Comparison of closed chamber and open chamber evaporimetry.

BACKGROUND: Recently it has been asserted that a closed chamber evaporimeter, the VapoMeter, offers advantages over standard open chamber devices in measuring transepidermal water loss (TEWL). Purported improvements include the ability to take measurements at any angle, short reading times and insensitivity to external air currents. These claims are compelling, considering that measuring TEWL at diverse skin sites can be tedious, especially with children. The primary aim of this study was to compare the performance of closed and open chamber instruments when they were held at various angles and, secondly to evaluate the ability of the devices to discriminate between test conditions. METHODS: The performance of closed chamber (VapoMeter) and open chamber (DermaLab) evaporimeters were compared by measuring water vapor emitted from IMS Vitro-skin that had been hydrated to a predetermined level. Measurements were taken at three angles from vertical - 0 degrees, 45 degrees, and 90 degrees. Vitro-skin samples were weighed periodically throughout the experimental phase to verify water loss rates. RESULTS: Both the VapoMeter and the DermaLab yielded significantly lower water loss values when held at angles that varied from the vertical (0 degrees) position, indicating that the closed chamber device is no more capable of accurately measuring TEWL at any angle than an open chamber instrument. The DermaLab provided better discrimination than the VapoMeter when the instruments were held vertically, as is the only prescribed testing position for open-chamber instruments. The VapoMeter was easier to use than the DermaLab; however, there was evidence that the sealed chamber could become saturated under high water loss conditions. CONCLUSIONS: Previous assertions that the VapoMeter closed chamber evaporimeter is capable of measuring TEWL regardless of angle were not validated. Each device appeared capable of accurately estimating water loss rates only in the vertical position. Although the VapoMeter was easier to use than the open chamber device, its tendency to become saturated under high water loss conditions could be a disadvantage when assessing dynamic TEWL.

Comparison of performances of transfer students and first-year acceptees.

Graduates of the Medical College of Pennsylvania during 1970-1977 were studied to determine the impact of three types of preclinical training on prelicensure clinical performance. The 586 students who comprised these groups consisted of 471 students admitted to the first year, 53 students admitted with advanced standing from U.S. medical or graduate programs, and 62 students admitted with advanced standing from foreign medical schools. Academic performances among the groups differed as measured by scores on the examinations of the National Board of Medical Examiners. However, perceived clinical performances of both transfer groups, as measured by honors awarded in year four and by first-year residency evaluation, were on a par with that of the original matriculants.