"The Bends"

[James A. Landau]

In a message dated 04/16/2002 3:02:46 PM Eastern Daylight Time,
gcohen at UMR.EDU writes:

>  The trouble started gradually, when the east caisson was
>  just 155 feet deep in the riverbed, with 24 pounds of pressure
>  filling the work chamber.  A number o f workmen suddenly began
>  suffering sharp pains in their limbs and joints after leaving the
>  caisson

"155 feet" in line 2 should read "55 feet", for which an air pressure of 24
pounds
(1 3/5 atmospheres) is correct.  At 155 feet you would need close to 5
atmospheres (70-75 pounds).


In a message dated 04/16/2002 10:36:00 AM Eastern Daylight Time,
rgage at INTRAH.ORG writes:

> What I find interesting in all this is the gap between the first
>  OED cite for the caisson method of bridge construction (1753) and
>  the first OED mention of caisson-sickness (1875 B. RICHARDSON _Dis.
>  Mod. Life_ 70) and "the bends" (1902). How soon after the adoption
>  of this construction method did workers begin complaining about
>  the symptoms of decompression?

While caissons were used as early as 1578 for the Pont Neuf in Paris (the
word obviously took a while to get into English), it was not until the 1860's
or so that caissons got below 55 feet or so, at which depth (see above)
caisson disease begins to strike.  There were two reasons.  First a deep (55
foot plus) caisson needed the technology and resources onlly available with
the Industrial Revolution.  The most obvious need was for steam-driven air
pumps to produce sufficient compressed air.  Second, until the coming of the
railroads, any time there was a river or bay that deep, people didn't even
try to build a bridge and instead depended on ferries.

In the United States there was a massive burst of railroad building
immediately following the Civil War, and in particular some of these
railroads needed to cross the Mississippi-Missouri (i.e. the Missouri and the
Mississippi below the mouth of the Missouri.  The Missouri is a much bigger
river than the upper Mississippi, but by historical accident the white man
met the upper Mississippi first and misnamed the joint river.)

Now the Mississippi-Missouri is an unusually deep river, 60 feet at Omaha and
93 feet at St. Louis.  Eads, who learned about caissons on a trip to Europe,
decided to use them.   At least one other bridge across the upper Missouri
also used caissons, with inspiration and considerable help from Eads.
Roebling pere at Brooklyn had a tricky situation with the East "River"
(actually a tidal strait) and went with caissons for the Brooklyn
Bridge---incidentally the largest caissons ever built.

All three caisson projects had considerable trouble and several deaths from
caisson disease.

I might add that the bends are also a problem with deep-sea divers.  I don't
have any data handy, but it is quite possible that divers suffered from the
bends before any of the above bridges were started.










> What term or terms did these "sandhogs" first use to describe this illness?


Afraid I don't know.

When did the medical profession
>  finally take note? Was this at first one of those misunderstood
>  occupational illnesses like "mad hatter's disease"?

Not "finally".  All three of the bridges had physicians who studied caisson
disease and did what they could to prevent and treat it.  Tragically, it was
not until many years after those bridges were completed before the nature of
the bends was worked out and decompression techniques that prevented the
bends became available.

      - James A. Landau
        systems (not civil) engineer


"as those caissons go rolling along"