Inside Examination Room 3, the medical student pulled out a gray cuff to check his patient’s blood pressure.

Not so fast, the patient said. The man, who dreamed of one day weighing less than 300 pounds, knew the tiny gray thing had no chance of wrapping around an arm. “You’re gonna need the purple one,” he said. “Is this your first time doing this?”

“Never used the purple one before,” the student said.

If a doctor had taken Omar Maniya’s blood pressure, it would have been high. Maniya, 22, a first-year medical student at Georgetown University, had never seen a patient on his own until this February night. The place was his school’s student-driven, free clinic in a Southeast Washington homeless shelter, where the line often blurs between instructor and instructed.

The patient, unemployed and uninsured, kept the mood light. He has been to the Hoya Clinic so often that he’s chummy with the school’s dean.

“You want me to put in a good word for you?” the patient asked.

“I’d love if you could put in any word,” the doctor-to-be responded.

White-coated and wide-eyed, the medical students gain an intimate glimpse at the many faces of the District’s homeless and health-challenged. For the students, the clinic is practice. For the patients, many of whom live at the shelter, it’s an oasis.

On the three floors below the clinic, young children carry basketballs and single moms carry empty purses into converted hospital rooms at the old D.C. General Hospital building. Security guards in the lobby sweat in the muggy air as families mill about under missing ceiling tiles and dim lighting. The medical wing, funded by $100,000 in grants and private contributions in 2010, has sparkling blue linoleum floors and air-conditioned cool.

As Maniya talks to his patients, 12 other students are doing everything from greeting families to playing the game “Connect Four” with children in a playroom. The clinic, under the advisement of medical director Eileen Moore, saw 532 patients last year.

Moore has double- and triple-checked the students’ diagnoses since the clinic, which is available to anyone, opened for one night a week starting in September 2007. By the end of 2009, the demand for medical care had become so great that the clinic was opened for a second night.

Now, working out of a shelter with a full parking lot, they are considering adding a third.

The waiting room is filled with single women not much older than the medical students. Keviette Mack, 22, a mother of three, rocked her youngest child in a stroller, sitting next to a woman who was describing how the police had arrested and charged her after she was caught stealing $100,000 worth of jewelry.

“Don’t ever take anything that’s not yours,” the woman told Mack’s baby, his cheeks freckled with crumbs of Combos snacks.

Four months ago, Mack decided to leave her friend’s house because it had a mold problem. The shelter, she figured, would be more healthy. But to stay, she needed a tuberculosis shot.

Mack stuck out her left arm as a registered nurse watched a student gingerly inserting the tuberculosis shot for the first time.

“You can push it farther in,” the nurse said. “That’s good. Now pull it out.”

A small bubble appeared on Mack’s arm, a sign of success. The student smiled.

“The people here are a lot friendlier than the actual doctors” elsewhere, Mack said.

Examining symptoms

Minutes later, Maniya put down the purple cuff. He had to deliver his first report to Moore.

She told him not to be nervous when she interrupted. It’s what the attending physician does.

Maniya took a deep breath.

“Keith Brown is a 54-year-old male who has had asthma since he was a child. . . . He went to the emergency room on Sunday, and he ran out of medication, which is what brought him here today.”

Has he been coughing? Moore asks. Unproductive or productive?

“It wasn’t on Sunday, but it has started being productive,” Maniya told her.

“Outstanding,” she said. “It shows there’s some progression.”

Yes, there have been recent factors aggravating Brown’s asthma, such as the winded feeling he gets when he runs to catch the bus. No, Maniya continued, Brown hasn’t been struggling to breathe while sleeping. No, the patient has had no changes in vision.

Soon afterward, Maniya gives Brown’s height and weight. He tells the doctor that the blood pressure is a little high.

“I want to double-check the cuff size,” Moore said. “We want to make sure that the cuff is bigger if the person is bigger. Eleven is normal. What’d you use? 12? 13?”

“Umm, the purple one.”

“I didn’t even know we had a purple one!” she said. “Outstanding!”

The Q&A took 20 minutes. But it touched on only some of what Maniya learned in the room.

Real-life experiences

He learned to deal with distractions. A 7-year-old boy started tiptoeing into the room to grab fried chicken wings that Brown had brought with him, so Maniya asked his patient who the little guy was.

Brown said he was raising the child, the son of a family friend, because his parents were out of the picture.

Brown had no work and no insurance, but he was not homeless. He learned about the clinic after an emergency room visit at Georgetown’s hospital two years ago. He’s been coming ever since. He gave permission for The Washington Post to describe his visit.

Earlier that night, Maniya, the son of two physicians, had jumped into his 2007 gray Camry and headed to Southeast for the first time. Now, as he completed his presentation, he followed the doctor back into Examination Room 3.

Moore, the supervising doctor, sat next to Brown. She noticed a faint wheeze in the center of his lung. To double-check the patient’s blood pressure, the medical student handed her the enlarged cuff.

“I’m disappointed,” she sighed. “You told me this cuff was purple. . . . It’s burgundy.”

Her blood pressure reading matched her student’s. And he had been right — it was a little high. The cuff fit just right.

If you have an idea for a story about the D.C. area at night, e-mail Robert Samuels at samuelsr@washpost.