Effect of flow direction on collateral ventilation in excised dog lung lobes

1986 ◽  
Vol 60 (3) ◽  
pp. 770-776 ◽  
Author(s):  
L. E. Olson ◽  
P. A. Socha
Keyword(s):  
Gas Flow ◽  
Flow Direction ◽  
Order Effect ◽  
Driving Pressure ◽  
Lung Segment ◽  
Peripheral Airway ◽  
Airway Opening ◽  
Collateral Pathways ◽  
Flow Pathways ◽  
Lung Lobes

We determined the effect of flow direction on the relationship between driving pressure and gas flow through a collaterally ventilating lung segment in excised cranial and caudal dog lung lobes. He, N2, and SF6 were passed through the lung segment distal to a catheter wedged in a peripheral airway. Gases were pushed through the segment by raising segment pressure (Ps) relative to airway opening pressure (Pao) and pulled from the segment by ventilating the lobe with the test gas, then lowering Ps relative to Pao. Driving pressures (Ps - Pao) between 0.25 and 2 cmH2O were evaluated at Pao values of 5, 10, and 15 cmH2O. Results were similar in cranial and caudal lobes. Flow increased as Ps - Pao increased and was greatest at Pao = 15 cmH2O for the least-dense gas (He). Although flow direction was not a significant first-order effect, there was significant interaction between volume, driving pressure, and flow direction. Dimensional analysis suggested that, although flow direction had no effect at Pao = 10 and 15 cmH2O, at Pao = 5 cmH2O, raising Ps relative to Pao increased the characteristic dimension of the flow pathways, and reducing Ps relative to Pao reduced the dimension. These data suggest that at large lobe volumes, airways (including collateral pathways) within the segment are maximally dilated and the stiffness of the parenchyma prevents any significant distortion when Ps is altered. At low lobe volumes, these pathways are affected by changes in transmural pressure due to the increased airway and parenchymal compliance.

Effect of transpulmonary and driving pressures on collateral gas flow in dog lungs

1985 ◽  
Vol 59 (6) ◽  
pp. 1757-1765 ◽  
Author(s):  
L. E. Olson
Keyword(s):  
Gas Flow ◽  
Dynamic Pressure ◽  
Opening Pressure ◽  
Lung Segment ◽  
Peripheral Airway ◽  
Airway Opening ◽  
Residual Capacity ◽  
Collateral Pathways ◽  
Flow Through ◽  
Flow Pathways

The effect of changing segment pressure (Ps) and airway opening pressure (Pao) on flow through a collaterally ventilating lung segment was evaluated in intact and excised dog lungs. He, N2, and SF6 were passed through the lung segment distal to a catheter wedged in a peripheral airway at driving pressures (Ps - Pao) between 0.25 and 2 cm H2O. Eight excised caudal lobes were studied at Pao = 5, 10, and 15 cm H2O. Flow was directly related to Ps - Pao and Pao and inversely related to the density of the gas. A dimensionless plot of the driving pressure normalized to a reference dynamic pressure as a function of Reynolds number (Re) indicated that flow through the segment behaved as if it were laminar at Re less than 100 and that increasing Pao increased the dimension of the pathways conducting flow as shown previously. Small changes in Ps had no effect on pathway geometry or on the pattern of flow through the segment at Pao = 10 and 15 cmH2O. At Pao = 5 cm H2O increasing segment pressure appeared to increase the dimensions of the flow pathways slightly. Similar changes in Ps - Pao had no consistent effect on flow pattern or pathway geometry in six anesthetized, paralyzed, vagotomized dogs at functional residual capacity or after widely opening the chest (Pao = 5 cm H2O). These results suggest that, at large lobe volumes, airways (including collateral pathways) are maximally dilated and therefore relatively insensitive to small changes in segment pressure.

Effect of isoproterenol on peripheral airway pressure-diameter behavior

1993 ◽  
Vol 75 (4) ◽  
pp. 1497-1501
Author(s):  
L. E. Olson
Keyword(s):  
Total Lung Capacity ◽  
Average Diameter ◽  
Homogeneous Case ◽  
Opening Pressure ◽  
Peripheral Airways ◽  
Lung Capacity ◽  
Lung Segment ◽  
Peripheral Airway ◽  
Airway Opening ◽  
Lung Lobes

I radiographically evaluated the pressure-diameter relationships of peripheral airways (average diameter approximately 2 mm at total lung capacity) in a collaterally ventilating lung segment in 22 caudal dog lung lobes. Eleven lobes were studied when freshly excised, and 11 lobes were studied after being rinsed with 0.5% isoproterenol. Airways within the segment (intrasegmental) and a control region of similarly sized airways external to the segment were studied. Radiographs were taken when airway opening pressure (Pao) equaled pressure in the segment (Ps) (homogeneous case) and when Pao was 5, 10, or 15 cmH2O greater than Ps (nonhomogeneous case). Airway diameter was calculated as a fraction of the diameter at Pao = Ps = 25 cmH2O. The response of intrasegmental airways to increases in pressure in the homogeneous case (Ps = Pao) and nonhomogeneous case (Ps > Pao) differed between freshly excised and isoproterenol-rinsed lobes. I conclude that dilating peripheral airways by decreasing bronchomotor tone limits the extent to which they can respond to a regional increase in alveolar pressure.

Use of collateral airways to assess airway reactivity

1991 ◽  
Vol 70 (1) ◽  
pp. 349-356 ◽  
Author(s):  
D. H. Corddry ◽  
R. A. Sauder ◽  
G. G. Weinmann ◽  
C. A. Hirshman ◽  
W. Mitzner
Keyword(s):  
Dose Response ◽  
Gas Flow ◽  
Response Curves ◽  
Airway Reactivity ◽  
Resistance Response ◽  
Peripheral Airways ◽  
Lung Segment ◽  
Peripheral Airway ◽  
The Mean ◽  
Dose Response Curves

We investigated the correlation between collateral airway reactivity and other indexes of lung reactivity in response to aerosol and intravenous (iv) challenges. In four anesthetized mongrel dogs, we measured the peripheral airway resistance (Rp) to gas flow out of a wedged lung segment in different lobes on multiple occasions. We obtained dose-response curves of peripheral airways challenged with iv histamine or aerosols through the bronchoscope. During the same iv bolus challenge, whole lung airway pressure (Paw) responses to histamine were also measured. On separate occasions, changes in lung resistance (RL) were measured after the whole lung was challenged with a histamine aerosol. Reactivity was assessed from the dose-response curves for Rp and RL as the PD50 (dose required to produce a 50% increase); for changes in Paw we calculated the PD15 (dose required to produce a 15% increase over baseline). Results for Rp showed considerably more variability among different lobes in a given animal with the aerosol challenge through the bronchoscope than with the iv challenge. With aerosol challenge there were no significant differences in the mean PD50 for Rp among any of the animals. However, with the iv challenge two of the dogs showed significant differences from the others in reactivity assessed with Rp (P less than 0.01). Moreover, the differences found in the peripheral airways with iv challenge reflected differences found in whole lung reactivity assessed with either iv challenge (Paw vs. Rp, r2 = 0.96) or whole lung aerosol challenge (RL vs. Rp, r2 = 0.84). We conclude that the measurement of the collateral resistance response to iv challenge may provide a sensitive method for assessing airway reactivity.

Propranolol-vagal-alveolar CO2 interactions on collateral gas flow in dog lungs

1982 ◽  
Vol 52 (6) ◽  
pp. 1426-1431 ◽  
Author(s):  
L. E. Olson ◽  
N. E. Robinson
Keyword(s):  
Gas Flow ◽  
Vagal Stimulation ◽  
High Co2 ◽  
Low Co2 ◽  
Co2 Levels ◽  
Lung Segment ◽  
Airway Opening ◽  
Residual Capacity ◽  
Propranolol Treatment ◽  
End Tidal

The mechanical properties of a collaterally ventilating lung segment were studied in 18 anesthetized paralyzed mongrel dogs artificially ventilated with room air end-tidal CO2 fraction = 5%. Nine dogs were pretreated with propranolol, and nine dogs were not. With 0, 5, or 12% CO2 in O2 flowing into the segment, steady-state resistance of segmental airways (Rss) and time for 90% pressure equilibration (T90) between the segment and airway opening after flow was discontinued were determined at functional residual capacity with the vagus nerve ipsilateral to the segment intact, sectioned, or electrically stimulated. Vagal stimulation increased Rss and T90 at all CO2 levels, whereas unilateral vagotomy had no effect. Propranolol treatment enhanced the increase in Rss caused by vagal stimulation at low but not at high CO2 levels, suggesting that high CO2 mimics the effect of propranolol on Rss. High levels of CO2 did not have the same effect as propranolol on T90, propranolol treatment reducing the increase in T90 caused by vagal stimulation at high but not at low CO2 levels. These results demonstrate that local changes in alveolar CO2 tensions modify but do not abolish the effect of vagal stimulation on collateral ventilation.

Effect of inflammation on peripheral airway reactivity in dogs

1993 ◽  
Vol 84 (1) ◽  
pp. 73-78 ◽  
Author(s):  
Y. Cormier ◽  
R. Whittom ◽  
L. P. Boulet ◽  
F. Sériès
Keyword(s):  
Bronchoalveolar Lavage ◽  
Bordetella Bronchiseptica ◽  
Local Inflammation ◽  
Airway Reactivity ◽  
Neutrophilic Inflammation ◽  
Lung Segment ◽  
Peripheral Airway ◽  
Collateral Pathways ◽  
The Relationship ◽  
Peak Value

1. Eight mongrel dogs were studied to evaluate the effect of local inflammation on the response of collateral airways to histamine. In each dog we measured the baseline collateral resistance and its response to increasing doses of nebulized histamine. These measurements were obtained at weekly intervals, twice under control conditions and in three subsequent weeks after a local instillation of the bacteria Bordetella bronchiseptica. On each study day, after the measurements of collateral resistance, we lavaged the studied lung segment by instilling and aspirating 100 ml of saline (four 25 ml aliquots). All studies were performed in the same lung segment. 2. Collateral resistance remained stable under control conditions at 19.5 ± 7.2 and 11.7 ± 32 cm H2OI−l mm. With a bacteria-induced, mostly neutrophilic, inflammation, collateral resistance initially increased to 70.2 ± 18.6 cm H2OI−1 min after 1 week and subsequently decreased towards control values (47.3 ± 13 and 30.7 ± 10.1 cm H2OI−1 min at 21 and 29 days, respectively). Collateral pathways reactivity, expressed as the slope of the relationship collateral resistance/log (1 + [histamine]), remained unchanged throughout the study. The values of this slope were (mean ± SEM) 0.021 ± 0.003 and 0.022 ± 0.004 in the two control studies and 0.025 ± 0.004, 0.030 ± 0.006 and 0.023 ± 0.003 in the three subsequent weekly studies. Inflammation, evaluated by the number of bronchoalveolar lavage cells and the percentage of neutrophils in bronchoalveolar cells, closely paralleled baseline collateral resistance with a peak value at the first week after the infection. 3. Local inflammation increases collateral resistance by its mechanical effects, and does not modify the responsiveness of collateral pathways to nebulized histamine.

Mechanical properties of small airways in excised pony lungs

1992 ◽  
Vol 73 (2) ◽  
pp. 522-529 ◽  
Author(s):  
L. E. Olson
Keyword(s):  
Reynolds Number ◽  
Reynolds Numbers ◽  
Small Airway ◽  
Small Airways ◽  
Radiographic Measurements ◽  
Lung Segment ◽  
Peripheral Airway ◽  
Airway Opening ◽  
Flow Through ◽  
High Reynolds

We evaluated the pressure-flow relationships in collaterally ventilating segments of excised pony lungs by infusing N2, He, Ne, or SF6 at known flows (V) through a catheter wedged in a peripheral airway. Measurements were made at segment- (Ps) to-airway opening (Pao) pressure differentials of 3–15 cmH2O when the lungs were held at transpulmonary pressures of 5, 10, and 15 cmH2O. The data were analyzed both by calculating collateral resistance (Ps-Pao/V) and by constructing Moody-type plots of normalized pressure drop [(Ps-Pao)/(1/2 rho U2, where rho is density and U is velocity)] against Reynolds number to assess the pattern of flow through the segment and the change in dimension of the flow channels as Ps and Pao were changed. The interpretations from these analyses were compared with radiographic measurements of the diameters of small airways within the collaterally ventilating lung segment at similar pressures. Collateral resistance increased as Ps-Pao increased at high Reynolds numbers, i.e., high flows or dense gas (SF6). Analysis of the Moody-type plots revealed that flow was density dependent at Reynolds number greater than 100, which frequently occurred when N2 was the inflow gas. The radiographic data revealed that small airway diameter increased as Ps-Pao increased at all lung volumes. In addition, at 5 cmH2O Pao, small-airway diameter was smaller for a given Ps in the nonhomogeneous case (Ps greater than Pao) than small-airway diameter for the same Ps in the homogeneous case (Ps = Pao). We interpret these data to suggest that the surrounding lung prevented the segment from expanding in the nonhomogeneous case.(ABSTRACT TRUNCATED AT 250 WORDS)

Pressure-flow relationships in a collaterally ventilating dog lung segment

1983 ◽  
Vol 54 (4) ◽  
pp. 956-960 ◽  
Author(s):  
L. E. Olson ◽  
J. R. Rodarte ◽  
N. E. Robinson
Keyword(s):  
Reynolds Number ◽  
Lung Volume ◽  
Dynamic Pressure ◽  
Reynolds Numbers ◽  
Pressure Losses ◽  
Lung Segment ◽  
Peripheral Airway ◽  
Airway Opening ◽  
Residual Capacity ◽  
Flow Through

We evaluated the pressure (P)-flow (V) relationship in collaterally ventilating dog lung segments by passing He, N2, and SF6 through a bronchoscope (5 mm OD) wedged in a peripheral airway. Measurements were made at functional residual capacity (FRC) and two higher lung volumes, keeping segment-to-airway opening pressure constant (3 cmH2O) in five anesthetized, paralyzed, vagotomized, supine dogs. Average flows ranged from 5.0 to 8.0 ml/s for He, 4.5 to 7.5 ml/s for N2, and 3.4 to 4.7 ml/s for SF6. When these data were fitted as P = K1/3/3 mu V + K2 rho V2, density-dependent pressure losses were unimportant when He and N2 were used, suggesting laminar flow with these gases. A dimensionless plot of the total pressure drop relative to a reference dynamic pressure as a function of Reynolds number at the bronchoscope tip suggested that flow through the segment behaved as if it were laminar at Reynolds numbers less than 100. Furthermore, when the airway diameter used to compute the normalized pressure and Reynolds number was scaled as the cubic root of lung volume, curves for all three gases were superimposed, suggesting that the dimensions of intrasegmental/collateral airways scale as lung volume 1/3.

EFFECT OF GAS FLOW DIRECTION ON PASSIVE SUBSEA COOLER EFFECTIVENESS

2019 ◽  
Vol 11 (1-2) ◽  
pp. 1-16 ◽  
Author(s):  
Nikolay Ivanov ◽  
Vladimir V. Ris ◽  
Nikolay A. Tschur ◽  
Marina Zasimova
Keyword(s):  
Gas Flow ◽  
Flow Direction

scholarly journals Elongated Wire-Like Zinc Oxide Nanostructures Synthesized from Metallic Zinc

2012 ◽  
Vol 15 (1) ◽  
pp. 19 ◽  
Author(s):  
El-Shazly M. Duraia ◽  
G.W. Beall ◽  
Zulkhair A. Mansurov ◽  
Tatyana A. Shabanova ◽  
Ahmed E. Hannora
Keyword(s):  
Electron Microscopy ◽  
Zinc Oxide ◽  
Silicon Substrate ◽  
Gas Flow ◽  
Flow Direction ◽  
Crystal Defects ◽  
Near Band Edge ◽  
Band Edge Emission ◽  
Metallic Zinc ◽  
Zinc Oxide Nanostructures

Elongated wire-like Zinc oxide, nanocombs and nanocrystals have been successfully synthesized on the silicon substrate from the metallic zinc as a starting material. The annealing temperature was as low as 450 ºC in argon atmosphere mixed with about 3% oxygen. Structural analysis using the X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) showed that the existence of two phases; nanowires and crystalline form. Moreover some nanoparticles aggregates were noticed to be attached in the bulk to the sides of the ZnO nanocrystals and sometimes these aggregate attached to the Zinc oxide hexagonal crystal and grow to form nanowire at different angles. Scanning electron microscopy (SEM) investigations for the zinc oxide nanostructure on the silicon substrate showed the formation of the nanocrystals in the gas flow direction and at the low energy sites over the silicon substrate. Photoluminescence (PL) measurements, performed at the room temperature, showed the existence of two basic emissions: narrow ultraviolet (UV) emission at 398 nm which attributed to the near band edge emission of the wide band gap and a very wide, more intensive, green emission at 471 nm corresponds to the crystal defects such as vacancies, interstitial sites in ZnO.

scholarly journals Numerical Simulation on Double-nozzle Spray Evaporation of Desulfurization Wastewater

2021 ◽  
Author(s):  
Hong Xu ◽  
Shuqin Feng ◽  
Liehui Xiao ◽  
Yazhen Hao ◽  
Xiaoze Du
Keyword(s):  
Flue Gas ◽  
Gas Flow ◽  
Evaporation Rate ◽  
Flow Direction ◽  
Droplet Diameter ◽  
Numerical Results ◽  
Least Square ◽  
Lagrangian Model ◽  
Support Vector ◽  
Exhaust Heat

To achieve the near zero emission of wastewater in the flue gas desulfurization (FGD) system in coal-fired power plant and better utilize the exhaust heat from flue gas, a feasible technology of spraying FGD wastewater in the flue duct for evaporation is discussed in the present study. A full-scale influencing factor investigation on the wastewater droplet evaporation performance is established under the Eulerian-Lagrangian model numerically. The dominant factors, including the characters of wastewater droplets, flue gas and the spray nozzles were analyzed under different conditions, respectively. Considering the multiple factors and conditions in the process, a Least-Square support vector machine (LSSVM) model is introduced to predict the evaporation rate based on the numerical results. Conclusions are made that the flue gas temperature and droplet diameter are of great importance in the evaporation process. The spray direction of droplet parallel with the flue gas flow direction is profitable for the dispersion of droplet, resulting the maximal evaporation rate. A double-nozzle arrangement optimized with relatively small flow rate is recommended. The LSSVM model can accurately predict the evaporation rate using the numerical results with different conditions.

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