Late last month, Raymond Johnson, 83, began feeling short of breath. “It was difficult just getting around,” he recently recalled by phone from his apartment in the Jamaica Plain neighborhood in Boston. “I could barely walk up and down the stairs without tiring.”

Like many older adults, Mr. Johnson contends with a variety of chronic health problems: arthritis, diabetes, high blood pressure, asthma, heart failure and the heart arrhythmia known as atrial fibrillation.

His doctor ordered a chest X-ray and, when it showed fluid accumulating in Mr. Johnson’s lungs, told him to head for the emergency room at Faulkner Hospital, which is part of the Mass General Brigham health system.

Mr. Johnson spent four days as an inpatient being treated for heart failure and an asthma exacerbation: one day in a hospital room and three in his own apartment, receiving hospital-level care through an increasingly popular — but possibly endangered — alternative that Medicare calls Acute Hospital Care at Home.

The eight-year-old Home Hospital program run by Brigham and Women’s Hospital, to which Faulkner Hospital belongs, is one of the country’s largest and provided care to 600 people last year; it will add more patients this year and is expanding to include several hospitals in and around Boston.

“Americans have been trained for 100 years to think that the hospital is the best place to be, the safest place,” said the program’s medical director, Dr. David M. Levine. “But we have strong evidence that the outcomes are actually better at home.”

A few such programs began 30 years ago, and the Veterans Health Administration adopted them more than a decade ago. But the hospital-at-home approach stalled, largely because Medicare would not reimburse hospitals for it. Then, in 2020, Covid-19 spurred significant changes.

With hospitals suddenly overwhelmed, “they needed beds,” said Ab Brody, a professor of geriatric nursing at New York University and an author of a recent editorial on hospital-at-home care in the Journal of the American Geriatrics Society. “And they needed a safe place for older adults, who were particularly at risk.”

In November 2020, Medicare officials announced that, while the federally declared public health emergency continued, hospitals could apply for a waiver of certain reimbursement requirements — notably, for 24/7 on-site nursing care. Hospitals whose applications were approved would receive the same payment for hospital-at-home care as for in-hospital care.

Since then, Medicare has granted waivers to 256 hospitals in 37 states, including to Mount Sinai in New York City and to Baylor Scott and White Medical Center in Temple, Texas. Initially, hospital-at-home programs treated mostly common acute illnesses like pneumonia, urinary tract infections and heart failure; more recently they have also started dealing with liver disease treatments, post-surgical care and aspects of cancer care.

Uncertainty over Medicare’s future involvement hinders the approach from being adopted more widely. “If this were made permanent, you’d see at least a thousand hospitals in the next few years” adopt hospital-at-home care, said Dr. Bruce Leff, a geriatrician at Johns Hopkins University School of Medicine who started one of these programs.

But Medicare’s waivers are not permanent. The public health emergency remains in effect until January; although the Biden administration will likely extend it, state health officials are anticipating its end at some point next year, perhaps by spring.

What will happen to hospital-at-home care then? Twenty-seven percent of programs that participated in a poll by the Hospital at Home Users Group said that they were unlikely to keep offering the option without a waiver, and 40 percent were unsure; 33 percent said that their programs were likely to continue.

Older adults and advocates for their well-being have reason to hope that these programs stay. Studies have repeatedly documented the risks of hospital stays to seniors, even when the conditions that made the stay necessary are adequately treated.

Older adults are vulnerable to cognitive problems and infections; they lose physical strength from inadequate nutrition and days of inactivity, and they may not regain it. Many patients require another hospitalization within a month. One prominent cardiologist has called this debilitating pattern “post-hospital syndrome.”

Had Mr. Johnson remained in the hospital, “he would have been lying in bed for four or five days,” Dr. Levine said, adding: “He would have become very deconditioned. He could have caught C. diff or MRSA” — two common hospital-acquired infections. “He could have caught Covid,” Dr. Levine continued. “He could have fallen. Twenty percent of people over 65 become delirious during a hospital stay.”

Patients must consent to hospital-at-home care. Almost one-third of Brigham and Women’s patients decline to participate because the hospital setting feels safer or is more convenient.

But Mr. Johnson was delighted to leave, when an attending doctor told him that his conditions were treatable through hospital-at-home care. “I wasn’t comfortable in the hospital’s surroundings,” he said.

At home, a doctor saw him three times, twice in person and once by video. A registered nurse or a specifically trained paramedic visited twice daily. They brought the drugs and the equipment Mr. Johnson needed: prednisone and a nebulizer for his asthma, and diuretics (including one administered intravenously) to reduce the excess fluid caused by heart failure. All the while, a small sensor attached to his chest transmitted his heart and respiratory rates, his temperature and his activity levels to the hospital.

Had Mr. Johnson needed additional monitoring (to ensure that he was taking medications as scheduled, for instance), food deliveries or home health aides, the program could have provided those. If he needed scans or experienced an emergency, an ambulance could have returned him to the hospital.

But he recovered well without any of those interventions. About a week after he was discharged, Mr. Johnson said he was “much better, much better,” and that he would recommend hospital-at-home care to anyone.

Studies have found that patients in hospital-at-home programs spend less time as inpatients and, afterward, in nursing homes. They are less sedentary, less likely to report disrupted sleep and more apt to rate their hospital care highly.

A New York City study found that hospital-at-home care also worked well for economically disadvantaged patients who qualified for Medicaid or lived in neighborhoods with high-poverty rates, including for those living in public housing.

A 2012 international meta-analysis of 61 clinical trials (hospital-at-home programs are more widely used in other industrialized countries) reported lower mortality and fewer readmissions to the hospital.

Most studies also found substantially lower costs. At Brigham and Women’s, the average cost per hospitalization was 38 percent lower for home patients than for those in an in-hospital control group, in part because of fewer laboratory tests, less imaging and fewer consultations with specialists.

“It’s not cheap to have amazing paramedics and nurses in the field, to have physicians available 24 hours a day, to have a biometric monitoring system,” Dr. Levine said. “But compared to in-hospital care, there are substantial cost savings.”

But the future of hospital-at-home care depends on federal action. A bill introduced in the House of Representatives this spring would have extended the Medicare waiver program for two years after the public-health emergency ends. The legislation did not advance, despite bipartisan support from 29 co-sponsors, but supporters believe that a similar bill could still pass.

Medicare could also authorize a multisite demonstration project, which would keep some hospital-at-home programs functioning.

“Are there people who need to be in a hospital?” Dr. Leff said. “Absolutely.” Surgeries, complex testing and intensive care still require a building and its staff. Nonetheless, he added, hospital-at-home initiatives demonstrate that more care could be provided outside bricks-and-mortar facilities.

“Hospitals in the future will be big emergency rooms, operating rooms and intensive care units,” Dr. Leff said. “Almost everything else will move to the community — or should.”