Asthma is an obstructive, expiratory disease
as noted, patients will have episodic wheezing,
cough and dyspnoea. Now, you can have cough
variants of these and these “cough variants”
or cough and primary symptom
characterize by coughing “fits” or can
be induced by viral infection. So these coughing
fits, some patients have a cough variant
of asthma as I said earlier well perhaps exacerbated
by a previous upper respiratory tract infection
perhaps viral or this coughing “fits”.
Nocturnal cough is dangerous. So, if a patient
suffering from asthma has nocturnal cough
then you should consider this patient who’s
never been treated. Untreated is your issue.
Now that could be very, very dangerous. If
asthma goes on to be untreated you can only
imagine that there’s increase mucous production.
And so therefore now, the patient has difficulty
with ventilation. Wow. So now this puts
you in the realm of, type 2 respiratory failure
which means what exactly? Well, the patient’s
already hypoxic we knew that. Hypoxemia set
in at PO2 of being less than 60, but then there
might be hypercapnic upper respiratory failure.
And at some point if the patient is untreated
for this asthma, the patient is always vulnerable
to severe asthma attacks and we call that
Let’s take a look at the flow volume loops
or the loop spirometries. Things that we have
become quite accustomed to. Once again, on
your left, this is perfectly normal. What then
represents the bottom half represents the
inspiration and your x-axis here represents
your volume. What is it called when you have
full inspiration and you filled up your lungs?
This is then referred to as being your total
lung capacity. The top half of the curve which
is what you’re paying attention to specifically
and I’ll show you next, well, that would
In asthma, which is obstructive, you’ll
then notice please, that there’s going to
be an increase in total lung capacity when
compared to normal and most importantly upon
expiration you’ll notice that first and
foremost you won’t be able to reach peak
expiration and the fact that you have a scalloped
type of formation or pattern upon further
exhalation. Remember the entire top half represents
exhalation. You probably want to divide that
into the first half, and the second
half, and what you always have
left over is your residual volume. But in a
patient with asthma, with obstructive, then
it would be a scalloped portion. Now, before
we move on, you tell me what the FEV1/FVC ratio
is? Good, decreased, always. This is obstructive.
I’ll tell you when it’s normal.