Abstract: Objective To investigate the effect of oxygen inhalation during labor on delivery in high altitude area(Lhasa of China). Methods Forty parturients who had no obstetric complications and would have term delivery in May 2008 in Lhasa Maternal and Child Health Care Hospital were recruited as study group. Forty-nine parturients of term delivery in the same month in 2007 were taken as control group. When parturients in the study group entered the second stage of labor, they had oxygen inhalation via double nasal catheter at 2L-3L/min till fetal delivery. The data of delivery were recorded to compare with the control group. The heart rate and oxygen saturation(SO₂) were also recorded before oxygen inhalation and after 10 minutes of inhalation to study the effect of oxygen inhalation on these data. Results 1 There were no significant difference in general status including age, the proportion of the tibetan ethnicity, gravida, parity, antenatal care, age of gestation, mean arterial pressure(MAP), heart beat rate(HR) and hemoglobin(Hb) between the two groups. 2 Time of the second stage was(32.51±22.8)min, the volume of postpartum hemorrhage was(211.25±95.06)mL, the ratio of lateral episiotomy was 55%(22/40), the ratio of amniotic fluid contamination was 20%(8/40) in study group. In the control group, time of the second stage was(32.27±25.98)min, the volume of postpartum hemorrhage was(248.47±107.62)mL, the ratio of lateral episiotomy 38.98%(23/59), the ratio of the amniotic fluid contamination was 35.59%(21/59). There was no significant difference in each corresponding data between the two groups. At the same time, the data of newborns including the Apgar score at 1 minute and at 5 minutes after birth, weight, length and the data of placenta including volume, length of umbilical cord,the ratio of cord around neck had no significant difference, either. 3 The HR was(77.75±9.12) beats per min after oxygen inhalation in the study group, that was significantly lower than HR before(84.29±2.3) beats per min(P=0.000). SO₂ after oxygen inhalation in the study group was(96.58±1.62)%, which was significantly higher than that(93.40±3.23)% before oxygen inhalation(P=0.000). Conclusion Parturients who live in the highland for long time have already adapted to the low pressure of oxygen. Even in the second stage of labor, with the compensation of the parturient, parturient would fulfill the delivery successfully. Oxygen inhalation during the second stage of labor did not change the labor. So for normal parturient that have no sign of hypoxia, there is no need for oxygen inhalation. But it is generally believed that the lower oxygen pressure of highland give some negative influence on the heart. Oxygen inhalation can increase the supplement of oxygen for the body, and then reduce the reaction of compensation when the oxygen consumption increases. This action can protect the parturient heart in the high altitude area especially for those whose hearts have already shown some evidence of the negative influence of high altitude.

Key words: high altitude area, parturient, oxygen therapy, high altitude heart disease, labor, oxygen saturation