Common misconceptions and mistakes
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The proper way to screen for a pneumothorax (PTX) is by looking for areas on the chest x-ray (CXR) that do not have lung markings
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A pneumothorax (PTX) occurring after an uncomplicated/successful thoracentesis likely represents air entrained around the needle/catheter
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A chest tube should always be placed on suction to physically suck the visceral pleura up against the chest wall (ie, to maintain pleural apposition) when a BPF exists
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Thinking that a PTX is synonymous with a bronchopleural fistula (BPF)
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Approach to the pneumothorax
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A PTX means air in the pleural space
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Commonly detected in three situations, when a chest radiograph is obtained to evaluate:
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Chest pain (pleura innervated with pain fibers) and/or SOB
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Elevated airway pressure in a mechanically ventilated patient
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For possible postprocedure complication (after thoracentesis, central line or chest tube placement)
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A PTX should be screened for (and is usually detected by) demonstration of a visceral pleural edge (separated from the parietal pleura and chest wall) appearing as an unexpected line:
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Often at the apex, because air will rise in a normal upright thorax ( Fig. 16.1 )
Fig. 16.1
(A) Left apical pneumothorax evidenced by an unexpected apical line (visceral pleural edge), (B) outlined in red. Note: A pacemaker with leads complicates the visual field.
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Supine patients (like those requiring mechanical ventilation) will have air rise and accumulate at the base of the lung (deep sulcus sign) because the apex is more dependent when supine ( Fig. 16.2 )
Fig. 16.2
(A) Right basilar deep sulcus sign. Note that the area of the sulcus appears excessively black (ie, as black as air outside of the chest) (B) Close-up.
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Although an absence of lung markings is also apparent when a PTX is large, this finding is less reliable in detecting a small PTX at the apex
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Especially with apical bullous disease, where lung markings are sparse
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Additionally, individuals with pleural parenchymal scarring may have a loculated PTX:
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The unexpected pleural line may not be apical if the apex is scarred
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A loculated PTX may have lung markings visible past the visceral pleural edge as aspects of the lung are tethered to the chest wall ( Fig. 16.3 )
Fig. 16.3
(A) Posteroanterior (PA) and lateral chest x-ray showing a left-sided pleural effusion. (B) Repeat PA and lateral chest x-ray after thoracentesis, showing a left hydropneumothorax as evidenced by a straight line (air-fluid interface) on the lateral film. (C) Close inspection of the frontal x-ray demonstrates a loculated pneumothorax (PTX) evidenced by a lateral pleural edge, with lung markings visible beyond it. The PTX was loculated because the patient had had radiation therapy for left upper lobe lung cancer (note the opacified left apex with left hilar retraction, indicating scarring and volume loss).
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Initial evaluation of the PTX should assess the size as small or large :
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Small : <~3 cm between the chest wall and the visceral pleural line (at any point)
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Large : > ~ 3 cm between the chest wall and the visceral pleural line (at any point)
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Very large PTXs (like those causing tension physiology) should be obvious on physical examination (absent breath sounds over a hemithorax) and imaging (no lung markings)
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Large PTXs should be screened for signs of tension (eg, mediastinal shift away from the PTX; see Chapter 4 )
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Tension physiology occurs when a persistent bronchopleural fistula (BPF) develops a check valve-like behavior:
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Inspiration generates negative intrathoracic pressure, which expands the lungs, opens the bronchi, and promotes airflow from the tracheobronchial tree through the BPF and into the pleural space
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Exhalation generates positive intrathoracic pressure, which collapses the bronchi, decreasing airflow through the BPF, thus trapping air in the pleural space
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Each respiratory cycle progressively increases the volume of air in the pleural space, increasing intrathoracic pressure and eventually decreasing venous return to the right atrium
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The right ventricle (RV), in the face of decreased preload (and diminished filling), attempts to maintain cardiac output (CO) by becoming tachycardic
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Eventually RV stroke volume and CO fall, leading to decreased left ventricle (LV) CO and systemic hypotension (cardiogenic shock)
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If unchecked, this process will lead to PEA cardiac arrest as venous return to the right atrium effectively falls to zero and the heart fails to fill
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Tension physiology mandates urgent decompression, or venting of the thorax
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Observation vs. small-bore chest tube placement
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Small PTXs in patients not requiring mechanical ventilation should be observed
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A repeat CXR in 4 to 6 hours demonstrating stability or decrease in size of the PTX suggests resolution of the BPF
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Any residual air should be reabsorbed in a matter of hours or days
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Patients should be instructed not to fly or go to high altitude while they have air in their pleural space because:
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Air that enters the pleural space at atmospheric pressure will expand when ambient pressure drops
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Small PTXs occurring in patients placed on mechanical ventilation can rapidly expand and create tension physiology such that the vast majority will require chest tube placement
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Repeat imaging (if indicated by extremely small initial size) should be done at short time intervals initially (30–60 minutes)
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Large PTXs, expanding PTXs, or PTXs occurring in a patient placed on mechanical ventilation typically require chest tube placement
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Patients without COPD (ie, primary spontaneous PTX) should be nonemergently evaluated for surgical intervention to excise apical blebs, thereby reducing the risk of recurrence (often on the contralateral side as well)
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These patients should be counseled never to scuba dive (without surgical intervention bilaterally)
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Patients with COPD (ie, secondary spontaneous PTX) also have high recurrence rates:
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The decision to intervene surgically involves many factors:
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Benign vs catastrophic nature of the initial presentation
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Morbidity of VATS in patients with severe parenchymal lung disease
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Difficulty finding normal lung to staple through (thereby risking the creation of additional BPFs)
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Recurrence is the most definitive indication for surgical intervention
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Large PTXs exhibiting tension physiology (tachycardia and hypotension from impaired venous return) should be urgently decompressed:
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18-gauge needle (of appropriate length to reach the pleural space) blindly inserted into the anterior second intercostal space at the midclavicular line
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Leading to an audible/tactile evacuation of air from the thorax
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This stabilizes the patient allowing for more definitive chest tube placement
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Required to prevent recurrent PTX and tension physiology as the BPF continues its check valve behavior
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A PTX occurring after uncomplicated thoracentesis or chest tube insertion for drainage of a pleural effusion is typically an ex-vacuo phenomenon, representing a vacuous space (ie, created by a vacuum) and not actually “air” occurring when:
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Fluid removal fails to lead to lung reexpansion because of a stiff, noncompliant, diseased visceral pleura, which encases the lung and prevents reexpansion
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Pleura may be visibly thickened on CT scan
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Lung entrapment vs trapped lung can only be determined over time, based on whether or not the lung ultimately reexpands
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The lung is said to be “entrapped” if over time it ultimately reexpands, implying that the pleural disease represented an acute inflammatory process ( Fig. 16.4 )
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