This article is part of Upstart, a series about companies harnessing new science and technology to solve challenges in their industries.

Paul Hall was thinking about his pool. In his mind, he was far from the nondescript clinic in Orange, Calif., where he was sitting quietly, his blood traveling through a hemodialysis machine, clearing it of toxins. Soon, he would be watching his three grandchildren splash around while doing his treatment. Or watching TV. And he would do it all at any hour he pleased.

“There’s no place like home,” Mr. Hall, 64, said.

He had just a few more sessions left to be trained on using the Tablo Hemodialysis System, a home dialysis product made by Outset Medical, based in San Jose. When he was done, he hoped to plug it in at his home in Moreno Valley.

The size of a college-dorm refrigerator, the hemodialysis machines of this generation look nothing like the hulking ones first introduced to the home market in the 1960s. A touch-screen, which uses 3-D animation to walk users through each step, is mounted atop a box with a built-in water purification system.

After a 30-minute setup process, which included inserting two 14-gauge needles into his left arm, the machine commended him, “Good job, Paul!”

Like most of the 780,000 Americans with the end-stage renal disease, Mr. Hall needs dialysis, or a transplant, to live. The number of people with chronic kidney disease in this country is expected only to grow. It already affects about one in seven adults, according to the 2022 annual report of the United States Renal Data System.

A transplant wouldn’t be Mr. Hall’s first; the one from his oldest child about two decades ago is failing. Without working kidneys, extra fluid and toxic waste can build up and poison the body. Each year, about one in six patients undertaking maintenance dialysis dies, according to the U.S.R.D.S. Others forgo the treatment, most likely because of other life-limiting conditions, such as advanced cancer or heart failure.

“Patient outcomes are definitely better, but are still unacceptably poor,” said Dr. Joseph Vassalotti, chief medical officer of the National Kidney Foundation.

The company that would become Outset Medical started in 2010; it launched commercially in 2018, when Tablo entered hospitals and clinics. The Food and Drug Administration cleared Tablo for home use in March 2020, just as vulnerable populations needed to isolate because of the coronavirus pandemic. Later that year, the company went public in a virtual I.P.O.

The only current alternative for home hemodialysis systems is the portable NxStage System One, made by Fresenius Medical Care, which has headquarters in Germany. It was introduced to homes in 2005, with a newer version, VersiHD, following more recently.

Of the hemodialysis units examined in a market analysis, Tablo is the most expensive hemodialysis unit on the market, according to a survey by ECRI, a federally certified nonprofit patient safety organization. Tablo costs an average price of $47,000, excluding service or operational costs, compared with $26,000 for the NxStage System One.

Dialysis is indeed costly. The Centers for Medicare & Medicaid Services is hoping to reduce its expenditures and improve quality of care for its beneficiaries with end-stage kidney disease. Through financial incentives to dialysis providers, physicians, health systems and kidney transplant programs, the agency is seeking to increase home dialysis, as well as kidney donation.

The clear need for home systems is another factor. A majority of dialysis patients travel to clinics for hemodialysis, with little flexibility for long distances, snowstorms or car trouble. Patients often rate themselves as having a low quality of life, as cramps, insomnia, depression and anxiety are all common.

Mr. Hall has missed so many life events, he said. And while he doesn’t complain, when clinics close for long holiday weekends, he notices a difference.

“I can tell how I feel after two days,” Mr. Hall said. “If it’s starting to get harder to breathe and I know there’s fluid on my lungs, I want to get that off of me.”

Home dialysis is not a novel idea, said Leslie Trigg, Outset Medical’s chief executive. In the early 1970s, over 30 percent of dialysis patients were estimated to have done their treatment at home. Often, they had little choice, with dialysis units unable to meet the demand, according to a 2017 review in the journal Seminars in Dialysis.

In 1972, this changed with the expansion of Medicare, which included coverage for people with end stage renal disease in need of dialysis or a kidney transplant; in turn, that funding from coverage allowed for the growth of outpatient dialysis clinics. In the half-century since, the patient population for dialysis has grown, as has for-profit in-center dialysis.

Now about 14 percent of dialysis patients treat at home, either by themselves, or with a care partner, and that number is growing, according to the U.S.R.D.S. An estimated 2 percent are on home hemodialysis. Most do peritoneal dialysis, which involves infusing dialysis solution into the lining of the abdomen to filter the wastes from the body. It is usually prescribed daily, and for significantly longer periods each day than hemodialysis.

Mr. Hall tried this, too, for two years. He preferred peritoneal, and wishes he could be back on it now, but developed an infection.

Training is required for all home dialysis candidates and the person helping them, and the company or home health agency usually visits the home during the initial period.

But even with these measures in place, there are other considerations.

“It’s not for everyone,” said Dr. Mark Sarnak, chief of the nephrology division at Tufts Medical Center. “Some people have needle phobia, some people may not have the eyesight to do peritoneal dialysis, some people may be too sick.”

And not all are comfortable with the technology, have the support of family members (if needed), or the extra room to store the supplies or machine. Others prefer having a trained professional overseeing treatment.

For Mr. Hall to do his three-hour Tablo treatment, he connects one needle to an arterial line to move the blood through the machine’s dialyzer, also known as an artificial kidney. He attaches the other to the venous line, through which his cleaned blood returns. The most challenging part to him, though, is the end of treatment, when he has to remove the needles and apply just the right amount of pressure to avoid significant blood loss. His ex-wife and daughter have trained on how to assist.

There are benefits to the easy access of home dialysis. Traditionally, in a clinic, a lot of fluid is removed within a short period of time, and many patients feel exhausted afterward. With peritoneal dialysis and more frequent hemodialysis, “it’s much gentler,” said Dr. Sarnak, the lead author of a recent statement by the American Heart Association. There are also potential cardiovascular benefits with more frequent hemodialysis, according to the statement.

(Risk of infection, however, may increase with higher frequency. And although uncommon, infection is a risk for peritoneal dialysis patients as well.)

The F.D.A. requires a care partner while using Tablo — another potential barrier to patients wishing to switch to home use; the clinic overseeing the patient at home confirms the availability of one, according to Outset Medical. (NxStage System One is cleared to be run alone, but if patients use it at night while sleeping, a care partner is encouraged.)

Another issue is that home dialysis has not reached all of the populations in need. Black and Hispanic patients, disproportionately affected by kidney disease, are less likely to begin home dialysis than white patients, according to the U.S.R.D.S.

More options may be on the horizon. One from Quanta Dialysis Technologies, already cleared for chronic and acute settings, is in clinical trials for the home. Another, from CVS and Deka Research & Development Corp., is in the final stages of a clinical study.

At the start of this year, 2,300 of Outset’s systems were being used in hospitals, rehab facilities and long-term care facilities. But the company’s home rollout has been slow, with an estimated 300 devices being used by patients in the home or in training locations, according to the company’s latest public numbers.

The research on Tablo is promising, doctors say, but limited because of its small sample size and relatively short-term follow up. Dr. Michael Aragon, a nephrologist based in Fort Worth, Texas, helped to oversee Tablo’s home safety and efficacy trial before joining the company as chief medical officer. The trial found that 28 patients with end-stage kidney failure who completed the study had adequate removal of toxins on Tablo, and the device was deemed to be safe both at home and in clinic.

During Mr. Hall’s test treatment at the clinic, he also had to learn how to troubleshoot. Two hours in, as the leaves of a tree on the machine progressively turned green to show the time remaining, an alarm sounded. The machine had tried to take his blood pressure but couldn’t. A nurse repositioned the cuff. (Although it’s uncommon, losing consciousness from a drop in blood pressure is a risk at home or in the center.)

Several reports of bleeding, loss of consciousness and deaths associated with the Tablo have been reported to the F.D.A.’s database of adverse events over the past four years. Ms. Trigg said none of the adverse events impacting patients had been adjudicated by the company as Tablo-related.

NxStage System One also has its own share of similar adverse events, though a spokesman for Fresenius Medical Care said that no injuries or deaths have been adjudicated as the fault of the machine’s equipment.

Ismael Cordero, senior project officer for device evaluations at ECRI, the safety organization, reviewed reports from both companies. Any potential hazards, he said, become “even more concerning when the devices are used outside of a clinical setting.”

Carly Kempler, a spokeswoman for the F.D.A. said that the database has limitations, and that “if the F.D.A. becomes aware of information that reveals a safety concern with a medical device, the F.D.A. will take action as appropriate.”

Mr. Hall hopes to be given another transplant. In the meantime, he’s finally treating himself at home, with his family’s help. Though the first Tablo he received had glitches, its replacement is working smoothly.

No longer commuting to the clinic, he’s happy for the choices each day holds — simple ones like, early morning treatment, or evening? “That’s a great feeling of knowing I can work around whatever comes up,” he said.