scholarly journals Post-Operative Flow-Volume Loops

1977 ◽  
Vol 5 (2) ◽  
pp. 146-148 ◽  
Author(s):  
A. Morton ◽  
P. Hansen ◽  
A. B. Baker
Keyword(s):  
Flow Volume ◽  
Lung Volumes ◽  
Flow Rates ◽  
Lower Flow

A study of flow-volume curves pre- and post-operatively demonstrated a marked difference between bronchitic and non-bronchitic patients. All bronchitic patients showed lower flow rates at low lung volumes post-operatively, when compared with their pre-operative values. Non-bronchitic patients all had higher flow rates for the same comparison.

Effects of thoracic gas compression on maximal and partial flow-volume maneuvers

1989 ◽  
Vol 67 (2) ◽  
pp. 780-785 ◽  
Author(s):  
R. D. Fairshter ◽  
R. B. Berry ◽  
A. F. Wilson ◽  
T. Brideshead ◽  
D. Mukai
Keyword(s):  
Pulmonary Function ◽  
Normal Subjects ◽  
Flow Volume ◽  
Maximal Flow ◽  
Alveolar Pressure ◽  
Lung Volumes ◽  
Flow Rates ◽  
Gas Compression ◽  
Expiratory Flow ◽  
Compression Artifacts

Airway hysteresis can be evaluated by comparing maximal (MEFV) and partial (PEFV) expiratory flow-volume curves. The maneuvers are often obtained from pulmonary function systems that are subject to gas-compression artifacts. Because gas-compression artifacts might differentially affect PEFV vs. MEFV curves, we simultaneously obtained MEFV and PEFV curves by use of a spirometer and a volume-displacement plethysmograph (a method not subject to gas-compression artifacts) in normal and asthmatic subjects. Plethysmographic flow rates exceeded spirometric flow rates on all MEFV and PEFV maneuvers. When maximal flow exceeded partial flow (or vice versa) in the plethysmograph, the same result was virtually always observed for spirometric measurements. Alveolar pressure (PA) was higher on MEFV than on PEFV maneuvers in asthmatic subjects; comparisons between PA (on PEFV and MEFV maneuvers) in normal subjects varied at different lung volumes. Ratios of Vmax on PEFV maneuvers to Vmax on MEFV maneuvers (Vmax-p/Vmax-c) obtained from a volume-displacement plethysmograph differ quantitatively from ratios determined in systems subject to gas-compression artifacts; qualitatively, however, failure to account for thoracic gas compression ordinarily will not influence the ability to identify airway hysteresis (or lack thereof) by use of Vmax-p-to-Vmax-c ratios.

Breathing at low lung volumes and chest strapping: a comparison of lung mechanics

1981 ◽  
Vol 50 (3) ◽  
pp. 650-657 ◽  
Author(s):  
N. J. Douglas ◽  
G. B. Drummond ◽  
M. F. Sudlow
Keyword(s):  
Lung Volume ◽  
Maximum Flow ◽  
Normal Subjects ◽  
Lung Mechanics ◽  
Lung Volumes ◽  
Flow Rates ◽  
Recoil Pressure ◽  
Forced Expiratory Flow ◽  
Expiratory Flow ◽  
Expiratory Flow Rates

In six normal subjects forced expiratory flow rates increased progressively with increasing degrees of chest strapping. In nine normal subjects forced expiratory flow rates increased with the time spent breathing with expiratory reserve volume 0.5 liters above residual volume, the increase being significant by 30 s (P less than 0.01), and flow rates were still increasing at 2 min, the longest time the subjects could breathe at this lung volume. The increase in flow after low lung volume breathing (LLVB) was similar to that produced by strapping. The effect of LLVB was diminished by the inhalation of the atropinelike drug ipratropium. Quasistatic recoil pressures were higher following strapping and LLVB than on partial or maximal expiration, but the rise in recoil pressure was insufficient to account for all the observed increased in maximum flow. We suggest that the effects of chest strapping are due to LLVB and that both cause bronchodilatation.

scholarly journals Powder flow down a vertical pipe: the effect of air flow

2002 ◽  
Vol 459 ◽  
pp. 317-345 ◽  
Author(s):  
Y. BERTHO ◽  
F. GIORGIUTTI-DAUPHINÉ ◽  
T. RAAFAT ◽  
E. J. HINCH ◽  
H. J. HERRMANN ◽  
...  
Keyword(s):  
Small Diameter ◽  
Stationary Flow ◽  
Momentum Conservation ◽  
Wall Friction ◽  
Particle Fraction ◽  
Friction Forces ◽  
Flow Rates ◽  
Lower Flow ◽  
Grain Flow ◽  
Grain Distribution

The dynamics of dry granular flows down a vertical glass pipe of small diameter have been studied experimentally. Simultaneous measurements of pressure profiles, air and grain flow rates and volume fractions of particles have been realized together with spatio-temporal diagrams of the grain distribution down the tube. At large grain flow rates, one observes a stationary flow characterized by high particle velocities, low particle fractions and a downflow of air resulting in an underpressure in the upper part of the pipe. A simple model assuming a free fall of the particles slowed down by air friction and taking into account finite particle fraction effects through Richardson–Zaki's law has been developed: it reproduces pressure and particle fraction variations with distance and estimates friction forces with the wall. At lower flow rates, sequences of high-density plugs separated by low-density bubbles moving down at a constant velocity are observed. The pressure is larger than outside the tube and its gradient reflects closely the weight of the grains. Writing mass and momentum conservation equations for the air and for the grains allows one to estimate the wall friction, which is less than 10% of the weight for grains with a clean smooth surface but up to 30% for grains with a rougher surface. At lower flow rates, oscillating-wave regimes resulting in large pressure fluctuations are observed and their frequency is predicted.

Mechanism of reduced maximum expiratory flow in dogs with compensatory lung growth

1986 ◽  
Vol 60 (2) ◽  
pp. 441-448 ◽  
Author(s):  
H. W. Greville ◽  
M. E. Arnup ◽  
S. N. Mink ◽  
L. Oppenheimer ◽  
N. R. Anthonisen
Keyword(s):  
Control Flow ◽  
Sham Operation ◽  
Forced Expiration ◽  
Flow Limitation ◽  
Lung Growth ◽  
Lung Volumes ◽  
Flow Rates ◽  
Compensatory Lung Growth ◽  
Maximum Expiratory Flow ◽  
Expiratory Flow

We examined the mechanism of the reduced maximum expiratory flow rates (Vmax) in a dog model of postpneumonectomy compensatory lung growth. During forced expiration, a Pitot-static tube was used to locate the airway site of flow limitation, or choke point, and to measure dynamic intrabronchial pressures. The factors determining Vmax were calculated and the results analyzed in terms of the wave-speed theory of flow limitation. Measurements were made at multiple lung volumes and during ventilation both with air and with HeO2. Five of the puppies had undergone a left pneumonectomy at 10 wk of age, and 5 littermate controls had undergone a sham operation. All dogs were studied at 26 wk of age, at which time compensatory lung growth had occurred in the postpneumonectomy group. Vmax was markedly decreased in the postpneumonectomy group compared with control, averaging 42% of the control flow rates from 58 to 35% of the vital capacity (VC). At 23% of the VC, Vmax was 15% less than control. Choke points were more peripheral in the postpneumonectomy dogs compared with controls at all volumes. The total airway pressure was the same at the choke-point airway in the postpneumonectomy dogs as that in the same airway in the control dogs, suggesting that the airways of the postpneumonectomy dogs displayed different bronchial area-pressure behavior from the control dogs. Despite the decreased Vmax on both air and HeO2, the density dependence of flow was high in the postpneumonectomy dogs and the same as controls at all lung volumes examined.

scholarly journals To the informative value of flow-volume curve in forced expiration

2008 ◽  
pp. 91-97 ◽  
Author(s):  
G. A. Lyubimov ◽  
I. M. Skobeleva ◽  
G. M. Sakharova ◽  
A. V. Suvorov
Keyword(s):  
Airway Resistance ◽  
Lung Compliance ◽  
Forced Expiration ◽  
Flow Volume ◽  
Functional Tests ◽  
Lung Volumes ◽  
Volume Curve ◽  
Quitting Smoking ◽  
Flow Volume Curve ◽  
Airway Walls

This report introduces a mathematical model of forced expiration to analyze pulmonary function. Results of 3-year lung function monitoring of an ex-smoker have been shown in the paper. Actual values of lung volumes and airway resistance were used for modeling. The computerized data were compared to the flow-volume curve parameters and lung volumes measured during the forced expiration. Weak correlation between the "flow-volume" curve parameters and the time after quitting smoking together with significant change in the lung volumes and the airway resistance seen in the study could be due to some processes which have not been followed in this study (lung compliance, airway resistance at forced expiration, and elastic properties of airway walls).The results demonstrated that mathematical models could increase informative value of pulmonary functional tests. In addition, the model could emphasize additional functional tests for better diagnostic usefulness of functional investigations.

Study on the effect of pore-scale heterogeneity and flow rate during repetitive two-phase fluid flow in microfluidic porous media

2021 ◽  
pp. petgeo2020-062
Author(s):  
Jingtao Zhang ◽  
Haipeng Zhang ◽  
Donghee Lee ◽  
Sangjin Ryu ◽  
Seunghee Kim
Keyword(s):  
Porous Media ◽  
Fluid Flow ◽  
Flow Rate ◽  
Sweep Efficiency ◽  
Residual Saturation ◽  
Flow Rates ◽  
Content Type ◽  
Lower Flow ◽  
Supplementary Material ◽  
Lower Flow Rate

Various energy recovery, storage, conversion, and environmental operations may involve repetitive fluid injection and, thus, cyclic drainage-imbibition processes. We conducted an experimental study for which polydimethylsiloxane (PDMS)-based micromodels were fabricated with three different levels of pore-space heterogeneity (coefficient of variation, where COV = 0, 0.25, and 0.5) to represent consolidated and/or partially consolidated sandstones. A total of ten injection-withdrawal cycles were applied to each micromodel at two different flow rates (0.01 and 0.1 mL/min). The experimental results were analyzed in terms of flow morphology, sweep efficiency, residual saturation, the connection of fluids, and the pressure gradient. The pattern of the invasion and displacement of nonwetting fluid converged more readily in the homogeneous model (COV = 0) as the repetitive drainage-imbibition process continued. The overall sweep efficiency converged between 0.4 and 0.6 at all tested flow rates, regardless of different flow rates and COV in this study. In contrast, the effective sweep efficiency was observed to increase with higher COV at the lower flow rate, while that trend became the opposite at the higher flow rate. Similarly, the residual saturation of the nonwetting fluid was largest at COV = 0 for the lower flow rate, but it was the opposite for the higher flow rate case. However, the Minkowski functionals for the boundary length and connectedness of the nonwetting fluid remained quite constant during repetitive fluid flow. Implications of the study results for porous media-compressed air energy storage (PM-CAES) are discussed as a complementary analysis at the end of this manuscript.Supplementary material: Figures S1 and S2 https://doi.org/10.6084/m9.figshare.c.5276814.Thematic collection: This article is part of the Energy Geoscience Series collection available at: https://www.lyellcollection.org/cc/energy-geoscience-series

Volume Adjustment of Maximal Expiratory Flow Rates of Flow-Volume Loops

CHEST Journal ◽  
1992 ◽  
Vol 102 (5) ◽  
pp. 1636-1637
Author(s):  
Sema Umut ◽  
Bilun Gemicioğlu ◽  
Nurhayat Yildirim
Keyword(s):  
Flow Volume ◽  
Flow Rates ◽  
Maximal Expiratory Flow ◽  
Expiratory Flow ◽  
Expiratory Flow Rates

scholarly journals The Effect of Variable Geometry on the Operating Range and Surge Margin of a Centrifugal Compressor

1976 ◽  
Author(s):  
A. Whitfield ◽  
F. J. Wallace ◽  
R. C. Atkey
Keyword(s):  
Centrifugal Compressor ◽  
Peak Pressure ◽  
Pressure Ratio ◽  
Variable Geometry ◽  
Vaneless Diffuser ◽  
Flow Rates ◽  
Lower Flow ◽  
Operating Range ◽  
Surge Margin ◽  
Isentropic Efficiency

Two variable geometry techniques have been applied to a small turbocharger compressor, with the objective of trying to move the peak pressure ratio operating point to lower flow rates, thereby yielding a broad flow range map. Variable prewhirl guide vanes and variable vaneless diffuser passage height have been studied separately. The results obtained with both techniques are compared and the relative merits and demerits with respect to improved flow range and isentropic efficiency penalties are considered.

Density-Dependence of Maximal Expiratory Flow Rates before and after Bronchodilators in Patients with Obstructive Airways Disease

1976 ◽  
Vol 51 (2) ◽  
pp. 133-139
Author(s):  
J. J. Wellman ◽  
E. R. McFadden ◽  
R. H. Ingram
Keyword(s):  
Density Dependence ◽  
Lung Volumes ◽  
Flow Rates ◽  
Maximal Expiratory Flow ◽  
Before And After ◽  
Group A ◽  
Obstructive Airways Disease ◽  
Expiratory Flow ◽  
Group B ◽  
Expiratory Flow Rates

1. Gas-density-dependence of maximal expiratory flow rates (V̇max), defined as the ratio of V̇max while breathing helium/oxygen (80:20) to V̇max. while breathing air at the same lung volume, was examined in relation to other measurements of airways obstruction in patients with obstructive airways disease before and after administration of bronchodilators. 2. Seventeen patients showed a 45% or greater increase in specific conductance(sGaw) after bronchodilator therapy (group A) and thirteen patients demonstrated a lesser response (group B). 3. Before the administration of bronchodilators, the degree of obstruction in the two groups was not different as measured by lung volumes, sGaw, forced expiratory volume in 1 s, and flow rates high in the vital capacity; yet the maximal mid-expiratory flow rate and the degree of density-dependence were significantly lower in group B. 4. After bronchodilators, both groups of patients showed significant improvements in sGaw flow rates and lung volumes. However, group A patients showed a significant increase in density-dependence whereas group B patients did not. 5. Increased density-dependence after bronchodilators in the group A patients was associated with an increase in the computed resistance of the upstream segment with air and a decrease in resistance with helium/oxygen. These changes could be explained by a more mouthward movement of equal pressure points, and therefore a further increase in the relative contribution of the larger density-dependent airways to limitation of flow. 6. The fact that density-dependence was not altered after bronchodilators in the group B patients suggests that the site of limitation of flow did not change appreciably. The shift in the pressure—flow curve for the upstream airways was such that the computed resistance of these airways fell. Thus it appears that the airways comprising the upstream segment were dilated.

Sign in / Sign up

Export Citation Format

Share Document