Abstract： Objective To observe the effects of hyperbaric oxygen (HBO) on blood pressure and heart rate in patients with different physical postures and conscious states.Methods Patients were divided into different groups based on their postures or conscious states.Blood pressure and heart rate were measured in 57patients prior to treatment,before termination of compression,during maintenance of pressure for 25 min,before termination of decompression and 1 hour after completion of treatment.Statistical analyses were also made in the study.Results In conscious patients,systolic pressure,diastolic pressure and mean arterial pressure[( 129.42 ± 21.47 ) mm Hg、(81.79 ± 12.65 ) mm Hg、(97.67 ± 14.38 ) mm Hg ]during the stage of decompression increased significantly,as compared with those of pre-treatment[( 121.72 ± 16.31 ) mm Hg、(75.51 ± 9.77 ) mm Hg、( 90.9 1 ± 9.64) mm Hg ],with statistical significance ( P ＜ 0.05 ).In sitting patients,diastolic pressure and mean arterial pressure[(81.30 ± 12.36 )mm Hg、(97.11 ± 13.99 )mm Hg]during the stage of decompression increased significantly,as compared with those of pre-treatment[( 75.38 ± 9.48 ) mm Hg、(91.14 ± 9.51 )mm Hg],also with statistical significance ( P ＜ 0.05 ).No significant differences could be noted in other time points,when comparisons were made between the groups ( P ＞ 0.05 ).From the start of compression to 1 h after treatment,heart rate in conscious and sitting patients all decreased significantly,as compared with that of pre-treatment,with statistical significance ( P ＜ 0.05 ).For patients in the conscious disorder group and the laid-up group,heart rate measured from the time of pressure maintenance to the start of decompression decreased significantly,as compared with that of pre-treatment,with statistical significance(P ＜ 0.05 ).One hour after treatment,heart rate retumed to pre-treatment level ( P ＞ 0.05 ) Conclusions HBO therapy could decrease heart rate of patients and elevate blood pressure during the stage of decompression.Besides the effect of high oxygen partial pressure,physical posture,psychological state and ambient temperature might all be influencing factors involved,to which attention should be paid.