The diagrams shows the relative weight of the factors retained in the logistic regression analysis as predictors of the SGRQ total scores for male and female COPD patients. SGRQ total = Saint George's Respiratory Questionaire total score. MMRC = Modified Medical Research Council scale. 6MWD = Six minute walking distance test. Charlson = Charlson index. IC/TLC = Inspiratory Capacity/Total Lung Capacity ratio. PaO2 = Arterial oxygen pressure.