Pressure-flow behavior of a bronchopleural fistula during mechanical ventilation with positive pressure

1989 ◽  
Vol 66 (4) ◽  
pp. 1789-1799 ◽  
Author(s):  
J. J. Perez Fontan ◽  
A. O. Ray
Keyword(s):  
Gas Flow ◽  
Flow Behavior ◽  
Bronchopleural Fistula ◽  
Transmural Pressure ◽  
Positive Pressure ◽  
Inflation Pressure ◽  
Tracheal Pressure ◽  
Flow Through ◽  
The Difference ◽  
The Relationship

We examined the mechanical behavior of a bronchopleural fistula created by sectioning a small subpleural bronchus in seven anesthetized lambs. The pressure across the fistula was measured as the difference between the pressure recorded by a retrograde bronchial catheter inserted in the vicinity of the fistula and the outflow pressure at the fistula exit. The effective resistance of the fistula (Rf) was computed by dividing this pressure difference by the gas flow through the fistula measured at the outlet of an intrapleural tube adjacent to the fistula. Rf increased by 114 +/- 25% (SE) when we inflated the lungs in a stepwise manner from a tracheal pressure of 2–20 cmH2O. Rf also increased when inflation pressure varied continuously; this increase, however, was less evident when we decreased the inflation time from 1.0 to 0.2 s. The relationship between Rf and lung volume was similar during the stepwise inflations and deflations but showed marked hysteresis during the continuous inflation-deflation maneuvers, when Rf was greater during deflation than inflation. Our results suggest that the fistula behaves as a compliant pathway whose relevant transmural pressure is the transmural pressure at or near the fistula's exit. We attribute the increase in Rf during inflation to decreases in transmural pressure caused by convective and dissipative losses inside the fistula and by the stress applied by the chest wall on the outer surface of the fistula.

scholarly journals The structure and dynamics of patch-clamped membranes: a study using differential interference contrast light microscopy.

1990 ◽  
Vol 111 (2) ◽  
pp. 599-606 ◽  
Author(s):  
M Sokabe ◽  
F Sachs
Keyword(s):  
Cell Surface ◽  
Transmural Pressure ◽  
Positive Pressure ◽  
Radius Of Curvature ◽  
Pressure Gradients ◽  
Structure And Motion ◽  
Excised Patches ◽  
Glass Interface ◽  
Pipette Tip ◽  
Flow Through

We have developed techniques for micromanipulation under high power video microscopy. We have used these to study the structure and motion of patch-clamped membranes when driven by pressure steps. Patch-clamped membranes do not consist of just a membrane, but rather a plug of membrane-covered cytoplasm. There are organelles and vesicles within the cytoplasm in the pipette tip of both cell-attached and excised patches. The cytoplasm is capable of active contraction normal to the plane of the membrane. With suction applied before seal formation, vesicles may be swept from the cell surface by shear stress generated from the flow of saline over the cell surface. In this case, patch recordings are made from membrane that was not originally present under the tip. The vesicles may break, or fuse and break, to form the gigasealed patch. Patch membranes adhere strongly to the wall of the pipette so that at zero transmural pressure the membranes tend to be normal to the wall. With transmural pressure gradients, the membranes generally become spherical; the radius of curvature decreasing with increasing pressure. Some patches have nonuniform curvature demonstrating that forces normal to the membrane may be significant. Membranes often do not respond quickly to changes in pipette pressure, probably because viscoelastic cytoplasm reduces the rate of flow through the tip of the pipette. Inside-out patches may be peeled from the walls of the pipette, and even everted (with positive pressure), without losing the seal. This suggests that the gigaseal is a distributed property of the membrane-glass interface.

A phrenic nerve-actuated electronically controlled positive-pressure ventilator

1987 ◽  
Vol 62 (5) ◽  
pp. 2121-2125 ◽  
Author(s):  
E. R. Schertel ◽  
D. A. Schneider ◽  
D. L. Howard ◽  
J. F. Green
Keyword(s):  
Moving Average ◽  
Inspiratory Flow ◽  
Positive Pressure ◽  
Feedback Signal ◽  
Position Signal ◽  
Tracheal Pressure ◽  
Valve Position ◽  
Air Valve ◽  
The Difference ◽  
Operational Modes

We have constructed an electronically controlled positive-pressure ventilator actuated by phrenic neural activity for use in open-chested or paralyzed experimental animals for the study of breathing pattern. A Bird Mark 14 positive-pressure ventilator was modified such that flow is a linear function of a command signal. Flow is delivered by advancing an air valve with a servo-motor that is controlled by one of three different operational modes. In two of the modes, the difference between the electronic average of inspiratory phrenic activity (moving average) and a feedback signal determines the inspiratory flow. The feedback signal is derived from either tracheal pressure or an electronic measure of inspired volume. In the third mode, the moving average is differentiated to provide control of inspiratory flow and volume. Physiological flow profiles were created using all three operational modes. Integration of an air-valve position signal provides an electronic measure of tidal volume. An additional feature of this ventilator allows inspiratory flow and duration to be predetermined for a given breath.

Permeability and Porosity of Bonded Hollow Sphere Foams for High Intensity Radiant Burners

1994 ◽  
Vol 372 ◽  
Author(s):  
J. E. McEntyre ◽  
J. K. Cochran ◽  
K. J. Lee
Keyword(s):  
Hollow Sphere ◽  
High Intensity ◽  
Gas Flow ◽  
Point Contact ◽  
Operating Characteristics ◽  
Flow Through ◽  
Bonding Phase ◽  
Radiant Burners ◽  
The Relationship

AbstractBonded hollow sphere foams for this study were made from point-contact, slurry-bonded monosized spheres, 2.5 mm in diameter. The permeabilities of these foams are compatible with the diffuser base in radiant burners. For this study, the effect of quantity of bonding phase on interstitial porosity, permeability, and uniformity of gas flow through the foams was investigated. The relationship between permeability and porosity was modeled with the Kozeny-Carman equation. Attempts were made to correlate diffuser base permeability to operating characteristics of these burners.

The Relationship Between Breach Development and the Depressurization Transient During Axial Rupture of a Gas-Pressurized Steel Pipe

1982 ◽  
Vol 104 (1) ◽  
pp. 20-24 ◽  
Author(s):  
M. R. Baum
Keyword(s):  
Rarefaction Wave ◽  
Gas Flow ◽  
Theoretical Models ◽  
Observation Point ◽  
Steel Pipe ◽  
Growth Data ◽  
Flow Through ◽  
The Relationship ◽  
Experimental Pressure ◽  
Good Agreement

Theoretical models are developed to predict the depressurization generated by a propagating axial rupture in a gas-pressurized steel pipe. The pressure transient is composed of a relatively slow depressurization within the rarefaction wave which propagates through the undisturbed gas ahead of the developing breach and a rapid depressurization within the breach zone. The models combine a simplified one-dimensional treatment of the gas flow local to the breach with experimental breach area growth data. An instantaneous steady flow through the developing breach is assumed to determine the boundary condition for the rarefaction wave. The breach zone depressurization is assumed to be dominated by the transverse wave action initiated by the arrival of the breach at the observation point. In both cases the predicted transients are in good agreement with experimental pressure histories.

scholarly journals Cyber-Physical Observer for Fluidized Bed-Chemical Looping Control Applications

2017 ◽  
Author(s):  
Lawrence Shadle ◽  
David Tucker ◽  
Ronald Breault ◽  
Samuel Bayham ◽  
Justin Weber ◽  
...  
Keyword(s):  
Multiphase Flow ◽  
Fluidized Bed ◽  
Gas Flow ◽  
Flow Behavior ◽  
Chemical Looping ◽  
Flow Paths ◽  
Response Data ◽  
Flow Through ◽  
And Performance ◽  
And Control

A cyber-physical fluidized bed-chemical looping reactor (FB-CLR) is proposed to observe and control the multiphase flow behavior and improve process operations, stability, and performance. The cyber-physical observer (CPO) provides an opportunity to probe a duplicate, or mirrored, non-reacting, multiphase flow system in real-time and provide response data not available from the hot reacting system in order to control the hot unit. A control strategy was developed to share and integrate this information between to the two systems. During test operations the data from the shifting inventory of granular particles in the cold flow unit will be used to control some of the valves controlling the gas flow paths in the hot unit. Taken in conjunction with the inlet flows, temperatures, and pressures in the hot unit a control system is proposed to balance the exhaust flow through the various gas outlets of the different vessels. System identification studies are needed to characterize the process delays, time constants, and interactions between control parameters.

Numerical Analysis of Flow Behavior Inside the Blast Furnace

2009 ◽  
Author(s):  
Dong Fu ◽  
Fengguo Tian ◽  
Guoheng Chen ◽  
D. Frank Huang ◽  
Chenn Q. Zhou
Keyword(s):  
Blast Furnace ◽  
Gas Flow ◽  
Cfd Simulation ◽  
Flow Behavior ◽  
Three Dimensional ◽  
Furnace Productivity ◽  
Gas Distribution ◽  
Furnace Shaft ◽  
Parametric Studies ◽  
Flow Through

Gas and burden distributions inside a blast furnace play an important role in optimizing gas utilization versus the furnace productivity and minimizing the CO2 emission in steel industries. In this paper, a mathematical model is presented to describe the burden descent in the blast furnace shaft and gas distribution, with the alternative structure of coke and ore layers being considered. Multi-dimensional Ergun’s equation is solved with considering the turbulent compressible gas flow through the burden column. The porosity of each material will be treated as a function of three dimensional functions which will be determined by the kinetics sub-models accordingly. A detailed investigation of gas flow through the blast furnace will be conducted with the given initial burden profiles along with the effects of redistribution during burden descending. Also, parametric studies will be carried out to analyze the gas distribution cross the blast furnace under different cohesive zone (CZ) shapes, charging rate, and furnace top pressure. A good agreement was obtained between the CFD simulation and published experimental data. Based on the results, the inverse V shape is proved to be the most desirable CZ profile.

Gas Flow Through a Bronchopleural Fistula

CHEST Journal ◽  
1988 ◽  
Vol 93 (1) ◽  
pp. 210-213 ◽  
Author(s):  
Michael D. Roth ◽  
John W. Wright ◽  
Paul E. Bellamy
Keyword(s):  
Gas Flow ◽  
Bronchopleural Fistula ◽  
Flow Through

Effect of chest-tube suction on gas flow through a bronchopleural fistula

1985 ◽  
Vol 13 (2) ◽  
pp. 99-101 ◽  
Author(s):  
DAVID J. POWNER ◽  
C. DEAN CLINE ◽  
GEORGE H. RODMAN
Keyword(s):  
Chest Tube ◽  
Gas Flow ◽  
Bronchopleural Fistula ◽  
Flow Through ◽  
Tube Suction

scholarly journals The mechanics of nectar offloading in the bumblebee Bombus terrestris and implications for optimal concentrations during nectar foraging

2020 ◽  
Vol 17 (162) ◽  
pp. 20190632 ◽  
Author(s):  
Jonathan G. Pattrick ◽  
Hamish A. Symington ◽  
Walter Federle ◽  
Beverley J. Glover
Keyword(s):  
Bombus Terrestris ◽  
Optimum Concentration ◽  
Transfer Rates ◽  
Rate Dependent ◽  
Sucrose Solutions ◽  
Nectar Sugar ◽  
Flow Through ◽  
The Difference ◽  
Foraging Energetics ◽  
The Relationship

Nectar is a common reward provided by plants for pollinators. More concentrated nectar is more rewarding, but also more viscous, and hence more time-consuming to drink. Consequently, theory predicts an optimum concentration for maximizing energy uptake rate, dependent on the mechanics of feeding. For social pollinators such as bumblebees, another important but little-studied aspect of foraging is nectar offloading upon return to the nest. Studying the bumblebee Bombus terrestris , we found that the relationship between viscosity ( µ ) and volumetric transfer rates ( Q ) of sucrose solutions differed between drinking and offloading. For drinking, Q ∝ µ −0.180 , in good agreement with previous work. Although offloading was quicker than drinking, offloading rate decreased faster with viscosity, with Q ∝ µ −0.502 , consistent with constraints imposed by fluid flow through a tube. The difference in mechanics between drinking and offloading nectar leads to a conflict in the optimum concentration for maximizing energy transfer rates. Building a model of foraging energetics, we show that including offloading lowers the maximum rate of energy return to the nest and reduces the concentration which maximizes this rate by around 3%. Using our model, we show that published values of preferred nectar sugar concentrations suggest that bumblebees maximize the overall energy return rather than the instantaneous energy uptake during drinking.

T-piece resuscitators: can they provide safe ventilation in a low compliant newborn lung?

2020 ◽  
Vol 106 (1) ◽  
pp. 25-30 ◽  
Author(s):  
Murray Kenneth Hinder ◽  
Thomas Drevhammar ◽  
Snorri Donaldsson ◽  
Matthew Boustred ◽  
Matthew Crott ◽  
...  
Keyword(s):  
Gas Flow ◽  
Lung Compliance ◽  
Lung Model ◽  
Bench Test ◽  
Positive Pressure ◽  
Test Model ◽  
Inflation Pressure ◽  
Emergency Rooms ◽  
Test Lung ◽  
Single Operator

BackgroundT-piece resuscitators (TPRs) are used for primary newborn resuscitation in birthing and emergency rooms worldwide. A recent study has shown spikes in peak inflation pressure (PIP) over set values with two brands of TPRs inbuilt into infant warmer/resuscitation platforms. We aimed to compare delivered ventilation between two TPR drivers with inflation pressure spikes to a standard handheld TPR in a low test lung compliance (Crs), leak-free bench test model.MethodsA single operator provided positive pressure ventilation to a low compliance test lung model (Crs 0.2–1 mL/cmH2O) at set PIP of 15, 25, 35 and 40 cmH2O. Two TPR devices with known spikes (Draeger Resuscitaire, GE Panda) were compared with handheld Neopuff (NP). Recommended settings for positive end-expiratory pressure (5 cmH2O), inflation rate of 60/min and gas flow rate 10 L/min were used.Results2293 inflations were analysed. Draeger and GE TPR drivers delivered higher mean PIP (Panda 18.9–49.5 cmH2O; Draeger 21.2–49.2 cmH2O and NP 14.8–39.9 cmH2O) compared with set PIP and tidal volumes (TVs) compared with the NP (Panda 2.9–7.8 mL; Draeger 3.8–8.1 mL; compared with NP 2.2–6.0 mL), outside the prespecified acceptable range (±10% of set PIP and ±10% TV compared with NP).ConclusionThe observed spike in PIP over set values with Draeger and GE Panda systems resulted in significantly higher delivered volumes compared with the NP with identical settings. Manufacturers need to address these differences. The effect on patient outcomes is unknown.

Sign in / Sign up

Export Citation Format

Share Document