A short silver or plated catheter is usually used. It is 5 inches in length and curved at its extremity. To indicate the position of the point of the catheter in the post-nasal space, a ring is attached to its outer and wider extremity corresponding with the concavity of the curvature of its beak (Fig. 209). The size of the catheter varies in diameter from Nos. 1 to 4 English size, that is, the same scale as used for urethral catheters. The source of compressed air used for the inflation is usually a Politzer bag having an india-rubber tube attached. At its end is a vulcanite pointed nozzle which accurately fits into the wider extremity of the catheter.
Technique. The patient is seated facing the surgeon, the head being supported by a prop or by an assistant. If the patient be at all sensitive, it is wiser to spray a very small quantity of a 2 or 5% solution of cocaine or eucaine into the nose, or, better still, to pass gently a probe tipped with a small pledget of cotton-wool soaked in the cocaine solution along the inferior meatus. This will effectively anæsthetize the region of the pharyngeal orifice of the Eustachian tube, which is the most sensitive part.
| Fig. 210. Passing the Eustachian Catheter. Introduction of the catheter within the nostril. | Fig. 211. Passing the Eustachian Catheter. Passage of the catheter along the floor of the nose. |
The surgeon stands in front of the patient. The larger extremity of the catheter is held lightly between the thumb and first finger of the right hand, its beak being turned downwards, whilst the tip of the nose is tilted up by the thumb of the left hand (Fig. 210). In introducing the catheter into the nostril, the right hand is kept low down so that the stem of the catheter is almost in a vertical position. In this way the tip passes over the floor of the vestibule. As the catheter is gently pushed through the nose the right hand is raised so that the instrument assumes the horizontal position and passes backwards between the septum and the inferior turbinal, its beak being kept in close contact with the floor of the nose (Fig. 211). As the beak of the catheter enters the post-nasal space, it will be felt to glide over the soft palate.
With regard to the best method of introducing the beak of the catheter into the orifice of the Eustachian tube, opinions vary. Of the many methods advised only two will be given.
The first is more suitable to those who have not had much experience in using a catheter; the second is the one naturally adopted by an expert.
The first method. The catheter is pushed backwards until it is felt to impinge against the posterior wall of the naso-pharynx. The beak, which at this stage is directed downwards, is next rotated a quarter of a circle inwards so that it points horizontally towards the opposite side; the position is shown by the ring at its outer extremity (Fig. 212). The catheter is now gently withdrawn until the beak is felt to catch against the posterior edge of the vomer. During these procedures the stem of the catheter should rest on the floor of the nasal cavity. The manipulations are carried out with the right hand whilst the outer extremity of the catheter is kept fixed in position by means of the thumb and finger of the left hand.
| Fig. 212. Passing the Eustachian Catheter. Beak of the catheter in the post-nasal space. The catheter is turned to the opposite side so that its beak impinges against the posterior border of the septum. | Fig. 213. Passing the Eustachian Catheter. Catheter in position; act of inflation. |
The catheter is next pushed a short distance backwards to free it from the soft palate and rotated downwards, and finally round in an outward direction until the ring points to the outer canthus of the eye on the side to be catheterized (Fig. 213).