Effect of electrode temperature on measurements of transcutaneous carbon dioxide partial pressure and oxygen partial pressure in very low birth weight infants.

OBJECTIVES:To evaluate the accuracy and safety of measurements of transcutaneous carbon dioxide partial pressure (TcPCO2) and transcutaneous oxygen partial pressure (TcPO2) at electrode temperatures lower than the value used in clinical practice in very low birth weight infants. METHODS:A total of 45 very low birth weight infants were enrolled. TcPCO2 and TcPO2 measurements were performed in these infants. Two transcutaneous monitors were placed simultaneously for each subject. One electrode was set and maintained at 42℃ used in clinical practice for neonates (control group), and the other was successively set at 38℃, 39℃, 40°C, and 41℃ (experimental group). The paired t-test was used to compare the measurement results between the groups. A Pearson correlation analysis was used to analyze the correlation between the measurement results of the experimental group and control group, and between the measurement results of experimental group and arterial blood gas parameters. RESULTS:There was no significant difference in TcPCO2 between each experimental subgroup (38-41℃) and the control group. TcPCO2 in each experimental subgroup (38-41℃) was strongly positively correlated with TcPCO2 in the control group (r>0.9, P<0.05) and arterial carbon dioxide partial pressure (r>0.8, P<0.05). There were significant differences in TcPO2 between each experimental subgroup (38-41℃) and the control group (P<0.05), but TcPO2 in each experimental subgroup (38-41℃) was positively correlated with TcPO2 in the control group (r=0.493-0.574, P<0.05) and arterial oxygen partial pressure (r=0.324-0.399, P<0.05). No skin injury occurred during transcutaneous measurements at all electrode temperatures. CONCLUSIONS:Lower electrode temperatures (38-41℃) can accurately measure blood carbon dioxide partial pressure in very low birth weight infants, and thus can be used to replace the electrode temperature of 42°C. Transcutaneous measurements at the lower electrode temperatures may be helpful for understanding the changing trend of blood oxygen partial pressure.