18 | New Scientist | 26 September 2020
Analysis Health technologyAPPLE’S recently released Series 6
smart watch has a new feature: it
can measure blood oxygen levels.
The tech must have been years
in the making, but the timing of
its release worked well given that
we are in the middle of a global
respiratory pandemic.
The amount of oxygen in
the blood is important medical
information. In hospitals, it is
usually measured with a device
called a pulse oximeter, which
shines a light through the finger
or earlobe. Blood carrying more
oxygen absorbs light differently.
It is already possible to buy a
fingertip pulse oximeter for use at
home for about £20. Now Apple
says it has replicated this function
in its high-tech watch, which
shines a light onto the back of
the wrist and measures the light
reflected back with embedded
sensors. The user must keep
their arm still for 15 seconds.
The device also takes periodic
readings when the person
happens to be still, day and night.
In a press statement, Apple was
vague about the purpose, saying
it offers “insight into overall
wellness”, and didn’t answerNew Scientist’s requests for further
details. A spokesperson couldn’t
share any published research
showing how oxygen monitoring
would help a typical healthy person.
But tools to track personal
health may come to the fore as the
coronavirus pandemic continues.
Home oxygen monitoring is in
no way a test for covid-19, yet it
could help those who have already
been diagnosed and are not sick
enough to be in hospital but want
reassurance about their condition.
Some UK clinics are piloting“virtual wards”, where people who
might otherwise be admitted to
hospital stay home and do phone
check-ups, and pulse oximetry
is a key part of their monitoring.
Other conditions could benefit
from home oxygen monitoring,
such as chronic obstructive
pulmonary disease, a long-term
lung condition that can cause a
need for supplementary oxygen.
It could also help when peopleuse the electrocardiogram (ECG)
function that was introduced with
the Series 4 watch, launched in- This can detect if electrical
activity in the heart is disturbed.
The criticism of that feature was
that it might detect harmless
small changes that have no effect
on the body, but if someone finds
they have low oxygen levels as
well as heart rhythm problems,
that becomes more useful.
The night-time monitoring
could help to alert people
about sleep apnoea, when they
have problems breathing at night,
usually due to being overweight.
This can cause people to wake
up when their blood oxygen
gets too low, although they
may not be aware of how much
their sleep is being disturbed.
Because most pulse oximeters
are applied to the finger or earlobe,
it is unclear how well this new
method will compare. Even highly
accurate devices sometimes give
erroneously low readings when
people’s hands are cold, says
Andy Whittamore, clinical lead for
Asthma UK and the British Lung
Foundation. “There are a few gaps
there in terms of how we interpret
this device,” says Whittamore.
Even Apple says in the small
print on its press statement that
the oxygen measurements are
“not intended for medical use,
including self-diagnosis or
consultation with a doctor, and
are only designed for general
fitness and wellness purposes”.
Until the firm releases data on the
accuracy of the watch’s readings,
it is hard to know how useful it
will be. “If we knew the device
was absolutely robust and
accurate, then there would be
a place for it,” says Whittamore. ❚
APPL
ENews
Lights on the back of
the latest Apple Watch
measure blood oxygen“ If we knew the device
was absolutely robust
and accurate, then there
would be a place for it”New Apple Watch monitors blood oxygen – is that useful?
The tech firm says its watch isn’t meant for medical purposes,
so what is its oxygen monitoring good for, asks Clare WilsonMarine biologyJake BuehlerA TITAN triggerfish, which can grow
to a length of 75 centimetres, has
been seen beaching itself to feed
on crabs along the shoreline.
In 2018, Matthew Tietbohl at
King Abdullah University of Science
and Technology in Saudi Arabia
was surveying a beach on the Red
Sea’s Mar Mar Island for sea turtle
tracks when he and his team heard
loud splashing at the water’s edge.
“We turned to see this triggerfish
launching itself into the shallows
and stranding itself,” says Tietbohl.
It soon became clear that the
fish was attempting to feed on
ghost crabs that were grazing on
algae-covered rocks at the water’s
edge. The triggerfish would stalk
the crabs from the water, turn
on its side and lunge out of the
shallows like a crocodile. At one
point, the fish gripped a crab and
pulled it back into the water (Journal
of Fish Biology, doi.org/d9d6).The determined diner was
about 35 centimetres long, but titan
triggerfish (Balistoides viridescens)
can be more than twice that length.
Tietbohl says the feeding
strategy may help avoid
competition with other predatory
fish. Supplementing a diet with
terrestrial prey “would open up a
whole new food source that other
fishes just can’t [exploit]”, he says.
Tietbohl wants to know if the
hunting style is used by related
species or is widespread among
titan triggerfish. The team did
see other triggerfish “patrolling”
the island’s shallows.
Because water and air refract
light differently, Tietbohl thinks
it is intriguing that triggerfish are
able to spot and track terrestrial
prey from below the water. ❚Triggerfish jumps
out of the water
to catch crabs75cm
The maximum body length
of an adult titan triggerfish