Wave-speed limitation on expiratory flow-a unifying concept

1977 ◽  
Vol 43 (3) ◽  
pp. 498-515 ◽  
Author(s):  
S. V. Dawson ◽  
E. A. Elliott
Keyword(s):  
Maximum Flow ◽  
Cross Sectional ◽  
Local Flow ◽  
Pressure Area ◽  
Forced Expiratory Flow ◽  
Quantitative Results ◽  
Expiratory Flow ◽  
Theoretical Results ◽  
Selection Of ◽  
Local Speed

The mechanism limiting forced expiratory flow is explained on the basis that a local flow velocity reaches the local speed of wave propagation at a point, called the choke point, in intrathoracic airways. This theoretical approach to the “waterfall effect” leads to selection of the analogy of constricted open-channel flow to apply to the elastic network of airway tubes. Quantitative results are derived for the case of negligible friction by use of the Bernoulli principle. Shapes predicted for the maximum-flow static recoil curves depend only upon the nature of the pressure-area curve at the choke point in the case of negligible friction; and the magnitude of the critical rate of flow depends on reference values of cross-sectional area and elastic modulus at the choke point, on gas density, and on the static recoil pressure. The present theoretical results are used to interpret previous experiments, but quantitative applicability is limited because of frictional effects and lack of knowledge of choke point conditions.

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 Viscoelasticity of the trachea and its effects on flow limitation

2006 ◽  
Vol 100 (2) ◽  
pp. 384-389 ◽  
Author(s):  
Nikolai Aljuri ◽  
Jose G. Venegas ◽  
Lutz Freitag
Keyword(s):  
Wave Speed ◽  
Mathematical Representation ◽  
Forced Expiration ◽  
Flow Limitation ◽  
Time Dependency ◽  
Cross Sectional ◽  
Elastic Tubes ◽  
Forced Expiratory Flow ◽  
Expiratory Flow ◽  
The Relationship

To test the hypothesis that peak expiratory flow is determined by the wave-speed-limiting mechanism, we studied the time dependency of the trachea and its effects on flow limitation. For this purpose, we assessed the relationship between transmural pressure and cross-sectional area [the tube law (TL)] of six excised human tracheae under controlled conditions of static (no flow) and forced expiratory flow. We found that TLs of isolated human tracheae followed quite well the mathematical representation proposed by Shapiro (Shapiro AH. J Biomech Eng 99: 126–147, 1977) for elastic tubes. Furthermore, we found that the TL measured at the onset of forced expiratory flow was significantly stiffer than the static TL. As a result, the stiffer TL measured at the onset of forced expiratory flow predicted theoretical maximal expiratory flows far greater than those predicted by the more compliant static TL, which in all cases studied failed to explain peak expiratory flows measured at the onset of forced expiration. We conclude that the observed viscoelasticity of the tracheal walls can account for the measured differences between maximal and “supramaximal” expiratory flows seen at the onset of forced expiration.

Mechanism of reduced maximum expiratory flow in methacholine-induced bronchoconstriction in dogs

1983 ◽  
Vol 55 (3) ◽  
pp. 897-912 ◽  
Author(s):  
S. N. Mink
Keyword(s):  
Wave Speed ◽  
Cross Sectional ◽  
Pressure Losses ◽  
Lung Capacity ◽  
Group I ◽  
Maximum Expiratory Flow ◽  
Pressure Area ◽  
Expiratory Flow ◽  
Group Ii ◽  
Viscous Pressure

Airway sites of flow limitation [“choke points” (CP)] were identified during forced deflation in open-chest dogs before (C) and after (B) bronchoconstriction was produced by nebulizing a solution of methacholine chloride into their airways. CP were identified in two respective groups. In group I (n = 8) a retrograde catheter was used to locate CP and in the other a Pitot static tube (group II, n = 5), CP were identified at multiple lung volumes (VL) over the lower one-half of total lung capacity. Both groups showed similar findings at each condition. At B, corresponding values of maximum expiratory flow (Vmax) at each VL decreased to about 10% of those at C. Movement of CP relative to their original location varied at each VL and, especially at the lower VL, showed little peripheral movement. In group I, equal pressure points were also measured and were found to move peripherally at all the measured VL. In group II, cross-sectional area (A*) and airway compliance (K) at CP were estimated. During bronchoconstriction, A* decreased at the respective VL, and airways became less compliant. The reduction in Vmax could be explained in terms of changes in A* and K as described by wave-speed theory, and Vmax decreased because A* decreased. The decrease in A* was related in part to an increase in viscous pressure losses that reduced total pressure at CP and also in part to a change in the pressure-area behavior of bronchi at CP. Their relative effects on reducing A* and Vmax were examined.

Relationship of ventilatory capacity to hyperbaric exposure in divers

1984 ◽  
Vol 56 (6) ◽  
pp. 1655-1658 ◽  
Author(s):  
I. S. Davey ◽  
J. E. Cotes ◽  
J. W. Reed
Keyword(s):  
Flow Rate ◽  
Vital Capacity ◽  
Positive Association ◽  
Forced Expiratory Volume ◽  
Elastic Tissue ◽  
Significant Positive Association ◽  
Cross Sectional ◽  
Maximal Depth ◽  
Forced Expiratory Flow ◽  
Expiratory Flow

The results of divers' annual medical examinations were used to assess the effects of diving exposure independent of age, stature, and smoking on forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1). Cross-sectional analysis of records for 858 men showed a significant positive association between the maximal depth that subjects had experienced and FVC but not FEV1. There was a significant negative association for FEV1/FVC%, and this index was also positively correlated with years of diving exposure. Among a subsample of 81 men the forced expiratory flow rate at low lung volume was reduced relative to that of control subjects similarly assessed; the extent of the reduction from the reference value was significantly correlated with the diving exposure. Longitudinal analysis of results for 255 men over a minimum of 5 yr showed that the change in FVC per annum (positive or negative) was correlated with the change in maximal depth; there were no similar associations for FEV1 or FEV1/FVC%. Thus diving exposure affects the vital capacity and the forced expiratory flow rate at small lung volumes. The latter is evidence for narrowing of airways that might be secondary to diving-induced loss of lung elastic tissue; this hypothesis merits further investigation.

scholarly journals Doctors’ views of disulfiram and their response to relapse in alcohol-dependent patients, Free State, 2009

2016 ◽  
Vol 8 (1) ◽  
Author(s):  
Paulina M. Van Zyl
Keyword(s):  
Free State ◽  
Structured Interviews ◽  
Cross Sectional ◽  
Study Population ◽  
Quantitative Results ◽  
Level Of Motivation ◽  
Effective Use ◽  
Selection Of ◽  
External Motivation

Background: Disulfiram is the oldest and best known drug to prevent relapse after detoxification from alcohol. Effective use of the drug is dependent on stringent monitoring and high levels of external motivation. Doctors’ perceptions about the drug have not been investigated extensively.Aim: We investigated the perceptions and practices of doctors involved in relapse prevention in alcoholics with regard to disulfiram and their response to relapse.Setting: The study population consisted of 60 doctors from the Free State Province, involved in the follow-up of alcoholics across various work settings.Methods: A cross-sectional descriptive study design was used, and data collection involved the use of a questionnaire and semi-structured interviews. Quantitative results are presented in figures and percentages to provide a background for the qualitative findings that are clustered in themes.Results: A quarter of participants did not prescribe disulfiram, another quarter prescribed disulfiram routinely after detoxification, and half of them prescribed it for selected cases only. Subject to affordability, selection of disulfiram was mainly determined by the perceived level of the patient’s motivation. External motivation sometimes took the form of threats of bodily harm or death caused by drinking. Some participants regarded relapse as confirmation of poor motivation and even a valid reason for terminating the doctor-patient relationship.Conclusion: Doctors perceive disulfiram as a psychological tool to induce motivation through creating fear of drinking. Failure and success are perceived as related to the level of motivation. These perceptions could be unfair as biological factors in inter-patient variability in response are ignored.

scholarly journals Comparative analysis of respiratory health profile among female beedi and non-beedi workers in a district of West Bengal

2021 ◽  
Vol 12 (7) ◽  
pp. 100-106
Author(s):  
Sujata Biswas ◽  
Nisha Bharti ◽  
Gandhari Basu
Keyword(s):  
Respiratory Health ◽  
Chronic Respiratory Disease ◽  
Cross Sectional Study ◽  
Forced Expiratory Volume ◽  
Health Profile ◽  
Cross Sectional ◽  
Chronic Respiratory Diseases ◽  
Forced Expiratory Flow ◽  
Expiratory Flow ◽  
Obesity Hypertension

Background: Beedi workers are more prone to develop chronic respiratory diseases over time. Aims and Objectives: The present research aimed to investigate and compare the respiratory health profile and the factors associated among the beedi workers and non-beedi workers. Materials and Methods: An analytical, community based, cross sectional study was conducted among 60 female beedi and non-beedi workers. Multistage sampling was used to select three wards out of twenty wards under a municipality of the study district. After interview with a pre-designed structured questionnaire, the respondents were examined clinically and pulmonary function test was done using a portable spirometer. Results: All beedi workers were married and 23.3% were illiterate. Most of them had 1to 10 years exposure. Half of them initiated their work between 11 to 20 years. Rate of tobacco smoking, obesity, hypertension, asthma, diabetes was high among beedi workers. Forced Vital Capacity, Forced Expiratory Flow 25-75 and Peak Expiratory Flow Rate were significantly more among non-beedi workers. Forced Expiratory Volume in 1st second was more among non-beedi workers but FEV1/FVC ratio was same for both the group. Conclusion: Significantly better respiratory health profile of non-beedi workers have reflected beedi binding as a reason behind chronic respiratory disease. Therefore, awareness generation session regarding occupation based adverse effects and safety measures must be conducted at regular interval to make the working condition favorable.

scholarly journals Interdisciplinarity in Higher Education: A Cross-Sectional Analysis of the Literature in the period 2014-2018

2019 ◽  
Vol 16 (1) ◽  
pp. 113-125
Author(s):  
Bernardo Vitor de Souza Marins ◽  
Hellen Costa Ramos ◽  
Geraldo Souza Ferreira ◽  
Stella Regina Reis Costa ◽  
Helder Gomes Costa
Keyword(s):  
Higher Education ◽  
Interdisciplinary Approach ◽  
Point Of View ◽  
Cross Sectional ◽  
Holistic View ◽  
Interdisciplinary Approaches ◽  
Quantitative Results ◽  
The Subject ◽  
Sectional Analysis ◽  
Selection Of

Goal: The growing complexity of problems induces the use of multi- and interdisciplinary approaches in their solution. This situation occurs in a number of fields, including in the field of Education. The results of research from the interdisciplinary point of view in Education are presented in several journals, addressing different subjects, which prevents a holistic view on the development of this area. In order to fill this gap, this article aims to study interdisciplinarity in education in order to understand how the concept of interdisciplinarity has been applied in this area. Design / Methodology / Approach: It consists of a bibliographical survey, with articles indexed in the SCOPUS database. The selection of articles was limited to a transversal research in the literature from 2014 to 2018, using the following keywords: interdisciplinarity and higher education. Limitations of the investigation: Through the methodology used, 60 articles were selected. Results: Few articles were related to interdisciplinary practices, demonstrating the need for research to cover this gap. Practical implications: Although the subject began in the 1970s, there is still much to be researched regarding interdisciplinarity in education, to allow a better dissemination and practice thereof, so that students have a systemic view of current complexity. Originality/ Value: The study points out a gap in the literature, and the quantitative results suggest that there is a greater deficiency of works directed to the application of the interdisciplinary approach in the development of this aspect for the improvement of society.

A forced expiratory flow at 25‐75% value <65% of predicted should be considered abnormal: A real-world, cross-sectional study

2012 ◽  
Vol 33 (1) ◽  
pp. 5-8 ◽  
Author(s):  
Giorgio Ciprandi ◽  
Michele Capasso ◽  
Mariangela Tosca ◽  
Carmelo Salpietro ◽  
Annamaria Salpietro ◽  
...  
Keyword(s):  
Real World ◽  
Cross Sectional Study ◽  
Sectional Study ◽  
Cross Sectional ◽  
Forced Expiratory Flow ◽  
Expiratory Flow

Fit and Congruency

2019 ◽  
Vol 18 (3) ◽  
pp. 148-156
Author(s):  
Mary Hogue ◽  
Lee Fox-Cardamone ◽  
Deborah Erdos Knapp
Keyword(s):  
Role Theory ◽  
Social Role ◽  
Gender Diversity ◽  
Job Fit ◽  
Cross Sectional Survey ◽  
Cross Sectional ◽  
Working Adults ◽  
Role Congruity ◽  
Self Selection ◽  
Selection Of

Abstract. Applicant job pursuit intentions impact the composition of an organization’s applicant pool, thereby influencing selection outcomes. An example is the self-selection of women and men into gender-congruent jobs. Such self-selection contributes to a lack of gender diversity across a variety of occupations. We use person-job fit and the role congruity perspective of social role theory to explore job pursuit intentions. We present research from two cross-sectional survey studies (520 students, 174 working adults) indicating that at different points in their careers women and men choose to pursue gender-congruent jobs. For students, the choice was mediated by value placed on the job’s associated gender-congruent outcomes, but for working adults it was not. We offer suggestions for practitioners and researchers.

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