To determine the time needed to heat hot packs to water temperature (73–75 °C) in 4- and 8-pack Hydrocollator® units.
Design and Setting:
A 2 × 2 factorial design, with heating unit (4- or 8-pack) and number of packs added (1 or 3/7) as independent variables. Dependent variables were hot-pack and Hydrocollator-water temperatures.
Temperatures were measured with type T thermocouples interfaced with a 16-channel Isothermex™. Hydrocollator temperatures were measured with 2 thermocouples, and hot-pack temperatures, with 6 thermocouples inserted in 6 cells of a hydrated, 10- by 12-in Hydrocollator pack. Temperature was measured every 30 s for 5 min before and 45 min after pack immersion.
Packs warmed rapidly from ~18 to 65–68 °C by 10 min and to 72.5–75 °C by 20 min. Heating slowed by ~5% when 7 packs were added to the large unit. Water temperatures decreased ~2 °C (from ~75 °C) after 7 packs were immersed and returned to preimmersion temperatures by 20 min.
Rewarming is quicker than commonly believed (20–150 min) and might be a function of the number of packs being simultaneously warmed.
Kaiser, Knight, and Jutte are with the Therapeutic Modality Research Laboratory, Brigham Young University, Provo, UT 84602. Huff is a medical student at the Arizona College of Health Sciences. Carlson is a graduate student at the University of Tennessee–Chattanooga.