Abstract

Every year, around 332,000 patients in the United States require post-surgery continuous bladder irrigation (CBI). During CBI, a sterile solution is continuously infused into the bladder through a catheter to flush out the bladder and prevent blood clots from forming. Ideally, nurses must readjust CBI every 15-30 minutes, but do so hourly in practice, leading to risks of unwanted incidents. Research has shown that automating CBI can decrease the incidence of adverse events such as clot retention and bladder perforation. In order to automate the CBI process, UroSmart integrates a flow sensor, color sensor, and a linear actuator to automatically adjust the inflow rate of the irrigation system based on the evaluation of the outflow color and flow rate every 10 seconds. In addition, our accompanying app allows healthcare professionals to quickly check up on CBI progress, such as inflow flow rates and the outflow color and flow rates over time, and other relevant patient data. When clogging is detected, UroSmart would stop the irrigation process and alert clinicians, preventing bladder distention and decreasing response time. By incorporating these features, we are able to create a solution that delivers high levels of responsiveness and reliability. The system achieves rapid, consistent, and precise inflow control and outflow detection, which reduces the labor burden on clinicians and mitigates the risks of adverse events. Our solution reduces the frequency of patient checks from every 15-30 minutes to once every 3 hours, resulting in time savings by an average of 87.7% and manual labor savings by an average of 8-fold.

Background

Continuous bladder irrigation (CBI) is a postoperative treatment used after many prostate and bladder surgeries. CBI is used to irrigate the bladder with saline to prevent blood clots from forming in the bladder. Most commonly, CBI is used after transurethral resection of the prostate (TURP), a procedure that is usually conducted to treat benign prostate hyperplasia (BPH). By age 85, about 90% of males will have BPH, making TURP extremely common with more than 150,000 procedures and subsequent CBIs, performed annually in the US.1 CBI requires a medical professional to hang saline bags, insert a 3 Way Foley Catheter into the bladder, hang a drainage bag, and manually adjust the inflow rate using a roller clamp. The roller clamp is adjusted such that if the urine becomes bloodier, the physicians increase the inflow rate (amount of saline) and as the bleeding stops, the flow rate can taper off. The full setup is seen in Figure 1.2 

CBI is monitored primarily by a nurse, with nurses being the ones doing checkups 86.6% of the time.3 Nurses in the US are notoriously overworked, especially given that they are supposed to have four patients per shift but routinely end up in charge of eight or nine.4 This leads to higher risk of error, lower time per patient, and much higher wait times for patients. CBI is meant to be monitored every 15-30 minutes, but due to this high workload volume placed on nurses, CBI is routinely monitored every 62 minutes.3 This is two to four times as long of a wait for patients, which can increase the risk of adverse effects such as discomfort or bladder distention. 

Current standards for CBI are also incredibly subjective. After speaking with clinicians, they describe the color of the outflow urine using analogies such as “pink lemonade” or “wine”. The mental image of what color pink lemonade is will vary between clinicians. This is demonstrated in Figure 2, where “pink lemonade” was used as a descriptor for grades 1-3.7 In addition, clinicians are unable to quantify the inflow rate of the saline. They tend to describe the rates as “drip… drip… drip…” (slow) or “dripdripdripdripdrip” (fast).

Overall, we wanted to automate CBI to decrease the workload burden that nurses face, increase the comfort, satisfaction, and safety  of patients, and reduce the high subjectivity of the current standard. To match or exceed the current standard of care, we defined our need specifications as seen in Table 1.

In addition to the above criteria, we considered various broader design, ethical, and professional elements. We primarily considered safety, global, and environmental factors when designing our device. We heavily considered patient safety and welfare as a motivator to make this project happen, as discussed previously. 

This product was also designed with the intent to be usable by the global market- it is powered by just two 9V batteries and is helpful both patients and physicians in low resource hospitals that lack a high volume of specialized physicians and an overall large workforce While the current standard of care requires a highly specialized physician to look at the urine and correctly identify how best to adjust the treatment, our team noticed that this led to a high degree of subjectivity. UroSmart was developed, in part, to reduce the subjectivity by allowing the device to determine the color grade and the proper inflow speed. In addition, the device continuously monitors the patient’s urine, meaning that work forces can be directed to other needs. In turn, this allows it to safely be used in lower resource hospitals. Physicians do not have to worry about their CBI patients while they are working to help other patients. It also allows clinicians who might not have experience with CBI to trust that their patient is receiving the correct care. 

  Lastly, we tackled environmental factors by making our inflow mechanism classified as a non-critical reusable device by the FDA. Given that none of the components come into direct contact with bodily fluid or sterile saline, they can be reused. This will help hospitals save money by buying fewer devices and also keeps plastic out of the landfills. 

Initially, we had planned to address economic factors by making sure our device was comparably priced to the current setup. In the end, that did not fully happen given that we spent $160 on the outflow valve. However, the emotional labor and burden on the nurses- as well as hospital fees from adverse effects of improperly monitored CBI- that can be avoided with our device is priceless. 

We acknowledge the potential cultural and social barriers that could arise with introducing this new technology. We worked to ensure that our solution was user-friendly and accessible to all patients. In the future, if this technology were implemented in other countries, we would want to ensure that users of all backgrounds felt comfortable with the device.

There are currently two other solutions that address various flaws with the current standard of care. The first is a homemade rate adjustment card produced by a team at the First Affiliated Hospital of Soochow University in China.5 This card (Figure 3) presented six color grades and an appropriate range of irrigation for each. They determined that clots, the volume of irrigation solution used, and the irrigation time were significantly lower or shorter and the patient satisfaction was higher when using the parameters on this card. Similarly, a study done at the University of Minnesota determined five clinically relevant color grades that they used to prove whether clinicians described color grades the same.7 This study addresses the subjectivity of CBI. They determined that creating this scale, as seen in Figure 3, significantly improved communication between clinicians. Neither of the above solutions sufficiently address the workload burden placed on clinicians and did not meet our need specifications due to the lack of an automated response. 

The second is a device produced in a study by researchers at the Second Affiliated Hospital of Nantong University.6 This team developed a device that had an automatic rate adjustment, a color sensor, and a microprocessor. Overall, this team discovered that automated CBI significantly reduced irrigation volume and clots. A similar product was developed by researchers from the University of British Columbia, Vancouver.8 These researchers created an open source hematuria monitor that consisted of a color sensor and an outflow flow rate calculator. They did not, however, automate the inflow pump. 

Both of the above studies demonstrate the desire and need for our device. As seen in Table 2, nothing currently available (either commercially or being studied) meets the five criteria- quantitative setting of the inflow rate, quantitative evaluation of the color, quantitative evaluation of the outflow rate, full automation, and eliminating labor required to monitor- other than our product. 

Product Overview

In designing a solution to automate CBI, we aimed to create a user-friendly device that would continuously monitor patients and accurately and automatically adjust inflow rate based on the color and outflow rate. We envisioned the device featuring an accompanying mobile application that would allow doctors and nurses to track and record this data for future reference. Ease of use was a major goal in light of the glaring shortage of labor required to give patients the level of attention needed during CBI. On the other hand, the integration of objective measures for accuracy and the ability to generate and save patient data were targeted to better the standard of care. 

As a result, we have created UroSmart, a catheter add-on comprising a color sensor, outflow flow rate sensor and inflow rate control linear actuator controlled by a computer interface. UroSmart is designed to be compatible with the 3 way foley catheter and IV bag setup currently used in CBI, and features a color sensor to monitor the color of the outflow solution, a flow sensor attached to the drainage tube to track the outflow rate, and a linear actuator interfacing with current IV setting to control the inflow rate. By automating the adjustment of the inflow rate, UroSmart can drastically reducing the labor required by nurses to monitor CBI as well as improving patient outcomes6 by ensuring inflow matches the patient’s immediate needs. In addition, we hope that by quantifying and recording patient data for CBI, UroSmart can provide new objective measures for research and improvement of future CBI patient protocols. Given the importance of CBI in TURP and thus its increased importance in aging populations like that of the USA1 and much of the developed world today, we believe the need for UroSmart will only grow over time. Finally, UroSmart’s compatibility with current devices and its identity as an add-on allow UroSmart to be easily incorporated into the current workflow and reused for multiple CBI patients, thus minimizing any possible increases in cost for patients or hospitals and minimizing environmental impacts by reducing waste. 

To achieve our design goal, UroSmart defined four criteria for our technical specifications: adapataility, usability, responsiveness, and reliability. First, for adaptability, we want to achieve a universal catheter-compatibility for our device through adjustable tubings, meaning that UroSmart should be able to fit the most common sizes of catheters (20-24 fr). As for usability, we want to achieve a quick and easy learning curve, with a target time of less than 10 minutes. For responsiveness, we are targeting a rapid detection and response rate. We want to be able to detect and respond to a color grade change in less than 10 seconds. Lastly, for reliability, we want to achieve consistent and precise inflow control and outflow detection by keeping the output inflow rate within the range of 0 to 100 ml/min and the detection of uutflow rate within the range of 0 to 600 ml/min.

Table 2 summarizes the differences among the current CBI setup, open source monitors, and our product. While some products are able to quantify outflow parameters, the CBI process has not been automated yet. For products that are considered automated, outflow parameters are not quantitative. Out of all options, UroSmart provides a consistent, responsive, and labor-free option for CBI. Potential limitations are explored in the Outlook section.

Standards and Regulations 

Our product would need to be regulated by the FDA in the US. Under regulation 890.5050, our device will be a Class I Medical Device (without exemption). A catheter is a Class II device under CFR Title 21 876.5130, but since UroSmart is not inserted into the body, it is considered a Class I device. It would not be eligible for exemption from a 510(k) due to the lack of a sufficiently comparable predicate device; however, UroSmart is not required to provide clinical trial data for a 510(k) clearance. Our device would also be subject to sterility guidelines set forth by the FDA. The inflow pump would need to be sterilized, as it comes in contact with the saline that enters the bladder. 

Furthermore, when we continue to develop an app, the product will be subject to the HIPAA Security Rule, as stated in the CFR part 160 and part 164 subparts A and C, which regulates the privacy of patients’ electronic records.

Inflow Valve

The inflow adjustment system consists of a stepper motor that gradually adjusts the opening of an inflow valve: as the motor changes its angle, the valve opening changes as well. To ensure repeatability and reproducibility, we quantified the relationship between the flow rate and the valve opening, which is based on the motor angle (Figure 6). This was done by measuring the flow rate similarly in our PoC testing for different motor angles (n=3 for each angled opening). The linear best fit was then used to determine 5 optimal valve opening angles (each leading to the desired inflow flow rates) to wash the 5 different color grades in the CBI process: color grade 1–0 ml/min; grade 2–22ml/min; grade 3–50ml/min; grade 4–70ml/min; grade 5–84ml/min. 

Our desired settings for the inflow valve come from a 2021 study11. This was the only quantification of the inflow rates we were able to find. Generally, this established that the flow rate would be from 0-100 mL/min, with lower flow rates corresponding to lower grades. We also wanted to limit uncertainty to below 10% as this was the lower bound of roller clamp accuracy, which is the current standard of care.

To set values for the linear actuator (Fisher Scientific 50822027 DC HOUSE Mini Electric Linear Actuator), we tested the actuator at different positions to determine five representative flow rates. Our chosen values were based on Figure 13 a,b and the unique values the actuator could produce. We settled on 10, 21, 45, 70, and 95 mL/min. These were determined by allowing saline to flow at a given position of the actuator for five minutes and then measuring the amount of saline collected. Two days later, we tested the system again to see what flow rates were produced. Through a t-test, they were determined to be statistically similar. We tested them again seven days later, and the results were the same- they were statistically similar to both our first day of testing and our second day of testing. The flow rates are summarized in Figure 13 b,c. In addition, uncertainty, which we took to be the standard error of the mean, was below 10% across our 3 trials except for the first flow setting, which had a standard error of the mean of 11.3% slightly above 10%. Thus we were able to meet our needs specifications in most use cases. However, we would want to do additional testing to see if this uncertainty persists over more trials and if so test different methods to reduce the uncertainty at low flow rates.

Prior to integrating the entire system, we wanted to test the response time of our valve to a change in color. We wrote a simple script to allow us to type in a color grade and allow the valve to respond. When changing from color grade 5 (95 mL/min) to color grade 1 (10 mL/min), it was less than half a second from hitting enter to when we heard the actuator moving and 1.63 seconds on average from hitting enter to visibly seeing a change in the flow rate. When doing the reverse and changing from grade 1 to grade 5, it was still less than half a second from hitting enter to when we heard the actuator moving and was 0.97 seconds from hitting enter to visibly seeing a change in the flow rate. In the future, we can determine exact times by including our outflow sensor in the tests. This will allow us to quantify how soon and at what rate the flow rate changes, as opposed to just doing it visually.  

In the future, we would like to further validate our chosen inflow values with medical professionals. We would like to get feedback on whether they think, after seeing the color of the outflow, that the drip rate of the inflow visibly looks like an appropriate rate. While we do give them the option to change the flow rate on the app, we want to validate that our preset values are appropriate. 

Future Steps

For our immediate future, we are planning to complete further validation by the beginning of August. The testing we'd like to try include replacing the artificial blood, which contains anticoagulants, to animal blood in order to verify the response time of our device when a clot is detected and testing sustainability of the device to ensure it cannot be easily broken in real world setting. Then, we'd like to continue refining the device based on the validation process, which should be completed by the beginning of next year. Lastly, we would like to submit a Penn IRB application by July 2024 to prepare us for patient testing. If we were to commercialize the device, we would like to get our FDA Clearance and complete our IP application by the beginning of September 2024 to secure our IP position. This will prepare us for our soft-launch. The reason that we are applying for our IP at a rather later stage is that we would like to submit the IP application after the device is fully completed so we can file a more comprehensive IP to prevent potential patent litigation. Regarding our future plan, one challenge we predicted is the potential need to recalibrate the color sensor and linear actuator based on the new testing data from animal blood due to the change in viscosity and protein concentration. In addition, our final prototype may not be suitable for the current clinical setting as it contains several device enclosurres that may be incompatible with the hospital bed rails thus we would need to redesign the enclosures and component placements for better integration with the clinical setting. 

Distribution Channel and Pricing Model

In preparation for potential commercialization, we identified our distribution channel for UroSmart and our pricing model for the device. As a product that helps healthcare providers more easily manage multiple patients on CBI, UroSmart is targetting large hospitals with substantial urology departments that perform CBI frequently. As for pricing, our pricing strategy for UroSmart includes a one-time up-front cost of $300 for the hardware, in addition to a monthly subscription fee of $50 for our proprietary software application. The subscription fee is based on the number of users who access and utilize the software service, which would be monitored based on the account registration and access to the app. Our pricing approach is based on a comprehensive evaluation of the value and impact our solution brings to healthcare institutions, as well as a thorough estimation of material costs for our device.

Market Analysis

With our device, we currently want to target the patients who have to go through TURP surgery, which is about 150k patients per year. We estimated that with our device we will be able to achieve a saving of $19.2M per year for the US Healthcare System. The market is comparatively stable, in which each year the number of TURP surgeries are around the same numbers. In addition, there is currently no primary competitors since the currently the only approach is still manual CBI. The barriers to entry is low; however, our team already has the advantage of developing a prototype that could be used for testing and IP application at least one year in advance to potential competitors. 

UroSmart can be used in any post-surgery CBI, meaning that besides our targeted 150k TURP patients, we can address other patients that require surgeries such as TURBT or radical prostatectomy patients. With this total addressable market size, we could achieve a healthcare saving of up to $41.2M per year for the US Healthcare System.