Alveolar lung diseases, are a group of diseases that mainly affect the

alveoli Alveolus (; pl. alveoli, adj. alveolar) is a general anatomical term for a concave cavity or pit. Uses in anatomy and zoology * Pulmonary alveolus, an air sac in the lungs ** Alveolar cell or pneumocyte ** Alveolar duct ** Alveolar macrophage * ...

of the lungs.

Causes

Alveoli Alveolus (; pl. alveoli, adj. alveolar) is a general anatomical term for a concave cavity or pit. Uses in anatomy and zoology * Pulmonary alveolus, an air sac in the lungs ** Alveolar cell or pneumocyte ** Alveolar duct ** Alveolar macrophage * ...

are the functional units of the lungs. Alveolar lung diseases are classified as processes that affect these units that ultimately lead to issues with ventilation. There are a number of different causes of insult to the alveoli including build up of fluid, hemorrhage, infection, malignancy and build up of protein and mineral deposits. Conditions classified under alveolar lung disease include pulmonary edema (cardiogenic or non-cardiogenic), pneumonia (bacterial or viral), bronchoalveolar carcinoma, pulmonary hemorrhage, alveolar proteinosis and amyloidosis, and alveolar microlithiasis. Alveolar lung disease may be divided into acute or chronic. Causes of acute alveolar lung disease include

pulmonary edema Pulmonary edema, also known as pulmonary congestion, is excessive edema, liquid accumulation in the parenchyma, tissue and pulmonary alveolus, air spaces (usually alveoli) of the lungs. It leads to impaired gas exchange and may cause hypoxemia an ...

(cardiogenic or neurogenic),

pneumonia Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severity ...

(bacterial or viral),

systemic lupus erythematosus Lupus, technically known as systemic lupus erythematosus (SLE), is an autoimmune disease in which the body's immune system mistakenly attacks healthy tissue in many parts of the body. Symptoms vary among people and may be mild to severe. Comm ...

, bleeding in the lungs (e.g.,

Goodpasture syndrome Goodpasture syndrome (GPS), also known as anti–glomerular basement membrane disease, is a rare autoimmune disease in which antibodies attack the basement membrane in lungs and kidneys, leading to bleeding from the lungs, glomerulonephritis ...

), idiopathic pulmonary hemosiderosis, and

granulomatosis with polyangiitis Granulomatosis with polyangiitis (GPA), previously known as Wegener's granulomatosis (WG), is a rare long-term systemic disorder that involves the formation of granulomas and inflammation of blood vessels (vasculitis). It is a form of vasculitis ...

. Chronic alveolar lung disease can be caused by

pulmonary alveolar proteinosis Pulmonary alveolar proteinosis (PAP) is a rare lung disorder characterized by an abnormal accumulation of surfactant-derived lipoprotein compounds within the alveoli of the lung. The accumulated substances interfere with the normal gas exchange and ...

, alveolar cell carcinoma, mineral oil

sarcoidosis Sarcoidosis (also known as ''Besnier-Boeck-Schaumann disease'') is a disease involving abnormal collections of inflammatory cells that form lumps known as granulomata. The disease usually begins in the lungs, skin, or lymph nodes. Less commonly af ...

(alveolar form),

lymphoma Lymphoma is a group of blood and lymph tumors that develop from lymphocytes (a type of white blood cell). In current usage the name usually refers to just the cancerous versions rather than all such tumours. Signs and symptoms may include enlar ...

tuberculosis Tuberculosis (TB) is an infectious disease usually caused by '' Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, in ...

metastases Metastasis is a pathogenic agent's spread from an initial or primary site to a different or secondary site within the host's body; the term is typically used when referring to metastasis by a cancerous tumor. The newly pathological sites, then, ...

, or desquamative interstitial pneumonia.

Diagnosis

Initial evaluation and Testing

Patients with alveolar lung disease may have difficulty breathing and/or a cough which may be productive of sputum or blood. A physician will listen to the patient's lungs to help determine if there is likely a lower lung disease. Depending on the type of alveolar lung disease, the listener may hear "crackles" that indicate an excess of fluid in the lungs or an absence of lung sounds in certain regions which may indicate poor ventilation due to consolidation of pus or fibrosis. A

pulse oximeter Pulse oximetry is a noninvasive method for monitoring a person's oxygen saturation. Peripheral oxygen saturation (SpO2) readings are typically within 2% accuracy (within 4% accuracy in 95% of cases) of the more accurate (and invasive) reading of ...

is a device that measures the amount of oxygen available in the blood. This is an important measurement in evaluation of a patient with difficulty breathing with suspected alveolar lung disease.

Imaging

Chest x-ray is the initial imaging modality of choice for evaluation of potential alveolar lung disease. Bedside ultrasound may also be utilized. The absence of radiographic evidence early on in the course of disease does not exclude alveolar disease. Alveolar disease is visible on chest radiography as small, ill-defined nodules of homogeneous density centered on the acini or bronchioles. The nodules coalesce early in the course of disease, such that the nodules may only be seen as soft fluffy edges in the periphery. When the nodules are centered on the hilar regions, the chest x-ray may develop what is called the "butterfly," or "batwing" appearance. The nodules may also have a segmental or lobar distribution. Air alveolograms and

air bronchogram An air bronchogram is defined as a pattern of air-filled bronchi on a background of airless lung. Material was copied from this source, which is available under Creative Commons Attribution 4.0 International License __TOC__ Consolidations In pulm ...

s can also be seen which indicate fluid in the alveoli with air in the terminal bronchioles indicating disease is alveolar. These findings appear soon after the onset of symptoms and change rapidly thereafter. A segmental or lobar pattern may be apparent after

aspiration pneumonia Aspiration pneumonia is a type of lung infection that is due to a relatively large amount of material from the stomach or mouth entering the lungs. Signs and symptoms often include fever and cough of relatively rapid onset. Complications may inclu ...

atelectasis Atelectasis is the collapse or closure of a lung resulting in reduced or absent gas exchange. It is usually unilateral, affecting part or all of one lung. It is a condition where the alveoli are deflated down to little or no volume, as distinct ...

lung contusion The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of t ...

, localized

, obstructive

pulmonary embolism Pulmonary embolism (PE) is a blockage of an pulmonary artery, artery in the lungs by a substance that has moved from elsewhere in the body through the bloodstream (embolism). Symptoms of a PE may include dyspnea, shortness of breath, chest pain p ...

with

infarction Infarction is tissue death (necrosis) due to inadequate blood supply to the affected area. It may be caused by artery blockages, rupture, mechanical compression, or vasoconstriction. The resulting lesion is referred to as an infarct (from the ...

, or

Management

The two focuses of management for alveolar disease is supportive care to maintain oxygenation and ventilation to ensure that adequate oxygen is being delivered to blood, and to treat the underlying insult to the alveoli.

Supportive Care

Maintaining oxygenation and ventilation in alveolar lung disease is achieved through a number of methods. The mechanism of these treatments is primarily to provide oxygen and keep the alveoli open so that they can take up oxygen from and deliver it to the bloodstream. Ventilatory support is recognized as an essential component to treat pulmonary edema and

acute respiratory distress syndrome Acute respiratory distress syndrome (ARDS) is a type of respiratory failure characterized by rapid onset of widespread inflammation in the lungs. Symptoms include shortness of breath (dyspnea), rapid breathing (tachypnea), and bluish skin colo ...

Non-invasive ventilation Non-invasive ventilation (NIV) is the use of breathing support administered through a face mask, nasal mask, or a helmet. Air, usually with added oxygen, is given through the mask under positive pressure; generally the amount of pressure is alter ...

is the first step for patient's who require ventilatory support. This can take the form of oxygen delivered via nasal cannula or non-rebreather mask. Patients who require additional support may be given a high-flow nasal cannula which has an added function of providing positive pressure on the alveoli, can warm and humidify air and decrease required inspiratory effort of the patient. BiPAP and CPAP can also be used as next level treatment. Finally, intubation with ventilator support can be used with positive pressure to improve ventilation and oxygenation. In cases where methods to support the lungs to provide oxygen to the blood fail, extracorporeal membrane oxygenation, or

ECMO Extracorporeal membrane oxygenation (ECMO), also known as extracorporeal life support (ECLS), is an extracorporeal technique of providing prolonged cardiac and respiratory support to persons whose heart and lungs are unable to provide an adequate ...

can be considered.

Treating underlying causes

Treating underlying causes of damage to alveoli is also essential in most alveolar lung disease. Some more commonly seen instances of alveolar lung disease include pulmonary edema and pneumonia. For

, medical treatment in addition to measures to maintain ventilation include diuretics to remove excess fluid from the lungs. Presumed bacterial

is typically treated with antibiotics.

References

{{reflist Lung disorders