1. Field of the Invention
This invention relates to a urinary catheter in which the lumen may be periodically flushed outward to prevent bacterial contamination of the bladder.
2. Description of the Prior Art
The construction and use of catheters for the purpose of periodic or continuous drainage of the urinary bladder is well known in the art. Such devices are useful, for instance, when the urethra is blocked for any reason, causing retention of urine; when voluntary voiding is inadequate; when voluntary control of the sphinchter has been lost due to trauma, neurological damage or surgery; when involuntary emptying of the bladder is desired to facilitate diagnostic or surgical procedures; or for a variety of other reasons.
A large variety of urinary catheters is known. These include simple tubes, tubes with expandable tips, and the Foley catheter which combines the advantages of the first two and is therefore the most popular for continuous catheterization beyond about 24 hours. In its simplest form, the Foley catheter consists of a flexible (rubber or plastic) tube of about 4-7 mm. diameter which is fabricated with a small diameter tube integral with the wall and leading to an expandable "balloon" chamber which is just below the tip which will drain the bladder. The chamber is collapsed for ease of insertion and once in place it is expanded with sterile medium such as air or saline solution to prevent the catheter from slipping out through the urethra.
The most common and troublesome complication of urinary catheterization is colonization of the bladder and eventually the entire urinary tract with pathogenic bacteria, yeast and/or fungi. It has been reported that even with the best of available equipment and sterile technique, more than 25% of patients with indwelling urinary catheters can be expected to develop urinary tract infections after 30 days of continuous catheter drainage. Many attempts have been made to overcome this problem. Prophylactic use of systemic antibiotics which are excreted in the urine has not been successful since colonization is only slightly delayed and occurs with organisms resistant to the antibiotics used. Bladder irrigation with a solution of 0.25% acetic acid or a solution of neomycin-polymyxin is moderately successful, but requires a large amount of extra nursing attention. When this method is used, it is usually done with a triple-lumen Foley catheter as shown in FIG. 44 in a text by Calvin M. Kunin entitled "Detection, Prevention and Management of Urinary Tract Infections", Lea & Febiger, Philadelphia, Pa., 1974, 2d edition, Section IV, entitled "Care of the Urinary Catheter".
The most common route of infection, once the closed drainage catheter has been placed using sterile technique, is colonization of the receiving bag, followed by retrograde ascent of the pathogens up the lumen of the catheter. In view of the non-motile nature of the pathogens, this occurrence was somewhat of a mystery until the early 1960's when careful observations revealed that small bubbles form along the walls of the catheter tubing and that over a period of hours, these bubbles grow and eventually separate from the wall and rise. The associated turbulent flow in the opposite direction of a slowly descending stream of urine eventually carries the organisms all the way to the bladder. The emplacement of a bubble trap in the line merely delays the process by a day or two, as the trap becomes infected and the process is repeated above it.