Exercise induced bronchodilation: a phenomenon more common, greater magnitude and more prolonged in older adults than in adolescents.

OBJECTIVE: There are few studies in clinically healthy subjects describing and quantifying exercise-induced bronchodilation (EIBd). This study aimed to describe and compare the magnitude and time course changes in post-exercise forced expired volume at the first second (FEV1) in healthy adolescents, younger adults, and older adults. METHODS: Adolescent (n = 73, aged 10-17 years), younger adult (n = 35, aged 18-25 years), and older adult (n = 25, aged 35-66 years) subjects with normal spirometry z-scores completed a maximal cardiopulmonary exercise test using the standardized exponential exercise test protocol on a cycle ergometer performed at stable temperature and humidity. Spirometry was performed pre-exercise and at 1-, 3-, 5-, and 10-minutes post-exercise to determine the percentage change in FEV1 compared to baseline. EIBd was defined as a ≥ 5% increase in post-exercise FEV1. RESULTS: Increases in FEV1 at one-minute post-exercise were observed in the adolescents (1.3%) and young adults (6.0%) with FEV1 returning to baseline after ten minutes. Compared to the adolescents, the older adults showed significantly greater and sustained increases in FEV1 at 1-, 3-, 5-, and 10-minutes post-exercise (6.4, 4.6, 4.7, and 3.8%, p < 0.05). At 1-minute post exercise a significantly greater proportion of younger adults (54%, p < 0.01) and older adults (64%, p < 0.01) demonstrated EIBd compared to the adolescent group (15%). CONCLUSION: Healthy older adults had a higher prevalence, greater magnitude and more prolonged EIBd compared to healthy adolescent and young adult subjects.

Quantifying tidal expiratory flow limitation using a vector-based analysis technique.

Objective. Tidal expiratory flow limitation (EFLT) is commonly identified by tidal breaths exceeding the forced vital capacity (FVC) loop. This technique, known as the Hyatt method, is limited by the difficulties in defining the FVC and tidal flow-volume (TV) loops. The vector-based analysis (VBA) technique described and piloted in this manuscript identifies and quantifies EFLTas tidal breaths that conform to the contour of the FVC loop.Approach. The FVC and TV loops are interpolated to generate uniformly spaced plots. VBA is performed to determine the smallest vector difference between each point on the FVC and TV curves, termed the flow reserve vector (FRV). From the FVC point yielding the lowest FRV, the tangential angles of the FVC and TV segments are recorded. If the TV and FVC loops become parallel, the difference between the tangential angles tends towards zero. We infer EFLTas parallel TV and FVC segments where the FRV is < 0.1 and the tangential angle is within ±18 degrees for ≥5% of TV. EFLTis quantified by the percent of TV loop fulfilling these criteria. We compared the presence and degree of EFLTat rest and during peak exercise using the Hyatt method and our VBA technique in 25 healthy subjects and 20 subjects with moderate-severe airflow obstruction.Main results. Compared to the Hyatt method, our VBA technique reported a significantly lower degree of EFLTin healthy subjects during peak exercise, and in obstructed subjects at rest and during peak exercise. In contrast to the Hyatt method, our VBA technique re-classified five subjects (one in the healthy group and four in the obstructed group) as demonstrating EFLT.Significance.Our VBA technique provides an alternative approach to determine and quantify EFLTwhich may reduce the overestimation of the degree EFLTand more accurately identify subjects experiencing EFLT.

Novel application of Poincaré analysis to detect and quantify exercise oscillatory ventilation.

Objective.Exercise oscillatory ventilation (EOV) is frequently observed in individuals with cardiac disease. Assessment of EOV relies on pattern recognition and this subjectivity and lack of quantification limits the widespread clinical use of EOV as a prognostic marker. Poincaré analysis quantifies the short (SD1) and long-term (SD2) variability of a signal and may provide an alternative means to identify and quantify unstable exercise breathing patterns. This study aimed to determine if Poincaré analysis can distinguish between the breathing patterns of healthy control subjects and individuals being assessed for heart transplantation with and without EOV.Approach.Thirty-nine subjects performed a cardiopulmonary exercise test as part of heart transplant assessment and were subjectively classified into two groups according to the presence of EOV: non-EOV (n = 19) and EOV (n = 20). The control group (n = 24) consisted of healthy adults. Poincaré analysis (SD1 and SD2) was performed for minute ventilation (V̇E) and tidal volume (VT) normalized to forced vital capacity (V̇EnandV̇Tn), and breathing frequency (BF) for breath-by-breath data over the 10-15 ml · min-1 · kg-1V̇O2range.Main results.Poincaré analysis showed similar exercise ventilatory responses between the non-EOV and control group. BF was found to discriminate between subjects with stable and unstable ventilation. BF SD1 was significantly higher in the EOV group compared to the non-EOV (7.9 versus 4.6,p < 0.01) and control (7.9 versus 4.2,p < 0.01) groups. The EOV group had significantly greater BF SD2 compared to the non-EOV (5.7 versus 3.5,p < 0.01) and control (5.7 versus 3.5,p < 0.01) groups.Significance.We demonstrated that this novel application of Poincaré analysis can objectively distinguish and quantify unstable from stable breathing patterns during exercise. In subjects being assessed for heart transplantation the presence of EOV is associated with greater BF variability. Poincaré analysis provides an objective measure to identify and quantify EOV.Summary at a glance.As EOV may indicate abnormal ventilatory control, there is a need for an objective measure to identify and quantify unstable from stable ventilation during exercise. We developed a method of quantifying BF variation by the application of Poincaré analysis and demonstrated higher than normal variability of BF in subjects being assessed for heart transplantation who demonstrated EOV.