Sex- and age-adjusted reference values for dynamic inspiratory constraints during incremental cycle ergometry

Activity-related dyspnea in chronic lung disease is centrally related to dynamic (_dyn) inspiratory constraints to tidal volume expansion. Lack of reference values for exertional inspiratory reserve (IR) has limited the yield of cardiopulmonary exercise testing in exposing the underpinnings of this disabling symptom. One hundred fifty apparently healthy subjects (82 males) aged 40–85 underwent incremental cycle ergometry. Based on exercise inspiratory capacity (IC_dyn), we generated centile-based reference values for the following metrics of IR as a function of absolute ventilation: IR_dyn1 ([1-(tidal volume/IC_dyn)] x 100) and IR_dyn2 ([1-(end-inspiratory lung volume/total lung capacity] x 100). IR_dyn1 and IR_dyn2 standards were typically lower in females and older subjects (p<0.05 for sex and age versus ventilation interactions). Low IR_dyn1 and IR_dyn2 significantly predicted the burden of exertional dyspnea in both sexes (p<0.01). Using these sex and age-adjusted limits of reference, the clinician can adequately judge the presence and severity of abnormally low inspiratory reserves in dyspneic subjects undergoing cardiopulmonary exercise testing.