Maximum static respiratory pressures in healthy elderly men and women: Issues of reproducibility and interpretation

Background: Respiratory muscle strength is assessed using the static pressu re generated at the mouth during a maximal inspiratory or expiratory effort [PImax and PEmax, respectively (MSRPs)]. Interpretation of MSRPs relies up on comparison with 'normal' values, but MSRPs show very weak associations w ith predictors such as physical characteristics. The influence of habitual physical activity upon MSRPs remains undefined. Objectives: We examined mea surement reproducibility, as well as the influence of physical characterist ics and habitual physical activity upon MSRPs in healthy elderly people. Me thods: MSRPs were assessed in 41 healthy subjects using a portable mouth pr essure meter on two occasions, 1 week apart. Physical activity was assessed in 10 subjects by diary record. Pearson product-moment correlation coeffic ients were used to assess the association of MSRPs with other measured vari ables. Results: There was good measurement reproducibility of MSRPs, with c oefficients of reproducibility of 10.2 and 12.8% for PImax and PEmax, respe ctively. MSRPs showed statistically significant negative correlations with age, but correlations with physical characteristics were poor, in contrast, MSRPs were highly correlated with physical activity. Conclusions: We concl ude that MSRPs can be measured reproducibly and that they decline with adva ncing age. Physical characteristics are not good predictors of MSRPs; this may be due to a strong confounding influence of physical activity making in terpretation of measurements problematic. We suggest that the poor predicti ve power of physical characteristics indicate that reference to 'normal' va lues be made with caution and that it may be more appropriate to consider f unctional interpretations of MSRPs based upon factors such as lung and ches t wall elastance.