Hyperinflation of bronchi in vitro impairs bronchodilation to simulated breathing and increases sensitivity to contractile activation

Abstract

Hyperinflated bronchi exhibit reduced bronchodilation to breathing and increased sensitivity to bronchoconstrictor stimuli. Findings suggest that hyperinflation may directly alter airway function by reducing the protective effects of DI and initiating contraction at low doses of contractile stimuli.

Contemporary Concise Review 2018: Asthma and chronic obstructive pulmonary disease

“…Cairncross et al . showed that hyperinflation directly alters the properties of isolated bronchial segments, reducing the protective effects of deep inspiration and making bronchi more sensitive to contractile stimuli . This work sheds light on the complex relationships between lung volume, bronchoconstriction and airway hyperresponsiveness …”

Sighs matter

“…In this issue of the journal, the study by Cairncross et al . examines yet another issue in the ongoing saga of lung inflation and airway responsiveness, albeit one that has thus far received little attention.…”

“…Perhaps, more important and peculiar to ASM versus other types of muscle is length adaptation. The bronchial rings investigated by Cairncross et al . were maintained at either 5 or 25 cm H 2 O for 2 h prior to being studied, which is probably long enough for the contractile machinery to adapt towards optimum forced generation at the corresponding ASM lengths, especially as viability studies were performed in the interim that would have facilitated adaptation.…”

“…A lung that operates chronically at an elevated volume may thus be subject to an elevated level of ASM contractility relatively to when lung volume is either normal or acutely elevated. Coupled with the reduced ability of breathing to stretch the airway wall for the reason proposed by Cairncross et al ., these additional factors have the potential to put the COPD lung at risk for unmitigated bronchospasm.…”

“…Cairncross et al . have thus put forward an interesting hypothesis that has a plausible physiological basis, and which may have clinical implications.…”