Atelectasis

Description of Medical Condition

Atelectasis (lung collapse) is a portion of lung which is non-aerated, but otherwise normal. May be an asymptomatic finding on CXR or associated with symptoms. Pulmonary blood flow to area of atelectasis is usually reduced, thereby limiting shunting and hypoxia. Diagnosis and therapy are directed at basic cause.

System(s) affected: Pulmonary, Cardiovascular

Genetics: Depends on basic condition e.g., cystic fibrosis, COPD, asthma, congenital heart disease, congestive heart failure, etc.

Incidence/Prevalence in USA: Common in general anesthesia and in intensive care with high inspired oxygen concentrations

Predominant age: All ages

Predominant sex: Male = Female

Medical Symptoms and Signs of Disease

Small atelectasis
- Commonly asymptomatic
- Produces no change in the overall clinical presentation
Large atelectasis:
- Tachypnea
- Cough
- Hypoxia which resolves in some cases over 24-48 hours — due to ventilation — periusion mismatch
- Dullness to percussion
- Absent breath sounds if airway is occluded
- Bronchial breathing if airway is patent
- Diminished chest expansion
- Tracheal or precordial impulse displacement
- Wheezing may be heard with focal obstruction

What Causes Disease?

Increased alveolar surface tension due to cardiogenic or non-cardiogenic pulmonary edema, primary surfactant deficiency, or infection
Resorptive atelectasis due to airway obstruction from lumenal blockage (mucus, tumor, foreign body), airway wall abnormality (edema, tumor, bronchomalacia, deformation), or extrinsic airway compression (cardiac, vascular, tumor, adenopathy)
Compression of the lung (lobar emphysema, cardiomegaly, tumor)
Increased pleural pressure due to fluid or air in the pleural space (pneumothorax, effusion, empyema. hemothorax, chylothorax)
Chest wall restriction due to skeletal deformity and/or muscular weakness (scoliosis, neuromuscular disease, phrenic nerve paralysis, anesthesia)

Risk Factors

Varies with condition producing atelectasis
Atelectasis following anesthesia is increased in smokers, obese individuals, and individuals with short, wide thoraces
Asthma — right middle lobe most common

Diagnosis of Disease

Differential Diagnosis

Atelectasis is not a specific diagnosis, but rather a result of disease or distorted anatomy. The differential is thus found under Causes.
The roentgenographic differential includes pneumonia, fluid accumulation, lung hypoplasia, or tumor

Drugs that may alter lab results: N/A

Disorders that may alter lab results: N/A

Pathological Findings

Pathology varies with cause
Obstructive atelectasis — non-aerated lung without inflammation or infiltration

Imaging

CXR

May demonstrate linear, round, or wedge shaped densities
Right middle lobe and lingular atelectasis will obscure the ipsilateral heart border
Lower lobe atelectasis will obscure the diaphragm
Air bronchograms are usually absent in obstructive atelectasis
Evidence of possible airway compression, pleural fluid or air should be sought
Diffuse microatelectasis in surfactant deficiency may lead to a ground-glass appearance with striking air bronchograms
Mediastinal structures and the diaphragm move toward the atelectatic region
Adjacent lung may show compensatory hyperinflation

Diagnostic Procedures

Bronchoscopy to assess airway patency. (Bronchos-copy as therapy is controversial with the exception of foreign body or other structural causes).
Echocardiography to assess cardiac status in cardio-megaly
Chest CT or MRI to visualize airway and mediastinal structures
Barium swallow to assess mediastinal vascular compression
Other procedures vary with potential cause

Treatment (Medical Therapy)

Appropriate Health Care

Varies with severity

General Measures

Varies with severity and cause of atelectasis
Maximize patient mobility
Ensure adequate oxygenation and humidification
Chest physiotherapy with percussion and postural drainage. Consider adding treatments using new airway clearance techniques such as Positive Expiratory Pressure (PEP) mask.
Incentive spirometry
Positive pressure ventilation or continuous positive airway pressure in subjects with neuromuscular weakness. In-exsufflator may also be helpful here.

Activity

Encourage activity, mobilization as tolerated

Diet

No special diet

Patient Education

Encourage activity as appropriate. Instruct in basic cause and its therapy.

Medications (Drugs, Medicines)

Drug(s) of Choice

Bronchodilator therapy (beta-agonist aerosol); efficacy controversial
Other therapies directed at basic cause — antibiotics, foreign body removal, tumor therapy, cardiac medication, steroids in asthma

Contraindications: Refer to manufacturer’s literature

Precautions: Refer to manufacturer’s literature

Significant possible interactions: Refer to manufacturer’s literature

Alternative Drugs

N/A

Patient Monitoring

Varies with cause and patient status
In simple atelectasis associated with asthma or infection, monthly visits are adequate

Prevention / Avoidance

Avoidance of 100% inspired oxygen (which can rapidly absorb causing atelectasis)
Foreign body/aspiration precautions
Postoperative mobilization and/or rotation
Institute therapies such as chest physiotherapy and incentive spirometry as preventive maneuvers in at-risk patients

Possible Complications

Infection with chronic lung damage is an unlikely, but unfortunate complication
Atelectasis is rarely life-threatening and usually spontaneously resolves

Expected Course / Prognosis

Resolution with medical therapy
Surgical therapy needed only for certain causes, or if chronic infection and bronchiectasis supervene

Miscellaneous

Associated Conditions

N/A

Age-Related Factors

Very young and very old patients with limited mobility at greater risk

Pediatric: Congenital airway obstruction due to mediastinal cysts, tumor, or vascular rings; foreign body aspiration

Geriatric: Primary and secondary lung tumors sometimes associated

Others: Asthma

Pregnancy

Management is similar to non-pregnant and varies with cause

Synonyms

Lung collapse

International Classification of Diseases

518.0 Pulmonary collapse

Other Notes

Round atelectasis:

A pleural based round density on CXR with a comet tail of vessel and airway
More common in patients with asbestos exposure
May mimic tumor, but can usually be definitively diagnosed with imaging studies thereby avoiding surgery