Prediction of Normal Spirometric Values for Adults Incapable of Standing: Discussion

A significant number are unable to stand for measurement of vertical height as part of pulmonary function testing. This is especially true for amputees, stroke victims, and spinal cord injured patients. We did not compare spirometric results in sitting and standing positions. Pierson et al made such a comparison in 235 men and women. These investigators found values obtained in the standing position to be greater than in the sitting position. The differences were statistically significant but small for the forced vital capacity (FVC) (0.04 ±0.01 L; p<0.01) and the forced expiratory volume in one second (FEVX) (0.02 ±0.01 L; p<0.05). They found no significant differences for the mean forced expiratory flow over the middle half of the FVC (FEF25-75%) (0.03 ±0.02 L) and the FEV/FVC ratio expressed as a percentage (FEV1/FVC%) (0.1 ±0.2 percent). Townsend tested 90 middle-aged men using a crossover sequence and found significantly larger values for FVC (0.06 L) and FEVX (0.07 L) in the standing position, but, again, the differences were small. comments

Hepper et al reported studies in patients with kyphoscoliosis. These investigators recommended that arm span measurements substitute for height in prediction equations for pulmonary values (vital capacity and lung volume). We did not study patients with spinal deformity, and the equations in Table 3 would probably not be appropriate. Ferris and Stroudt compared various body measurements in relation to spirometric results. They concluded that sitting height was less accurate than standing height measured against a wall. Their data suggest that this is true for FVC, but essentially there was no difference in the correlation coefficients for sitting and standing heights for FEVj . Ferris and Stroudt suggest that arm span be used for predicting normal values when an accurate standing height was not attainable. Their correlation coefficient for arm span was reasonable for FVC but poor for FEVX.
Three methods for estimating standing height from sitting height have been presented (a fixed standing-to-sitting height ratio, simple, and multiple regression equations). Although the multiple regression equations have the smallest values for SEE, the maximum difference between the methods values for SEE was 0.3 inch, which translates into a volume difference of approximately 30 ml for both FVC and FEV1 using typical prediction equations. The method to be selected depends upon the discretion of the user. We recommend the fixed ratio for manual or nonprogrammable calculator calculations. The multiple regression equations or the sitting height spirometric prediction equations are appropriate for programmable calculators or computers because they are slightly more accurate for prediction and are convenient once they have been installed in the programs. The principal value of these height prediction methods is that they allow the use of customary equations to predict spiro-metric values for subjects incapable of standing but able to sit erect.

Category: Health

Tags: adults incapable of standing, physical characteristics, Pulmonary Function