Jaime Pinto, 69, a retired boat mechanic with chronic spinal problems, has just become part of a new world envisioned by federal healthcare reform.

It’s called an accountable care organization, a vague phrase with deep implications that policy makers say could revolutionize the nation’s healthcare, lowering medical costs and increasing quality — if it works as planned.

While the concept could lead to huge changes in the system, many ACOs will be virtually invisible to the patient. “I’m not seeing any differences,” said Pinto. “I’m still seeing the same doctors, getting my medications the same way. I don’t want to be guided, and I’m not being guided.”

ACOs — and a related concept, “medical homes” — were pushed hard by creators of the Affordable Care Act to improve quality and lower costs for Medicare patients, but the concept is expected to spread to others in the healthcare system.

Superficially, the concepts seem much like the old health maintenance organizations, but there are major differences. HMOs generally get a specific number of dollars per year for each patient, and the fewer dollars they spend on healthcare, the larger their profit. HMOs often have gatekeepers that must approve visits to specialists.

With ACOs, quality is a major factor in measuring results. Hospital readmissions and other poor health outcomes could penalize the organizations. But if patients remain healthy and cost Medicare less, the ACO member providers — which can be hospitals, doctors, home health agencies and others — share in the savings.

The concept is meant to fix the present system in which many providers offer no coordination whatsoever. One example often cited by lawmakers is that Medicare patients leaving the hospital are usually given prescriptions to fill and an order to seek follow-up care with their doctor in a short time. Often, those orders go unheeded, and the patient ends up back in the hospital. Medicare is now tightening the screws on hospitals, threatening not to pay for needless readmissions.

With an ACO, a care coordinator can keep track of discharged patients, making sure prescriptions are filled and doctor appointments made — and providing direct help if necessary, such as getting the drugs from pharmacy to home. Coordinators, working with shared electronic records, can also be sure, for example, that different specialists don’t duplicate tests or treatments.

Such a concept is especially important for patients in Miami, where the average Medicare recipient has close to the highest costs in the country — costing the federal government about twice what the average senior costs in Minneapolis.

Repeated studies by Dartmouth Atlas researchers have shown that Miami’s high costs often come from seniors bounced from specialist to specialist, frequently with duplicate tests. One Dartmouth study found that in the last two years of life, Medicare patients in Miami with any of 12 chronic conditions saw almost twice as many specialists as similar patients in Fort Myers.

With the Affordable Care Act offering incentives for ACOs, many large players are entering the competition, including major hospital chains, health insurers and even Walgreens. Some hospitals have gone on hiring sprees to get doctors to help provide the integrated care that ACOs require.