The term parenchyma is used to refer to a tissue in the human body whose cells have physiological activity, as opposed to connective tissues, which serve as a support or link. 

Lung parenchyma is the functional tissue of the lung. It is made up of the respiratory bronchioles, alveolar ducts and alveoli, the seat of gas exchange between blood and air. The lung parenchyma is the intimate part of the lung. Its structure is composed of blood capillaries serving to facilitate contact with the alveolar air. 

It is linked to the interstitium, which is the supporting tissue of the lung, located between the walls of the pulmonary alveoli.

In the pulmonary parenchyma, the bronchial passages open out into dilations filled with air which are the alveoli, the shape of which is polyhedral and quite irregular; their size, very variable, is from 0,1 to 0,3 mm. For this respiratory function, the human body has 300 million alveoli in adults for a total interior surface area of ​​about fifty square meters.

The lung parenchyma therefore ensures the respiratory function of the human body.

In the alveolus, air and blood are separated by a thin cell layer, the air-blood barrier, formed by the alveolar wall. Despite its extreme thinness, this wall is very complex.

When the parenchyma is damaged, it gives way to scar connective tissue, which has no physiological activity. However, the liver, unlike the lung or kidney, is able to reconstitute new parenchyma.

There are many abnormalities or diseases related to the lung parenchyma and they are often difficult for healthcare professionals to diagnose.

Among the most common infections related to the lung parenchyma are: 

Pneumonia

This results in inflammation of the pulmonary parenchyma. It is an infectious attack that affects the pulmonary alveoli. Germs are different depending on the age of the patient’s history.

Infant bronchiolitis

It also has an inflammatory character, but is seasonal in winter. It is rare in adults and often associated with bronchial involvement and rather has a chronic course. Bronchiolitis in children lasts on average for a few days in most cases, but hospitalization may be advised in the event of a severe lack of oxygen.

Alveolitis

Third possible inflammation, that of the pulmonary alveoli. This is called a dry socket. This inflammation, also called chronic or acute interstitial lung disease, causes respiratory hypersensitivity. It may be due to certain allergens inhaled daily by the patient: hay molds, bird excrement. This disease is therefore found among farmers. The alveolitis can be seen, apart from any infectious context

The pulmonary nodule

A pulmonary nodule is very often discovered during an X-ray examination performed as part of pulmonary symptoms or a simple surveillance.

This pulmonary nodule can be “benign” in the case of infectious, inflammatory, congenital or vascular causes.

When it contains tumor cells, it is said to be “malignant”. In this case, cancer cells have infiltrated the alveoli and cause tumor damage, lung cancer or lung metastasis from another organ.  

Pulmonary edema

Of cardiac origin, this edema can be the consequence of a gradual increase of water in the lungs, which saturates the interstitial space in the event of a severe attack of heart failure.

 Acute lung edema (pulmonary edema or OAP) is therefore caused by heart disease. It is a life-threatening medical emergency and the patient should be hospitalized and treated as quickly as possible.

In the event of respiratory problems, it is the attending physician who will first establish an initial assessment. It establishes a summary of the symptoms including the level of pain or difficulty in breathing, as well as the duration or chronicity of the symptoms. Depending on the severity and the pain, he quickly refers the patient to a pulmonologist or has the patient hospitalized in the emergency or radiology departments to perform a chest x-ray.

Depending on these results, other more in-depth examinations will be considered such as:

• blood test,
• blood gas,
• chest scanner,
• bronchoscopy,
• bronchioloalveolar lavage,
• bronchial biopsies,
• Echocardiography.

This additional information will make it possible to identify the cause of these respiratory disorders and depending on this cause, healthcare professionals will adapt the treatment.