Doctors at University Medical Center in Tucson, Ariz., said they are "slightly more optimistic" as Rep. Gabrielle Giffords reaches a third day without increased swelling on her brain following the tragic shooting on Saturday that left her in critical condition and claimed the lives of six of her supporters.

Dr. Michael LeMole, the university’s chief of neurosurgery, told reporters at a press conference Monday afternoon that at this point in the Congresswomans’ recovery, “no change is good.”

“And we have no change. That is to say she is still following those basic commands. On top of that, the CAT scans are showing that there is no progression of that swelling, we are not out of the woods yet. That swelling can sometimes take three days, four days or five days to maximize, but everyday that goes by and we don't see and increase, we are slightly more optimistic.”

On Saturday, Giffords was shot in the head at close range during an event at Safeway supermarket in Tucson. The bullet went through the left side of her brain, but miraculously, she is still able to respond nonverbally to simple commands.

“When I say someone follows simple commands, this could be showing us their thumb, perhaps two fingers, gripping a hand, wiggling toes,” LeMole said. “All of those are simple commands that she can do even though she, for example, has a breathing tube in place that would preclude more complex communication.”

Officials at University Medical Center credited several reasons for Giffords’ survival, including good luck and the fact that she was in the operating room only 38 minutes from the time of the shooting where doctors worked to reduce pressure and swelling in her head by removing bone fragments and a small amount of damaged tissue.

Dr. Manny Alvarez, senior managing health editor at FoxNews.com, said this type of procedure is key to survival with severe head trauma patients.

“After you go and clean the broken pieces of bone fragments after a gunshot wound, typically you cauterize any broken vessels and you remove any small particles that you find,” Alvarez said.

Surgeons had to remove part of Giffords’ skull, in what’s called a decompressive craniectomy, to allow the swelling brain to expand without being squeezed – something Alvarez said is indicative to the severity of the injury.

“Right now, in half of her brain, she doesn't have a skull,” Dr. Peter Rhee, the trauma director at University Medical Center, told reporters on Sunday. “It’s preserved in the hospital right now so we can re-implant that later on.”

RELATED SLIDESHOW: Doctor Saves 25-Year-Old By Freezing His Skull

They are taking a very aggressive type of treatment in giving the brain time to swell, and hopefully the swelling will minimize over the next three or four days and then they are able to see if she will have sufficient neuro deficiencies, Alvarez said.

“Swelling typically peaks around the third day,” LeMole said. “I've seen it go out to as far as 10 days, but most often in the third day, that's why we are much, much more optimistic and we can breathe a collective sigh of relief after about the third or fourth day.”

Giffords can’t speak because she is currently on a ventilator and remains in a medically-induced coma.

Doctors at University Medical Center would not speculate on Giffords’ degree of recovery telling reporters that with this kind of injury, it’s a matter of months to years.

“At this point, we can’t measure psychological function, nor would we try,” LeMole said. “The important thing is that the needs of the family are met, and to anticipate needs down the road – think about rehab and physical therapy – but it’s premature to go into specifics now.”

Because the left side of the brain controls language and speech, it is very unforgiving. For a successful recovery, it would be a matter of rehab and how Giffords' body recuperates.

“When you get shot in the head and the bullet goes through your brain, the chances of you living is very small and the chances of you waking up and actually following commands is much smaller than that,” Rhee said on Sunday. “So far, it has been a very good situation – hopefully it will stay that way.”

Of those injured in the deadly shooting Saturday in Tucson, eight are still hospitalized. One is in critical condition. Five are in serious condition, and two in good condition.

The Associated Press contributed to this report.