atelectasis

Generality

Atelectasis is the total or partial collapse of a lung, due to the deflation of the pulmonary alveoli.

Figure: comparison between a healthy lung and a lung affected by atelectasis. From the asbetos.com website

A cause of alveolar deflation can be a physical obstruction in the upper airways (for example, an excess of mucus or a foreign body), or an external pressure in the lung that prevents the lungs from injecting air (this is which usually occurs after a thoracic trauma).

Atelectasis can cause respiratory problems, ineffective cough, fever and cyanosis, but it can also be asymptomatic, that is, it does not cause any obvious symptoms.

The diagnosis is mainly based on a very common radiological examination, such as chest radiography.

The therapy depends on the triggering causes.

What is atelectasis

Atelectasis is the total or partial collapse of a lung, which takes place following a deflation of the pulmonary alveoli.

WHAT ARE THE PULMONARY CAVLES?

The alveoli are small cavities, located inside the lungs, where gas exchange between the blood and the atmosphere takes place. In fact, in them the blood is enriched with oxygen, coming from the inhaled air, and "free" of the carbon dioxide, resulting from the spraying of the tissues.

Figure: The alveoli are small air chambers, similar to small bags. They are located at the ends of the terminal bronchioles, that is the final branches of the bronchi.

The alveoli reside at the end of each terminal bronchiol; the terminal bronchioles are among the last branches of the airways, which begin with the nasal cavities and continue with nasopharynx, pharynx, larynx, trachea, primary bronchi, secondary bronchi, tertiary bronchi, bronchioles and, precisely, terminal bronchioles.

The airways are didactically divided into upper airways (from the nasal cavities to the larynx), and into the lower airways (from the larynx to the alveoli).

Causes

Atelectasis occurs after the deflation, due to lack of air, of the pulmonary alveoli. But what causes the deflation of the latter?

The lack of air inside the pulmonary alveoli can be the result of:

• a physical blockage in the upper airways ( obstructive block atelectasis );
• an external pressure to the damage of the lung, such that the latter fails to expand and to absorb air ( atelectasis from non-obstructive blockage or non-obstructive atelectasis ).

BLOSSOM ATELECTASIA

To physically block the passage of air, through the upper airways, it can be:

• An accumulation of mucus . The mucus can accumulate when its overproduction is not followed by an equivalent expulsion by coughing, or when deep breaths cannot be performed. In addition, mucus accumulation usually occurs both during and after surgical procedures concerning the chest or lung (because the patient cannot cough effectively), in case of cystic fibrosis (which is a very serious genetic disease). ) and in case of severe asthma attacks.
• A foreign body . Foreign body atelectasis is typical in children, when they inadvertently inhale some very small toys or a bite of food (the classic bean or pea).
• The narrowing, due to chronic infections, of the upper respiratory tract . The usually responsible infections are fungal infections and tuberculosis.
• An upper airway tumor . Tumors cause the growth of an abnormal cell mass within the airways, which blocks the passage of air.
• A blood clot inside the lungs . Formed due to a loss of blood, it becomes a cause of atelectasis when it is not expelled by coughing.

NON-OSTRUCTIVE BLOCKED ATELECTASIA

Non-obstructive atelectasis is caused by an external compression of the lungs; can therefore derive from:

• A chest injury . Severe chest strokes, for example after a car accident, cause intense pain, so that it is difficult to breathe deeply. The lack of deep breaths progressively reduces the air contained in the alveoli, until their exhaustion.
• A pleural effusion . It is the medical term used to identify an excessive accumulation of fluid (the so-called pleural fluid) within the pleural cavity. Accumulation is usually due to inadequate disposal.
• A pneumonia . Pneumonia is inflammation of the lungs. Most often caused by viral or bacterial agents, it causes temporary atelectasis.
• A pneumothorax . Pneumothorax is the medical term for abnormal air infiltration within the pleural cavity.
• A deep scarring of the lung tissue . Scarring at the level of the lungs can be due to trauma, severe lung disease or surgery in the thoracic area. A scarred lung is an inefficient lung and at risk of complications.
• A tumor located near the lungs (but not the upper airways) . A tumor that arises near the lungs compresses the latter and blocks the passage of air inside them.

ATELECTASIA DA ANESTESIA GENERALE

Individuals who are subjected to general anesthesia in preparation for surgery are often protagonists of atelectasis. The general anesthesia, in fact, consists in the administration of particular drugs, which can vary the pressure of the gases exchanged inside the alveoli. These variations can sometimes lead to the emptying of the alveoli and then the total or partial collapse of the lungs.

This dangerous mechanism, which usually (if it occurs) occurs at the end of a surgical operation, is one of the reasons why, after an operation preceded by general anesthesia, an observation period of at least 24 hours is required.

RISK FACTORS

Atelectasis is more common in some situations and in some individuals.

They are at risk:

• premature babies, because their lungs are immature and lack the right amounts of surfactant (NB: the surfactant is a liquid composed of proteins and lipids, essential for good lung health);
• those who, due to different pathological conditions ( asthma, cystic fibrosis, etc.), produce a lot of mucus and are unable to breathe or cough effectively;
• people confined to bed and almost total immobility;
• and people who have had surgery on their abdomen or chest ;
• people who were subjected, a few hours before, to general anesthesia ;
• those who cannot breathe deeply due to a thoracic or abdominal trauma ;
• the sick of some muscular dystrophy ;
• people with spinal cord injury ;
• young children (12-36 months), as they inhale food or bites more frequently;
• smokers, because smoking promotes mucus production;
• finally, obese people, because abdominal fat pushes the diaphragm upwards and the diaphragm, thus modified, prevents the lungs from expanding completely.

Symptoms and Complications

Atelectasis can be asymptomatic, ie it does not cause any obvious symptoms. Other times it is characterized by manifest symptoms and signs, which usually consist of: difficulty breathing ( dyspnea ), weak but rapid breathing, ineffective cough, low oxygen saturation, high heart rate and mild fever .

In more rare cases, cyanosis and chest pain may also appear.

WHEN TO REFER TO THE DOCTOR?

When atelectasis is characterized by evident manifestations, the most characteristic sign that deserves medical attention is difficulty in breathing .

COMPLICATIONS

At an advanced stage, atelectasis can involve several complications, sometimes even very serious and dangerous, such as:

• Low blood oxygen levels ( hypoxemia ). An atelectatic lung (that is to say struck by atelectasis) does not allow gas exchange which "loads" the blood with oxygen, therefore the circulating blood will inevitably be poorly oxygenated
• More or less evident scarring of lung tissue . The damages that traumatize the atelectatic lungs or the lungs could be so severe as to leave more or less deep scars. Lung scars represent a serious danger for the patient who is a carrier.
• Pneumonia . Atelectasis pneumonia occurs when there is an accumulation of mucus in the collapsed lung. In fact, mucus is an ideal place for the proliferation of bacteria and other pathogens.
• State of respiratory failure . Typical of more severe cases or people with severe lung diseases, it is the inability to breathe effectively.

Diagnosis

A very simple radiological examination, called chest X-ray or chest X-ray, is required to diagnose atelectasis. This investigation shows quite clearly the appearance of the lung and which part of it collapsed (if the collapse was partial); however, very often it does not clarify the causes.

For the latter, more in-depth examinations are needed, such as CT, ultrasound, oximetry or bronchoscopy.

Going back to the causes of atelectasis is extremely important, as it allows the doctor to plan the best and most appropriate treatment for the case.

CHEST RADIOGRAPHY

Figure: postero-anterior chest radiograph; the red arrows indicate an atelectasis of the lower left lobe. Note the underlying elevation of the left half of the diaphragm.

From the site: www.med-ed.virginia.edu

The chest X-ray, or chest X -ray, is a radiological examination that allows the visualization of the main thoracic structures: the heart, the lungs, the main blood vessels, most of the ribs and a portion of the spine.

The resulting images are derived from the patient's exposure to a certain dose of ionizing radiation ( X-rays ); these images, commonly called radiographic plates, are quite clear and sufficiently comprehensive. However, they do not always clarify the exact origin of atelectasis.

TAC

The CT ( Computerized Axial Tomography ) is a more sensitive diagnostic imaging test for chest radiography, which can show the collapsed lung from multiple angles.

It is particularly suitable for recognizing tumors at the thoracic level.

CT scan exposes the patient to a non-negligible dose of ionizing radiation.

ULTRASOUND

Ultrasound is a completely bloodless diagnostic imaging test for the patient. Thanks to ultrasound, pulmonary ultrasound shows what the appearance of the pleural cavity is and whether there is an abnormal accumulation of pleural fluid (pleural effusion).

OXIMETRY

Oximetry is a very simple test that measures oxygen saturation in the blood. To do this he relies on an instrument, called an oximeter, which is applied to a finger or an ear lobe (in both cases, these are two highly vascularized areas).

BRONCHOSCOPY

Bronchoscopy is a diagnostic procedure, and in some cases even therapeutic, aimed at exploring the larger airways, such as the larynx, trachea and bronchi. The examination is carried out by inserting a very thin, flexible tube with a fiber optic camera into the nose or mouth.

The use of the bronchoscope allows the doctor to identify the accumulations of mucus, the tumors present in the upper airways and the inhaled foreign bodies.

Treatment

The therapy for atelectasis episodes depends on the triggering causes and is based on the principle that, by "freeing" the airways from obstruction, the alveoli fill up again with air.

Since mucus occlusions are among the most frequent reasons of atelectatic lung, the attention of this article will focus mainly on the so-called thoracic physiotherapy for the mobilization of mucus, on mucolytic pharmacological treatments (that is, which thin the mucous secretions) and on cleaning, by surgery, airway.

However, before analyzing the aforementioned treatments one by one, it is worth remembering that, in the case of partial non-severe atelectasis, healing can take place even without any particular treatment.

THORACIC PHYSIOTHERAPY

Chest physiotherapy, also known as respiratory physiotherapy or respiratory rehabilitation, consists of a series of techniques aimed at: improving deep breathing, allowing adequate expansion of the lungs and, finally, mobilizing the mucus that occludes the upper airways.

Chest physiotherapy has a fundamental importance in case of recovery from a chest surgery (due to a problem with the lungs but not only) or to the abdomen, but also in case of cystic fibrosis . The therapist's job is to teach the patient:

• How to cough effectively
• How to beat the chest to mobilize the mucus
• How to use the VestTM system, ie the airway clearance system, which serves to mobilize excess mucus.
• Techniques for improving deep breathing. For this purpose, incentive spirometry is also considered effective, which involves the use of a respiratory instrument built specifically to favor deep breaths.
• Postural drainage techniques. Postural drainage consists of a series of maneuvers and positions aimed at removing mucus from the lungs.

PHARMACOLOGICAL TREATMENTS

The drugs suitable for atelectasis are: inhaled bronchodilators (or inhaled bronchodilators), acetylcysteine-based medicines (such as Fluimucil and Solmucol) and Pulmozyme.

Going into more detail, inhaled bronchodilators "open" the pulmonary airways (bronchi and bronchioles), facilitating breathing and mucus mobilization. Acetylcysteine- based medicines, on the other hand, thin the mucous secretions, thereby facilitating their expulsion. Finally, the Pulmozyme is used in case of cystic fibrosis due to the dissolution of the mucus located inside the bronchi. Its mechanism of action is based on the destruction of the DNA of the cells that make up the mucous secretions.

CLEANING OF AIRWAYS VIA SURGICAL INTERVENTION

When the pulmonary airways are severely obstructed, the doctor may have to resort to surgical procedures, such as tracheobronchial aspiration and operative bronchoscopy.

Tracheobronchial aspiration, or bronchial aspiration, serves to free the nasopharyngeal tract, trachea and bronchi from mucus, saliva, blood and other abnormal pulmonary secretions. It is a somewhat invasive, annoying and potentially dangerous procedure for the patient, because it involves the insertion (via nasal route or oral route) of a flexible and sterile tube, called a tube. The tube, once conducted in the obstructed points, is connected to an aspirator, which sucks up the unwanted material. Bronchoaspiration is put into practice only if strictly necessary.

We have already talked about bronchoscopy before, during diagnostic procedures. In fact, the principle by which the upper airways are released is not very different from tracheobronchial aspiration, however there is a difference: the bronchoscope is also useful for removing tumors and foreign bodies.

Prognosis

The prognosis depends on the severity of the atelectasis and the reasons for its onset.

If the collapse is total and is due, for example, to cystic fibrosis, the prognosis tends to be negative. Conversely, if the collapse is partial and following a treatable cause (for example after a general anesthesia), the prognosis tends to be positive (or at least not negative).

Prevention

To prevent atelectasis, or at least reduce the chances of its appearance, it is advisable:

• Check very young children when playing with small and potentially dangerous objects.
• Avoid giving children under 3 certain foods, such as peanuts, peas and beans, because they are easily inhaled.
• Do not smoke, because smoking increases mucous secretion.
• Change position often when you are in bed, to facilitate the mobilization of the mucus (NB: This is a particularly suitable advice for individuals at risk of atelectasis).
• Continuous practice of respiratory rehabilitation exercises, taught just as a countermeasure to atelectasis.