Effects of high environmental humidity on the measurement of urine output using diaper weights in the very low birth weight infant

The purpose of this descriptive study was to determine if the accumulation of water onto an open diaper from an environment of 85% to 95% relative humidity is clinically significant in the accurate measurement of urine output in the very low birth weight infant. Since normal urine output in a 500 grams (g) infant is exceedingly small, precise measurement is important. This study used no human subjects. A 500 millimeter (ml) bag of normal saline solution was substituted for a 'baby.' This 'baby' was placed in a high humidity environment on an open, premature-sized diaper. The diaper was then weighed at 1 hour, 2 hours, and 3 hours. Sixty diapers were measured. Clinically significant amounts of environmental fluid accumulated over the 3-hour time period, with a mean weight increase of 1.3 g in 3 hours. An incidental finding was that there was a significant weight variation among dry diapers, with a range of 2.1 g.