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Atelectasis

Atelectasis

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Page 1: Atelectasis

Atelectasis

Page 2: 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

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What is atelectasis?

2 schools of thought Alveolar collapse (volume loss) Fluid accumulation

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Types

Obstructive Compression atelectasis Right middle lobe syndrome

Non-obstructive Relaxation/passive atelectasis Adhesive atelectasis Cicatrization atelectasis Rounded atelectasis

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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

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Pathophysiology

Obstructive atelectasis

Obstruction of a bronchus

Circulating blood absorbs gas in the peripheral alveoli

Retraction of the affected lung

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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

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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

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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

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Pathophysiology

Post operative atelectasis Due to diaphragmatic dysfunction and

diminished surfactant activity Typically basilar and segmental

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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

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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

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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

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Causes

Abnormalities of surfactant production In ARDS

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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

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Causes

Relaxation atelectasis Pleural effusion Pneumothorax Large emphysematous bullae

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Causes

Compression atelectasis Chest wall, pleural, or intraparenchymal

masses Loculated collections of pleural fluid

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Causes

Adhesive atelectasis Hyaline membrane disease ARDS Smoke inhalation Cardiac bypass surgery Prolonged shallow breathing

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Causes

Cicatrization atelectasis Idiopathic pulmonary fibrosis Chronic tuberculosis Fungal infections

Replacement atelectasis Alveoli filling of fluid or tumor

Rounded atelectasis Asbestos pleural plaques

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Consequences

Impaired gas exchange Impaired lung mechanics Increased pulmonary vascular

resistance Worsening lung injury

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Consequences

Impaired gas exchange Most obvious effect Basis: absence of ventilation with

persistent perfusion (VQ mismatch)

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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

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Consequences

Increased pulmonary vascular resistance Due to regional alveolar hypoxia with

reduced alveolar and mixed oxygen venous oxygen tension

Local hypoxic pulmonary vasoconstriction

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Consequences

Worsening of lung injury Potentiation of lung injury Ventilator induced lung injury

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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

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Imaging Studies

Complete atelectasis of an entire lung Opacification of entire hemithorax Ipsilateral shift of the mediastinum

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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

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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

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Imaging Studies

RLL collapse RLL shifts posteriorly and inferiorly Triangular opacity obscuring the RLL

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Imaging Studies

LUL collapse Shifts anteriorly and superiorly On lat views – major fissure displaced

anteriorly and the hyperexpanded RUL may herniate across the midline…

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Imaging Studies

LLL collapse Increased retrocardiac opacity

silhouettes the LLL pulmonary artery and L hemidiaphragm

Flat waist sign Superior mediastinum may shift and

obliterate…

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Procedures

Flexible fiberoptic bronchoscopy Help evaluate the cause of the obstruction Helps clear mucous plugs Limitations: distal endobronchial lesions are

not accessible

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Treatment

Medical care Non-pharmacologic Pharmacologic

Surgical care

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Treatment

Non-pharmacologic Chest physiotherapy

Postural drainage, chest wall percussion and vibration

Positive end-expiratory pressure

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Non-pharmacologic treatment

Post operative atelectasis Prevention Avoid anesthetic agents associated with

postanesthesia narcosis Early ambulation Incentive spirometry If lobar atelectasis, vigorous chest

physiotherapy

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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

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Pharmacologic treatment

Bronchodilators Mucolytics

N-acetylcysteine Inhaled recombinant human dNase

Antibiotics Antitussives

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Pharmacologic treatment

Bronchodilators Encourage sputum expectoration Of underlying airflow is present, may

also improve ventilation

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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

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Pharmacologic treatment

Antibiotics To treat underlying bronchitis or post

obstructive infection Because secondary atelectasis usually

becomes infected regardless of the cause of obstruction

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Pharmacologic treatment

Antitussives Reduces the cough reflex Obstruction of a major bronchus may

cause severe hacking or coughing

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Surgical Care

Segmental resection or lobectomy – for chronic atelectasis

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Complications

Acute pneumonia Bronchiectasis Hypoxemia and respiratory failure Postobstructive drowning of the lung Sepsis Pleural effusion and empyema