Respiratory muscle performance in normal elderly subjects and patients with COPD.

We studied the reproducibility of tests of RM performance in normal elderly subjects and compared their performance with that of patients with COPD. The RM strength was measured as MIP and MEP. The RM endurance was measured using a two-minute incremental threshold loading test. The max load, the average Ppk as %MIP at max load and the Pmean at max load were taken as measures of respiratory muscle endurance. The MIP, but not MEP, was less in COPD patients than in normal subjects (p less than 0.05). There was a small increase in between visits, in MIP in the normal subjects. All measures of RM endurance were much lower in the COPD group than in the normal elderly (p less than 0.05). We conclude that (1) RM strength and endurance are reproducible in normal elderly subjects and patients with COPD, (2) that COPD subjects have decreased RM strength and endurance compared with normal elderly subjects, and (3) that in COPD subjects RM endurance is compromised more than RM strength.