Relationship of relevant factors to P(v-a)CO/C(a-v)O ratio in critically ill patients

Objective This study investigated the factors related to the ratio of the venoarterial carbon dioxide tension difference [P(v-a)CO 2 ] to the arteriovenous oxygen content difference [C(a-v)O 2 ] (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)CO 2 ≤ 6 mmHg/central venous oxygen saturation (ScvO 2 ) 6 mmHg/ScvO 2 ≥ 70%], and Group IV [P(v-a)CO 2 > 6 mmHg/ScvO 2 1.68) than low Ratio measurements (≤1.68). The P(v-a)CO 2 was best for predicting a high Ratio. A P(v-a)CO 2 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)CO 2 is the most relevant contributor to a high Ratio among all related factors in critically ill patients