Maximal static mouth respiratory pressure in spinal cord injured patients: correlation with motor level

STUDY DESIGN: Transversal. OBJECTIVES: The few studies concerning maximal static mouth respiratory pressures in patients with spinal cord lesions suggest a marked reduction. We studied the correlation of these parameters with the motor level of injury. SETTING: Rehabilitation Center, Brasília/DF, Brazil. METHODS: One hundred and thirty-one patients with traumatic spinal cord injury (C4-L3) were recruited. The participants were assessed by standard spirometry and maximal static mouth respiratory pressure. RESULTS: Forced vital capacity was most reduced in tetraplegics (subgroup C4-C5, 49%+/-25 predicted) and increase successively for each descending subgroup (C6-C8, 61%+/-22 predicted; T1-T6, 70%+/-15 predicted), becoming normal in low paraplegia (T7-L3, 84%+/-15 predicted). There is no evidence of an obstructive disturbance throughout all groups. The lowest average percent predicted of maximal static inspiratory pressure (MIP) was in the subgroup C4-C5 (50%+/-23). The average percent predicted of maximal static expiratory pressure (MEP) improved from 19%+/-14 in the C4-C5 subgroup to 51%+/-19 for T7-L3 subgroup. The average percent predicted of all participants for MIP was 74%+/-30 and for MEP was 37%+/-21. In patients with complete motor lesion, the correlation with the level of injury was stronger for MEP (r=0.81, P<0.0001; r (2)=0.65) than for MIP (r=0.62, P=0.004; r (2)=0.38). No correlation was found among incomplete motor lesion patients. CONCLUSIONS: The linear regression equations for the relationship of percent predicted MIP or MEP to level of injury are applicable only to complete motor lesions and may be useful to establish normative association between them.