Objective This study investigated the factors related to the ratio of the venoarterial carbon dioxide tension difference [P(v-a)CO2] to the arteriovenous oxygen content difference [C(a-v)O2] (hereafter termed “Ratio”).

Methods We retrospectively studied 1294 pairs of arterial and central venous blood gas measurements in 352 critically ill patients. A high Ratio was defined as > 1.68 based on published literature. Measurements were divided into four groups: Group I [P(v-a)CO2 ≤ 6 mmHg/central venous oxygen saturation (ScvO2) < 70%], Group II [P(v-a)CO2 ≤ 6 mmHg/ScvO2 ≥ 70%], Group III [P(v-a)CO2 > 6 mmHg/ScvO2 ≥ 70%], and Group IV [P(v-a)CO2 > 6 mmHg/ScvO2 < 70%].

Results The Ratio’s strongest correlation was with P(v-a)CO2 when compared with ScvO2 and hemoglobin in all data. The P(v-a)CO2 and ScvO2 were significantly higher and the hemoglobin and arterial oxygen saturation were significantly lower in the high Ratio measurements (>1.68) than low Ratio measurements (≤1.68). The P(v-a)CO2 was best for predicting a high Ratio. A P(v-a)CO2 threshold of 7 mmHg was associated with a sensitivity of 41.77% and specificity of 90.62% for predicting a high Ratio.

Conclusions A high P(v-a)CO2 is the most relevant contributor to a high Ratio among all related factors in critically ill patients.

Additional Metadata
Keywords ScvO2, P(v-a)CO2, P(v-a)CO2/C(a-v)O2 ratio, oxygen delivery (DO2), oxygen consumption (VO2), intensive care unit
Persistent URL dx.doi.org/10.1177/0300060519854633, hdl.handle.net/1765/119484
Journal Journal of International Medical Research
He, H.W., Long, Y., Liu, D.W., Tang, B, & Ince, C. (2019). Relationship of relevant factors to P(v-a)CO2/C(a-v)O-2 ratio in critically ill patients. Journal of International Medical Research. doi:10.1177/0300060519854633