P0837 - Maximal Voluntary Ventilation (MVV) Testing in Orthopaedic Clinic Demonstrates Pulmonary Improvement Following PSF for AIS

Background: In patients with severe adolescent idiopathic scoliosis (AIS), maximal voluntary ventilation (MVV) has been shown to be more strongly correlated with Cobb angle than forced vital capacity (FVC) in an orthopaedic office setting. We sought to evaluate pulmonary function of AIS patients with changes in Cobb angle over time.

Methods: 49 AIS patients with thoracic curves of 10° or greater were enrolled. Patients performed the PFTs using the Carefusion MicroLoop Spirometer. MVV (liters/min) values were collected. Results were considered reliable when ATS/ERS criteria were met according to the incentive spirometer guidelines. Patients made at least 3 attempts to perform a reliable test. Testing was conducted at time of enrollment and 1 year later. Cobb angle worsening of >5° was considered curve progression.

Results: At enrollment, 49 patients had a mean Cobb angle of 38° (range: 10°-79°). One year later 18 patients had undergone fusion, 10 patients had a Cobb angle progression >5°, and 21 patients did not have progression (mean: 31° range: 10°-51°). At 1 year, 100% (49/49) of patients met ATS criteria for the MVV test. There was a significant negative correlation between MVV and Cobb angle (r=-0.3724, p=0.04). MVV scores showed significant improvement in patients who had a PSF (presumably due to improvement in thoracic deformity) (p<0.01), and in curves that did not worsen (presumably due to normal improvement of MVV with growth) (p=0.01). In non-surgical patients whose curves worsened a mean of 13°, there was no significant change in MVV (p=0.41) (Table 1).

Conclusion: This is the first study using an office-based, pulmonary test performed in the orthopaedic clinic that shows improved pulmonary function with growth and PSF in AIS patients.