scholarly journals A geometric model analysis of conductive airways in expiratory flow limitation during artificial ventilation

2003 ◽  
Author(s):  
G. Cevenini
Keyword(s):  
Artificial Ventilation ◽  
Geometric Model ◽  
Model Analysis ◽  
Flow Limitation ◽  
Expiratory Flow Limitation ◽  
Expiratory Flow

Modeling expiratory flow from excised tracheal tube laws

1999 ◽  
Vol 87 (5) ◽  
pp. 1973-1980 ◽  
Author(s):  
Nikolai Aljuri ◽  
Lutz Freitag ◽  
José G. Venegas
Keyword(s):  
Static Pressure ◽  
Pressure Recovery ◽  
High Frequency Ventilation ◽  
Flow Limitation ◽  
Flow Conditions ◽  
Expiratory Flow Limitation ◽  
Elastic Tubes ◽  
Viscous Losses ◽  
Forced Expiratory Flow ◽  
Expiratory Flow

Flow limitation during forced exhalation and gas trapping during high-frequency ventilation are affected by upstream viscous losses and by the relationship between transmural pressure (Ptm) and cross-sectional area ( A tr) of the airways, i.e., tube law (TL). Our objective was to test the validity of a simple lumped-parameter model of expiratory flow limitation, including the measured TL, static pressure recovery, and upstream viscous losses. To accomplish this objective, we assessed the TLs of various excised animal tracheae in controlled conditions of quasi-static (no flow) and steady forced expiratory flow. A tr was measured from digitized images of inner tracheal walls delineated by transillumination at an axial location defining the minimal area during forced expiratory flow. Tracheal TLs followed closely the exponential form proposed by Shapiro (A. H. Shapiro. J. Biomech. Eng. 99: 126–147, 1977) for elastic tubes: Ptm = K p[( A tr/ A tr0)− n − 1], where A tr0 is A tr at Ptm = 0 and K p is a parametric factor related to the stiffness of the tube wall. Using these TLs, we found that the simple model of expiratory flow limitation described well the experimental data. Independent of upstream resistance, all tracheae with an exponent n < 2 experienced flow limitation, whereas a trachea with n > 2 did not. Upstream viscous losses, as expected, reduced maximal expiratory flow. The TL measured under steady-flow conditions was stiffer than that measured under expiratory no-flow conditions, only if a significant static pressure recovery from the choke point to atmosphere was assumed in the measurement.

scholarly journals Clinical characteristics of COPD patients with tidal expiratory flow limitation

2017 ◽  
Vol Volume 12 ◽  
pp. 1503-1506 ◽  
Author(s):  
James Dean ◽  
Umme Kolsum ◽  
Paul Hitchen ◽  
Vanadana Gupta ◽  
Dave Singh
Keyword(s):  
Clinical Characteristics ◽  
Flow Limitation ◽  
Expiratory Flow Limitation ◽  
Copd Patients ◽  
Expiratory Flow

Expiratory flow limitation during exercise in prepubescent boys and girls: prevalence and implications

2010 ◽  
Vol 108 (5) ◽  
pp. 1267-1274 ◽  
Author(s):  
Katherine E. Swain ◽  
Sara K. Rosenkranz ◽  
Bethany Beckman ◽  
Craig A. Harms
Keyword(s):  
Body Composition ◽  
Oxygen Saturation ◽  
Tidal Volume ◽  
Lean Body Mass ◽  
Lung Volume ◽  
Arterial Oxygen Saturation ◽  
Arterial Oxygen ◽  
Flow Limitation ◽  
Expiratory Flow Limitation ◽  
Expiratory Flow

The purpose of this study was to compare the prevalence and implications of expiratory flow limitation (EFL) during exercise in boys and girls. Forty healthy, prepubescent boys (B; n = 20) and girls (G; n = 20) were tested. Subjects completed pulmonary function tests and an incremental cycle maximal oxygen uptake (V̇o2max) test. EFL was recorded at the end of each exercise stage using the % tidal volume overlap method. Ventilatory and metabolic data were recorded throughout exercise. Arterial oxygen saturation (SpO2) was determined via pulse oximetry. Body composition was determined using dual-energy X-ray absorptiometry. There were no differences ( P > 0.05) in height, weight, or body composition between boys and girls. At rest, boys had significantly higher lung volumes (total lung capacity, B = 2.6 ± 0.5 liters, G = 2.1 ± 0.5 liters) and peak expiratory flow rates (B = 3.6 ± 0.6 l/s; G = 1.6 ± 0.3 l/s). Boys also had significantly higher V̇o2max (B = 46.9 ± 5.9 ml·kg lean body mass−1·min−1, G = 41.7 ± 6.6 ml·kg lean body mass−1·min−1) and maximal ventilation (B = 49.8 ± 8.8 l/min, G = 41.2 ± 8.3 l/min) compared with girls. There were no sex differences ( P > 0.05) at V̇o2max in VE /Vco2, end-tidal Pco2, heart rate, respiratory exchange ratio, or SpO2. The prevalence (B = 19/20 vs. G = 18/20) and severity (B = 58 ± 7% vs. G = 43 ± 8% tidal volume) of EFL was not significantly different in boys compared with girls at V̇o2max. A significant relationship existed between % EFL at V̇o2max and the change in end-expiratory lung volume from rest to maximal exercise in boys ( r = 0.77) and girls ( r = 0.75). In summary, our data suggests that EFL is highly and equally prevalent in prepubescent boys and girls during heavy exercise, which led to an increased end-expiratory lung volume but not to decreases in arterial oxygen saturation.

scholarly journals Clinical characteristics of COPD patients with tidal expiratory flow limitation

2017 ◽  
Author(s):  
James Dean ◽  
Umme Kolsum ◽  
Paul Hitchen ◽  
Vandana Gupta ◽  
Dave Singh
Keyword(s):  
Clinical Characteristics ◽  
Flow Limitation ◽  
Expiratory Flow Limitation ◽  
Copd Patients ◽  
Expiratory Flow

Influence of airway geometry on expiratory flow limitation and density dependence

1983 ◽  
Vol 52 (1) ◽  
pp. 113-123 ◽  
Author(s):  
Ronald J. Knudson ◽  
Robert C. Schroter ◽  
Dwyn E. Knudson ◽  
Stuart Sugihara
Keyword(s):  
Density Dependence ◽  
Flow Limitation ◽  
Expiratory Flow Limitation ◽  
Expiratory Flow

scholarly journals Maximal Oxygen Uptake Validation in Children With Expiratory Flow Limitation

2013 ◽  
Vol 25 (1) ◽  
pp. 84-100 ◽  
Author(s):  
Katherine E. Robben ◽  
David C. Poole ◽  
Craig A. Harms
Keyword(s):  
Oxygen Uptake ◽  
Maximal Oxygen Uptake ◽  
Constant Load ◽  
Work Rate ◽  
Flow Limitation ◽  
Expiratory Flow Limitation ◽  
Test Protocol ◽  
Wide Range ◽  
Rate Relationship ◽  
Expiratory Flow

A two-test protocol (incremental/ramp (IWT) + supramaximal constant-load (CWR)) to affirm max and obviate reliance on secondary criteria has only been validated in highly fit children. In girls (n = 15) and boys (n = 12) with a wide range of VO2max (17–47 ml/kg/min), we hypothesized that this procedure would evince a VO2-WR plateau and unambiguous VO2max even in the presence of expiratory flow limitation (EFL). A plateau in the VO2-work rate relationship occurred in 75% of subjects irrespective of EFL There was a range in RER at max exercise for girls (0.97–1.14; mean 1.06 ± 0.04) and boys (0.98−1.09; mean 1.03 ± 0.03) such that 3/15 girls and 2/12 boys did not achieve the criterion RER. Moreover, in girls with RER > 1.0 it would have been possible to achieve this criterion at 78% VO2max. Boys achieved 92% VO2max at RER = 1.0. This was true also for HRmax where 8/15 girls’ and 6/12 boys’ VO2max would have been rejected based on HRmax being < 90% of age-predicted HRmax. In those who achieved the HRmax criterion, it represented a VO2 of 86% (girls) and 87% (boys) VO2max. We conclude that this two-test protocol confirms VO2max in children across a threefold range of VO2max irrespective of EFL and circumvents reliance on secondary criteria.

Plethysmographic assessment of tidal expiratory flow limitation

2021 ◽  
pp. 103801
Author(s):  
Edgardo D’Angelo ◽  
Dejan Radovanovic ◽  
Paolo Barbini ◽  
Pierachille Santus ◽  
Matteo Pecchiari
Keyword(s):  
Flow Limitation ◽  
Expiratory Flow Limitation ◽  
Expiratory Flow

scholarly journals Effect of nocturnal EPAP titration to abolish tidal expiratory flow limitation in COPD patients with chronic hypercapnia: a randomized, cross-over pilot study

2020 ◽  
Vol 21 (1) ◽  
Author(s):  
Emanuela Zannin ◽  
Ilaria Milesi ◽  
Roberto Porta ◽  
Simona Cacciatore ◽  
Luca Barbano ◽  
...  
Keyword(s):  
Oxygen Saturation ◽  
Work Of Breathing ◽  
Lung Mechanics ◽  
Intrinsic Peep ◽  
Chronic Obstructive ◽  
Flow Limitation ◽  
Expiratory Flow Limitation ◽  
Copd Patients ◽  
Ineffective Efforts ◽  
Expiratory Flow

Abstract Background Tidal expiratory flow limitation (EFLT) promotes intrinsic PEEP (PEEPi) in patients with chronic obstructive pulmonary disease (COPD). Applying non-invasive ventilation (NIV) with an expiratory positive airway pressure (EPAP) matching PEEPi improves gas exchange, reduces work of breathing and ineffective efforts. We aimed to evaluate the effects of a novel NIV mode that continuously adjusts EPAP to the minimum level that abolishes EFLT. Methods This prospective, cross-over, open-label study randomized patients to one night of fixed-EPAP and one night of EFLT-abolishing-EPAP. The primary outcome was transcutaneous carbon dioxide pressure (PtcCO2). Secondary outcomes were: peripheral oxygen saturation (SpO2), frequency of ineffective efforts, breathing patterns and oscillatory mechanics. Results We screened 36 patients and included 12 in the analysis (age 72 ± 8 years, FEV1 38 ± 14%Pred). The median EPAP did not differ between the EFLT-abolishing-EPAP and the fixed-EPAP night (median (IQR) = 7.0 (6.0, 8.8) cmH2O during night vs 7.5 (6.5, 10.5) cmH2O, p = 0.365). We found no differences in mean PtcCO2 (44.9 (41.6, 57.2) mmHg vs 54.5 (51.1, 59.0), p = 0.365), the percentage of night time with PtcCO2 > 45 mm Hg was lower (62(8,100)% vs 98(94,100)%, p = 0.031) and ineffective efforts were fewer (126(93,205) vs 261(205,351) events/hour, p = 0.003) during the EFLT-abolishing-EPAP than during the fixed-EPAP night. We found no differences in oxygen saturation and lung mechanics between nights. Conclusion An adaptive ventilation mode targeted to abolish EFLT has the potential to reduce hypercapnia and ineffective efforts in stable COPD patients receiving nocturnal NIV. Trial registration: ClicalTrials.gov, NCT04497090. Registered 29 July 2020—Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT04497090.

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