He wants to continue working as a nurse well into his 70s, but the high-paced, high-stress job has taken its toll. Instead of working about 52 hours per week admitting patients at Providence Hospital in Washington, D.C., he now logs about half as many hours.

In many ways, Zwerdling is typical of a trend in nursing: He is approaching retirement age.

According to a survey released this week by the Association of Maryland Hospitals and Health Systems, a shortage of nurses in the state -- which is mirrored nationwide -- is getting worse, and threatens to deteriorate further.

"It's an aging work force with not enough to replenish the work force in the pipeline," said Barbara R. Heller, dean of the University of Maryland's School of Nursing in Baltimore.

The average age of registered nurses in the state is about 43, and the average nursing student is 31 -- both numbers that should be lower, she said.

Enrollment at nursing schools has remained steady over the last five years, and many are operating at capacity, but Heller said it is not enough to satisfy demand.

As the nursing workforce ages and inches toward retirement, the general population is also aging and will require more health care services, said survey coordinator Catherine Crowley.

The hospitals association did not project how many nurses are needed to fill demand, but estimates from the U.S. Department of Labor Statistics show that demand for health care workers -- including nurses -- will grow from 10.9 million last year to 14 million by 2010. About half of those jobs would be new positions, and the other half would be to replace retirees or people who leave the field.

"I think the fact that nurses are leaving traditional settings tells you everything you need to know about the work environment," said Vickie L. Milazzo, CEO of Medical-Legal Consulting Institute Inc. in Houston. She left nursing in 1982 to form her company, which trains nurses to become consultants. She conducts about eight six-day seminars a year nationwide.

This year, nurses are complaining more than ever that they are stretched too thin to provide adequate care for their patients rather than about pay and benefits, she said.

But insufficient pay, long hours and high stress are still big factors in the nursing shortage, said Zwerdling, who has started his own Internet business on the side selling nursing artwork to textbook and greeting card companies.

The biggest problem in replenishing supply, said the nurse who also doubles as a martial arts instructor, is that stereotypes about nursing persist.

The profession needs to reach out to more people like himself -- namely, men.

"Medicine has attracted more women," he said. "There's no reason nursing couldn't attract more men."

Heller agreed, noting that a recent informal survey of middle school students found that nursing is not on the vocational radar screen for boys or girls. Nurses perform complex and life-saving tasks just as important as doctors, such as administering medication and identifying abnormal heart rhythms that could lead to cardiac arrest for new admissions to the emergency room, Zwerdling said.

"People still think nurses just carry bedpans," Zwerdling explained. "We still do, but that's only a small part of what we do."

Heller, who is leaving the nursing school to become executive director of the university's new Center for Health Workforce Development opening in July, said there are a number of strategies to attract more students. They include adding more scholarships, possible marketing campaigns that show paratroopers becoming nurses instead of women holding babies.

The university is also trying to improve access to nursing schools. It started a program at its Shady Grove satellite campus in Rockville, where the first class of 23 nursing students will graduate May 24.

And changes at the state level could help alleviate the shortage, Crowley said. The state can help pay for expansions and new construction of classrooms and laboratories, as well as more training programs for nursing teachers. She said that, while more scholarships are available, it is still not enough. More than 100 qualified applicants were turned away.

"As it is now, our nurses and other caregivers are providing excellent care to the patients and they're working hard to do that," she said. "But one must question how long they're going to be able to do that."