Table 5

Test of possible mediation effect of airflow measures on association of maximum exercise capacity with air trapping

Mediating variableEffect of RV/TLC on VO2max (mL/min)
Airflow-mediated effect (%)P valuesNon-mediated effect (%)P values
FEV1/FVC6.90.28693.1 0.020
FEV1 15.20.23784.8 0.042
FEF25–75 1.60.60998.4 0.011
FEF75 2.00.65598.0 0.014
  • To see if the association of hyperinflation (RV/TLC) with maximum exercise capacity (VO2max) was mediated through airflow indices, mediation analyses were performed with adjustment for age, sex, height, and weight and inclusion of one airflow index at a time based on the model: Work=β01(age)+β2(sex)+β3(height)+β4(weight)+β5(RV/TLC)+β6(airflow index). n=179. Significant p-values are shown in bold.

  • FEF25–75, maximum airflow at mid-lung volume; FEF75, maximum airflow at low-lung volume; FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity; RV, residual volume; TLC, total lung capacity; VO2max, maximum oxygen uptake.