Vital capacity in tetraplegics twenty years and beyond.

Objectives: To observe the trends in vital capacity (VC) over time in tetraplegics 20 years and more after injury, the effects of age at injury, severity of injury and gender on this trend.

Methods: The medical records of all spinal cord injured persons admitted to a regional spinal injury center from January 1960 to December 1996 were reviewed. Fifty-seven patients had documented post-rehabilitation VC (mean 1.3+/-1.1 years) and VC at 10 (mean 11.8+/-2.69) and 20 (20.60+/-2.67) years post injury and beyond.

Results: The mean age at injury was 23.2+/-9.1 years. Severity of injury when classified according the system proposed by Coll et al were: Group 1: C1-4 Frankel A injury: 11.6%, Group 2: C5-8 Frankel A injury: 55.6%, Group 3: C2-8 Frankel B and C: 29.8% and Group 4: C2-8 Frankel D: 3.5% respectively. The mean VC at initial, 10 and 20 years post injury was 2586+/-948, 2803+/-940 and 2525+/-818 cc respectively. Multivariate analysis of variance revealed that there was significant difference in VC over a 20 year period, (F(2,54)=8.43, P<0.05). The difference between VC at 10 years and VC at 20 years accounted for the 19.8% of the variance in VC over time (F(1,55)=12.35, P<0.05). Age at injury, gender and severity of injury did not have a significant influence on the rate of decline in VC. Analysis of a subset of 26 patients who were followed up more than 20 years post injury (range 22 to 34.5 years) revealed similar, with a greater drop in the VC from 10 years post injury (F(1,23)=6.52, P<0.05). In this subset of patients, the mean VC at initial injury was 2840.9+/-847.3 cc, at 10 years was 2549.6+/-750.3 cc, at 20 years was 2400.9+/-724.1 cc and beyond 20 years was 2194.2+/-738.7 cc. There was no significant difference in mean VC between non smokers and ex/current smokers at initial, 10 and 20 years post injury, using the independent t-test (P>0.05).

Conclusion: Vital capacity in tetraplegics declines significantly over the years, with a greater decline occurring at more than 20 years post injury.