# Impact of mechanical power and positive end expiratory pressure on central vs. mixed oxygen and carbon dioxide related variables in a population of female piglets

## TL;DR

This study compares oxygen and carbon dioxide measurements from central and mixed venous blood in piglets under different ventilation settings.

## Contribution

The study reveals that mechanical ventilation affects oxygen but not carbon dioxide measurements between central and mixed venous samples.

## Key findings

- Oxygen saturation differs significantly between central and mixed venous samples.
- Higher mechanical power and PEEP increase the difference in oxygen saturation.
- Carbon dioxide parameters remain stable and similar across sampling sites.

## Abstract

The use of the pulmonary artery catheter has decreased overtime; central venous blood gases are generally used in place of mixed venous samples. We want to evaluate the accuracy of oxygen and carbon dioxide related parameters from a central versus a mixed venous sample, and whether this difference is influenced by mechanical ventilation.

We analyzed 78 healthy female piglets ventilated with different mechanical power.

There was a significant difference in oxygen‐derived parameters between samples taken from the central venous and mixed venous blood (Sv¯O2 = 74.6%, ScvO2 = 83%, p < 0.0001). Conversely, CO2‐related parameters were similar, with strong correlation. Ventilation with higher mechanical power and PEEP increased the difference between oxygen saturations, (Δ[ScvO2−Sv¯O2 ] = 7.22% vs. 10.0% respectively in the low and high MP groups, p = 0.020); carbon dioxide‐related parameters remained unchanged (p = 0.344).

The venous oxygen saturation (central or mixed) may be influenced by the effects of mechanical ventilation. Therefore, central venous data should be interpreted with more caution when using higher mechanical power. On the contrary, carbon dioxide‐derived parameters are more stable and similar between the two sampling sites, independently of mechanical power or positive end expiratory pressures.