Breathing Heliox Reduces Expiratory Flow Limitation And Improves Exercise Performance In Adult Survivors Of Very Preterm Birth

Adult survivors of very preterm birth (PRET) have significantly lower aerobic exercise capacities than their counterparts born at term (CONT), but the underlying cause is unknown. To test whether expiratory flow limitation (EFL) during exercise negatively affects exercise endurance in PRET, we had PRET and CONT exercise to exhaustion breathing air and again breathing heliox. In PRET, EFL decreased and time-to-exhaustion increased significantly while breathing heliox. Heliox had a minimal effect on EFL and had no effect on time-to-exhaustion in CONT. We conclude that aerobic exercise endurance in PRET is limited, in part, by mechanical ventilatory constraints, specifically EFL.

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

Journal of Applied Physiology ◽

10.1152/japplphysiol.00400.2014 ◽

2015 ◽

Vol 118 (3) ◽

pp. 255-264 ◽

Cited By ~ 7

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.

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

Journal of Applied Physiology ◽

10.1152/japplphysiol.00393.2000 ◽

2002 ◽

Vol 92 (5) ◽

pp. 1943-1952 ◽

Cited By ~ 58

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.

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

European Journal of Applied Physiology ◽

10.1007/s00421-015-3145-5 ◽

2015 ◽

Vol 115 (8) ◽

pp. 1653-1663 ◽

Cited By ~ 9

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

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Analysis of maximal expiratory flow-volume curves in adult survivors of preterm birth

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00114.2019 ◽

2019 ◽

Vol 317 (4) ◽

pp. R588-R596 ◽

Cited By ~ 2

Author(s):

Yannick Molgat-Seon ◽

Paolo B. Dominelli ◽

Carli M. Peters ◽

Jordan A. Guenette ◽

A. William Sheel ◽

...

Keyword(s):

Preterm Birth ◽

Gestational Age ◽

Vital Capacity ◽

Airflow Obstruction ◽

Adult Survivors ◽

Flow Volume ◽

Very Preterm ◽

Maximal Expiratory Flow ◽

Expiratory Flow ◽

Do So

Adult survivors of very preterm (≤32 wk gestational age) birth without (PRE) and with bronchopulmonary dysplasia (BPD) have variable degrees of airflow obstruction at rest. Assessment of the shape of the maximal expiratory flow-volume (MEFV) curve in PRE and BPD may provide information concerning their unique pattern of airflow obstruction. The purposes of the present study were to 1) quantitatively assess the shape of the MEFV curve in PRE, BPD, and healthy adults born at full-term (CON), 2) identify where along the MEFV curve differences in shape existed between groups, and 3) determine the association between an index of MEFV curve shape and characteristics of preterm birth (i.e., gestational age, mass at birth, duration of oxygen therapy) in PRE and BPD. To do so, we calculated the average slope ratio (SR) throughout the effort-independent portion of the MEFV curve and at increments of 5% of forced vital capacity (FVC) between 20 and 80% of FVC in PRE ( n = 19), BPD ( n = 25), and CON ( n = 20). We found that average SR was significantly higher in PRE (1.34 ± 0.35) and BPD (1.33 ± 0.45) compared with CON (1.03 ± 0.22; both P < 0.05) but similar between PRE and BPD ( P = 0.99). Differences in SR between groups occurred early in expiration (i.e., 20–30% of FVC). There was no association between SR and characteristics of preterm birth in PRE and BPD groups (all P > 0.05). The mechanism(s) of increased SR during early expiration in PRE/BPD relative to CON is unknown but may be due to differences in the structural and mechanical properties of the airways.

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