Parachutes are not an argument against RCTs for medical treatments!

Another doctor has recently used parachutes as an example of why some medical treatments don’t need to be tested before using them on patients. That historical claim is wrong.

Arguing for “The search for perfect evidence may be the enemy of good policy,” Greenhalgh, a physician and expert in health care delivery at the University of Oxford, fumed in the Boston Review. “As with parachutes for jumping out of airplanes, it is time to act without waiting for randomized controlled trial evidence.” [emphasis added]….

COVID-19, she argues, has revealed the limits of evidence-based medicine—masks being a potent case in point.

The United Kingdom’s mask crusader
Ellen Ruppel Shell
Science 16 Oct 2020: Vol. 370, Issue 6514, pp. 276-277
DOI: 10.1126/science.370.6514.276

A 2003 article in British Medical Journal claimed after a literature search that “No randomised controlled trials of parachute use have been undertaken,[sic]” and went on to claim that “Individuals who insist that all interventions need to be validated by a randomised controlled trial need to come down to earth with a bump.” This is nonsense. Parachutes were heavily tested by the British air force late in WW I, for example. The issue was controversial at the time because German pilots already had parachutes, and the British military was slow to adopt, perhaps because of NIH (Not Invented Here). Continued trials delayed deployment until after the war was over.

Jet ejection seats, a “super-parachute” invented in the 1940s, received comprehensive engineering tests as various designs were experimented on. Tests ultimately included multiple human trials with volunteers. Despite that, many pilots at the time were hesitant to trust them, but field experience (and lack of alternatives when you were about to crash) led to still-reluctant acceptance. The reluctance stemmed from the dangers of ejection – severe injuries were common, due to high accelerations, collisons with pieces of the aircraft, and so forth. Continued experimentation at many levels (simulations, scale models, dummy pilots, etc.) have led to many improvements over the early designs, and most pilots who eject now are not permanently injured.

Test of a 0/0 ejection by Major Jim Hall, 1965

So parachutes have been, and new designs continue to be, heavily tested. Perhaps the 2003 authors missed them because they did not search obscure engineering and in-house journals written decades before the Internet. What about the “controlled” part of Randomized Controlled Trials? They had not even been invented in 1918; R.A. Fisher’s seminal work on experimental statistics was done in the 1920s and 30s.

More important, engineering trials have something better than randomization: deliberate “corner tests.” With humans and diseases we don’t know all the variables that affect treatment effectiveness, and even if we knew them, we couldn’t measure many of them. But with engineered systems we can figure out most key variables ahead of time. So trials can be run with:

  • Low pilot weight / high pilot weight
  • Low airspeed/high airspeed
  • Low, intermediate, and high altitudes
  • Aircraft at 0 pitch and yaw, all the way to aircraft inverted.
  • Delayed or early seat ejection.
  • Testing prototypes (and now, finite element simulations) can tell us which conditions are most extreme, so not all corners need full-scale tests.

Of course some of these tests will “fail,” e.g. early ejection seats did not work at low altitude and airspeed. Those limits are then written into pilots’ manuals. That is considerably better than we do with many RCT’s, which deliberately choose trial subjects who are more healthy than patients who will ultimately take the medicine.

So let’s stop using this analogy. Parachutes were never adopted without (the equivalent of) RCTs. Thereare many reasons to adopt masks without years of testing, but this is not one of them.

(I have written more about this in my book draft about the evolution of flying from an art to a science.)

Automation and the Future of Work – Lecture Notes 2017

One of my students reported that he was having trouble finding my lecture notes from this course, so I am putting them in one place. I will update this for the last few classes.

 Topic  Date of class  File name+link
Final projects;
Diffusion of innovation;
financial evaluation;
technology life cycles
 May 15, 17 A+W 2017 May 17 Bohn adoption

3 cases of service automation  May 8   Internet of things
Human expertise
& AI in medicine
April 17   Q+W week 3 medicine
 Trends in employment  April 4  A+W17 Bohn April 4

Some of the aviation discussions are not yet here.

Medicine Grand Rounds at Stanford

Yesterday I gave a Grand Rounds presentation at Stanford Med School. My title was

Craft, Standardization and Automation: Powerful yet Perilous Paradigms for Control when Lives are at Stake

Most of my talk was about the adoption of procedures (checklists) by US military aviation, during and after WW II. It has close analogies to the situation of health-care today.  Here is my short presentation.  A much longer presentation, with more examples but without discussion of medicine, is here.

Initially, I was concerned that my topic might seem too esoteric for Stanford’s medical faculty. However, their Medical Grand Rounds program covers a lot of ground. My topic was only 1.5 standard deviations away from the mean.

For more of my research on flying paradigms and how technologies evolve from crafts to sciences, please see this page.


How flying changed from a craft to a science: Chapter 1 available

I have just uploaded Chapter 1 of my book manuscript. It summarizes four revolutionary changes in how people flew. It outlines some themes of the full book, including People and Work and Is Science Inevitable?. And of course it includes a few gripping tales of accidents averted – or not.

Commercial aviation today is very safe and scientific. But it wasn’t always. Please send comments, anything from typos to critiques.

Over August I will put up some photographs and key tables from the full book.

Drones Hunt Down Poachers in South Africa | Flying Magazine

The Lindbergh Foundation’s Air Shepherd initiative uses drones to catch poachers in South Africa.

My comment: Flying at night, up to 40km away, is technically difficult. But smart autopilots, using GPS and accelerometers, mean that the operators (pilots) don’t have to do hands-on flying except landing and takeoff.  Probably every component in the system except the ground vehicles is hobbyist level, although some of the specialized long-range radio gear might need to be hand built.  Nothing from aerospace companies.  Battery powered, so essentially noiseless. Also, the aircraft itself is the cheapest part of the system.

The article mentions flights of “up to 4 hours.” That is a very long duration, and would require lots of batteries. 2 hours or even less sounds more realistic. Efficient cruising speed is probably is probably around 40 kph (25 mph). If anyone finds other discussions of this project, please let me know.

Source: Drones Hunt Down Poachers in South Africa | Flying Magazine

Death by GPS | Ars Technica

Why do we follow digital maps into dodgy places? Something is happening to us. Anyone who has driven a car through an unfamiliar place can attest to how easy it is to let GPS do all the work. We have come to depend on GPS, a technology that, in theory, makes it impossible to get lost. Not only are we still getting lost, we may actually be losing a part of ourselves. Source: Death by GPS | Ars Technica

As usual, aviation is way “ahead.” Use of automated navigation reduces pilots’ navigation skills; automated flight reduces hand-flying skills. Commercial aviation is starting to grapple with this, but there is no easy solution.

Tumblr? Pinterest? What should I use?

What’s a good place to put supplemental information, especially photos and tables, for my book? I have a lot of old photographs, and putting them into the book itself gets expensive. Some are in color and some are very large. Here are a few examples.
I could set up my own site, or use my publisher’s, but places like Tumblr know how to run photo sites. The ideal features I want include being able to link to pictures on other sites (due to copyright restrictions), able to create tables of contents, etc. Straight chronology won’t suffice.

Obvious candidates

include Tumblr, Pinterest, Instagram. I don’t use any of them except to dabble, so I don’t know their strengths. Possibly Twitter or Facebook?

All advice welcome. Email me, or post comments here.