Reference values and repeatability of inspiratory capacity for men and women aged 65-85

The inspiratory capacity (IC) has recently gained importance because it may signal the occurrence of dynamic hyperinflation at rest or during exercise by reflecting changes in the end expiratory lung volume (EELV). However, reliable predicted values for IC are not currently available. The aim of the study was to generate predictive equations for reference values of IC in adults aged 65-85 living in Italy and to determine its limits of the within test-session repeatability. From the control group (n=429) of the SARA study data base, 241 (161 females) never smoked, non-obese (BMI<30 kg/m2) healthy subjects aged 65-85 who were able to correctly perform at least two manoeuvres of IC were selected. A model that incorporated age, height and body mass index as significant predictors in either sexes produced predicting equations for IC with a coefficient of determination of r2=.36 and .34 for females and males, respectively. Ninety per cent of all the subjects were able to keep the second highest IC within 200 ml (<9%) from the best IC. No significant gender difference was found for IC repeatability. We provided the equations for deriving reliable IC reference values that can be applied in the elderly people living in southern Europe. In this population IC showed limits of the within-session repeatability similar to those accepted for other spirometric indices such as FEV1 and FVC.