The healing touch of a young hand Nurse, 25, feels right at home

She is young, wears a jean jacket. This is her first real job. She is chipper in her office in Charlestown, even now before 8 a.m. Says things to her co-workers like ''happy Friday" and then smiles. Sarah Penyack likes being a nurse.

He is old, wears gray pants with an elastic waistband. His legs are swollen, and the oxygen tubes attached to his face give him nose bleeds from time to time. Once a swimmer, Joseph O'Brien now sits in his Somerville house waiting for Penyack to arrive and look after him. He is a sick man.

''You fixed your hair different," O'Brien says when she gets there this morning.

''I showered," she replies.

''You didn't."

''I did."

This is how Penyack, 25, knows O'Brien, 88, is doing all right. He is a funny man, a flirt. His wife, Bette, knows it.

''You should see him," Bette says, ''down at the pool with the women in the bathing suits."

The retired bus driver is quick with one-liners. But not always, not anymore, not since his bouts with pneumonia last year and the hospital visits that followed, including long stays this spring. It was a bad time. O'Brien was diagnosed with congestive heart failure and sent home on oxygen. And that's when Penyack -- his Florence Nightingale, as he calls her -- walked into his life.

She is, at once, both typical and rare. Massachusetts has more registered nurses per capita than any other state but one. But very few of these people go directly from school into a job as a home-care nurse like the one Penyack landed nine months ago with the Visiting Nurse Association of Boston.

Out there, in the homes of the sick, nurses are on their own. There is no one with whom an inexperienced nurse can easily consult. No fellow nurses or doctors around the corner. No supplies stocked in the hallway.

''You're out there by yourself most of the time," says Paula Griffin, a manager for the association and Penyack's supervisor. And for this reason, most home-care nurses have years of experience working in hospitals. The average age of VNAB's 250 nurses, says Griffin, is probably in the 40s.

But in a nurse's market, in which job applicants can often pick and choose the positions they want, the Visiting Nurse Association decided to take a look at Penyack after she graduated last year from Boston College with a master's degree. She was young, it's true, but this was the job that Penyack wanted.

''The nursing that I want to do is in the patient's environment," she says. ''You're dealing with real people, with real lives, and you can't control them. It's not a hospital."

It's someone's home. They're sitting in their kitchen or their living room, and they are waiting, often alone, for someone to change their dressings or check their blood pressure or simply remind them that they are not forgotten.

''You may be the only person," says Penyack, ''that they see in a long time."

She got the job.

''Can you be quiet for a minute?" Penyack chides O'Brien, who, as usual, is talking nonstop, dropping witty one-liners and getting fresh, as she tries to listen to his labored breathing.

''Yes, dear," he relents.

He is not well. He knows it. O'Brien's days of swimming are probably over, his future unknown. He and Bette talk about maybe moving into an assisted-living facility, where he could get 24-hour care and she could relax a bit instead of running up and down the stairs, worried about her husband. But more than anything, like most people, they want to stay right where they are. They want to stay at home.

Penyack monitors O'Brien's breathing. He is the second of several people she will see today.

There will be the 91-year-old woman suffering from incontinence, and the 89-year-old man suffering from diabetes. Two of her patients are legally blind. Two do not speak English. One is obese. A few are depressed.

By tonight, if it's like most nights, Penyack will be exhausted. The good part about being young and a nurse may also be the hard part: Everything is still new to her.

She is still learning, and yet the O'Briens say they have never had a better nurse, in a hospital or their home or anywhere else.

Joe O'Brien looks at her over his oxygen tubes. Their visit is almost over now. His breathing is good, or at least as good as can be expected.

But both of them know that could change at any moment.

''If your breathing gets worse," Penyack tells him, ''and you start coughing up stuff that's green --"

''Green?" he asks.

She nods. ''Call 911."

But if it's anything else, she tells O'Brien, just call her directly.

''OK?" she asks.

''All right, love," he replies.

Got a subject to suggest for Heart of the City? E-mail Keith O'Brien at kobrien@globe.com.