Capnography: modifying a Novametrix/Philips Respironics neonatal airway adapter for small animal use

Here we show how to modify a Novametrix (old company name) / Philips Respironics (new company name) neonatal airway adapter for small animal use (reorder number: 6312-00 for a box of 10). The "dead space" in the neonatal adapter is too large for small animals like tree shrews and ferrets, so we chop off the edges and replace them with narrow barbed tubing fittings.

1) Start with a regular Philips Respironics neonatal adapter:

The finished product will look like this: one end will have a 'Y' connector to receive the input and output tubing from the respirator; the other end will receive a straight piece of tubing that connects to the trachea tube or intubation tube.

2) Find a dremmel or some other small cutting tool (a hack saw and a vice works, too). Cut off the 2 tubings ends:

3) You'll be left with just the center piece. Be careful not to touch the plastic window that encloses the airway in the center; I imagine that fingerprints make it harder for the machine to detect CO₂.

4) Next, obtain a 'Y' adapter and a straight adapter. We use the following parts from Harvard Apparatus:

5) Glue the adapters into the 2 ends. Be sure the glue makes a perfect seal around the adapters so no air leaks out. The air pathway to the animal's lungs is a fairly high resistance path, so if there are small gaps the air would rather leak out the edges of the adapters. Note that the straight adapter goes on the side with the "triangle" (see orange arrow; inspect the neonatal adapter to find it on the actual piece). Finally, after the glue has dried, test the system for leaks by blowing into each end of the adapter while covering the other 2 openings with your fingers. You shouldn't be able to pass air through.

6) Snap the finish product into the CapnoStat sensor and you're good to go!