Cardiovascular reactions for whole-body thermal therapy with a hot pack and Waon therapy

Background: Waon therapy (WT) is the predominant thermal therapy for chronic heart failure in Japan, involving use of a far-infrared dry sauna. As sauna therapy requires certain equipment not readily available in hospitals, we tested the use of whole-body hot pack thermal therapy (HPTT). We compared the magnitude of skin vasodilation post-HPTT with that post-WT.Methods: We recruited 19 healthy men (age [mean ± S.D.]: 26.8 ± 4.6 years) and employed a simple randomized crossover design. The HPTT required subjects to remain in a supine position on a bed for at least 10 min. Hot packs were then applied on the back, lower abdomen, and popliteal regions for 15 min (warming phase). Participants continued bed rest for 30 min (heat-retention phase) after removal of the hot pack. WT was performed as previously described. Blood pressure (BP), heart rate (HR), tympanic temperature (TT), and peak and average flow velocity of the right radial artery (PFV and AFV, respectively) and right brachial artery (BA) diameter were measured during HPTT and WT.Results: HR, TT, PFV, and AFV persistently and significantly increased during warming and heat-retention phases of HPTT. In WT, HR and TT significantly increased during warming but decreased and plateaued during heat-retention. BP did not change significantly after either therapy; however, BA was dilated equally in both (HPTT: 3.70 ± 0.57 ⇒ 4.05 ± 0.59 mm, p = .001; WT: 3.63 ± 0.63 ⇒ 3.93 ± 0.61 mm, p < .001).Conclusion: HPTT may be equivalent to WT with respect to vasodilation response of the skin.