Evaluation of maximum inspiratory and expiratory pressure in patients with chronic obstructive pulmonary disease

Respiratory muscle dysfunction is a cardinal feature of acute and chronic respiratory failure in COPD. Diaphragm and accessory inspiratory muscles face increased load due to increased lung resistance and elastance, as well as increased ventilatory demand. Aim of the work: The objective of this work is to measure maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) in stable COPD patients and to correlate it with degree of airway obstruction and functional disability. Subjects, methods and result: Forty known COPD male patients were enrolled in this study with mean age 56.8 ± 7.7. Spirometry was done for all patients with mean FEV1 39.5 ± 15.1%, mean FVC 59.5 ± 19.2%, mean FEV1/FVC 52.9 ± 10.3%. Maximum inspiratory and expiratory pressures were done with mean 43.6 ± 26.9% and 46.8 ± 26% respectively. As regards 6 min walk distance, its mean was 131.41 ± 41.73 m. A quantification of dyspnea using the Modified Medical Research Council Scale (MRC) was done. The results of the present study showed: a highly significant positive statistical correlation between MIP, MEP and 6 min walk distance, also highly significant negative statistical correlation between MIP, MEP and MRC dyspnea scale. We note a significant positive correlation between MIP and each of PaO2 and SaO2, while MEP has a significant correlation with SaO2, also a highly significant negative statistical correlation between MIP, MEP and PaCO2. Conclusion: A highly significant positive statistical correlation between MIP, MEP and 6 min walk distance and a highly significant negative statistical correlation between MIP, MEP and subjective dyspnea evaluated by MRC dyspnea scale were found