Annette,
I used a portex trach for many years. The disposable inner canula fits
completely inside the outer canula and the swivel adapter connects to
the outer canula. Since the inner canula fits inside the outer canula,
you won't have the problem of air leaking between the two canulas. With
Shiley tubes, the swivel adapter connects to the inner canula (if I
remember correctly.) The Portex inner canulas have a ring on the end
for pulling the inner canula out when you change inner canulas. I have
swithced to a Bivona. I didn't switch because there was something wrong
with the Portex per se, it was because the hard plastic tube was rubbing
the inside of my trachea and causing it to bleed. That would have
happened with any hard tube. The only problem I have with the Bivona
tubes is that they don't have an inner canula.
Eric