How Is Pulmonary Function and Exercise Tolerance Affected in Patients With AIS Who Have Undergone Spinal Fusion?

STUDY DESIGN: Prospectively enrolled AIS patients who underwent spinal fusion, with 2 year follow-up.

OBJECTIVES: To evaluate the cardiovascular fitness and activity level in patients with AIS pre- and post-spinal fusion and to determine if initial curve magnitude or pulmonary function is predictive of exercise capacity.

SUMMARY OF BACKGROUND DATA: Researchers have tried to link pulmonary function testing (PFT) to exercise capacity; the results are mixed. Some report no improvement in PFTs or aerobic activity after surgical correction, and PFT measures were not predictive of exercise capacity. Conflicting results have shown Vo2max results to fall within normal range in AIS patients while PFTs show minimal impairment.

METHODS: AIS patients underwent PFT and oxygen consumption (VO2 ) testing during a submaximal graded exercise test (GXT) pre- and post-spinal fusion. Vo2max was predicted in those patients who completed the test to 85% of maximal heart rate. Pre- to postoperative changes were assessed and then compared to age-matched control subjects. Correlations between Vo2max and curve severity, pulmonary function, and activity level were assessed.

RESULTS: Thirty-seven patients participated. Vo2max was predicted in 23 patients pre- and postoperation. There was a significant reduction in Vo2max postfusion (39.5 ± 6.5 mL/kg/min vs 42.1 ± 8.1 mL/kg/min, p = .033); however, compared with controls (40.5 ± 6.5 mL/kg/min), all data were within the normal range (p > .05). AIS patients reporting high activity had significantly greater Vo2max than those reporting low activity both pre and postoperatively, but this difference only met statistical significance preop (p < .05). Curve magnitude and PFT measures were not found to correlate with Vo2max (p > .05).

CONCLUSIONS: Vo2max in patients with AIS is within normal range both pre- and postfusion. Pulmonary limitations are accommodated for with a slightly increased breathing rate and a slightly reduced overall workload. Activity level rather than curve severity affects Vo2max outcomes following fusion in AIS.