Needle cricothyrotomy cannulas are available from several manufacturers. We use the one described here.
The device has an outer diameter of 6 Fr, which is equal to 14.4 G, and an internal diameter of 2 mm.
The internal diameter of this needle cricothyrotomy cannula is slightly larger than that of a 14 G iv cannula, i.e. the needle trochar of the cricothyrotomy cannula does not fit inside the iv cannula.
The question often arises whether a simple 14 G iv cannula could be used instead of the specifically designed needle cricothyrotomy cannula. While this is certainly possible, an iv cannula is much more likely to kink after placement as illustrated below.
At UCSF we have this particular needle cricothyrotomy cannula available as part of a kit which also includes an Enk oxygen flow modulator.