Endurance exercise performance in acute hypoxia is influenced by expiratory flow limitation

2015 ◽  
Vol 115 (8) ◽  
pp. 1653-1663 ◽  
Author(s):  
Joshua C. Weavil ◽  
Joseph W. Duke ◽  
Jonathon L. Stickford ◽  
Joel M. Stager ◽  
Robert F. Chapman ◽  
...  
Keyword(s):  
Endurance Exercise ◽  
Exercise Performance ◽  
Acute Hypoxia ◽  
Flow Limitation ◽  
Expiratory Flow Limitation ◽  
Expiratory Flow

scholarly journals Heliox breathing equally influences respiratory mechanics and cycling performance in trained males and females

2015 ◽  
Vol 118 (3) ◽  
pp. 255-264 ◽  
Author(s):  
Sabrina S. Wilkie ◽  
Paolo B. Dominelli ◽  
Benjamin C. Sporer ◽  
Michael S. Koehle ◽  
A. William Sheel
Keyword(s):  
Exercise Performance ◽  
Respiratory Mechanics ◽  
Work Of Breathing ◽  
Time Trial ◽  
Whole Body ◽  
Flow Limitation ◽  
Maximal Aerobic Capacity ◽  
Expiratory Flow Limitation ◽  
Ventilatory Capacity ◽  
Expiratory Flow

In this study we tested the hypothesis that inspiring a low-density gas mixture (helium-oxygen; HeO2) would minimize mechanical ventilatory constraints and preferentially increase exercise performance in females relative to males. Trained male ( n = 11, 31 yr) and female ( n = 10, 26 yr) cyclists performed an incremental cycle test to exhaustion to determine maximal aerobic capacity (V̇o2max; male = 61, female = 56 ml·kg−1·min−1). A randomized, single-blinded crossover design was used for two experimental days where subjects completed a 5-km cycling time trial breathing humidified compressed room air or HeO2 (21% O2:balance He). Subjects were instrumented with an esophageal balloon for the assessment of respiratory mechanics. During the time trial, we assessed the ability of HeO2 to alleviate mechanical ventilatory constraints in three ways: 1) expiratory flow limitation, 2) utilization of ventilatory capacity, and 3) the work of breathing. We found that HeO2 significantly reduced the work of breathing, increased the size of the maximal flow-volume envelope, and reduced the fractional utilization of the maximal ventilatory capacity equally between men and women. The primary finding of this study was that inspiring HeO2 was associated with a statistically significant performance improvement of 0.7% (3.2 s) for males and 1.5% (8.1 s) for females ( P < 0.05); however, there were no sex differences with respect to improvement in time trial performance ( P > 0.05). Our results suggest that the extent of sex-based differences in airway anatomy, work of breathing, and expiratory flow limitation is not great enough to differentially affect whole body exercise performance.

Determinants of exercise performance in normal men with externally imposed expiratory flow limitation

2002 ◽  
Vol 92 (5) ◽  
pp. 1943-1952 ◽  
Author(s):  
Iacopo Iandelli ◽  
Andrea Aliverti ◽  
Bengt Kayser ◽  
Raffaele Dellacà ◽  
Stephen J. Cala ◽  
...  
Keyword(s):  
Exercise Performance ◽  
Valsalva Maneuver ◽  
Flow Limitation ◽  
Expiratory Flow Limitation ◽  
Optoelectronic Plethysmography ◽  
Expiratory Flow ◽  
The Difference ◽  
Blood Volume Shift ◽  
Normal Men ◽  
Gas Volume

To understand how externally applied expiratory flow limitation (EFL) leads to impaired exercise performance and dyspnea, we studied six healthy males during control incremental exercise to exhaustion (C) and with EFL at ∼1. We measured volume at the mouth (Vm), esophageal, gastric and transdiaphragmatic (Pdi) pressures, maximal exercise power (W˙max) and the difference (Δ) in Borg scale ratings of breathlessness between C and EFL exercise. Optoelectronic plethysmography measured chest wall and lung volume (Vl). From Campbell diagrams, we measured alveolar (Pa) and expiratory muscle (Pmus) pressures, and from Pdi and abdominal motion, an index of diaphragmatic power (W˙di). Four subjects hyperinflated and two did not. EFL limited performance equally to 65%W˙max with Borg = 9–10 in both. At EFLW˙max, inspiratory time (Ti) was 0.66s ± 0.08, expiratory time (Te) 2.12 ± 0.26 s, Pmus ∼40 cmH2O and ΔVl-ΔVm = 488.7 ± 74.1 ml. From Pa and Vl, we calculated compressed gas volume (Vc) = 163.0 ± 4.6 ml. The difference, ΔVl-ΔVm-Vc (estimated blood volume shift) was 326 ml ± 66 or 7.2 ml/cmH2O Pa. The high Pmus and long Te mimicked a Valsalva maneuver from which the short Ti did not allow recovery. Multiple stepwise linear regression revealed that the difference between C and EFL Pmus accounted for 70.3% of the variance in ΔBorg. ΔW˙di added 12.5%. We conclude that high expiratory pressures cause severe dyspnea and the possibility of adverse circulatory events, both of which would impair exercise performance.

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.

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.

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