Ever visited the ER in a hospital? Chances are that you may not have met a doctor and instead checked by a nurse. The reason why there is no guarantee that one will see a doctor on their visit to ER is the little-known ‘blended model.’

Many hospitals outsource their emergency rooms to medical staffing companies such as American Physician Partners (APP). APP, a company owned by private equity investors, employs fewer doctors in its ERs as a way of cost-saving to increase revenue, according to a confidential company document.

Doctors are now being sidelined by nurse practitioners and physician assistants, collectively known as “midlevel practitioners.” These professionals are capable of performing many of the duties and generate almost the same revenue, but have less than half of a doctor's pay.

“It’s a relatively simple equation,” Dr. Robert McNamara, a founder of the American Academy of Emergency Medicine and chair of emergency medicine at Temple University, said, according to CNN. ”Their No. 1 expense is the board-certified emergency physician. So, they are going to want to keep that expense as low as possible."

Calling it a “blended model,” APP said that it is a way of making sure all ERs stay fully staffed. In this way, doctors, nurse practitioners, and physician assistants can “provide care to their fullest potential,” it further said.

Besides the obvious fear that a person may not receive adequate care, critics posit that the model increases the likelihood of misdiagnoses and higher medical bills.

In a study, published in October by the National Bureau of Economic Research, about 1.1 million visits to 44 ERs throughout the Veterans Health Administration were analyzed. Here, nurse practitioners are allowed to treat patients without oversight from doctors.

Treatment by a nurse practitioner led to a 7% increase in the cost of care and an 11% increase in length of stay, the study found.

“It’s not just a simple question of if we can substitute physicians with nurse practitioners or not,” Yiqun Chen, co-author and an assistant professor of economics at the University of Illinois-Chicago said. “It depends on how we use them. If we just use them as independent providers, especially … for relatively complicated patients, it doesn’t seem to be a very good use.”

Due to a lack of definite evidence on the negative impact of substituting doctors with nonphysicians, the blended model is likely to continue, Dr. Cameron Gettel, an assistant professor of emergency medicine at Yale, said.

“Worse patient outcomes haven’t really been shown across the board,” he said. “And I think until that is shown, then they will continue to play an increasing role.”