This transcript has been edited for clarity.
Welcome to Impact Factor, your weekly dose of commentary on a new medical study. I’m Dr F. Perry Wilson from the Yale School of Medicine.
You
don’t need to think about it until you think about it: breathing. The
most fundamental physical function. The most basic act that our bodies
undertake to keep our brains alive, exchanging cardon dioxide for
oxygen, nourishing every cell inside us.
The reason you don’t
need to think about breathing is because of an area of the brainstem
called the pre-Bötzinger complex. It’s a group of cells that acts as a
pacemaker clicking off about 12 times a minute, triggering your body,
without conscious thought at all, to breathe.
Of
course, you know it’s more complicated than that. You can hold your
breath, after all — you are in control of the process. And it’s more
complicated than that. Higher levels of your brain feed into
the pre-Bötzinger complex to increase your breathing rate when your body
is moving, or when energy expenditure goes up.
And
it’s even more complicated than that. You may never have noticed, but
when you are breathing through your nose, you’re mostly breathing
through one nostril at a time, oscillating back and forth, allowing one
nasal passage to regain some moisture while the other does the work.
For something you don’t think about at all, breathing is taking up a lot of brain space.
Could
these complex respiratory patterns reveal something, then, about the
state of our brains? Are all the yogis and gurus and influencers right
about the importance of how we breathe? Is the breath the window to the
soul?
If
you want to really interrogate the way we breathe, you need to do some
pretty precise measurements — which is why I was so intrigued by this paper, appearing this week in Current Biology.
The centerpiece of the article is a new technology: a nasal cannula, but not of the sort you’ve seen before.
Researchers
led by Timna Soroka created this device, which precisely measures the
airflow in and out of each nostril. They recruited 100 people to wear it
for 24 full hours.
At
a sampling rate of 6 Hz, this is a ton of data. In fact, compressing
that stream of data into interpretable metrics is a feat in and of
itself. The primary analysis derived 24 different measures from this
airflow data. Some of these are intuitive: the volume of air inhaled and
exhaled, the rate of airflow, the rate of oscillation between one
nostril and the other.
This graph, which colors airflow from the
right nostril in purple and the left in blue, shows that oscillation in a
single participant.
Some
metrics are less obvious: the coefficient of variation of the breathing
duty cycle, for example, appears to quantify how much one breath
changes compared to others.
Our brains are unique, and, it turns
out, so are our breathing patterns. The researchers wanted to know
whether the 24 metrics derived from someone’s breathing pattern could be
used to identify them. Can breathing act like a fingerprint?
The results were impressive.
This
graph shows how a computer model did when predicting which of the 100
patients a given airflow pattern came from. The diagonal lines are
correct predictions. If airflow patterns were random, the machine would
only get this right 1% of the time. Instead, it was correct 91% of the
time. This approaches biometric levels of accuracy, similar to voice
recognition.
These
unique respiratory fingerprints were stable over time. Forty-two of the
participants came back for another round of 24-hour monitoring,
somewhere between 5 days and 2 years later. The system could identify
who was who with 95% accuracy even all that time later.
This
is all pretty cool, but let’s be honest: You’re never going to unlock
your laptop by strapping a nasal cannula to your face and breathing for a
while.
Where this study gets really interesting is in the links
between breathing parameters and other physical and psychological
parameters.
For example, the breathing pattern was associated with
body mass index. People with a higher BMI had a higher tidal volume — a
larger volume of air during a typical respiration — than people with a
lower BMI.
That makes some sense. People with more mass might need to exchange more air to keep oxygen and carbon dioxide levels normal.
But our psychology changes how we breathe as well. The researchers divided people into low and high scorers on the Beck Depression
Inventory. Now, it’s worth noting that none of these participants
suffered from clinical depression, but of course some had higher scores
and some had lower scores. You can see here that the peak inspiratory
flow, the fastest rate at which we breathe in, was substantially higher
in those with more depressive symptoms.
This
is not a conscious process. This is the state of your brain controlling
subtle features about how you breathe that can only be revealed with
new technology.
It
didn’t stop with depression. The researchers could distinguish between
people with high vs low anxiety scores by looking at the variation in
their inspiratory pause.
And you could determine who was more likely to have autistic features — again, none of these individuals had clinical autism — by looking at the percentage of breaths with an inspiratory pause.
This
is where this stuff starts to get interesting, because it suggests that
there are physiologic links between brain states and breathing patterns
and that those links can be mapped with careful measurement.
I
actually think there is a practical application to this. No, I don’t
think we’ll all be walking around with tubes in our noses like
stillsuits from Dune. But plenty of people are wearing nasal
cannulas at night — for CPAP treatment. Adding technology like this to
those devices could give insights into how these metrics change over
time, perhaps cluing us into changes in our mood or anxiety or other
health conditions before we are even consciously aware of them.
Our
breathing says a lot about us. So, to paraphrase Sylvia Plath, take a
deep breath and listen to the old brag of your heart. I am, I am, I am.
