Longitudinal association between respiratory muscle strength and cough capacity in persons with spinal cord injury: An explorative analysis of data from a randomized controlled trial

To assess the longitudinal association between respiratory muscle strength and cough capacity in persons with recent spinal cord injury. Longitudinal analyses. Forty persons with recent spinal cord injury and impaired pulmonary function. Measurements were performed 4 weeks after the start of rehabilitation, 9 and 17 weeks after the first measurement, and one year after discharge from inpatient rehabilitation. Peak cough flow was measured with a spirometer. Maximum inspiratory and expiratory pressures (MIP and MEP), expressed in cmH2O, were measured at the mouth. Both MIP and MEP were significantly positively associated with peak cough flow. After correction for confounders and time 10 cmH2O higher MIP was associated with a 0.32 l/s higher peak cough flow, and a 10 cmH2O higher MEP was associated with a 0.15 l/s higher peak cough flow. The association between MIP and peak cough flow was mainly based on within-subject variance. The association between MIP and peak cough flow was stronger than between MEP and peak cough flow. Improvement in respiratory muscle strength is associated with improvement in cough capacity in persons with recent spinal cord injury who have impaired pulmonary function.