Atelectasis
Transcript of Atelectasis
Atelectasis
Background
Greek words ateles and ektasis meaning incomplete expansion
One of the most commonly encountered abnormalities in chest radiology
Divided physiologically into Obstructive causes Non obstructive causes
What is atelectasis?
2 schools of thought Alveolar collapse (volume loss) Fluid accumulation
Types
Obstructive Compression atelectasis Right middle lobe syndrome
Non-obstructive Relaxation/passive atelectasis Adhesive atelectasis Cicatrization atelectasis Rounded atelectasis
Obstructive Atelectasis
Most common Causes: foreign body, tumor and
mucus plugging Rate of development and extent
depend on: Extent of collateral ventilation Composition of inspired gas
Pathophysiology
Obstructive atelectasis
Obstruction of a bronchus
Circulating blood absorbs gas in the peripheral alveoli
Retraction of the affected lung
Pathophysiology
Uninvolved surrounding lung tissue distends
Displacing the surrounding structures and mediastinal shift toward the atelectatic
area
Diaphragm is elevated and chest wall flattens
Obstructive atelectasis
Pathophysiology
Non obstructive atelectasis Loss of contact between the visceral and
parietal pleura Adhesive atelectasis
Due to lack of surfactant Replacement atelectasis
Due to filling by a tumor Cicatrization atelectasis
Due to scarring of the lung parenchyma
Pathophysiology
Platelike atelectasis Also called discoid or subsegmental
atelectasis Most commonly seen in CXR Probably occur because of obstruction of
a small bronchus In hypoventilation, pulmonary embolism
or LRTI
Pathophysiology
Post operative atelectasis Due to diaphragmatic dysfunction and
diminished surfactant activity Typically basilar and segmental
History
Signs and symptoms are determined by the rapidity with which the occlusion occurs
Rapid bronchial occlusion – sudden onset of dyspnea and cyanosis
Slowly developing atelectasis – maybe asymptomatic or with only minor symptoms Middle lobe syndrome is often asymptomatic Irritation in the middle and right lower lobe
bronchi may cause a severe hacking, non productive cough
Physical Examination
Dullness on the affected area Diminished or absent breath sounds
In atelectasis of the upper lobes – bronchial breath sounds
Chest excursion is reduced or absent Trachea and heart are deviated on
the affected side
Causes
Primary cause: bronchial obstruction Plugs of tenacious sputum Foreign bodies Endobronchial tumors Tumors, lymph node or an aneurysm
External pulmonary compression By pleural fluid or air
Causes
Abnormalities of surfactant production In ARDS
Causes
Resorptive atelectasis Bronchogenic carcinoma Obstruction from metastatic neoplasm Inflammatory etiology (TB, fungal infection) Aspirated foreign body Mucous plug Malpositioned endotracheal tube Extrinsic compression of an airway
Neoplasm, lymphadenopathy, aortic aneurysm or cardiac enlargement
Causes
Relaxation atelectasis Pleural effusion Pneumothorax Large emphysematous bullae
Causes
Compression atelectasis Chest wall, pleural, or intraparenchymal
masses Loculated collections of pleural fluid
Causes
Adhesive atelectasis Hyaline membrane disease ARDS Smoke inhalation Cardiac bypass surgery Prolonged shallow breathing
Causes
Cicatrization atelectasis Idiopathic pulmonary fibrosis Chronic tuberculosis Fungal infections
Replacement atelectasis Alveoli filling of fluid or tumor
Rounded atelectasis Asbestos pleural plaques
Consequences
Impaired gas exchange Impaired lung mechanics Increased pulmonary vascular
resistance Worsening lung injury
Consequences
Impaired gas exchange Most obvious effect Basis: absence of ventilation with
persistent perfusion (VQ mismatch)
Consequences
Impaired lung mechanics Worsened compliance Larger transpulmonary pressure are
required to generate a given tidal volume
Work of breathing is increased In mechanically ventilated children,
increased ventilatory pressured are required
Consequences
Increased pulmonary vascular resistance Due to regional alveolar hypoxia with
reduced alveolar and mixed oxygen venous oxygen tension
Local hypoxic pulmonary vasoconstriction
Consequences
Worsening of lung injury Potentiation of lung injury Ventilator induced lung injury
Imaging Studies
Direct signs Displacement of fissures Opacification of the collapsed lobe
Indirect signs Displacement of the hilum Mediastinal shift towards the side of the
collapse Loss of volume on ipsilateral hemithorax Elevation of ipsilateral diaphragm, rib crowding Compensatory hyperlucency of the remaining
lobes Silhouetting of the diaphragm or the heart
border
Imaging Studies
Complete atelectasis of an entire lung Opacification of entire hemithorax Ipsilateral shift of the mediastinum
Imaging Studies
RUL collapse RUL shifts medially and superiorly,
resulting in elevation of the right hilum and minor fissure
Tenting of the diaphragmatic pleura juxtaphrenic peak
Imaging Studies
RML collapse Obscures the right heart border on PA Occasionally, a triangular opacity may
be seen because the major fissure shifts upward and minor fissure shifts downward
Imaging Studies
RLL collapse RLL shifts posteriorly and inferiorly Triangular opacity obscuring the RLL
Imaging Studies
LUL collapse Shifts anteriorly and superiorly On lat views – major fissure displaced
anteriorly and the hyperexpanded RUL may herniate across the midline…
Imaging Studies
LLL collapse Increased retrocardiac opacity
silhouettes the LLL pulmonary artery and L hemidiaphragm
Flat waist sign Superior mediastinum may shift and
obliterate…
Procedures
Flexible fiberoptic bronchoscopy Help evaluate the cause of the obstruction Helps clear mucous plugs Limitations: distal endobronchial lesions are
not accessible
Treatment
Medical care Non-pharmacologic Pharmacologic
Surgical care
Treatment
Non-pharmacologic Chest physiotherapy
Postural drainage, chest wall percussion and vibration
Positive end-expiratory pressure
Non-pharmacologic treatment
Post operative atelectasis Prevention Avoid anesthetic agents associated with
postanesthesia narcosis Early ambulation Incentive spirometry If lobar atelectasis, vigorous chest
physiotherapy
Non-pharmacologic treatment
Post operative atelectasis Adequate oxygenation Supplemental oxygen If with severe hypoxemia – mechanical
ventilation Positive pressure and larger tidal volumes
help to re-expand collapsed lung segments Continuous positive airway pressure Fiberoptic bronchoscopy
Pharmacologic treatment
Bronchodilators Mucolytics
N-acetylcysteine Inhaled recombinant human dNase
Antibiotics Antitussives
Pharmacologic treatment
Bronchodilators Encourage sputum expectoration Of underlying airflow is present, may
also improve ventilation
Pharmacologic treatment
Mucolytics May promote sputum removal of thick
mucous plugs N-acetylcysteine – only recommended
for direst installation via fiberoptic bronchoscopy or in an intubated patient.
Inhaled recombinant human dNase Decreases viscoelasticity and surface
tension of purulent sputum
Pharmacologic treatment
Antibiotics To treat underlying bronchitis or post
obstructive infection Because secondary atelectasis usually
becomes infected regardless of the cause of obstruction
Pharmacologic treatment
Antitussives Reduces the cough reflex Obstruction of a major bronchus may
cause severe hacking or coughing
Surgical Care
Segmental resection or lobectomy – for chronic atelectasis
Complications
Acute pneumonia Bronchiectasis Hypoxemia and respiratory failure Postobstructive drowning of the lung Sepsis Pleural effusion and empyema