The Magnetically Guided Bronchial Catheter of Modified POD Design

The ability to selectively catheterize pulmonary bronchial segments and subsegments has many applications in clinical diagnostic radiology. Most of the reported technics for selective bronchial catheterization have evolved from the methods of selective arteriography (1, 4, 12, 14, 15), which utilize some means of mechanical guidance. The catheter is sometimes preshaped, or the guide wire tip may be directed from a remote controlling device. Multiple variations and combinations of these approaches are in use. The selective approach to bronchial catheterization has increased the accuracy of bronchography (12), allowed selective cytological and bacteriological sampling (1, 4, 9), made possible the introduction of the brush biopsy technic (3, 5, 9, 12), and suggested further application of the method of selective delivery of medication for the treatment of suitable localized pulmonary lesions. This concept was first successfully employed by Ramirez (11) in the endobronchial treatment of aspergillosis with potassium iodide and amphotericin B. The purpose of this report is to describe a new approach to the selective study of the bronchial tree. This approach depends upon the magnetically guided POD catheter, basically a variation of the previously described POD catheter used for vascular exploration (2, 6). The instrument is constructed with a magnet inserted at the tip of a flexible silicon rubber tubing and guided from without by a hand-held permanent magnet or solenoid. The technic is simple and makes possible the selective exploration of the peripheral segments of the lung, regardless of their location. Methods The Magnetic POD Bronchial Catheter: In selective bronchial catheterization, the caliber of the bronchi permits the use of a 2 by 8-mm cylindrical magnet in the catheter tip. The magnet is made of Alnico V and has an 0.8-mm hole drilled along the longitudinal axis. The magnet is inserted into 0.058 by 0.077-inch silicon rubber tubing which in turn is passed into 0.082 by 0.114-inch polyethylene tubing. This construction imparts enough rigidity to provide easy passage in the bronchial lumen, and yet the catheter maintains sufficient flexibility that it may be directed by small external magnetic fields. The external magnet, also made of Alnico V, creates a magnetic field of about 50–100 gauss in the vicinity of the catheter tip. Animal Experimentation: The catheter was tested on 8 anesthetized mongrel dogs. It was passed into the trachea via an endotracheal tube or directly through the larynx. Once in the trachea, the POD catheter can be advanced under fluoroscopic control to the carina. The external magnet is then held in a position to deflect the catheter tip into the right or left mainstem bronchus. In a similar manner the catheter can be directed into selected lobes, segments, and subsegments by altering the position of the external magnet.