Pneumonia: types, causes, and treatment

Literal definition of pneumonia is the combination
of an acute respiratory illness – and when I say acute, I mean short lived.
In other words, the patient was well up until a few days ago and then developed a classic range
of symptoms, which include fever, generally feeling unwell, they may appreciate some pleurisy,
they’ll have a cough. They may be coughing up phlegm, which is often
a purulent or yellow. And these symptoms in combination with
a chest x-ray which shows new shadowing that wasn’t previously known about or that doesn’t have an alternative or known cause, in those circumstances
we would make the diagnosis of pneumonia. Pneumonia can be classified
in a number of different ways. Firstly, you can consider where
the patient contracted the infection. And then in that context you would
classify the patient was having either a community acquired pneumonia
or a hospital acquired pneumonia. Another way of considering pneumonia
is to think about the type of organisms, which can be the bacteria, viruses, or fungi that
are the responsible for pneumonia. You can also classify the pneumonia in terms of its
severity. So not thinking about the organism as such or even where the patient contracted
the infection, but just looking at the consequence of infection in the patient and make a decision
as to how serious the illness is that the patient has. And in the majority of people,
pneumonia can be a relatively mild illness, but as in many cases in medicine, patients
can present with a spectrum of severity from the mild to the life-threatening. To answer the question what causes pneumonia, I think it’s helpful to separate that out
into two parts. Firstly, think about the potential organism that the patient’s
contracted that’s causing the illness. And then secondly, think of it
at the level of the lung. So, dealing with the first area,
the most common causes of pneumonia are organisms that come from either
a virus, bacteria, or more rarely fungal infections. Dealing with the second area which
is at the lung and airway level, I think patients and perhaps even some doctors get confused
about one what actually pneumonia is, and if asked the question: “how does pneumonia
different for example from bronchitis?” I think it’s useful to think of it in this way, that
bronchitis is in effect inflammation of the airway lining and it can cause a cough and
breathlessness and phlegm production and fever and you can feel unwell with it. However, pneumonia is different.
Pneumonia is where the air sacks fill up with fluid, so the lung becomes consolidated or solid.
And that’s what you can see on the chest x ray. So you get all those symptoms,
but the distinguishing feature is that the air sacks fill up with
inflammatory debris and fluid. And it’s a more serious infection, an infection
that can lead to more serious consequences. So we always take it very seriously. To answer that question:
“Is pneumonia contagious?” I think the simple and very short answer is
yes. It is an infection which is reliant upon host to host transmission. And therefore,
to be successful and to continue, it needs to be passed on
from one person to another. However, the relative ease with which infection
is passed from individual to individual can vary depending on the organism.
But they all rely on this capacity to spread. The simple analogy is – and I’m sure many of us
have seen the slow motion photography, watching somebody sneeze, and the velocity
of the micro droplets that emanate out from the patient when that happens,
if you can imagine that some of those micro droplets will contain bacteria or virus, then you can see
how easily it might be that sharing a living space with somebody that has an infection of this type, how easy it is to either touch a surface
which has the organism on it, or even to inhale micro droplets
directly in the air. And in this way infection spreads
from one person to another. It’s true to say that majority of patients
that develop a lower respiratory tract infection which is in fact a pneumonia, often don’t
get diagnosed as such and will contact a GP and complain of the common symptoms of
breathlessness, cough, fever, mucky phlegm, sometimes pleurisy. And the GP will make a clinical assessment
and provide a course of antibiotics. And for the majority of these patients, that is
absolutely the right approach to take. If the patient is sick enough to warrant
hospital admission and that decision is often made or usually made by the GP,
then in these circumstances our approach is very different.
We take a whole system approach they have a formal assessment
which includes the history, clinical history where we talk to the patient, understand
the sequence of events that led up to that day. We examine the patient and we rearrange
for a variety of tests. Firstly, imaging test to confirm pneumonia, and then secondly, a
variety of blood tests and sputum tests to assess the severity of the illness, its
impact on other organ systems, and try to identify the cause of organism. If we believe
the patient has a viral cause, the test, the kits that we use will allow us to pinpoint
exactly what virus. So, it may be one of the subtypes of influenza for example, then we
will consider anti-influenza medication in the form of Tamiflu for example. If, however, we believe
it to be a bacterial infection, then the approach of treatment would be primarily antibiotics.
And the type of antibiotic would be in part determined by the severity of illness and
in part determined by what information we have initially as to the potential cause.

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