Hi Team

We are keen to start using end tidal CO2 monitoring in our unit. We currently use transcutaneous CO2 monitoring as standard of care for all of extremely preterm infants who are on HFOV or HFJV but thought that end tidal CO2 monitoring may be more useful for our bigger surgical babies, chronic BPD babies or babies with hydrops fetalis.

I was wondering if anyone had a unit policy on the use of end-tidal CO2 that we could possibly review just so that we don't have to reinvent the wheel.

Many thanks from Down Under.

Richard

Hi,

A couple of thoughts from my experience.

We have generally found transcutaneous CO₂ more useful for estimating/trending PaCO₂ in very preterm babies than end-tidal CO₂. One advantage of EtCO₂, though, is that you are likely to recognise a displaced or dislodged ETT much more quickly from loss or sudden change in the capnogram. This can be particularly useful in babies who are not sedated or muscle-relaxed. Transcutaneous CO₂ obviously has a significant lag in this situation.

The other thing to consider, particularly in very small preterm babies, is the additional dead space. Depending on the equipment, the flow sensor itself may add around 0.8 mL, and adding an EtCO₂ adaptor may add approximately another 0.5 mL — although the exact figures need to be checked with the manufacturer for the system being used. In an extremely preterm baby this is quite significant relative to the delivered tidal volume and may need to be taken into account when setting ventilation. In a 3 kg baby, the proportional effect is obviously much smaller.

For our preterm babies, we therefore did not routinely use continuous EtCO₂ monitoring. We tended to connect it intermittently, perhaps 3–4 times per day, obtain a reading/trend and then disconnect it, with the aim of getting useful additional information while minimising added dead space and hopefully reducing the number of blood gases/heel pricks.

I would also be interested to see what protocols other units are using.

Hope this is helpful