Tuesday, January 4, 2011

Patients Are Not Airplanes

As promised in my post “Surgeons Are Not Pilots,” today I will address the issue of whether patients can be compared to airplanes. Honestly, I cannot think of even one thing that patients have in common with airplanes.

As alluded to yesterday, probably the most glaring difference is that, unlike an airplane, each patient is unique. If a pilot sits at the controls of any Airbus A320 aircraft, he can be reasonably sure that pulling back the stick a certain amount will result in a very consistent response from the plane. Therefore, practicing on a simulator will enable the pilot to prepare for any emergency with the knowledge that what he did on the simulator will in fact be reproducible in a real emergency.

Contrast that with a patient. Often patients with similar illnesses will behave very differently because human beings are not engineered like airplanes. For example, let’s say I am performing a difficult laparoscopic cholecystectomy (removal of the gallbladder) and I am having trouble locating the cystic artery (artery to the gallbladder). I know that the anatomy of the cystic artery is highly variable. This link illustrates 11 of the most common anatomic variations in the location of that vessel. This means that there is not a simple maneuver that will help me find the artery in every case.

A pilot can be confident that a 5% increase in power will result in a very predictable response in airspeed. Contrast that with a patient’s response to a medication. I have had patients fall asleep with an intravenous injection of only 2 mg of morphine and I’ve had other patients who loudly complain of persistent pain after receiving 10 mg of the same drug.

A word about simulators. Because all stimuli are external to a fixed object, the pilot, aircraft simulators are easy to design and are very realistic. They recreate the motion, sounds and visuals of flying very well. When I was in the Navy stationed on an aircraft carrier, I heard pilots talk about their experiences in simulators. They said the intensity of the experience was very similar to that of flying a real plane. While surgical simulators have become more sophisticated, they still lack the realism of aircraft simulators because the action is all occurring on a video screen and the surgeon is sitting in a lab somewhere. There is no way that a surgical simulator can give you the adrenaline rush and anal sphincter-puckering feeling of seeing a sudden squirt of blood that covers your laparoscope and totally obscures your vision during a tough case. And there are no realistic surgical simulators for open (non-laparoscopic) cases. Operating on a pig just doesn’t cut it. (Pun intended.)

So please, stop trying to compare patients to airplanes.

A postscript on yesterday’s “Surgeons Are Not Pilots” blog.

Captain Chesley Sullenberger, the appropriately acclaimed hero of the successful Hudson River landing of US Airways Flight 1549, is hardly a typical pilot. According to one biography, he had over 27,000 hours of flying experience with more than 19,000 of those hours in Airbus A320s or like aircraft. He also had written about air safety and worked as an NTSB investigator. The hours alone qualified him as an “expert” pilot.

Compare Sully’s background with that of the pilots of Colgan Air Flight 3407, which crashed in Buffalo two years ago, killing 50 people. The following is from the Wikipedia entry about this incident, “The crew of four was led by Captain Marvin Renslow … who was hired by Colgan in 2005 and had flown 3,379 hours. 261 of these hours were on the Dash-8 Q400 (including 109 as a captain). First Officer Rebecca Lynne Shaw … was hired by Colgan in January 2008, and had flown 2,200 hours, 772 of them on the Q400.” The cause of the fatal accident was several pilot errors and failures to follow protocols.

All the checklists in the world didn’t prevent that crash. As long as humans are going to perform surgery on other humans, bad outcomes will occur. Yes, we should endeavor to minimize errors as much as possible, but “zero defects” and Six Sigma are not possible in medicine (or even in manufacturing).


webhill said...

OK, I have to ask you, because I consulted with a physician friend already but he didn't have an answer. You state that "a pig doesn't cut it" (ha ha) as a realistic surgical simulator. Why not? As a veterinarian who has done a fair share of surgery, I completely understand that a pig has anatomical and physiological variations from a human, and as such it's not quite exactly the same thing. However, it's still surgery on something alive that you want to keep that way. My only "practice" surgeries (as surgeon-in-charge, as opposed to assistant - I assisted in surgeries on many species) before I started operating on privately owned pets were on dogs. I did not feel inadequately prepared when I encountered my first surgical case in a cat, or my first in a rabbit, or my first on a rat. I feel the same sphincter-tightening regardless of species! What does the pig lack? I haven't done any surgery on pigs except for a minor laceration repair years ago.


Skeptical Scalpel said...

Thanks for the thoughtful comments and the question. The pig differs from a sick human in several ways. For instance, the gallbladder (GB) of a pig is remarkably free of any fat in the area of Calot's triangle (where the cystic artery and duct are located). The structures are quite easy to see. Laboratory pigs do not have any inflammation around their GBs and dissecting the GB free of the liver is very easy. Pigs are smaller than humans. There is really no realistic drama involved in operating on them. If they die, you don't have a lawsuit; you have pork chops (not really). There is also the problem of using any animal to practice on as far as anti-vivisectionists are concerned.

webhill said...

Oh, ok. So you think the pig isn't a good model because you feel any anxiety associated with the outcome, is what it sounds like? I feel a lot of "realistic drama" with my own patients, because the outcome is really important to me, to the animal, and to the owner. Beyond that, I wasn't really thinking about a specific procedure when it comes to simulation... I was thinking more general surgical techniques, which I guess you'd agree you can learn pretty well from operating on a healthy pig regardless of which species you'll later work on, right? There is a lot of variation between the species, especially the GI tracts of carnivores vs herbivores of course but lots of other stuff too, but I guess to me that's just something you can learn separately as needed for each species you plan to work on. As long as you know the general techniques of good surgical practice (and are willing to extend your incision to get good exposure if you're in a sketchy area you've not seen before!) I think you're good to go :)

Bruffie said...

Captain Sully had 27,000 hours of sitting on his butt, but only 3 minutes of on-the-job training for an experience that he never once trained for. And he blew it. In every possible way. He forgot his call sign, he forgot to return to LGA, he forgot to declare an emergency, he forgot that when you land, you use flaps to slow down, he forgot to turn into the wind, he forgot to advise the cabin what he was doing, and when he was down, he even forgot to call 911 and advise that was going on. But he did call his wife. It is fortunate that he was flying an aircraft designed to outwit fools. Only through the some of most incredible luck in the history of aviation did the stars align and the water and ferry boats appear. When the feathers settle in this, the gentleman will be lucky not to be facing charges of reckless endangerment.

Skeptical Scalpel said...

Bruffe, thanks for the comments. But you seem really angry at Sully. Somehow despite all your criticisms, all 155 passengers and crew survived. He made a one-number error regarding the call sign, having said 1539 instead of 1549, which seems trivial. The cockpit voice recording suggests he considered going back to LGA. Here's a quote, "Hit birds. We've lost thrust on both engines. We're turning back towards LaGuardia." But he was unable to do so.

Also from the Wikipedia article [http://tiny.cc/txzvr] about the crash is this: "The NTSB ran a series of tests using Airbus simulators in France, to see if Flight 1549 could have returned safely to LaGuardia. The simulation started immediately following the bird strike and '...knowing in advance that they were going to suffer a bird strike and that the engines could not be restarted, four out of four pilots were able to turn the A320 back to LaGuardia and land on Runway 13.' When the NTSB later imposed a 30 second delay before they could respond, in recognition that it wasn't reasonable to expect a pilot to assess the situation and react instantly, all four pilots crashed."

You would think the "feathers" would have settled by now, some 2 years later.

PS: Your comments help make an excellent point that one cannot simulate every possible disaster scenario.

Koopy said...


You appear to have respect for Captain Sully. I would hazard a guess that regardless of his flight hours and his phenomenal experience he still uses a checklist before he goes up in the air.


Skeptical Scalpel said...

As per my response to your comment on my previous post. I never said I didn't like checklists. Here is what I did say in the blog Surgeons Are Not Pilots. "For example, I am a big fan of checklists, having used them in both the operating room and intensive care settings."

Unknown said...

This is not absolutely right. Every time of pulling back the side stick for A320 it does not react in the same way for everytime. Depends on the altitude , temperature , wind direction and velocity including gust, weight and balance , fuel distribution , flight control law at that moment , configuration eg, flaps or gears , thrust setting , etc.
I think both surgeon and pilot have similar things to do their job.
First is basic knowledge which mostly in deep technical.
Second is how to percept or recieve ongoing information
Third is analyse by using the basic knowledge + memorization from experience
Fourth is decision making.
Last is action which differ only in hand movement from scapel to sidestick.
Many of many aviation safety concept can be applied not only the checklists eg. communication skill , hands off among surgeon between extra longggggg surgery , Human factors knowledge , man - machine interface , level of automation usage, personality gradient in team , safety management system , etc.


Skeptical Scalpel said...

Thanks for the comments and the links. You could make a case that anesthesia is a bit more like flying a plane. Tension at the beginning and end, usually smooth in the middle. I still don't see it with surgeons and pilots. As I said in another post, there's no autopilot in the OR. The fact is that planes can take off and land without input from pilots. Operations still must be done by surgeons.

Unknown said...

Nope , Airplane cannot take off or even landing without any input from pilot so you have to program the flight management system (FMS) select configuration and speed ,set baro meter , check the identification of nav aids bla bla bla lots things to do Autopilot just like using stapler for skin closure instead of simple suture however still need some input from surgeon who know how ,when and why to use the stapler sir! How about open heart Sx start CPB on CPB weaning CPB I think it is very similar to fly the aircraft takeoff cruise landing which high workload become a treat during fatique from long hour of duty especially wean of cardiopulmonary bypass vs landing in a strong crosswind.

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