Investigation of dynamic hyperinflation and its relationship with exercise capacity in children with bronchiectasis

Dynamic hyperinflation (DH) is a major contributor to exercise intolerance in patients with obstructive lung diseases. However, it has not been investigated in children with bronchiectasis (BE). We aimed to investigate dynamic ventilatory responses and their influence on functional exercise capacity in children with BE.

Forty children with BE (mean forced expiratory volume in 1 s [FEV₁ ] = 78 ± 19%pred) were included. Six-minute walk test (6MWT) was conducted using Spiropalm 6MWT® for evaluating dynamic ventilatory responses including inspiratory capacity (IC), minute ventilation (VE), breathing reserve (BR) and respiratory rate (RR). A decrease of ≥100 ml in IC during exertion was defined as DH. Also, spirometry was performed, and peripheral muscle strength were measured.

Twenty patients (50%) developed DH, and four patients (10%) were ventilatory limited (BR < %30) during 6MWT. There was a 176 [100-590] ml decrease in IC after exertion in patients with DH. DH did not correlate to clinical or functional indicators of the disease, except for an increase in RR (∆RR) during exertion. High ∆RR was associated with presence of DH (r_pb = 0.390; p < 0.05). Clinical features, peripheral muscle strength, and Spiropalm 6MWT metrics including 6MWT distance did not differ between patients with and without DH. Univariate analysis revealed FVC% (R = 0.340), VE_peak (R = 0.565), quadriceps strength (R = 0.698) and handgrip strength (R = 0.711) were the only predictors of 6MWT distance (p < 0.05).

Although DH is common in children with BE, the severity of DH is rather low and may not seem to affect functional exercise capacity. However, peripheral muscle strength was a major contributor to functional exercise capacity.