These reactions and observations typically aren’t given the clinical weight of test results and lab values. Similarly, a large part of every nursing shift is spent on the computer documenting how patients are doing, but the content of these notes is more often than not ignored, particularly by physicians.

It doesn’t have to be this way, and it may not be for much longer. The change began in 2003, when an 87-year-old woman named Florence Rothman was hospitalized for a heart-valve replacement. She was in good health and initially did well, but experienced a slow, unnoticed deterioration in the hospital. She eventually received treatment for her symptoms, but no one investigated the cause. However, she improved and was sent home.

Four days later Ms. Rothman was seen by a home health nurse during an episode of severe breathlessness. When it happened again the same day, her family called 911, but it was too late: Her heart stopped in the emergency room, crushed by fluid surrounding it.

Ms. Rothman’s sons — Michael, a data scientist, and Steven, an engineer — wondered if their mother’s death could have been avoided, had there been a better way to track her signs of distress. Doctors later determined that she had developed a condition called cardiac tamponade, and it probably started during that first deterioration in the hospital. If her overall condition had been thoroughly examined at that point, the tamponade likely could have been detected and treated.

Together the Rothman brothers came up with the Rothman Index, a commercial product that uses data from standard electronic health records — including lab values, vital signs, cardiac rhythms and key aspects of nursing assessments — to monitor hospital patients. It tracks their status as a graph that falls into a blue, yellow or red zone, based on whether they are at low, medium or high risk of an acute event. Michael Rothman said cartoons about hospitals that show a chart with a zigzag line appended to the foot of each patients’ bed reflect the visual power of the Rothman Index.