Inspiratory muscle performance predicts response to physical therapy in patients with chronic low back pain

Abstract

Introduction: Chronic low back pain (CLBP) is prevalent, costly, and has a high rate of poor outcomes worldwide. There are few known predictors for treatment response of CLBP to physical therapy (PT). However, an association between breathing dysfunction and CLBP has been suggested. The Test of Incremental Respiratory Endurance (TIRE) is a novel examination of strength and inspiratory endurance/work reflected primarily by the sustained maximal inspiratory pressure (SMIP) which may provide insight into breathing and CLBP. Aim: To examine the predictive value of SMIP on perceived disability (PD) in subjects with CLBP. Methods: TIRE SMIP was measured from residual volume to total lung capacity in seventeen CLBP patients (8 men, 9 women) prior to 1 month of standard PT (exercise, manual therapy, and physical agents). The Oswestry Disability Index (ODI) was administered before and after PT using standard methods to measure PD. Results: Prior to PT, the mean±SD age, SMIP, and ODI were 56±13 years, 477±226 PTU, and 33±12%, respectively. After 1 month of PT, the mean ODI score decreased 4±8%, with only 6/17 subjects exceeding the minimal detectable change of 5% for ODI scores. Baseline SMIP was a significant predictor of ODI change scores (r=.56; p=.03). Conclusions: Baseline SMIP predicts change in PD after 1 month of PT. Lower baseline SMIP scores were associated with greater improvements in PD. Thus, PD in subjects with CLBP, and concurrent low SMIP, may be associated with deconditioning rather than structural pathology and therefore be more responsive to PT. PT targeted at improving SMIP may improve PD in CLBP.