Sustained maximal inspiratory pressure is significantly related to mortality risk in COPD

Abstract

Introduction: The body mass index (BMI), airway obstruction, dyspnea, and exercise capacity (BODE) index is a multidimensional grading system that considers the systemic nature of COPD and predicts the risk of death among patients. The Test of Incremental Respiratory Endurance (TIRE) is a novel assessment of inspiratory muscle performance providing the sustained maximal inspiratory pressure (SMIP) reflecting inspiratory work. The relationship between these two measures is unknown. Aim: We examined the correlation between SMIP and the BODE index in patients with COPD. Methods: Twenty-three male COPD patients with mild to very severe obstruction (aged 71±6 years) underwent measurement of BMI, pulmonary function, the modified Medical Research Council dyspnea scale and 6-minute walk test from which the BODE index was calculated. SMIP was measured from residual volume to total lung capacity via the TIRE. Subjects were instructed to inspire deeply generating as much pressure as possible and to inspire maximally as long as possible. The best of 3-5 consistent trials was recorded. Results: The mean±SD height, weight, % predicted FEV1 and % predicted FVC were 176.9±6.9 cm, 82.4±22.9 kg, 37.1±15.9%, and 66±16.2%, respectively. The mean±SD SMIP and BODE score were 380.9±96 PTU and 4.4±1.9, respectively. SMIP significantly correlated positively to height (r=.44, p=.01) and weight (r=.37, p=.03) and negatively to the BODE index (r= -.494, p=.01). Conclusion: Greater SMIP was associated with lower BODE scores which may provide another method by which mortality risk in COPD can be assessed. Improving SMIP via inspiratory muscle training may facilitate greater survival. Further investigation is warranted.