Impact of 60 Days of 6° head down bed rest on cardiopulmonary function, and the effects of Taikong Yangxin Prescription (太空养心方) as a countermeasure

Objective To study the changes in cardiopulmonary function induced by mid/long-term simulated microgravity with 6° head down bed rest (HDBR), and the effects of Taikong Yangxin Prescription (太空养心方, TYP) as a countermeasure. Methods: Fourteen healthy male volunteers were randomly divided into a control group and a Chinese medicine (CM) group (7 in each group) by a random digital table based on their body weight. Both groups underwent 6° HDBR for 60 days. Subjects in the CM group received daily TYP pills and subjects in the control group received daily placebo pills. Cardiac systolic and pumping functions were measured by echocardiography before HDBR; on days 20, 42, and 57 of HDBR; and on day 3 of recovery after HDBR (R+3). Cardiopulmonary functional reserve and exercise capacity were evaluated before HDBR, on day 29, and on day R+3 by exercise testing. Results The heart rate (HR) increased gradually during HDBR. The HR was significantly higher on day 57 than before HDBR in the control group ( P