00:01
If you're giving somebody some oxygen for
type II respiratory failure and it's worsening
the type II respiratory failure, and they're
developing a respiratory acidosis, then you
might need to consider nasal ventilation,
or noninvasive ventilation. Now this is given
via nasal or full face mask; what it does,
is that unlike CPAP which gives a constant
pressure during inspiration and expiration,
this is a bi-level form of noninvasive ventilation,
where on inspiration, it pushes the air in
at a higher pressure than it does when the
patient breathes out. That allows a better
ventilation of the lung, it counteracts the
hypoventilation that the disease is causing
and will allow the CO2 to be removed and correction
of the respiratory acidosis. And it's known
that if you use nasal ventilation or noninvasive
ventilation in patients presenting with type
II respiratory failure due to COPD for example,
then that reduces the need for intubation
and mechanical ventilation. But there are
some issues with this. The patient has to
be able to take the mask on the face and coordinate
with the breathing and feel comfortable with
it. They have to be cooperative if not too
agitated. And also you need to decide whether
the patient, if they cannot cope with the
nasal ventilation, the noninvasive ventilation,
whether they would be suitable for intubation
and ventilation and I'll discuss that in a
little bit more detail later. Type II respiratory
failure then, what are
the common causes, well, the acute and chronic
causes are pretty much the same, it's largely
airways disease, COPD and severe asthma. Sometimes
with patient with severe bronchiectasis, although
in fact the diseases that cause type I respiratory
failure such as interstitial lung disease,
when they are end-stage, the CO2 will start
to rise as well. So the common presentation
in hospital type II respiratory failure would
be an exacerbation of COPD. However, there
are a range of diseases, which don't affect
the lungs directly, but affect the chest wall
and the ventilation of the lungs. So for example,
obstructive sleep apnea, which we will discuss
later in this lecture. That causes obstruction
of the upper airways and that leads to type
II respiratory failure in some patients. If
you give somebody sedative drugs then they
are going to breathe at a lower level and
that will cause type II respiratory failure.
02:39
This is important because if you give people
who have other reasons for type II respiratory
failure such as COPD or chest wall disease
or obstructive sleep apnea, if you give
them opiates and sedatives, you are likely
to make the type II respiratory failure worse
and that is often something that can be altered
in those patients to improve the respiratory
failure that they are presenting with. Obesity
hypoventilation is a very specific
cause of type II respiratory failure, which
we will discuss later in this lecture.
03:05
And then if you have problems affecting the chest
wall and the muscles and the nerves that control
the chest movements during ventilation, and
we're talking about Guillam-Barre syndrome,
motor neuron disease, various nerve palsies
or the kyphoscoliosis that you can get in
some patients affecting the ability of the
chest movement during ventilation. They will
all lead to type II respiratory failure and
need to be considered in some patients.