high volume) and 7.1 +/- 2.1 (low volume), and the corresponding results for epithelium were 32.8 +/- 11.9 and 11.4 +/- 3.7. At 32.5 cmH2O Ptm, the thickness of the blood-gas barrier was greater at the higher lung volume, consistent with the development of more interstitial edema. Ballooning of the epithelium caused by accumulation of edema fluid between the epithelial cell and its basement membrane was seen at 32.5 and 52.5 cmH2O Ptm. At high lung volume, the breaks tended to be narrower and fewer were oriented perpendicular to the axis of the pulmonary capillaries than at low lung volumes. Transmission and scanning electron microscopy measurements agreed well. Our findings provide a physiological mechanism for other studies showing increased capillary permeability at high states of lung inflation.

scholarly journals ANALISIS AERODINAMIKA PADA PERMUKAAN BODI KENDARAAN MOBIL LISTRIK GASKI (GANESHA SAKTI) DENGAN PERANGKAT LUNAK ANSYS 14.5

2017 ◽  
Vol 5 (2) ◽  
Author(s):  
Yudi Prihadnyana ◽  
Gede Widayana ◽  
Kadek Rihendra Dantes
Keyword(s):  
Fluid Flow ◽  
Flow Rate ◽  
Body Modification ◽  
The Body ◽  
Vehicle Body ◽  
Maximum Pressure ◽  
Air Velocity ◽  
Electric Cars ◽  
Minimum Pressure ◽  
Electric Car

Dengan perkembangan teknologi yang semakin maju bentuk dari bodi sebuah kendaraan sangatlah diperhitungkan untuk mencapai tujuan-tujuan tertentu. Untuk itu, dilakukan analisis Aerodinamika pada pemukaan bodi mobil listrik gaski dengan menggunakan perangkat lunak Ansys 14.5, yang bertujuan untuk mengetahui aliran fluida dan nilai koefisient drag pada mobil listrik Gaski bodi standar dan modifikasi. Setelah proses analisis dilakukan, didapatkan hasil velocity udara maksimum body standar sebesar 17,4324 m/s dan body modifikasi sebesar 17,7321 m/s dan pressure maksimum yang terjadi pada mobil listrik Gaski body standar sebesar 83,2143 Pa, dan minimum sebesar -189,879 Pa. sedangkan pressure maksimum yang terjadi pada mobil listrik Gaski body modifikasi sebesar 83,2143 Pa. dan minimum pressure diperoleh -182,128 Pa. nilai Koefisient drag dari mobil listrik Gaski body standar sebesar 0,00474 sedangkan pada body modifikasi sebesar 0,00407. Dari hasil peneletian tersebut didapatkan bahwa setalah dilakukan modifikasi pada bodi mobil listrik gaski terdapat beberapa perubahan diantaranya terjadi peningkatan kecepatan laju aliran udara atau velocity udara meningkat 1,72 % sedangkan tekanan yang diterima oleh bodi setelah dimodifikasi menurun 1,39 % dan Nilai koefisien drag pada mobil listrik gaski dapat diturunkan 14,14 % setelah dimodifikasi.Kata Kunci : kata kunci : Aerodinamika, aliran fluida, bodi kendaraan, With the technological development of the more advanced form of the body of a vehicle is very calculated to achieve certain goals. For that purpose, Aerodynamic analysis was performed on the electric car body surface by using Ansys 14.5 software, which aims to find out the fluid flow and coefficient value of drag on electric car Gaski standard body and modification. After the analysis process is done, the result of the maximum air velocity of the standard body is 17,4324 m / s and body modification of 17,7321 m / s and the maximum pressure happened to electric car Gaski body standard equal to 83,2143 Pa, 189,879 Pa. While the maximum pressure that occurs on electric cars Gaski body modification of 83.2143 Pa. And the minimum pressure obtained -182.128 Pa. Coefficient value of drag from electric car Gaski body standard of 0,00474 while at body modification equal to 0,00407. From the results of the research was found that after modification on the body of electric car gaski there are some changes such as increase the speed of air flow rate or air velocity increased by 1.72%, while the pressure received by the body after modification decreased 1.39% and the value of drag coefficient on Electric car gaski can be derived 14.14% after modified.keyword : Keywords : Aerodynamic, fluid flow rate, Vehicle body.

Interstitial fibrosis and collateral ventilation

1986 ◽  
Vol 61 (1) ◽  
pp. 300-303 ◽  
Author(s):  
D. M. Berzon ◽  
H. Menkes ◽  
A. M. Dannenberg ◽  
A. Gertner ◽  
P. Terry ◽  
...  
Keyword(s):  
Lung Volume ◽  
Interstitial Fibrosis ◽  
Local Treatment ◽  
Transpulmonary Pressure ◽  
Small Region ◽  
Similar Proportion ◽  
Collateral Flow ◽  
Lung Inflation ◽  
Fibrotic Process ◽  
Residual Capacity

Interstitial fibrosis may increase resistance to collateral flow (Rcoll) because of decreased lung volume and destruction of collateral channels or it may decrease Rcoll because of emphysematous changes around fibrotic regions. In addition, if interstitial fibrosis involves a small region of lung periphery, interdependence from surrounding unaffected lung should produce relatively large changes in volume of the fibrotic region during lung inflation. We studied the effects of interstitial fibrosis on collateral airflow by measuring Rcoll at functional residual capacity (FRC) in nine mongrel dogs before and 28 days after the local instillation of bleomycin into selected lung segments. In six of these dogs Rcoll was also measured at a higher lung volume (transpulmonary pressure = 12 cmH2O above FRC pressure). Rcoll increased in fibrotic lung segments following local treatment with bleomycin. With lung inflation (high transpulmonary pressure) Rcoll fell a similar proportion in fibrotic and nonfibrotic lung regions. These observations suggest that collateral resistance increases in fibrotic segments because lung volume decreases or because collateral pathways are involved directly in the fibrotic process. Compensatory increases in collateral communications do not occur. In addition, pulmonary interdependence does not cause disproportionate increases in volume and decreases in Rcoll of the fibrotic region during lung inflation.

Effect of lung volume on collateral ventilation in the dog

1980 ◽  
Vol 49 (1) ◽  
pp. 9-15 ◽  
Author(s):  
J. Kaplan ◽  
R. C. Koehler ◽  
P. B. Terry ◽  
H. A. Menkes ◽  
R. J. Traystman
Keyword(s):  
Lung Volume ◽  
Transpulmonary Pressure ◽  
Relative Increase ◽  
Small Airways ◽  
Lung Inflation ◽  
Before And After ◽  
Collateral Pathways ◽  
Flow Through ◽  
Collateral Ventilation

We studied the effect of lung volume on resistance through collateral pathways (Rcoll) and small airways (Rsaw) before and after the injection of methacholine into obstructed segments of intact dogs. Before methacholine, Rcoll decreased 15.0 ± 4.9 (SE)% per cmH2O increase in transpulmonary pressure (Ptp) and Rsaw decreased 5.1 ± 7.0 (SE)% per cmH2O increase in Ptp. Following methacholine, lung inflation resulted in similar decreases in Rcoll and Rsaw. The fall in Rcoll was significantly greater than the fall in Rsaw. When pressure in an obstructed segment (Ps) was increased with constant Ptp (nonhomogeneous inflation), Rcoll fell approximately half as much for each cmH2O increase in pressure compared to when Ptp was increased (homogeneous inflation). We conclude 1) that increases in lung volume have small effects on Rsaw so that there is a relative increase in flow through collateral channels serving obstructed poritons of lung and 2) that Rcoll is a function of the size of the obstructed segment that increases more under homogeneous than nonhomogeneous conditions.

Hering–Breuer inflation reflex in young and adult mammals

1981 ◽  
Vol 59 (9) ◽  
pp. 1017-1021 ◽  
Author(s):  
C. Gaultier ◽  
J. P. Mortola
Keyword(s):  
Mechanical Properties ◽  
Respiratory System ◽  
Lung Volume ◽  
Young Animal ◽  
Transpulmonary Pressure ◽  
Lung Inflation ◽  
Stretch Receptors ◽  
Pulmonary Stretch Receptors ◽  
Chemical Stimuli ◽  
Underlying Mechanisms

The apnea following lung inflation (Hering–Breuer expiratory promoting reflex) is a vagally mediated reflex which is initiated by the activation of pulmonary stretch receptors (PSR) and terminated by the interaction of several factors, which include adaptation of PSR, chemical stimuli, level of anaesthesia, and body temperature. Since PSR activity is determined by the changes in airway tension, the interpretation of the strength of vagal reflexes on the basis of changes in lung volume rather than transpulmonary pressure can be misleading when the mechanical properties of the respiratory system are not constant. In this study we compared the reflex apnea resulting from lung inflation of young and adult mammals, the respiratory system of which have very different mechanical properties. If the response is compared on the basis of similar changes in lung volume, it can be considered weaker or stronger in the young depending upon the normalizing parameter used. However, when considered on the basis of the relative changes in transpulmonary pressure, which better reflects the activation of PSR, the reflex is weaker in young rats and rabbits than in their adult counterparts and similar in dogs. The analysis of the underlying mechanisms suggests a weaker vagal contribution in the young animal, but a satisfactory conclusion requires a better knowledge of the factors which, in the younger animals, result in the termination of the apnea.

Elastic moduli of excised constricted rat lungs

1999 ◽  
Vol 86 (1) ◽  
pp. 66-70 ◽  
Author(s):  
Francesco G. Salerno ◽  
Mara S. Ludwig
Keyword(s):  
Elastic Moduli ◽  
Small Volume ◽  
Indentation Test ◽  
Transpulmonary Pressure ◽  
Lung Inflation ◽  
Airway Narrowing ◽  
Rat Lungs ◽  
Airway Opening ◽  
Cylindrical Punch ◽  
Surrounding Parenchyma

When airways constrict, the surrounding parenchyma undergoes stretch and distortion. Because of the mechanical interdependence between airways and parenchyma, the material properties of the parenchyma are important factors that modulate the degree of bronchoconstriction. The purpose of this study was to investigate the effect of changes in transpulmonary pressure (Ptp) and induced constriction on parenchymal bulk ( k) and shear (μ) moduli. In excised rat lungs, pressure was measured at the airway opening, and pressure-volume curves were obtained by imposing step decreases in volume with a calibrated syringe from total lung inflation. Calculation was made of k during small-volume oscillations (1 Hz). Absolute lung volume at 0 cmH2O Ptp was obtained by saline displacement. To calculate μ, a lung-indentation test was performed. The lung surface was deformed with a cylindrical punch (diameter = 0.45 cm) in 0.25-mm increments, and the force required to effect this displacement was measured by a weight balance. Measurements of k and μ were obtained at 4 and 10 cmH2O Ptp, and again at 4 cmH2O Ptp, after delivery of methacholine aerosol (100 mg/ml) into the trachea. Values of k and μ in rat lungs were similar to those reported in other species. In addition, k and μ were dependent on Ptp. After induced constriction, k and μ increased significantly. That k and μ can increase after induced constriction has important implications vis a vis the factors modulating airway narrowing.

Response of pulmonary rapidly adapting receptors during lung inflation

1983 ◽  
Vol 55 (3) ◽  
pp. 955-963 ◽  
Author(s):  
A. I. Pack ◽  
R. G. DeLaney
Keyword(s):  
Flow Rate ◽  
Transpulmonary Pressure ◽  
Quantitative Information ◽  
Lung Mechanics ◽  
Lung Inflation ◽  
Response Characteristics ◽  
Major Response ◽  
Constant Rate ◽  
The Mean ◽  
Inflation Volume

Studies were conducted to establish the factors that determine the response of canine pulmonary rapidly adapting receptors (RAR) during lung inflation. Inflations of the lung were performed at several constant rates during which the activity of individual RAR was counted. At each rate of inflation tested multiple identical tests were performed. The volume of each test inflation was controlled. Data obtained in all tests at each flow rate were averaged to give the mean response of the receptor at that rate of inflation. These studies indicate the major response characteristics of RAR during lung inflation in conditions of relatively constant lung mechanics. First, at a constant rate of inflation, the activity of RAR augments increasingly as the lung is expanded. Second, their activity is influenced markedly by the rate of inflation. However, this sensitivity is nonlinear. Specifically, at low rates of inflation increases in flow rate produce more marked augmentation of RAR firing than do identical increases in flow at higher rates of inflation. The major difference between receptors is in their threshold; however, this too is a function of flow rate. With increasing flow rate the threshold, whether measured as the inflation volume or transpulmonary pressure at which receptors begin to fire, declines. The response of receptors, however, with thresholds over the entire range show the major features discussed above. The present results provide quantitative information which are necessary to begin to eludicate the transduction properties of this receptor type.

Effect of lung volume history on rate of edema formation in isolated canine lobe

1978 ◽  
Vol 45 (6) ◽  
pp. 880-884 ◽  
Author(s):  
H. S. Goldberg
Keyword(s):  
Weight Gain ◽  
Hydrostatic Pressure ◽  
Lung Volume ◽  
Interstitial Fluid ◽  
Venous Pressure ◽  
Transpulmonary Pressure ◽  
Fluid Accumulation ◽  
Edema Formation ◽  
Lung Inflation ◽  
Volume History

The effect of lung volume history and prior accumulation of interstitial fluid on rate of edema formation in isolated canine lobes was investigated. Mean pulmonary artery pressure and mean pulmonary venous pressure were kept constant at 40 and 30 cmH2O, respectively. Transpulmonary pressure (Ptp) was varied among 5, 15, and 25 cmH2O by progressive stepwise inflation and deflation. Rate of fluid accumulation was estimated by changes in slow weight gain after a change in Ptp. Although there is continuous interstitial fluid accumulation over the course of the experiment the results indicate that interstitial hydrostatic pressure around leaky vessels at Ptp of 15 cmH2O is reduced by prior lung inflation to Ptp of 25 cmH2O and increased by prior deflation to Ptp of 5 cmH2O. These results suggest that the distribution of interstitial fluid may vary as a function of lung volume history.

Effect of liquid inflation on the viscoelastic behavior of the lungs in developing piglets

1994 ◽  
Vol 77 (4) ◽  
pp. 1653-1658 ◽  
Author(s):  
J. La Rocca ◽  
J. J. Perez Fontan
Keyword(s):  
Stress Relaxation ◽  
Time Constant ◽  
Lung Volume ◽  
Inflation Rate ◽  
Viscoelastic Behavior ◽  
Transpulmonary Pressure ◽  
Liquid Interface ◽  
Developmental Changes ◽  
Elastic Recoil ◽  
Airway Opening

Viscoelastic dissipation through stress relaxation decreases during the first weeks after birth in the piglet's lungs (J. Appl. Physiol. 73: 1297–1309, 1992). To characterize the mechanism of this decrease, we compared the stress relaxation undergone by the lungs of six newborn and six 9-wk-old piglets when the airway opening was occluded in the course of air and saline inflations. The amplitude of stress relaxation, determined from the mono-exponential decay ultimately adopted by the transpulmonary pressure during the occlusions, related linearly to the increases in lung elastic recoil preceding the occlusions. The slope of this relationship was greater in the newborn than in the 9-wk-old piglets during air inflations and similar at the two ages during saline inflations. Both the ratio of stress relaxation to elastic recoil and the time constant of the relaxations were similar during air and saline inflations and were independent of inflation rate and lung volume at the start of the inflations. These findings indicate that the postnatal decrease in stress relaxation is caused primarily by developmental changes in the geometry of the gas-liquid interface. They are also consistent with the notion that the viscoelastic stresses generated by the gas liquid interface and lung tissue are well matched for a given elastic recoil.

scholarly journals A Model of the Recruitment-Derecruitment and Volume of Lung Units in an Excised Lung as it is Inflated-Deflated Between Minimum and Maximum Lung Volume

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
D. G. Frazer ◽  
W. G. Lindsley ◽  
W. McKinney ◽  
J. S. Reynolds ◽  
G. N. Franz ◽  
...  
Keyword(s):  
Lung Volume ◽  
Unit Volume ◽  
Transpulmonary Pressure ◽  
Small Signal ◽  
Average Volume ◽  
Static Compliance ◽  
Lung Inflation ◽  
Tissue Properties ◽  
Open Lung ◽  
Lung Unit

The role of the recruitment-derecruitment of small structures in the lung (lung units) as the lung increases and decreases in volume has been debated. The objective of this study was to develop a model to estimate the change in the number and volume of open lung units as an excised lung is inflated-deflated between minimum and maximum lung volume. The model was formulated based on the observation that the compliance of the slowly changing quasi-static pressure-volume (P-V) curve of an excised rat lung can differ from the compliance of a faster changing small sinusoidal pressure volume perturbations superimposed on the curve. In those regions of the curve where differences in compliance occur, the lung tissue properties exhibit nonlinear characteristics, which cannot be linearized using “incremental” or “small signal” analysis. The model attributes the differences between the perturbation and quasi-static compliance to an additional nonlinear compliance term that results from the sequential opening and closing of lung units. Using this approach, it was possible to calculate the normalized average volume and the normalized number of open units as the lung is slowly inflated-deflated. Results indicate that the normalized average volume and the normalized number of open units are not linearly related to normalized lung volume, and at equal lung volumes the normalized number of open units is greater and the normalized average lung unit volume is smaller during lung deflation when compared to lung inflation. In summary, a model was developed to describe the recruitment-derecruitment process in excised lungs based on the differences between small signal perturbation compliance and quasi-static compliance. Values of normalized lung unit volume and the normalized number of open lung units were shown to be nonlinear functions of both transpulmonary pressure and normalized lung volume.

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