00:00
So ARDS, now this is a
disorder of an over
activation of the inflammatory response and this
occurs for multiple different reasons.
00:09
It was first recognized in Vietnam, where American
soldiers with gunshot wounds were developing
bilateral infiltrations in their lung and
hypoxia. And that was the first time that
ARDS was identified, and that's trauma as a cause.
But it doesn't have to be a traumatic
cause, it could be in any sort of inflammatory
problem where it's in the lung or distal to
the lung, will cause a systemic inflammatory
response. And that affects the lungs directly
by through the body's own immune reaction.
The cytokines they release, the activation
of the neutrophils, the activation of the coagulation
cascade leads to bystander damage to the respiratory
endothelium and epithelium. And, as a consequence
of that, you get leaked fluid into the alveoli,
and that's called noncardiac pulmonary oedema,
and that causes a rapid fall in the oxygenation
level. You also can get proliferation of the
epithelial and fibroblast cells, and that,
as a complication of ARDS can result in
lung fibrosis.
01:19
So what are the causes of ARDS? As we mentioned
there are multiple causes, we can divide those
into lung causes, pulmonary, direct lung injury
leading to ARDS causing more widespread lung
injury, or extra-prolonged causes, something
happening elsewhere in the body that leads
to lung injury, which was otherwise not affected.
So the pulmonary cause is mainly pneumonia
aspiration but also occurs in environmental
problems, if you had a near drowning or smoke
inhalation. The extra pulmonary causes, where
we mentioned severe trauma, gunshot wounds,
road traffic accidents, but also extensive
surgery is probably one of the commonest causes
of ARDS and any sort of extensive surgery
done in hospital could potentially lead to
ARDS as a complication. Sepsis outside of
the lungs, so septicemia due to a previous
surgery or whatever could also lead to ARDS.
Acute pancreatitis, drug overdose are also
common causes of ARDS. The clinical presentation
is basically a rapidly
developing, breathlessness and hypoxemia. And the
patient remains hypoxic despite receiving
high flow oxygen and if you do the X ray,
it will show bilateral airspace shadowing
as you can see on this chest X ray. Both lungs
are affected and it's quite hard to find any
part of the lung, which is normal. Importantly,
this is oedema of the lungs unexplained by cardiac
cause. So the wedge pressure, the pressure
of the pulmonary vessels is usually normal
So how do we treat ARDS? Well, it's a severe
disease and essentially the treatment is intubation
and ventilation until the lungs can recover
from the inflammatory insult that's occurring
and this may be in a few days, but actually
often can take weeks. There is, as yet no
effective drug therapy for ARDS, although
multiple different agents have been tried. And
unfortunately, it's often goes hand-in-hand
with other severe systemic upset problems
such as septic shock and multiorgan failure
is common with hypotension, renal failure
etc. The overall mortality, perhaps 50% is
a bit high, is probably lower than that now
with the more effective ventilation mechanisms
that we have and it can be complicated, as
I've mentioned already by lung fibrosis during
the recovery period.