Abstract： Objective To investigate effects of simulated heliox diving on the renal function of the divers at different high altitudes.Methods In the dual-purpose hyperbaric and hypobaric chamber complex,4 divers conducted a series of simulated dives for a succession of 9 days at various altitudes and under different simulated environmental conditions:the 30 m dive at an altitude of 3 000 m,the 30 m dive at an altitude of 4000 m,and the 30 m and 50 m dives at an altitude of 5 200 m.Blood samples were taken respectively at the following time points:i.e.on the morning of the first day of the experiment before they entered the chamber on an empty stomach ; on the morning of the third day of the experiment at an altitude of 3 000 m also on an empty stomach; at 17:30 pm before supper on the fourth day of the experiment,when the divers were decompressed and returned to the surface at an altitude of 3 000 m,upon completion of the 30 m-dive; at 17:30 pm before supper on the sixth day,when the divers returned to the surface at an altitude of 4 000 m,upon completion of the 30 m-dive; on the morning of the seventh day on an empty stomach,the divers stayed overnight at an altitude of 5 200 m.Related renal function indices,such as serum creatinine,serum urea nitrogen,blood glucose,K+,Na+,Cl- were measured with biochemical auto-analyzer at 1st,3rd,4th,6th,7th,8th and 9thdays respectively.Morning midstream urine samples were collected for successive 9 days and routine urine examinations were made with urine flow cytometry.Results Upon decompression to the surface at an altitude of 4 000 m after the 30-m dive,serum creatinine and blood urea nitrogen tended to elevate to a certain degree,but without statistical significance ( P ＞ 0.05 ).Serum creatinine,blood urea nitrogen,blood glucose,electrolytes,urine pH,K+,Na+,Cl-,urine specific gravity detected at different time points were all within normal range,without statistical significance( P ＞ 0.05 ).The detection results of urine red blood cells,urine white blood cells,urine protein,urine acetone bodies,urine glucose,urobilinogen,urine bilirubin were all negative.Conclusions The simulated heliox diving at different high altitudes did not have obvious effects on the renal function of the divers.