Márcio Lança, M.D., Pneumology. Medical Residency in Internal Medicine and Pneumology, Catholic University São Lucas Hospital (PUC-RS).


Lung infection or lower respiratory tract infection

What is it?

Pneumonia is an infection or inflammation in the lungs. It can be caused by several different microorganisms, including viruses, bacteria, parasites or fungi.

This disease is still quite frequent and affects people at any age. Many individuals die annually due to pneumonia. Half of all pneumonia cases are caused by bacteria, and, amongst these, Pneumococcus is the most frequently found.

How does it develop?

Usually, the disease develops when, for some reason, a failure occurs in the defense mechanisms of the organism.

Pneumonia can develop through 3 different mechanisms: br> 

One of them, quite frequent, occurs when the individual inhales a microorganism through respiration, and this makes its way into one or both lungs, where it leads to the disease.
Another frequent form of development is when bacteria, which habitually dwell in the mouth, proliferate and are eventually sucked to a site in the lung.
The most uncommon form of contracting this disease is through blood circulation. An infection by a microorganism elsewhere in the body spreads and arrives through the circulating blood at the lungs, where it causes the infection.

Protection mechanisms

It's important to remember that, on normal circumstances, the respiratory airways (including the lungs) have effective protection mechanisms against microorganisms' infections.

The first mechanism takes place in the nose, where large particles are filtered, and fail to arrive at the lungs to cause infections.

Small particles, when inhaled through the respiratory airways (which lead the air to the lungs), are fought off by reflex mechanisms. Among these are the reflexes of sneezing, clearing the throat and coughing, which expel the invading particles, preventing infections (pneumonias). When people have a bad cold, the filtration normally taking place in the nose and the organism's immunity may be impaired, favoring the onset of pneumonia.

In those cases in which a suppression of the aforementioned reflexes takes place, there's also a greater risk of pneumonia onset. This may occur when, for instance, an individual falls asleep drunk, has used sedatives, has lost their senses due to a convulsive seizure or has some neurological sequela.

The lungs own a clearance mechanism as well, in which the cilia available in their interior perform, by means of their motions, the removal of secretions with microorganisms that might have defeated the previously described defense mechanisms.

These cilia are located in the inner side of the bronchi, which are tubes that take the air to the lungs. It's important to remember that this clearance mechanism is impaired in smokers, as smoking has the ability of paralyzing the cilia involved in this task.

The last defense mechanism of the respiratory airways takes place in the alveoli, where gas interchanges occur (oxygen enters and carbon dioxide exits), and is the place where the macrophages act. These are the cells specialized in the organism's defense, and they envelop microorganisms that, by any chance, might have survived the nasal filtration, the reflexes of throat-cleaning, coughing or sneezing, in addition to the clearance performed by the cilia in the respiratory airways.

What does one feel?

Traditional bacterial pneumonia has a sudden onset, with fever, chills, chest pain and cough with yellowish or greenish expectoration (sputum) that may have some blood mixed with the secretion. The cough can be dry in the beginning.

Respiration may become shorter and painful, the individual may suffer from shortness of air, and around the lips the skin color may become blue in more severe cases.

In the elderly, mental confusion may be a frequent symptom, in addition to a worsened general condition (e.g., weakness, loss of appetite and discouragement). In children, symptoms can be vague (decreased appetite, crying, fever).

Another alteration that can occur is the appearance of herpes lesions in the lips, since the immune system is debilitated.

In some cases, abdominal pain, vomit, nausea and symptoms in the upper respiratory tract, such as sore throat, sneezing, running nose, and headache, may be experienced.

How does the doctor diagnose it?

The diagnosis can be made based just on the altered physical examination and the conversation the physician had with his/her patient reporting signs and symptoms compatible with the disease. Supplementary tests are important to support the diagnosis and will help determine the best treatment for each case. Usually, the physician uses imaging tests (chest radiography or even chest computerized tomography) and blood tests as an aid to the diagnosis.

Sputum testing is also important to attempt at identifying the causative microorganism of the pneumonia. With this, the physician will be able to predict, in most cases, the disease course and also determine the most adequate antibiotics for each case.

How is it treated?

Bacterial pneumonia must be treated with antibiotics. Every case is evaluated individually, and , besides the kind of antibiotics, it will also be determined whether there's need for hospitalization or not.

In severe cases, even hospitalization in Intensive Care Units (ICU) may be entailed.

The antibiotics and further medications can be administered orally or by means of shots in the veins or muscle.

In some cases, in addition to medications, we can use respiratory physiotherapy as an aid to the treatment. Physiotherapists use respiratory exercises, chest vibrators and tapotement (chest percussion with the fists) with the intent of removing secretions that are inside the lungs, accelerating the healing process in the patients.

In viral pneumonias, the treatment is practically supportive only. It aims at improving the organism's conditions so that it fights the infection. A suitable diet, oxygen (if necessary) and pain or fever medications are used.

In cases of parasitic or fungal pneumonia, specific antimicrobial drugs are used.

How is it prevented?

As previously mentioned, many times the flu or a bad cold can precede pneumonia. In order to prevent that, vaccines have been created.

There's a vaccine available in the market against the influenza virus, and another one against Pneumococcus, which can decrease the chances of attack of diseases caused by these germs.

We must remember that these vaccines should preferentially be taken prior to early winter.

The vaccine against the influenza virus must be taken annually by the elderly and those at greater risk of developing pneumonia. The vaccine against Pneumoccocus must be taken by the elderly and individuals suffering from HIV infection, renal disease, spleen disorders, alcohol addiction, or other conditions that debilitate the organism's defense system. This vaccine lasts approximately five years.

In some cases, another shot must be given after the end of this period. In select cases, the vaccine against Haemophilus influenzae should be applied. This, too, is a frequent germ that may cause pneumonia. Other vaccines exist, against other germs, which are still under study.

Simple measures for pneumonia prevention include hygiene care, such as washing the hands with ordinary soaps.

A diet rich in fruit and vegetables, which contain vitamins, help strengthen the organism's defensive system against infections.

Questions you can ask your doctor

How long must antibiotics be taken for treating bacterial pneumonia?

What's the indicated treatment for viral pneumonia?

How long does it take for a chest radiograph to show a normal result after pneumonia treatment?

What complications can occur with pneumonia?

What's the importance of finding the causative microorganism of pneumonia?