We have compared a new Porter tracheal tube with the Oxford tube in pe
rforming simulated grade 3 difficult intubations. The Pouter tube was
modified so that the bevel faced backwards, as in the Oxford tube. A g
um elastic introducer was used with both tubes. The time taken and num
ber of attempts needed were recorded, with changes in arterial pressur
e, heart rate and incidence of sore throat. Both tubes were successful
in avoiding the problem of obstruction at the cords, which occurs whe
n a standard Magill tube is used with an introducer. Thus the new tube
has the merits of the Oxford tube without the disadvantages of rubber
. It is suitable for both easy and difficult intubations with advantag
es in safety, cost and convenience. An unexpected but important findin
g was a clear learning effect, despite both investigators being famili
ar with the technique at the outset. Over the course of the study, int
ubation time decreased progressively (P < 0.001). This provides new ev
idence of the need for trainees to practise the art of intubation when
the cords are not visible. Our estimate of the learning ''half-life''
was 15 intubations; we conclude that 30 simulated grade 3 intubations
would be a reasonable objective for trainees before handling high-ris
k cases.