Medical Terms for Fluid in the Lungs
The medical term for fluid in the lungs is pulmonary edema, which refers to the abnormal accumulation of fluid in the alveolar walls and alveolar spaces of the lungs. 1
Types of Pulmonary Edema
Pulmonary edema can be classified into several categories based on the underlying mechanism:
Hydrostatic (Cardiogenic) Pulmonary Edema: Results from elevated pulmonary capillary pressure due to left-sided heart failure, causing fluid to move from the vasculature into the interstitium and alveoli 2
Permeability (Non-cardiogenic) Pulmonary Edema: Occurs due to injury to the endothelial and epithelial barriers, allowing fluid to leak into the lungs regardless of pressure 2
Mixed Edema: Involves both increased hydrostatic pressure and increased membrane permeability 1
Pathophysiology
The development of pulmonary edema involves several mechanisms:
Starling Forces: When fluid deposition exceeds the capacity of the lungs to remove fluid through lymphatic flow, accumulation of extravascular water occurs 3
Increased Permeability: In conditions like sepsis, increased capillary permeability allows plasma proteins to cross into the alveolar space, creating interstitial edema 3
Fluid Redistribution: In many cases, pulmonary edema is not caused by fluid accumulation but rather fluid redistribution directed into the lungs because of heart failure 4
Extravascular Lung Water: Accumulation occurs when the balance of hydrostatic and oncotic pressure gradients is disrupted, particularly when capillary permeability is increased 3
Clinical Manifestations
Pulmonary edema presents with:
- Dyspnea (shortness of breath) that may be out of proportion to the size of the effusion 3
- Crackles (rales) heard on auscultation, which are the audible manifestations of fluid in the alveoli
- Decreased lung compliance due to alveolar edema and surfactant dysfunction 3
- Hypoxemia resulting from intrapulmonary shunting 3
Specific Terms for Different Types of Fluid in the Lungs
Pleural Effusion: Accumulation of fluid in the pleural space (between the lung and chest wall) rather than within the lung tissue itself 3
Alveolar Edema: Fluid specifically within the air sacs (alveoli) of the lungs 3
Interstitial Edema: Fluid accumulation in the interstitial spaces between alveoli 3
Exudative Effusion: Inflammatory fluid with high protein content, often due to increased vascular permeability 3
Transudative Effusion: Fluid with low protein content, typically due to increased hydrostatic pressure or decreased oncotic pressure 3
Diagnostic Considerations
When fluid is heard in the lungs during auscultation:
- The sound is typically described as "crackles" or "rales"
- These sounds occur due to the sudden opening of small airways and alveoli filled with fluid 3
- The distribution of these sounds can help determine the cause and severity of the pulmonary edema
Treatment Implications
The treatment approach depends on correctly identifying the type of fluid:
Cardiogenic Pulmonary Edema: Often treated with diuretics like furosemide, vasodilators, and positive pressure ventilation 5, 6
Non-cardiogenic Pulmonary Edema: Treatment focuses on addressing the underlying cause and supportive care 2
Pleural Effusions: May require drainage through thoracentesis depending on size and symptoms 3
Pitfalls and Caveats
- Not all fluid in the lungs presents with audible crackles; silent pulmonary edema can occur
- The presence of fluid in the lungs can be mistaken for other conditions like pneumonia or atelectasis
- Bilateral effusions in a clinical setting strongly suggestive of a transudate (like heart failure) may not require diagnostic sampling unless there are atypical features 3
- The term "wet lungs" is a colloquial expression and not a proper medical term for pulmonary edema