D.C. Fire Chief Kenneth B. Ellerbe acknowledged Friday that ambulance response times to medical emergencies have been unacceptable in a growing number of incidents reported across the city.

Ellerbe said the problems have been isolated and do not reflect a citywide crisis. But he said he will to try to push through long-sought reforms to do a better job delivering urgent care to residents, an issue that has bedeviled the department for years.

“We know that we are at a tipping point in terms of providing service to the community,” Ellerbe said at a news conference Friday. “I’ve been saying that to the council. I’ve been saying that for almost two years. It’s time for us to make a change in the way we deliver service.”

Ellerbe’s remarks follow at least three high-profile cases in which ambulances took an unusually long time to respond to medical emergencies.

In the first, just after New Year’s Eve, a heart-attack victim died after waiting 29 minutes for an ambulance. On Tuesday, a motorcycle police officer struck by a car waited 15 minutes with a badly broken leg for a ride to the hospital. And late Thursday, an elderly man who suffered a stroke was transported in a fire engine because the nearest ambulance was seven miles away.

Types of first responders

The controversy reignites a debate from seven years ago, when retired New York Times reporter and editor David E. Rosenbaum died after emergency personnel mistook his injuries from a vicious mugging for public intoxication and had considered him a low-priority call. The case, which stained the District’s fire department on a national stage, prompted recommendations for improvements that still have not been fully implemented.

The case revealed a long series of failures and remains the benchmark for evaluating the quality of emergency care in the District. Rosenbaum’s family dropped a lawsuit against the city in exchange for a promise to implement recommendations from a task force.

For weeks, Ellerbe has been pushing to overhaul how paramedics are deployed — changes, he said Friday, that would have prevented the recent delays. A key element of the plan, he said, is to take advanced life-support paramedics off the streets during the overnight hours so more can be deployed during peak daytime and evening hours.

Complicating his proposal are inflamed labor relations and the reality that contract talks with the 1,800-member firefighters’ union have been stalled for months. Angry union officials who have fought vociferously against Ellerbe’s reforms say his plan would do nothing to improve across-the-board response times. The problem, they say, is insufficient staffing and poor management.

Managers are critical of the union, too. They point to, among other things, the fact that more than 100 firefighters mysteriously called in sick New Year’s Eve, which was the shift when the heart-attack victim died.

Edward C. Smith, president of the firefighters union Local 36, called Ellerbe’s proposal a shell game, saying that “the department needs to grow, not steal resources from one time frame and give them to another.”

“There’s no argument there is a higher demand,” Smith said. “We’re not growing to meet that demand.”

The number of emergency calls has steadily increased over the past 10 years, and virtually all of the growth is in medical emergencies, not fires. In fiscal 2012, 82 percent of the 167,000 service calls were for medical emergencies. Over 10 years, the total number of calls has grown 22 percent.

As a result, fire engines and ambulances are traveling farther and handling more calls, he said — resulting in 15-minute delays for ambulances in some neighborhoods. “Response times have grown longer,” he said at a D.C. Council hearing last month.

At that meeting, Ellerbe presented a list of statistics to show that his deployment plan should be implemented. Tommy Wells (D-Ward 6), who chairs the public safety committee, said that Ellerbe doesn’t need the council’s approval on vehicle deployment, adding “I’m not sure we should legislate a deployment scheme.”

Less clear was whether city leaders would see fit to hire more paramedics or firefighters.

Fire officials emphasized this week that when a fire engine beats an ambulance to the scene of a medical emergency, patients often receive the same level of care they would get if the ambulance had arrived first. That’s because two dozen of the city’s 33 fire engines are staffed with firefighters who are also trained as paramedics, capable of delivering the same advanced life support as the city’s 14 medic units.

Engines typically show up at a routine medical call long ahead of one of the 26 basic-life-support ambulances or 14 advanced-life-support medic units. With fewer fires than medical emergencies across the city, engines are typically more readily available.

One goal everyone supports is to have enough firefighter-trained paramedics to staff all the fire engines. The firefighter union says there aren’t enough paramedics to staff medic units on most nights, let alone engines.

In the cases of the injured police officer and the man suffering the stroke, paramedics aboard fire engines responded and rendered care.

Fire officials said that a combination of heavy calls, traffic accidents and clogged streets made it nearly impossible for an ambulance to get to the stroke victim quickly. Deputy Fire Chief Demetrios Vlassopoulos said that it would have taken about 22 minutes and that firefighters decided to use the fire engine for transport.

“That was an outstanding decision,” the deputy chief said.

Smith, the union chief, also supported the decision, but he said it proves only that more hires are needed. The man could not be stabilized as he would have been inside an ambulance, he said.

Paul A. Quander Jr., deputy mayor for public safety, said his investigation into the delays involving the police officer is continuing.

He said that of the 39 ambulances and medic units on the street Tuesday evening, 10 were out of service. Some crews might have had mechanical problems, he said, but at least two and possibly three might have been off duty for non-legitimate reasons.

Carefully watching the latest dispute unfold is Patrick M. Regan, the attorney for Rosenbaum’s family. The current signs of dysfunction, Regan said Friday, “sound eerily similar” to the Rosenbaum case.

“At the time the task force concluded its work, I think we were all satisfied that the fire department was moving in the right direction and with all appropriate speed,” Regan said. “Everyone recognized there was a huge problem. . . . From the reports I’m seeing now in the media, it sounds like there’s been a significant regression. If it’s problems with the city council, or a lack of funding or with the union, the problems need to be addressed immediately.”