Taavoni et al.
evaluated pain in women before they left the labor ward, usually in 3–4 hours after the birth. In this study, the pain was assessed at 30, 60, 90, and 120 minutes during first stage of labor. Despite these differences, the findings were comparable, and this might be credited to the heat mechanism. When the heat is applied, touch and tem- perature receptors are stimulated, creating a pleasant sensation. Pain signals compete with these pleasurable feelings to access the spinal cord, thus leading to a dimin- ished sensation of pain [25]. Pain relief experienced with heat application can also be explained through the action of released endorphins [26].
Because no data are available about the best temperature or duration of heat therapy, care should be taken to avoid burns. In this study, the subjects were asked to check the temperature of towels manually to avoid burning.
In this study, there were no significant differences in the mean score of pain in 30 minutes after intervention between the heat therapy group and control group. Heat transfer is directly related to the temperature gradient, the surface area covered, and the duration of application [24]. However, it is unknown to what depth heat would pen- etrate when applied to the perineum. Moreover, duration and the temperature required to cause physiological changes are still not clear [23]. Heat applied directly to the skin at 40°C increases muscle tissue temperature by at least 1°C at depths ranging from 2.0 to 3.8 cm below the surface of the skin [27]. A 1°C increase in tissue tempera- ture is associated with a 10–15% increase in tissue metabolism [28], but this requires time [29], possibly explaining why pain was not significantly decreased during the first 30 minutes of heat therapy. It is possible that different tissues, such as perineal muscle or sphincter fibers, would respond differently to the applied heat [23]. The application of the heat over the perineum is consid- ered helpful in encouraging perineal stretching, higher blood supply to the perineum, and in the prevention of perineal tearing [30].
In recent decades, measuring patient satisfaction has been in focus of attention [31] of health care managers in assessing the quality of care [32]. There are different methods to evaluate satisfaction, and VAS is one of the well-recognized methods to measure satisfaction. However, VAS is a rudimentary measurement of satisfac- tion because it does not distinguish individual causes [22].