Are room temperature and thermal neutral synonymous terms? An investigation of common therapeutic modality control variables

Context: Therapeutic modality control variables are thought to be thermal neutral, a term sometimes used interchangeably with room temperature. We question this common assumption. Objective: To determine thermal neutrality of common therapeutic modality control variables. Design: We performed 5 laboratory experiments, including (1) water temperature over 3 weeks in 3 different containers (glass, plastic, and polystyrene); (2) water temperature and volume of 4 beakers (2 insulated, 2 uninsulated) over 4 weeks, with 1 beaker of each type covered by polyethylene; and skin interface temperature of (3) a dry, nonheated hydrocollator pack held against the chest, (4) kitty litter applied to the knee, and (5) room-temperature ultrasound gel to the forearm. Setting: Therapeutic modalities laboratory. Patients or Other Participants: College student volunteers were subjects in experiments 3, 4, and 5. Main Outcome Measure(s): We measured temperature and volume change. Data were evaluated using descriptive and interferential statistics. Results: Water temperature plateaued significantly below room temperature. Temperatures significantly increased in all but the open, insulated container. Open containers plateaued at approximately 2°C below room temperature and lost significant amounts of water; closed containers plateaued at room temperature with negligible water loss. In experiments 3 through 5, skin temperatures rose significantly during hydrocollator pack, kitty litter, and ultrasound gel application. Conclusions: Room-temperature water baths, dry hydrocollator packs, kitty litter, and ultrasound gel were not thermally neutral. Room temperature should not be used synonymously with thermal neutral. Care must be taken to ensure that control variables truly are controlled.