How to pronounce "sheath"

Translator: Bob Prottas Reviewer: Ariana Bleau Lugo

The first time I stood in the operating room

and watched a real surgery,

I had no idea what to expect.

I was a college student in engineering.

I thought it was going to be like on TV.

Ominous music playing in the background,

beads of sweat pouring down the surgeon's face.

But it wasn't like that at all.

There was music playing on this day,

I think it was Madonna's greatest hits. (Laughter)

And there was plenty of conversation,

not just about the patient's heart rate,

but about sports and weekend plans.

And since then, the more surgeries I watched,

the more I realized this is how it is.

In some weird way, it's just another day at the office.

But every so often

the music gets turned down,

everyone stops talking,

and stares at exactly the same thing.

And that's when you know that something absolutely critical

and dangerous is happening.

The first time I saw that

I was watching a type of surgery

called laparoscopic surgery

And for those of you who are unfamiliar,

laparoscopic surgery, instead of the large

open incision you might be used to with surgery,

a laparoscopic surgery is where the surgeon creates

these three or more small incisions in the patient.

And then inserts these long, thin instruments

and a camera,

and actually does the procedure inside the patient.

This is great because there's much less risk of infection,

much less pain, shorter recovery time.

But there is a trade-off,

because these incisions are created

with a long, pointed device

called a trocar.

And the way the surgeon uses this device

is that he takes it

and he presses it into the abdomen

until it punctures through.

And now the reason why everyone in the operating room

was staring at that device on that day

was because he had to be absolutely careful

not to plunge it through

and puncture it into the organs and blood vessels below.

But this problem should seem pretty familiar to all of you

because I'm pretty sure you've seen it somewhere else.

(Laughter)

Remember this?

(Applause)

You knew that at any second

that straw was going to plunge through,

and you didn't know if it was going to go out the other side

and straight into your hand,

or if you were going to get juice everywhere,

but you were terrified. Right?

Every single time you did this,

you experienced the same fundamental physics

that I was watching in the operating room that day.

And it turns out it really is a problem.

In 2003, the FDA actually came out and said

that trocar incisions might be the most dangerous step

in minimally invasive surgery.

Again in 2009, we see a paper that says

that trocars account for over half

of all major complications in laparoscopic surgery.

And, oh by the way,

this hasn't changed for 25 years.

So when I got to graduate school,

this is what I wanted to work on.

I was trying to explain to a friend of mine

what exactly I was spending my time doing,

and I said,

"It's like when you're drilling through a wall

to hang something in your apartment.

There's that moment when the drill first punctures through the wall

and there's this plunge. Right?

And he looked at me and he said,

"You mean like when they drill into people's brains?"

And I said, "Excuse me?" (Laughter)

And then I looked it up and they do drill into people's brains.

A lot of neurosurgical procedures

actually start with a drill incision through the skull.

And if the surgeon isn't careful,

he can plunge directly into the brain.

So this is the moment when I started thinking,

okay, cranial drilling, laparoscopic surgery,

why not other areas of medicine?

Because think about it, when was the last time you went to the doctor

and you didn't get stuck with something? Right?

So the truth is

in medicine puncture is everywhere.

And here are just a couple of the procedures that I've found

that involve some tissue puncture step.

And if we take just three of them —

laparoscopic surgery, epidurals, and cranial drilling —

these procedures account for over 30,000 complications

every year in this country alone.

I call that a problem worth solving.

So let's take a look at some of the devices

that are used in these types of procedures.

I mentioned epidurals. This is an epidural needle.

It's used to puncture through the ligaments in the spine

and deliver anesthesia during childbirth.

Here's a set of bone marrow biopsy tools.

These are actually used to burrow into the bone

and collect bone marrow or sample bone lesions.

Here's a bayonette from the Civil War.

(Laughter)

If I had told you it was a medical puncture device

you probably would have believed me.

Because what's the difference?

So, the more I did this research

the more I thought there has to be

a better way to do this.

And for me the key to this problem

is that all these different puncture devices

share a common set of fundamental physics.

So what are those physics?

Let's go back to drilling through a wall.

So you're applying a force on a drill towards the wall.

And Newton says the wall is going to apply force back,

equal and opposite.

So, as you drill through the wall,

those forces balance.

But then there's that moment

when the drill first punctures through the other side of the wall,

and right at that moment the wall can't push back anymore.

But your brain hasn't reacted to that change in force.

So for that millisecond,

or however long it takes you to react, you're still pushing,

and that unbalanced force causes an acceleration,

and that is the plunge.

But what if right at the moment of puncture

you could pull that tip back,

actually oppose the forward acceleration?

That's what I set out to do.

So imagine you have a device

and it's got some kind of sharp tip to cut through tissue.

What's the simplest way you could pull that tip back?

I chose a spring.

So when you extend that spring, you extend that tip out

so it's ready to puncture tissue,

the spring wants to pull the tip back.

How do you keep the tip in place

until the moment of puncture?

I used this mechanism.

When the tip of the device is pressed against tissue,

the mechanism expands outwards and wedges in place against the wall.

And the friction that's generated

locks it in place and prevents the spring from retracting the tip.

But right at the moment of puncture,

the tissue can't push back on the tip anymore.

So the mechanism unlocks and the spring retracts the tip.

Let me show you that happening in slow motion.

This is about 2,000 frames a second,

and I'd like you to notice the tip

that's right there on the bottom, about to puncture through tissue.

And you'll see that right at the moment of puncture,

right there, the mechanism unlocks and retracts that tip back.

I want to show it to you again, a little closer up.

You're going to see the sharp bladed tip,

and right when it punctures that rubber membrane

it's going to disappear into this white blunt sheath.

Right there.

That happens within four 100ths of a second after puncture.

And because this device is designed to address the physics of puncture

and not the specifics of cranial drilling

or laparoscopic surgery, or another procedure,

it's applicable across these different medical disciplines

and across different length scales.

But it didn't always look like this.

This was my first prototype.

Yes, those are popsicle sticks,

and there's a rubber band at the top.

It took about 30 minutes to do this, but it worked.

And it proved to me that my idea worked

and it justified the next couple years of work on this project.

I worked on this because

this problem really fascinated me.

It kept me up at night.

But I think it should fascinate you too,

because I said puncture is everywhere.

That means at some point it's going to be your problem too.

That first day in the operating room

I never expected to find myself on the other end of a trocar.

But last year, I got appendicitis when I was visiting Greece.

So I was in the hospital in Athens,

and the surgeon was telling me

he was going to perform a laparoscopic surgery.

He was going to remove my appendix through these tiny incisions,

and he was talking about what I could expect for the recovery,

and what was going to happen.

He said, "Do you have any questions?" And I said, "Just one, doc.

What kind of trocar do you use?"

So my favorite quote about laparoscopic surgery

comes from a Doctor H. C. Jacobaeus:

"It is puncture itself that causes risk."

That's my favorite quote because H.C. Jacobaeus

was the first person to ever perform laparoscopic surgery on humans,

and he wrote that in 1912.

This is a problem that's been injuring and even killing people for over 100 years.

So it's easy to think that for every major problem out there

there's some team of experts working around the clock to solve it.

The truth is that's not always the case.

We have to be better at finding those problems

and finding ways to solve them.

So if you come across a problem that grabs you,

let it keep you up at night.

Allow yourself to be fascinated,

because there are so many lives to save.

(Applause)