In this talk, I'll describe the different
types of lung disease that'll be covered by
the course. Why bother learning about lung
diseases? Well, simply, lung diseases are
Asthma and COPD, which are chronic lung diseases
affecting the airways, together probably affect
about 10% of the population, and they are
individually someâ€¦ one of the commonest
chronic diseases that affect man. Lung cancer
is the commonest fatal lung cancer, and it's
responsible for more deaths than the next
three or four common cancers added together.
And that's both true for men and for women.
And lung diseases encompasses three of the
most important pathogens that affect humans:
influenza A, the commonest cause of viral
death; tuberculosis and pneumococcus, which
are the two commonest causes of bacterial
death, causing TB and pneumonia respectively.
So learning about lung diseasesâ€”about these
specific lung diseasesâ€”is essential, pretty
much, for every doctor.
In addition, there are a range of lung conditions
which are also, although not as common as,
say, asthma or pneumonia or lung cancer, are
still very common. That includes pulmonary
emboli, bronchiectasis, the interstitial lung
diseases, problems such as pleural effusions,
and obstructive sleep apnea. For example,
obstructive sleep apnea is estimated to affect
about 1% of the population and is particularly
prevalent in middle-aged men. So these are
all diseases that you need to know something
about if you'd like to practice as a clinician.
So, how can we categorize lung diseases? Well,
we can do this anatomically. We can see
about which part of the lung has
been affected by the disease. So there are
diseases of the lower airways: the upper part
and the lower lower airways. There are diseases
of the lung parenchyma, the interstitium,
and the alveoli themselves. There are diseases
that affect the circulationâ€”largely, the
pulmonary artery circulation. And there are
diseases that affect the pleura. Plus, in
addition, there are diseases of physiology
of the control of respiration. And each of
these areas will be covered by separate talks
in a subsequent course.
Taking each of those areas individually: If
we're talking about diseases of the airways,
we can break those down into large airways
obstruction diseases: cancers and benign problems
affecting the trachea and the larger bronchi
that obstruct those airways.
And then there are the diseases that affect
the lower airways, and those tend to cause
airways obstruction, and the commonest one
isâ€¦ commonest ones are asthma, which causes
reversible airways obstruction; and smoking-related
lung disease: COPD, chronic obstructive pulmonary
disease, which causes irreversible airways
obstruction. And there are a range of other
causesâ€”which are much rarerâ€”of airways
obstruction as well.
In addition, the airways can be affected by
infection, and that can be an acute infection,
a bronchitis, a tracheobronchitis, a bacterial
or viral infection affecting the upper part
of the lower airways, or it could be a chronic
infection, and that's largely bronchiectasis.
And cystic fibrosis is a particularly aggressive
form of bronchiectasis which is a genetically
inherited disorder and the commonest one of
those which causes death in the Western world.
And the central airways are also a site where
cancer can ariseâ€”mainly squamous cell and
small-cell lung cancerâ€”but there are rarer
tumors that can affect that as well, such
as carcinoid or metastases from extrathoracic
And then you move deeper into the lung and
you get to the alveoli and the interstitium,
and the commonest diseases are because
problems there are the infections,
pneumonia and tuberculosis, which are the
prevalentâ€¦ most prevalent serious infectious
diseases across the globe.
And then there are a large range of less common
but important noninfective infiltrations that
can affect the alveoli and the interstitium,
and the most important ones of those are pulmonary
fibrosis and sarcoidosis, but there are a
very large number of rarer types of infiltrations
that can affect that area.
And then another noninfective problem, which
is very important, is the adult respiratory
distress syndrome (ARDS), and this is a physiological
response to an excessive inflammatory insult
to the body, where you get non-cardiogenic
pulmonary edemaâ€”filling up of water of the
alveoliâ€”and that presents with respiratory
failure coming on very quickly.
And many lung cancers actually arise in what
looks like the alveoli and the interstitium,
probably from the small airways in that area,
but they will be peripheral tumors, visible
on the x-ray growing in the periphery of the
lung. And adenocarcinoma is the most common
type of lung cancer that does that. And pulmonary
metastases from extrathoracic malignancies
are often seen in the parenchyma of the lung.
The vascular system: The main problem there
is pulmonary emboli. These are clots that
have traveled from other parts of the body
from the systemic venous circulation to the
right side of the heart and then are shot
into the pulmonary artery circulation, where
they block a pulmonary artery and cause problems.
And this is a very common condition, which
can present in a myriad different ways.
The other major problem with the pulmonary
vasculature is called pulmonary hypertension,
and that is largeâ€”that'sâ€¦ so that's high
blood pressure in the pulmonary arteryâ€”and
that's largely a consequence of chronic lung
disease of the hypoxia driving
the formation of a high blood pressure in
the pulmonary arteries but can occur in other
conditions as well.
I've listed hemoptysis and vasculitis here.
Vasculitis is a very rare inflammatory condition
of the pulmonary arteriesâ€”bronchial arteriesâ€”is
not really particularly common. Hemoptysis,
though, is a very common symptom, and we need
to know about the causes of that and how major
hemoptysisâ€”when patients present coughing
up very large amounts of bloodâ€”are treated.
Moving outside of the lung to the pleura:
The pleural effusionsâ€”fluid
in the pleural spaceâ€”is an incredibly common
problem in many different medical specialties.
And those are normally divided into transudates,
which means the pleura is normal, but the
cause is a cardiac or renal or other problem,
and which is why pleural effusions are common
in other specialties. Or it's when theâ€¦
or it's an exudate, where the pleura is abnormal
due to tumor infiltration or inflammation
In addition, you can get air in the pleural
space, which is called a pneumothorax, and
that's a relatively common condition that
can affect otherwise totally fit young people.
Pleural infection is a form of exudative pleural
effusion but is a little bit more complex,
and that's broken down into empyema and complex
parapneumonic effusions. These areâ€¦ that's
infection arising in the pleural space as
a consequence of pneumonia, and tuberculosis,
because one of the common presentations of
tuberculosis will be with pleural effusions.
And then there are malignancies that affect
the pleura. There's a primary malignancy of
the pleura called the mesothelioma. Now that's
relatively common unless you've been exposed
to asbestos, and in those people, it's relatively
common. And then the pleura is a very common
site for secondary spread of malignancy from
other sites. So for example, a primary lung
cancer will frequently spread to affect the
pleura, as will breast cancer, colon cancer,
and many other malignancies outside the lung,
and they will present with an exudative pleural
The last major area of respiratory disease
that will be discussed in the course are disorders
of physiology. And what we're talking about
here are problems with ventilation of the
lung, largely: obstructive sleep apnea, which
is a condition which affects middle-aged men
largely and is a intermittent obstruction
of the pharynx during sleep. And there's obesity
hypoventilation, which is a situation where
very obese people are unable to ventilate
their lungs effectively. And there are rarer
causes of this ventilation defect as well
that canâ€¦ will be discussed.