Respiratory Muscle Strength During and After Hospitalization for COPD Exacerbation

BACKGROUND: A more profound investigation of respiratory muscle strength during COPD exacerbation was needed, so we investigated respiratory muscle strength and related factors in patients with COPD during and after hospitalization for COPD exacerbation. METHODS: In 19 subjects hospitalized for COPD exacerbation (12 males, mean age 67 11 y, median percent-of-predicted FEV1 26 % [IQR 19–32%]) we measured lung function and respiratory and quadriceps muscle strength at admission (day 1), at discharge, and 1 month after discharge. RESULTS: At admission, 68 % of the subjects had inspiratory muscle dysfunction (maximum inspiratory pressure < 70 % of predicted). Inspiratory muscle strength increased between day 1 (56 cm H2O [IQR 45–64 cm H2O]) and 1 month after discharge (65 cm H2O [IQR 51–74 cm H2O], P .007). Expiratory muscle strength increased between day 1 (99 cm H2O [65–117 cm H2O]) and discharge (109 cm H2O [77–136 cm H2O], P .005), and between day 1 and 1 month after discharge (114 cm H2O [90–139 cm H2O], P .001). Inspiratory capacity increased between discharge (1.59 0.44 L) and 1 month after discharge (1.99 0.54 L, P .02). There was no significant change in other lung function variables or quadriceps strength. At admission the inspiratory muscle dysfunction and reduction in inspiratory capacity (< 80 % of predicted) correlated linearly (phi coefficient 0.62, P .03), whereas the expiratory muscle strength correlated inversely with FEV1 (Spearman rho 0.61, P .005) and inspiratory capacity (Spearman rho 0.54, P .02). CONCLUSIONS: There was a high prevalence of inspiratory muscle dysfunction in patients hos-pitalized for COPD exacerbation. Inspiratory and expiratory muscle strength increased markedly during and after hospitalization. The degree of air-flow obstruction and hyperinflation were related to inspiratory and expiratory muscle strength. Key words: COPD; exacerbation; hospitalization; respiratory muscles; respiratory muscle strength. [Respir Care 2013;58(12):2142–2149. © 2013 Daeda-lus Enterprises