[O-RS-01-1] Optimal cut-off value of inspiratory muscle strength to predict exercise intolerance in patients with chronic heart failure
Keywords:Inspiratory Muscle Strength, Heart Failure, Exercise Intolerance
【Background】Inspiratory muscle weakness is present in 50% of chronic heart failure（CHF）patients and has been documented as an independent predictor for mortality. Although inspiratory muscle strength is thought to improve with inspiratory muscle training, the optimal cut-off value to determine the inspiratory muscle weakness has not been thoroughly evaluated in these patients. The aim of this study was to identify the cut-off value of inspiratory muscle strength to predict exercise intolerance in CHF patients.
【Methods】We studied 256 patients with CHF（60.3±12.0 years, 202 males）who performed cardiac rehabilitation during hospitalization and after hospital discharge. We measured maximal inspiratory pressure（PImax）as an inspiratory muscle strength using spirometer and calculated the percentage of predictive value（%PImax）. We also measured peak oxygen uptake（VO2）during symptom-limited cardiopulmonary exercise test and determined the peak VO2＜14 mL/kg/min as an exercise intolerance. All parameters were measured three months after hospital discharge. We identified the cut-off value of %PImax for peak VO2＜14 mL/kg/min and analyzed the influence of that value on exercise intolerance.
【Results】Forty-two patients showed peak VO2＜14 mL/min in this study. Analysis of receiver operating characteristic（ROC）curve revealed the %PImax as a significant predictor for peak VO2＜14 mL/kg/min with an area under the ROC curve of 0.727（95%CI：0.642-0.812, P＜0.001）. The cut-off value of %PImax for peak VO2＜14 mL/kg/min was 79.5%（sensitivity：0.685, specificity：0.690）. When the patients' %PImax showed ＜79.5%, the odds ratio to predict peak VO2＜14 mL/kg/min was 4.688（95%CI：1.928-11.401, P=0.001）.
【Discussion】This study demonstrated that the cut-off value of %PImax to predict exercise intolerance was 79.5%. This cut-off value is helpful in determining the inspiratory muscle weakness and identifying the criteria for inspiratory muscle training in CHF patients.
【Methods】We studied 256 patients with CHF（60.3±12.0 years, 202 males）who performed cardiac rehabilitation during hospitalization and after hospital discharge. We measured maximal inspiratory pressure（PImax）as an inspiratory muscle strength using spirometer and calculated the percentage of predictive value（%PImax）. We also measured peak oxygen uptake（VO2）during symptom-limited cardiopulmonary exercise test and determined the peak VO2＜14 mL/kg/min as an exercise intolerance. All parameters were measured three months after hospital discharge. We identified the cut-off value of %PImax for peak VO2＜14 mL/kg/min and analyzed the influence of that value on exercise intolerance.
【Results】Forty-two patients showed peak VO2＜14 mL/min in this study. Analysis of receiver operating characteristic（ROC）curve revealed the %PImax as a significant predictor for peak VO2＜14 mL/kg/min with an area under the ROC curve of 0.727（95%CI：0.642-0.812, P＜0.001）. The cut-off value of %PImax for peak VO2＜14 mL/kg/min was 79.5%（sensitivity：0.685, specificity：0.690）. When the patients' %PImax showed ＜79.5%, the odds ratio to predict peak VO2＜14 mL/kg/min was 4.688（95%CI：1.928-11.401, P=0.001）.
【Discussion】This study demonstrated that the cut-off value of %PImax to predict exercise intolerance was 79.5%. This cut-off value is helpful in determining the inspiratory muscle weakness and identifying the criteria for inspiratory muscle training in CHF patients.