a nasally introduced catheter has a portion in which a user &# 39 ; s breath air travels internally and a portion in which the breath travels externally . the portion in which air flow travels internally preferably includes a mesh or a whisk - like portion that expands and contracts , and the portion in which air flow travels externally preferably comprises a proximal tubular element having a sufficiently small cross - sectional area that at least 50 % of the breathing air flows externally to the proximal portion . a sheath can optionally be positioned about the distal portion , and pulled back along the proximal portion to allow the distal portion to expand . in other aspects users can anchor the proximal and distal portions relative to the sheath using a nose clip or by removably coupling an extension arm to proximal portion .