Changes in lung mechanics during asthma induced by exercise

Abstract

Pulmonary and airway mechanics were assessed in seven asthmatic patients in remission, when asthma was induced by exercise and again after spontaneous recovery or bronchodilator treatment. After exercise there was a sustained fall in forced expiratory volume in 1 s (FEV 1.0) in all patients, varying from 30 to 80 percent of the initial value. Total lung capacity (TLC) increased significantly in four of the seven patients. In one of the four patients the increase in TLC was associated with an increase in static transpulmonary pressure at full inflation but in the remaining three patients it was associated with a parallel shift of the pressure-volume curve of the lung without change in its slope. In all patients residual volume increased, regardless of change in TLC; both pressure-volume and maximum expiratory flow-volume curves suggested that widespread airway closure (or virtual closure) occurred at positive transpulmonary pressures when asthma was induced. Loss of lung recoli pressure sometimes contributed to the reduction in maximum expiratory flow but diffuse airway narrowing was probably the dominant abnormality. When air-flow obstruction became more severe the ratio of expiratory to inspiratory time was increased and although expiratory flow limitation was present excessive expiratory pressures were not generated.

Exercise‐Induced Asthma

“…In a group of children Benatar & Konig (6) found that EIA caused similar and significant changes in both crude and sensitive tests of lung function, but of particular interest was an increase in residual volume, fall in flow rates in the terminal part of the flow-volume curve and a decrease in the slope of the curve, which they felt indicated closure of some lung units. Similar conclusions were reached by Freedman et al (20) in a study of adults with EIA, but they also noted a substandal increase in total lung capacity in some subjects with a parallel shift of the pressure-volume curve to the left suggesting decreased elasdc recoil, closure of lung units and widespread airway narrowing.…”

“…The changes in crude tests of lung function such as the PEFR and FEV, implicate gross changes in larger airnays, but changes in lung recoil pressure or closure of lung units could also be involved (20). In a group of children Benatar & Konig (6) found that EIA caused similar and significant changes in both crude and sensitive tests of lung function, but of particular interest was an increase in residual volume, fall in flow rates in the terminal part of the flow-volume curve and a decrease in the slope of the curve, which they felt indicated closure of some lung units.…”

Pulmonary hyperinflation a clinical overview

“…In a subsequent study [28] based on plethysmographic measurements, the falls in FRC during recovery and the proportion of patients showing a reduction in TLC were even greater. Other studies suggested acute increases in TLC (measured plethysmographically) following exercise challenge [29,30] and inhalation of histamine [31]. WOOLCOCK and co-workers [28] had originally acknowledged the possibility that plethysmographic volume measurement might be an overestimate if changes in mouth pressure did not correspond to changes in alveolar pressure.…”

Budesonide reverses lung hyperinflation in childhood asthma: a controlled study

“…Based on the inflammatory theory of asthma, it was hypothesised that this was due, not only to an increase in airway calibre [23][24][25], but also to a reduction in peribronchial and alveolar inflammation [26] which, when present, causes a temporary loss of the relationship between small bronchi and parenchyma, thus reducing elastic recoil [27,28]. This is suggested in this study by the fact that a small improvement in airway calibre after budesonide, demonstrated by the increase in sG aw , was not accompanied by a change in RV, which remained higher and not different from placebo.…”