Maximal oesophageal pressure closely correlates to exercise tolerance and is one of parameters which seems to predict distance walked during 6 minute walking test (6MWT). Since such studies are invasive we assessed non-invasive parameters of respiratory muscle function in a group of patients with moderate to severe chronic obstructive pulmonary disease (COPD) to investigate their relationship to pulmonary function and exercise tolerance.
41 patients with moderate to severe COPD (FEV1 42,5± 14,1% predicted) entered this cross-sectional study and underwent measurement of pulmonary function tests, diffusion capacity for carbon monooxide (DLCO), occlusion mouth pressures and 6 minute walking test. Saint George′s respiratory questionnaire (SGRQ) was used for assessing quality of life.
Distance walked in 6MWT was best related to RV/TLC, FEV1/VC (p<0,001 for both parameters), FEV1 and PImax (p<0,01 for both parameters). Maximal inspiratory mouth pressure (PImax) and tension-time index (TTmus) correlated with static lung hyperinflation (RV/TLC, p<0,05) and distance walked during 6MWT (p<0,01). There were no relationship between respiratory muscle function and quality of life in this group of patients. Backward linear regression analysis selected PImax as one of the most significant determinants for 6MWT. Only distance walked in 6MWT almost reached statistical significance with total score of SGRQ.CONCLUSIONS: Respiratory muscle function seems to predict, at least to some extent, exercise capacity.CLINICAL IMPLICATION: Non-invasive parameters (PImax and TTmus as an index of inspiratory muscle activity) are useful in assessing respiratory muscle function and together with other parameters in predicting exercise capacity in patients with COPD.
J. Chlumsky, None.