12 | New Scientist | 30 November 2019WE ARE a step closer to
having wearable artificial
kidneys, after a prototype
device that is worn like a small
handbag was used successfully
in people for the first time.
While the technology
still needs refining, it could
eventually free people from
being tied to large dialysis
machines or hooked up to
bags of fluid and tubing, says
its developer Marjorie Foo at
Singapore General Hospital.
“For some patients, dialysis
is controlling their life – this
gives a bit more freedom.”
People whose kidneys
are failing usually need a
transplant, but they may
spend years on a waiting list.
In the meantime, they have
to undergo dialysis to remove
toxins from their blood.
The most common form
is haemodialysis, which takes
about 4 hours at hospital, three
days a week. This can interfere
with people’s daily lives.
The alternative, peritoneal
dialysis, involves putting fluid
into part of the abdomen,
which allows toxins to pass
from the blood into the fluid.
The fluid is then drained away.
This can be done at home daily
so toxins don’t build up, but it
can be time-consuming to
exchange the large volumes
of liquid.
The new wearable kidney
is a more portable form of
peritoneal dialysis. The system
recycles the waste liquid by
passing it through a cleaning
device kept in the bag then
returning it to the abdomen.
This avoids the user having
to deal with large volumes
of fluid.
The device is about the
size of a small handbag and is
joined with a tube to a port inthe abdomen. Users must change
a cartridge in the device every
7 hours to replace the chemicals.
In a trial last year, the device
was used successfully for three
days by 15 people. Blood tests
suggested it worked as well
as both conventional forms of
dialysis and would only need to
be used for two 7-hour sessions
a day, says Foo, who presented
the work at the American
Society of Nephrology Kidney
Week conference in Washington
DC earlier this month.
Some users complained
it made them feel bloated,
but this can also happen with
conventional peritoneal dialysis.
Foo says the device wouldn’t
suit everyone as some prefer
to have their dialysis done in
hospital rather than managing
it themselves.
It would give people
whose kidneys are failing
more independence, says Susie
Lew at George Washington
University School of Medicine &
Health Sciences, who co-chairedthe conference session. “They
would not need to store boxes
of dialysis fluid,” she says.
Most other groups trying
to develop wearable artificial
kidneys have attempted
to create a portable version
of haemodialysis.
Meanwhile, a team at
the University of California,
San Francisco, is developing
an implantable artificial
kidney that uses human
kidney cells kept separate from
the patient’s blood supply, so
immune-suppressing drugs
won’t be needed. ❚THERE is now one game to rule
them all. Whenever two parties
face off, the possible outcomes
can be analysed with a unified
theory, rather than the various
methods used in the past.
Game theory uses maths to
analyse strategic scenarios. It can
help work out what will happen
between two “players”, such as
kids fighting at school, nations
locked in a trade war or animals
vying for food. It can also assess
the best strategy for winning.
Jin Yoshimura at Shizuoka
University in Japan and his
colleagues have created a single
game that can account for all the
variables in two-player encounters
where each person has the option
to choose between cooperation
and betrayal or disengagement.
The most famous of these is the
prisoner’s dilemma, in which each
of two inmates are told they can
either cooperate with the other
inmate and stay silent or betray
them by testifying against the
other person. There is also the
hawk-dove game, a bit like a game
of chicken to avoid a collision,A unified theory for
two-player games
Mathematics Medical technologyChelsea Whyte Clare WilsonIMA
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and the stag hunt, which requires
cooperation to get better prey.
To study all of these possible
games as one, the research team
imagines two players who must
lift a heavy bag. There is an energy
cost associated with lifting the
bag. Each player gets a reward or
is fined depending on whether
the bag is lifted (Royal Society
Open Science, doi.org/dftw).
The bag can be carried by one
or two people, and by varying
the number of players choosing
to cooperate and the rewards or
costs in the scenario, Yoshimura
says their game can encompass
all other two-player games.
This approach may make it
clearer how to move from a
scenario in which cooperation
is hard to one where it is easier,
and that could help us devise
social interventions that
encourage cooperation, says
Kevin Zollman at Carnegie Mellon
University in Pennsylvania. ❚The classic prisoner’s
dilemma weighs the costs
of betrayal or cooperationWearable
artificial kidney
trialled in people
“ For some patients,
dialysis is controlling
their life. This device
gives more freedom”