In the first section of this article we discussed some of the incredible functions of the brain and how the brain can accomplish these tasks in a very energy efficient manner. In the second section of this article we will go into more details on rest and sleep that are so crucial to optimal brain function.  

In addition to supplying the brain with energy that was detailed in part one, we also need to understand the need for quality rest time and undisturbed sleep so the brain can “process” all the information that we download into our brains during the day. The significance of poor sleep habits can impact brain performance in areas critical to safe flight.  This is shown in a often quoted study a while back in a very reputable science journal (Science) that compared cognitive function and dexterity in a group of subjects who were kept awake for 24 hours and a group of much more fortunate and fun loving folks who got drunk.  The happy group partied their way to blood alcohol concentrations of 0.9 and then were tested for dexterity, problem solving skills and cognitive function – sort of the ultimate buzz kill. Critical task performance was then compared to the tired and likely much more feisty group who had been kept awake all night listening to the party in the other room.  It turns out the skill levels in the group with the BAC of 0.9 were the same as the subjects after 22 hours without sleep.  If you’re driving and get pulled over with a BAC of 0.9 you will loose your drivers license for a while and probably your pilots license too when you fess up to the FAA and also spend a few nights in jail so you can think over the fine you’ll have to pay when they let you out.

Individually, humans possess a genetically hard-wired sleep requirement. Sleep is a physiologic drive as strong as hunger or thirst. Basic sleep requirements average about 8 hours per day (somewhere between 6 to10 h) and if this is not met a “sleep debt” ensues and sleepiness, with all its mental impairments, manifests. The only way to pay off this “sleep debt” is to get adequate sleep. You also can’t “bank sleep” and get a few days of rest and think it will last.  Fatigues sets in and sleep debt starts accumulating after about 16-18 hours of wakefulness. Additionally, there are very real implications for long life and health. It has been shown that lack of sleep and insomnia are associated with lower life span in all of us.  The American Cancer Society, in a study of more than a million people, found that men who had less than 4 hours of daily sleep were almost three times more likely to die within a 6-year follow-up as compared to those who got 7-8 hours of sleep.   Women fare better but still are at more risk of early death that increased by almost 50%.  

In our capacity as pilot in command with responsibility for the safety of ourselves, our passengers and our aircraft there is, quite obviously, little room for error. So it is easy to see why the most common thread through many accident and incident investigations are errors brought on by fatigue. Reviewing data from the NTSB and FAA show that about half of accident investigations implicate fatigue as one of the factors in the root cause of the incident.  Just think about it, almost every well known disaster from the Titanic, Exxon Valdez, Bhopal chemical spill, Chernobyl nuclear accident all happened at night and were caused by fatigue induced error.  Managing accidents due to fatigue has been on the NTSB “most wanted” list of error control since 1990. 

There is awesome research carried out by a British scientist, J. C. Williams, who developed a mathematical predictor of the risk of accident occurrence and developed a set of Error Producing Conditions (EPCs).  These are a series of circumstances that, when they exist in given scenario basically portend that things will end badly with bent metal and even possibly death.  Consistent with NTSB data, it’s no surprise that the most important of Williams’ error producing conditions is fatigue.  When a fatigued crew is operating in a complex and time compressed environment the chances of an accident are 50X greater than when a rested crew carries out the same tasks! There are obviously other error producing factors and they multiply the risks not just add to the risks so put a tried operator into a risky situation and disaster soon follows.   For all these reasons, lean back that incredible engine in your head and do it every day.  Get enough rest and sleep to be fresh and to store knowledge where it can be called up to solve complex problems and assure safe outcomes. 

In the next post we will see just how much fatigue impacts our performance and make some comparisons between the marvelous human machine we operate to some of the most advanced flying machines.  A kind of contest to see who (or what) is really the best engineered and let the best man (or machine) win. 

Find part three HERE.

Kenneth Stahl, MD, FACS
Kenneth Stahl, MD, FACS is an expert in principles of aviation safety and has adapted those lessons to healthcare and industry for maximizing patient safety and minimizing human error. He also writes and teaches pilot and patient safety principles and error avoidance. He is triple board-certified in cardiac surgery, trauma surgery/surgical critical care and general surgery. Dr. Stahl holds an active ATP certification and a 25-year member of the AOPA with thousands of hours as pilot in command in multiple airframes. He serves on the AOPA Board of Aviation Medical Advisors and is a published author with numerous peer reviewed journal and medical textbook contributions. Dr. Stahl practices surgery and is active in writing and industry consulting. He can be reached at [email protected].
Topics: Pilot Health and Medical Certification

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