Sample Collection

Accessing the middle ear by myringotomy has been previously discussed. In order to get a culture or cytology sample from the bulla in an ear without an eardrum, a sheathed catheter is used.

Figure 14-12

A 5-Fr polypropylene urinary catheter with the closed end cut off acts as a shroud for a 3½-Fr catheter, which is used for sampling the middle ear without contamination from the external ear canal.

threaded into a 5-Fr polypropylene urinary catheter (Figure 14-12). With the closed irrigating ends removed, the 5-Fr catheter is first threaded through the external ear canal until it reaches the bulla. This acts as a shroud to prevent contamination of the sample with debris from the external ear canal. It should be inserted into the bulla along the floor of the horizontal canal and directed ventrally into the bulla. After this catheter is placed, the 3½-Fr catheter is threaded into the 5-Fr catheter and extended beyond the cut end. The sample is aspirated with a syringe or suction apparatus using the flanged end of the 3½-Fr catheter. If no liquid is in the bulla, 1 cc of sterile saline can be infused and suctioned back. Any fluid or mucus that enters the lumen of the 3½-Fr catheter is submitted to the laboratory for cytology and culture and sensitivity.

If a myringotomy incision is made with a sharp-pointed 5-Fr catheter, as the inci­sion is made the catheter is extended into the bulla and the contents aspirated. The lumen contents are submitted to the laboratory. If a laser myringotomy was made, a sterile catheter is inserted through the hole and a sample is taken.