Diaphragm ultrasonography and pulmonary function tests in patients with spinal cord injury

Study design Cross-sectional study. Objective To investigate the role of ultrasonographic measurement of the diaphragm thickness on pulmonary function tests in patients with spinal cord injury (SCI). Setting Rehabilitation center in Ankara, Turkey. Methods A total of 42 patients (34 M, 8 F) with SCI and 20 able-bodied volunteers (8 M, 12 F) were enrolled. Patients with SCI were divided into three groups according to their neurological (injury) levels. All participants underwent ultrasonographic measurements for diaphragm thickness on both sides and spirometric tests for pulmonary functions. The thickness ratio of the diaphragm was also calculated. Results There were seven patients (5 M, 2 F) in C2-C4 injury group, 14 patients (12 M, 2 F) in C5-T5 group, 21 patients (14 M, 7 F) in T6-L2 group, and 20 able-bodied volunteers (8 M, 12 F). The diaphragms of C2-C4 group were thicker than those of the controls at end-inspirium on the right side (2.7 +/- 0.7 mm vs. 2.0 +/- 0.5 mm; p = 0.035). The thickness ratios of C2-C4 group were lower than those of controls on the right (0.8 +/- 0.4 vs. 1.5 +/- 0.5; p = 0.005) and left (0.8 +/- 0.5 vs. 1.6 +/- 0.7; p = 0.003) sides. For all the pulmonary function tests (except for FLV1/FVC); patients with SCI had worse results than controls; and among the SCI groups, the higher the injury level, the worse the results. Conclusion Although patients with high-level SCI had worse pulmonary function tests and decreased the contractile capacity of the diaphragm, they had thicker diaphragm muscles than controls. This may have been due to the compensatory effect of the diaphragm (performing its maximum contraction capacity and increasing frequency of inspiration).