A sobering warning was sounded last week, an alert to patients and potential patients about an American health care system that is "approaching a critical condition."

The warning came from a former Reagan administration health official and the 10-year-old National Committee for Quality Care, a coalition of health and hospital systems and companies.

"If present trends continue, the future of the American health system is in serious jeopardy," said Dr. Robert J. Rubin, speaking for the coalition and reading from an alarming report that spoke of "many early warning signals" and "the beginnings of a disturbing future."

Coming from a coalition that would benefit from more spending on health, such accusations might be suspect were it not for the fact that the health world they describe is described in the same way by many other persons.

And the deterioration they warn about is not simply part of "a disturbing future." It is now going on.

Hospitals are increasingly sending persons who can't pay for treatment to public hospitals that are ill equipped to care for them. A growing number of Americans can't pay for care because they lack any -- or adequate -- health insurance.

There is a serious shortage of nurses to care for hospital patients. One major reason is the failure to pay nurses the improved salaries that hospitals, hard pressed to control costs, claim they can't afford.

The malpractice insurance crisis is creating shortages of some important kinds of doctors in some parts of the country. The brightest young men and women are no longer heading for the schools that train our future doctors.

There's more.

Rubin, head of Health Sciences and Research Inc., the consulting firm whose Lewin/ICF division produced this report, from 1981 to 1984 was assistant secretary for planning in the Department of Health and Human Services. At HHS, he was one of the architects of some of the very hospital cost controls that -- said the report he presented -- "have begun to adversely affect the availability and access of certain types of health care services."

Some of the evidence from this report and other sources:

Some hospitals have been closing, squeezed by tighter payments from the government and private insurers. There are 50,000 fewer hospital beds than there were five years ago. This would be economically to the good if all the closed hospitals were surplus hospitals with surplus beds. Unfortunately, many have been small-town and rural hospitals or public hospitals "providing essential services to vulnerable groups."

Among possible results: A study in eight rural Florida counties with no hospitals found that both infant mortality and the death rate from accidents was higher than in rural counties with hospitals.

Doctors are disappearing in some areas, some because a hospital has disappeared, some because they are either quitting medicine or abandoning some practices -- especially obstetrics and to some extent neurosurgery -- because of high malpractice premiums. This may be good where there are doctor surpluses. But women in small towns in Iowa, Alabama, North Carolina, Kentucky, Georgia and other states are being forced to travel a half-hour to 45 minutes, sometimes longer -- in the best weather -- for prenatal care or delivery.

Partly because of much advertised pressures on doctors, partly because of the crushing cost of medical school and the fact that other fields promise quicker returns, the number -- and, some say, the quality -- of medical school applicants is declining.

A medical school admissions director said a few weeks ago: "In the mid-'70s we had five applicants for every place; now we have two. We're not getting the superstars, and if the trend continues, we may be taking almost anyone we can get." Something less than the best students may make something less than the best doctors.

Hospitals need more nurses to deliver new lifesaving medical technologies. In 1977, hospitals hired nearly one registered nurse for each two patients for round-the-clock duty. Today they try to hire almost one for each patient, but fewer nurses are being trained and nursing schools are closing as young women head for better-paying jobs. Hospitals in Maryland, for example, are failing to fill 20 percent of their nursing slots. They often cope by hiring many part-time nurses and shifting nurses from ward to ward, day by day. One patient told me: "I was in the hospital three days, and I didn't see the same nurse twice."

Nursing homes, good and bad -- there are both -- are likely to have an especially hard time hiring qualified nurses. This while "the number of nursing home beds per thousand elderly has declined since 1977" and "the demand currently exceeds supply and can only keep growing."

Medicaid -- medical assistance for some low-income persons -- finances about half of all nursing-home care but in 1985 paid only $50 a day on the average, while the average industry charge for skilled nursing was $65. "It is difficult to consider what will happen to the growing number of elderly who will be unable to obtain long-term care services." Let alone high-quality services.

The cost of health care is continuing to rise, and patients are being forced to shoulder a growing percentage of their medical and hospital bills. More employers are requiring increased employee contributions. Insurers and prepaid health plans (HMOs and others) are adding co-payments, decreasing coverage or increasing premiums. Health insurance premiums went up sharply in l987, with increases of a third common.

The number of uninsured Americans is 35 to 37 million, and millions of others are inadequately insured. Small companies may increasingly fail to provide costly health coverage. Medicare, intended to protect the elderly, finances less than half of this group's health bills. Medicaid, the program for the poor, is covering less than 40 percent of the poverty population.

Apparent results: A Robert Wood Johnson Foundation study found that nearly 39 million Americans had trouble getting necessary health services; nearly half said the reason was financial. The number of children going unvaccinated is on the increase. So is the number of babies born to women getting late or no pre-birth care. So is infant mortality in some states or cities.

Another result: Half of the nation's hospitals lost money on patient care in 1986, though many scraped by with other types of income. The hospitals say they have squeezed out all the fat they can manage; federal regulators and other critics say they must achieve more efficiency.

Whichever is the truth -- and different truths may apply to different hospitals -- many hospitals may slow down their purchase of costly new devices that can save some patients' lives.

"What we have described," said Dr. Rubin, "are symptoms of a national dilemma. Do we want more care or less costs? . . . Robert Browning wrote that the 'business of life' is making 'terrible choices.' Never has this been more true than in the field of health care."

Next Week: What can we do as patients to look out for our own health in this atmosphere? What can we do as a nation?