As humanity races toward a higher-tech future, researchers recognize the “man-in-the-loop” as the least reliable part of the machine — most susceptible to error.

Since the 1970s, analysis of more than 30,000 aviation and space flights by American scientists has revealed a central truth about the human component of any system: Errors are inevitable and ubiquitous. As NASA and other space agencies plan to soon push further into space, human error remains a nettlesome pest stowing away for the ride. To manage these risks, researchers with NASA and the Federal Aviation Administration devised a “threat and error model” helping astronauts and aviators to recognize and mitigate mistakes made in the cockpit and on the ground.

Now, the same model is proving useful for lowering the error rate in children’s heart surgeries, says Edward J. Hickey, a heart surgeon at the Labatt Family Heart Centre in Toronto. "We considered every patient's peri-operative journey to be a 'flight,' and we tracked it from patient arrival in the operating room until the point of discharge, with the aim of identifying 'threats,' 'errors,' unintended clinical states, and harmful outcomes,” he said in a press release.

Graphic courtesy of Edward J. Hickey Edward J. Hickey.

Hickey presented his findings on 524 “patient flights” involving 500 children hospitalized for heart surgery, 85 percent of whom underwent a cardiopulmonary bypass. Among those cases, he identified a total of 763 “threats,” including errors, unintended clinical states, and harmful outcomes. Eighty-five percent of these threats included end-organ dysfunction, noncardiac congenital lesions, and many variations of a particular type of lesion.

Interestingly, Hickey found that most of the errors were of consequence but could be detected prior to surgery. Human error was found in half of the cases with consequential mistakes — affecting one in five patients — leading to decreased margins of safety during the operation. Errors leading to such unintended clinical states were highly associated with deleterious patient outcomes such as brain injury, residual heart lesions, and even death.

Medical errors were found to have preceded most of the deaths among children in the study.

"We conclude that the progressive degradation of safety margins that occurs in most aviation disasters, and I use Air France 447 as an example, has direct corollaries in medicine," Hickey said, referring to the 2009 jetliner crash that killed all 228 passengers and crew aboard a Paris flight from Rio de Janeiro. Two years after the crash, investigators recovered the black box from the bottom of the Atlantic Ocean to determine the precise cause of the crash, finding human error to blame.

Hickey and his colleagues say scientists and technicians must expect human error as an integral part of the machine, one to be better managed.