Cardiorespiratory fitness in patients with post-infectious bronchiolitis obliterans: a cross-sectional study

Post-infectious bronchiolitis obliterans (PIBO) arises after lower respiratory tract infection during childhood and is marked by impaired lung function. Despite possible impacts on exercise capacity, cardiorespiratory fitness in PIBO patients remain largely unknown. This study aimed to examine cardiorespiratory fitness and identify possible demographic and clinical-functional associations.

The following variables were examined in a multicentre, cross-sectional study conducted in clinically stable PIBO patients aged 6-20 years: cardiorespiratory fitness (exercise testing), lung function (spirometry and impulse oscillometry), muscle strength (handgrip, upper and lower extremities), functional capacity (30-s sit-to-stand (STS) test), physical activity level (physical activity questionnaire adolescents and children; PAQ-A-C), body mass index (BMI), quality of life (Saint George's respiratory questionnaire; SGRQ) and dyspnoea perception (modified Medical Research Council scale).

51 patients were enrolled (mean age 13.2±4.2 years, 49% female). BMI z-score was 0.06±1.20. Lung function tests indicated moderate-to-severe obstruction (forced expiratory volume in 1 s (FEV₁) z-score -3.55±1.30) and elevated airway resistance (R5 Hz 165.8±53.64%). Peak oxygen consumption (V' _{O2 peak}) was 36.8±8.58 mL·kg^-1·min^-1 (47% ≤10 percentile) and breathing reserve 7.08±8.29%, indicating ventilatory limitation. Handgrip strength was 0.49±0.14 kg·kg^-1. The 30-s STS test was 27.2±5.7 repetitions. PAQ-A/PAQ-C was 1.89±0.46 indicating a low physical activity level. SGRQ was 20.1±10.8%. There was no resting dyspnoea. Multivariate regression identified significant associations between V' _{O2 peak} and FEV₁ (p<0.001), BMI (p<0.001), SGRQ (p=0.005), female sex (p=0.002) and age (p=0.033).

In these patients, cardiorespiratory fitness was impaired mainly due to ventilatory limitations. Lung function, upper and lower limb muscle strength, BMI, quality of life, sex and age were all associated with fitness level.