Dynamic skinfold measurements to assess fluid status in low birthweight infants. Part 1: Data acquisition and processing.

To evaluate the measurement of fluid status in the premature neonate using dynamic skinfold thickness (DST) measurement, a pair of calipers were interfaced to a computer, and weight and digital DST at four sites were measured daily in 24 neonates in the postnatal weight loss period. A biexponential equation was fitted to each curve from the instant the rate of caliper closure fell below 2 mm/s, and the five constants obtained used in a search for a parameter that correlated with the percentage of weight loss. The percentage of fall in the DST from 0.4 to 30 seconds yielded highest mean of individual coefficients of determination (COD) (0.83); the percentage of fall from 0.7 to 35 seconds yielded highest COD in pooled data (0.56). Expected weight loss can be predicted with standard error of 2.9% with pooled regression but with standard error of 1.3% using individual correlations. We conclude that individuals lose fluid in a consistent manner during this period but that interindividual differences are large and require further investigation.