A 4-year-old boy slips into a swimming pool, possibly injuring his head. A truck driver is struck head-on by a semi, ejecting him into a busy rural construction zone of a highway. A stroke victim has minutes to receive treatment with the hope of fully recovering brain function.

In these scenarios, people in medical crisis — caused by illness or accident or trauma — were transported by air ambulance from Douglas County to an area hospital. Each was a helicopter ride that may have saved a life.

Three area companies operate air ambulance services used by Lawrence-Douglas County Fire Medical and Lawrence Memorial Hospital. Called LifeStar, LifeFlight Eagle and LifeNet, they employ nurses, EMTs, doctors and pilots around the clock to be ready for medical emergencies.

Air ambulance transfers are a potentially life-saving measure by first responders to quickly move patients to specialized care. But it’s an expensive service — usually around $15,000 before any insurance coverage — and a “limited resource,” as Fire Chief Mark Bradford put it. If one helicopter is dispatched, it’s out of service.

When a serious accident happens in the county, dispatchers can notify the air ambulances to be on standby. First responders then assess patients and consult with an emergency room physician at LMH. This doctor then makes the call on whether to ask for a transfer by air.

LifeStar is used most often, Bradford said, because its helicopter base is at Lawrence Municipal Airport. (There’s also a LifeStar helicopter based in Junction City.) LifeStar of Kansas is a not-for-profit company owned by Stormont-Vail and St. Francis hospitals in Topeka. LifeFlight Eagle runs out of Kansas City, Mo., and LifeNet from St. Joseph, Mo.

Greg Hildenbrand, executive director of LifeStar, said that there are strict standards in place for determining who needs to be life-flighted, and that the first responders on the ground determine which hospital the patient goes to.

Because LMH is not a trauma center (it doesn’t employ a full-time neurosurgeon), people with extensive traumatic injuries frequently are sent to hospitals that are: Kansas University Medical Center in Kansas City, Kan., Overland Park Regional and Stormont-Vail.

Where a patient goes also depends on where in the county he or she got hurt, Bradford said. Some areas are closer to the hospitals to the east, while some are closer to Topeka.

And some have particular specializations of care. Kansas University Hospital, for instance, has a burn unit and pediatric surgeons who are always present. People sometimes accuse the fire-medical services of sending patients only to KU Hospital because of the university tie, Bradford said, “but it’s because of the staff available there. You wouldn’t believe the team that’s always ready to go.”

First responders practice the theory of the “golden hour” in “traumatic insult,” as it’s called. The idea is that a patient has a significantly higher chance of surviving a traumatic injury if the time from the beginning of a medical crisis to the time its victim goes into surgery is an hour or less. So, if a patient with a head injury needs to get from Lawrence to Kansas City, a straight-line helicopter ride will take about 15 minutes (at about 130 mph) of the golden hour while a ground ambulance would take at least twice as long, if not longer.

Still, it is an extraordinary expense. But Hildenbrand said that LifeStar and other air ambulances weigh that against the potential to save a life and provide a high-quality resource for Douglas County residents.

“It’s a service that you don’t want to ever have to use,” he said, “but it’s good to know it’s there.”