Bibasilar Atelectasis: Definition and Clinical Significance
Bibasilar atelectasis refers to collapsed, non-aerated lung tissue located at the bases (lower portions) of both lungs. 1
What This Term Means
"Bibasilar" indicates involvement of both lung bases, while "atelectasis" describes a state of collapsed lung parenchyma that is otherwise structurally normal. 1 This is a pathological finding rather than a disease itself—it represents a manifestation of an underlying condition or physiological process. 1
Anatomical Context
- The term specifically refers to the dependent (lower) portions of both lungs, which are most susceptible to collapse due to gravitational effects and reduced ventilation. 2, 3
- This pattern is commonly seen on chest X-rays or CT scans as reticular abnormalities or areas of increased opacity at both lung bases. 4
Common Clinical Scenarios
Bibasilar atelectasis occurs frequently in several contexts:
Perioperative Setting
- Appears in approximately 90% of anesthetized patients, with 15-20% of lung tissue regularly collapsed at the base during routine anesthesia. 3
- Can persist for several days postoperatively and may serve as a focus for infection. 3
Hospitalized or Bedridden Patients
- Develops due to prolonged supine positioning, reduced mobility, and shallow breathing patterns. 2, 5
- Associated with decreased lung compliance and impaired oxygenation. 2, 5
Chronic Conditions
- May be seen in patients with COPD, pleural effusions, or other pulmonary conditions that compress or restrict lung expansion. 6
- Can occur with compressive processes such as pleural effusions that push on the lung bases. 6
Clinical Significance
The consequences of bibasilar atelectasis range from minor to serious depending on extent, patient vulnerability, and underlying cardiopulmonary reserve. 7
- Impairs gas exchange through increased intrapulmonary shunting and ventilation-perfusion mismatch. 2, 5
- Increases pulmonary vascular resistance and can contribute to acute lung injury. 2, 5
- May be asymptomatic or present with dyspnea, reduced exercise tolerance, or hypoxemia depending on severity. 7
Key Diagnostic Features
On imaging studies, bibasilar atelectasis appears as:
- Bibasilar reticular abnormalities on high-resolution CT scans. 4
- Areas of increased density at both lung bases on chest radiographs. 1
- Bibasilar inspiratory crackles (dry or "Velcro" type) may be heard on physical examination. 4
Important Distinction
Bibasilar atelectasis must be differentiated from lobar consolidation, which represents alveolar filling with fluid, pus, or blood rather than collapse. 1 This distinction requires careful evaluation of imaging characteristics and clinical context.