Blood gas analyzers are set at 37°C. However, many critical care patients may have a temperature other than 37°C, and some tests differ according to the patient’s temperature. Therefore, the patient’s temperature should be determined at the time the specimen is taken. Most blood gas systems allow the operator to enter the patient’s temperature. The system will then adjust the measured pH, PO2, and PCO2 values and the oxygen saturation with respect to the patient’s actual temperature. The following are generally accepted correction factors1:
|
°C |
pH |
PCO2 |
PO2 |
|
29 |
+ 0.120 |
x 0.720 |
x 0.560 |
|
30 |
+ 0.105 |
x 0.750 |
x 0.600 |
|
31 |
+ 0.090 |
x 0.780 |
x 0.650 |
|
32 |
+ 0.075 |
x 0.815 |
x 0.700 |
|
33 |
+ 0.060 |
x 0.850 |
x 0.750 |
|
34 |
+ 0.045 |
x 0.885 |
x 0.805 |
|
35 |
+ 0.030 |
x 0.920 |
x 0.865 |
|
36 |
+ 0.015 |
x 0.960 |
x 0.930 |
|
37 |
+ 0.000 |
x 1.000 |
x 1.000 |
|
38 |
– 0.015 |
x 1.040 |
x 1.070 |
|
39 |
– 0.030 |
x 1.080 |
x 1.145 |
|
40 |
– 0.045 |
x 1.125 |
x 1.225 |
|
41 |
– 0.060 |
x 1.170 |
x 1.310 |
Reference
1. Mikulcik P. Rapid Analysis—Blood Gases and More. Tarrytown, NY: Siemens Healthcare Diagnostics; 2012.