Singh et al. (2018) attempted to correlate anthropometric measurements (height and weight) to predict respiratory parameters in children with SCI and compare them with typically developing children and found, as expected, that children with SCI produced significantly lower forced vital capacity and forced expiratory volume at 1 second. A strong, positive correlation between age and forced vital capacity and forced expiratory volume was demonstrated in both the SCI group and typically developing group. However, while in typically developing children, a strong positive correlation was observed between forced vital capacity, forced expiratory volume and height, and weight, in the SCI group, height and weight did not significantly correlate to forced vital capacity or forced expiratory volume values. The typically developing children generated significantly higher expiratory pressures than children in the SCI group (related to significantly better recruitment of abdominal muscles as assessed by surface electromyography), but there was no significant difference in the inspiratory pressures between the two groups (again, confirmed by surface electromyography). Height and weight did not significantly correlate with inspiratory and expiratory pressures in children with SCI as opposed to the typically developing group. Age did not influence these pressures in either typically developing children or children with SCI.
In their observational study of 12 children with different levels and severity of SCI (C8-L11, Frankel A-D), Bergstrom et al. (2003) assumed a correlation between height and respiratory parameters (total lung capacity, forced vital capacity, forced expiratory volume, peak expiratory flow rate, and residual volume) and found that using height is better at predicting these values than using arm span (which overestimate the pulmonary function tests predicted values). The predicted lung function calculated by using height closely reflected the measured lung function. The authors postulated that the over-prediction of pulmonary function tests using arm span is related to the fact that the SCI triggers impaired growth (limbs and trunk) below injury level and might facilitate the development of soft tissue contractures and scoliosis, which, in turn, affect the lung volumes and airway pressures.