How are different types of pneumonia classified?

Photo of a doctor listening to a patient’s lung (PantherMedia / imagepointfr)

Doctors classify different types of pneumonia into various groups. This allows them to describe the disease more exactly, and more importantly, to start off with the correct treatment.

The various types of pneumonia are classified according to a number of characteristics. To treat these types, it's essential to know whether somebody caught pneumonia at home, in a hospital, or in a nursing home.

Community-acquired and nosocomial pneumonia

If you develop pneumonia at home, it's referred to as community-acquired pneumonia (or CAP for short), even if you are admitted to the hospital during the course of the illness.

If you develop pneumonia while in the hospital, it is called hospital-acquired (HAP for short) or nocosomial pneumonia. Pneumonia is considered to be nocosomial if it starts at least two days after you are admitted to the hospital, or within three months of a hospital stay.

Doctors can also classify pneumonia even more exactly, giving consideration to whether somebody became infected in a retirement or a nursing home, at a medical facility such as a dialysis center, or while receiving artificial respiration.

Why is classification important for the treatment?

Community-acquired pneumonia is usually caused by pneumococci, whereas nocosomial pneumonia is often connected with staphylococci, various intestinal bacteria, and special germs such as Pseudomonas aeruginosa. Some of those bacteria can be multi-resistant, meaning they are resistant to several antibiotics. That is why different antibiotics are usually need than for treating community-acquired pneumonia.

Mild, moderate or severe pneumonia

To be able to provide the right treatment, doctors also classify community-acquired pneumonia as mild, moderate or severe. They take the risk of complications into account as well.

Pneumonia is considered to be mild with no increased risk if the patient

  • is younger than 65 years old,
  • is conscious and lucid,
  • has normal blood pressure and pulse,
  • is not breathing too fast (fewer than 30 breaths per minute),
  • has enough oxygen in their blood,
  • has not been given any antibiotics in the past three months,
  • has not been in the hospital in the past three months, and
  • does not have any other severe medical conditions.

People with mild pneumonia can be treated at home and are given antibiotics in tablet form.

The signs of moderate pneumonia include drowsiness and confusion, low blood pressure, worsening shortness of breath, and risk factors such as old age and underlying diseases. People with these symptoms need to have treatment at a hospital. Some will be given a combination of two different antibiotics, at least at the beginning of the treatment.

Pneumonia is classified as severe when the heart, the kidneys or the circulatory system are at risk of failing, or if the lungs can no longer take in enough oxygen. Treatment with an antibiotic infusion in intensive care is then usually needed, sometimes with artificial respiration or additional drugs such as corticosteroids.

Pneumonia in children is only classified as either “not severe” or “severe.”

How can pneumonia be described more exactly?

Experts also classify pneumonia according to factors other than where the patient was infected and the severity. But that typically doesn't affect how the pneumonia is treated. Instead, it's useful for getting a better description of the illness.

Atypical pneumonia

Typical pneumonia generally begins with a sudden high fever and chills, and then coughing with phlegm coming later.

Atypical pneumonia is caused by other germs, which are also referred to as "atypical." Older people in particular have fewer or slightly different symptoms if they have atypical pneumonia: It then starts off rather slowly with a mild fever and/or headache and aching limbs. Rather than coughing with phlegm, they have a dry, tickly cough.

Atypical symptoms don't mean that the lungs are less severely inflamed or that the disease will take a milder course though.

Upper, middle and lower lobe pneumonia

X-rays play an important role in distinguishing between these types: the term lobar pneumonia is used if an entire lung lobe is visibly inflamed. Depending on which lung lobe is affected, the pneumonia is referred to as upper, middle or lower lobe pneumonia.

If there are several multi-lobe focal inflammations in the lungs, the term focal pneumonia is used. Some people use the term bronchopneumonia if the focal inflammations started in inflamed airways (bronchi).

Sometimes, it's the air sacs that are more inflamed (alveolar pneumonia), and sometimes it's the tissue between the sacs (interstitial pneumonia).