Emergency medical care in the United States is on the verge of collapse, with the nation's declining number of emergency rooms dangerously overcrowded and often unable to provide the expertise needed to treat seriously ill people in a safe and efficient manner.

That's the grim conclusion of three reports released yesterday by the Institute of Medicine, the product of an extensive two-year look at emergency care.

Long waits for treatment are epidemic, the reports said, with ambulances sometimes idling for hours to unload patients. Once in the ER, patients sometimes wait up to two days to be admitted to a hospital bed.

As a system, U.S. emergency care lacks stability and the capacity to respond to large disasters or epidemics, according to the 25 experts who conducted the study. It provides care of variable and often unknown quality and depends on the willingness of doctors and hospitals to lose large amounts of money.

Fixing the problems is likely to cost billions of dollars and will require the leadership of a new federal agency, which Congress should create in the next two years, they wrote.

"This is a crisis that could jeopardize everyone in this room, and all their loved ones," A. Brent Eastman, a surgeon and chief medical officer of the ScrippsHealth hospitals in San Diego, said at a daylong conference on the reports, which were prepared by the National Academy of Sciences' Institute of Medicine.

"There is just such a gap between what the public knows, or thinks it knows, and the reality. And it is getting worse," said Robert B. Giffin, the Institute of Medicine staffer who headed the study.

The reports -- on hospital ERs, on pediatric emergency care and on pre-hospital care given by ambulance services -- were embraced by the 24,000-member American College of Emergency Physicians, and its president said that the endorsement was telling.

"What other industry says, 'Hey, look at us, our whole system is broken'?" said the group's president, Frederick C. Blum, a physician in Morgantown, W.Va.

Two key steps for improving emergency care are regional planning and creating a standard way to measure outcomes, so that low-quality ERs and ambulance services can be identified and fixed, the committee wrote.

Emergency medical care is a legal right for all Americans. Under a law enacted in 1986, emergency rooms must evaluate and stabilize anyone who shows up. That requirement -- bolstered by physicians' ethical duty to treat the ill -- has made hospital emergency departments subject to unique pressures.

From 1993 to 2003, the U.S. population grew by 12 percent but emergency room visits grew by 27 percent, from 90 million to 114 million. In that same period, however, 425 emergency departments closed, along with about 700 hospitals and nearly 200,000 beds.

ERs are notorious money losers. About 14 percent of ER patients are uninsured. About 16 percent are covered by Medicaid, the federal-state insurance program for the poor, and 21 percent by Medicare, the program for the elderly. More than half of hospitals report losing money on emergency care of both groups of government-insured patients.

All of this has led to extreme bottlenecks in ERs, manifested by delays in every step of treatment, according to the reports.

In 2003, 501,000 ambulances were diverted from the hospital where they normally would have delivered a patient because the ER was full. In 2004, 70 percent of urban hospitals reported that their emergency departments had been "on diversion" at least once.

Nationwide, about 14 percent of ER patients end up admitted to the hospital. A study by the Government Accountability Office in 2003 found that 20 percent of emergency departments had to "board" patients in hallways or other temporary space, for an average of eight hours, before a bed opened. The American College of Emergency Physicians several years ago surveyed 90 emergency departments on a single Monday evening. Seventy-three percent reported that they had two or more patients boarding.

A 2004 study found that ERs at university-based hospitals were classified as crowded 35 percent of the time, meaning all emergency beds were occupied, patients were in the hallways, the waiting room was full, and the waiting time for treatment was more than one hour.

Another hazard largely unrecognized by Americans is that hospitals, especially in rural areas, often cannot find specialists such as orthopedic surgeons and neurosurgeons willing to cover the ER.

In some cases, this is because doctors are unwilling to treat high-risk patients with complicated ailments, many of them uninsured, at inconvenient times. Sometimes it is simply a function of shortages. In 2002, there were fewer practicing neurosurgeons in the United States (about 3,000) than a decade earlier.

Largely unknown is the human cost of these problems.

Many studies have shown that high-stress, chaotic environments contribute to errors. One from 1991 showed that though relatively few "adverse outcomes" occur in the ER, it was the site of 70 percent of those attributable to negligence.

The number of deaths caused by a delay in treatment or lack of expertise is especially uncertain, though it may not be small. San Diego established a trauma system in 1984 after autopsies of accident victims who died after reaching the ER suggested that 22 percent of the deaths were preventable, said Eastman, one of the Institute of Medicine committee members.

Trauma care in many ways is the model on which the committee hopes the emergency care system will be rebuilt.

Some states and urban areas have systems in which the level of trauma care every hospital is capable of providing is known and a centralized dispatching agency directs patients based on real-time information about each hospital's capacity and staffing.

Although the vast majority of ER patients have not suffered trauma, about half need attention within an hour of arrival at the hospital, according to a study in 2003. Because not every hospital or even every city can provide all services, "the committee supports further regionalization of emergency care services," the authors wrote.

Even without systemwide reform, hospitals can do many things to make the flow of patients more efficient and to be ready for predictable spikes in demand, said Benjamin K. Chu, an ER physician and regional president of a Kaiser Health Plan in California who was also on the expert panel.

The report on ambulance service called for standardizing the training of paramedics and creating guidelines for pre-hospital care based on research.

The report on pediatric care emphasized that 27 percent of ER patients are children and that many hospitals lack the expertise or the equipment to meet the needs of those who are critically ill.

The District's emergency and trauma services measure up well. A report this year gave the city an A-plus in "its support of an emergency care system."

Though the assessment was somewhat skewed by the District's compact geography and urban makeup, population-adjusted numbers showed more emergency departments, board-certified emergency doctors, hospital-staffed beds and trauma centers than in any state, and probably more than in many local jurisdictions, although the report did not look so narrowly.

Still, the American College of Emergency Physicians noted, emergency services in the city "are regularly reaching their capacity, and patients are frequently and increasingly diverted to other facilities." In 2004, for example, Washington Hospital Center's ER was "on diversion" for nearly 2,100 hours. Howard University Hospital's ER turned away patients for the same reasons for almost 1,200 hours.