Restrictive lung disease is the most commonly reported pulmonary abnormality in adolescents with idiopathic scoliosis(IS). There is limited data on respiratory muscle function in IS. Since spinal deformity and decrease in lung volumes may lead to reduction in respiratory muscle strength, we studied these relationships.
Between 1999-2004, we retrospectively studied pre-operative IS. All performed spirometry, lung volumes and respiratory muscle assessments. Degree of scoliosis was measured radiographically by the Cobb Angle(CA). The following parameters were analyzed: CA,FEV1,FVC,FEV1/FVC,FEF 25-75,MVV,PImax,PEmax,and static lung volumes. Neuromuscular disease,lung disease patients and incomplete records were excluded.
Seventy four IS met the criteria for the study. The average age was 13.8± 2.1 years. Cobb Angles(CA) ranged between 23° and 84°, mean 50.7± 13.6°. Patients were divided into two groups, CA ≤ 45° (M), and CA > 45° (S).]. There were significant differences in FVC (97.9±14.9(M) vs 84.5±14.6%(S), P<0.05) and PEmax (85.4±22.5(M) vs 64.9±28.3%(S), P<0.05. between M and S groups. However, there were no significant differences in PImax, MVV or ERV between the two groups. Using linear regression analysis, there was a strong negative correlation between CA and FVC (r= -0.36; p = 0.002). There was a correlation approaching significant between CA and PImax (r= -0.23; p = 0.05). But there were no significant correlations between the CA and PEmax, MVV, or ERV.
FVC is the most sensitive marker of abnormal lung function in adolescents with idiopathic scoliosis. Respiratory muscle function, such as PEmax is significantly decreased in moderate to severe IS. But there is also a trend toward significant correlation between PImax and the degree of spinal curvature.
We speculate that the rib cage deformity and secondary respiratory muscle dysfunction in these patients impairs the ability to generate normal inspiratory and expiratory pressures. Assessment of respiratory muscle function may be a useful additional tool in adolescents with IS who are evaluated preoperatively for spinal stabilization procedures.
Rupali Bansal, None.