The Sponge Shrinks after exposing to the vacuum due to contracting and closing the porous (low-pressure energy). Then once it contacts to a fluid (high-pressure energy), the fluid is absorbed by the sponge as a result of capillary effect and moving high-pressure energy to low-pressure energy until the system reaches to an equilibrium state and all the porous are filled by the fluid.
Different design of bag, sponge, and tube (catheter) were investigated to optimize the flow rate and the negative pressure. (a) The best result was for the sponge with an inner Parallel tube. (b) A balloon was used as a urinary bladder mimicking.
The pressure and flow rate of the system were analyzed. (a) The sponge after applying vacuum, the pressure gauge shows the negative pressure. (b) The flow rate vs. volume of draining liquid with 1 mm inner diameter tube.
A bacterial test was designed to evaluate the effect of negative pressure via sponge on bacterial growth in the bladder mimicking container. (a) The schematic of the design. (b) The experiment.
Drainage Sponge
A catheter-associated urinary tract infection (CAUTI) is one of the most common infections a person can contract in the hospital. Indwelling catheters are the cause of this infection. It is a tube inserted into the urethra and drains urine from the bladder into a drainage bag. Between 15-25% of hospitalized patients receive urinary catheters during their hospital stay. This number is even higher amongst surgical patients and patients in the ICU (>80%). 10-25% of these patients will go on to be diagnosed with CAUTI. Urine backflow and stagnation are the primary cause of CAUTI. Preventing the backflow and using the unidirectional flow (anti-gravitational) can solve many of the complications associated with urinary catheters.
we assumed that negative pressure in the drainage bag could make unidirectional flow and prevent backflow. ÙŽAlso it could increase the flow rate, and as a result, we could decrease the size of the catheter diameter which larger causes more discomfort and pain. By using smaller sized catheters, we can also decrease the bacterial entry into bladder along biofilm that forms between catheter and urethra.
Accordingly, we suggested sponge as a suitable means for generating the negative pressure in the drainage bag. Also, the capillary effect of the sponge is an additional help. The sponge is inserted in the impermeable bag equipped with a one-way valve. Then the negative pressure is applied through the one-way valve so the vacuum remains in the bag. Once the catheter is connected to the bag, the negative pressure is applied to the bladder, and the urine is drained from it unidirectionally, with higher flow rate. So urine backflow and stagnation in the catheter are eliminated.
Different design of bag, sponge, and tube (catheter) were investigated to optimize the flow rate and the negative pressure. Also, a bacterial test was designed to evaluate the effect of negative pressure via sponge on bacterial growth in the bladder mimicking container.
