It is often difficult to identify a pneumothorax on a supine CXR in a ventilated patient.
All of the following signs on the CXR suggest the presence of pneumothorax EXCEPT:
Answer: C: It is often difficult to identify a pneumothorax on a supine CXR. ED patients who are ventilated may develop pneumothoraces due to barotrauma, as well as due to attempted central line insertion. In the supine position in a patient with pneumothorax, the air in the pleural cavity collects anterior to the lung, therefore the collapsed lung edge is not often visible in this position. This is true even for a pneumothorax under tension. Furthermore, the presence of a presumed well-positioned intercostal catheter (ICC) alone is not helpful in excluding a tension pneumothorax in a similar patient. Tension can develop even in a patient with an ICC. A number of features have been described to help identify a pneumothorax in a supine patient including:
References:
Regarding the diagnosis of a spontaneous pneumothorax in a patient with severe chronic obstructive pulmonary disease (COPD), which ONE of the following statements is TRUE?
Answer: B: Both inspiratory and expiratory posteroanterior (PA) films are equally sensitive (sensitivity only 83%) in the diagnosis of a pneumothorax. However, in COPD patients often the issue is to differentiate bullae from a spontaneous pneumothorax. On a CXR a bulla appears with a concave inner margin (lung edge) and rounded edges, but a pneumothorax has a convex lung edge. CT has a higher sensitivity in detection of a pneumothorax, as well as in the differentiation of a bulla from a pneumothorax in a COPD patient. This is very significant as, if a chest tube is inadvertently inserted into a bullous, it may cause a large pneumothorax and a resultant bronchopulmonary fistula and associated sequelae.
Reference:
All of the following statements are correct regarding detection of a pneumothorax in a supine patient using bedside ultrasound in the ED EXCEPT:
Answer: C: In a supine patient, including trauma patient, bedside ultrasound can be used to detect or exclude an anteriorly placed pneumothorax. Some of these pneumothoraces are not visualized on a supine chest radiograph. In a trauma patient, the low-frequency curvilinear probe can be used in an extended FAST (eFAST) to look for a pneumothorax. In others, either high-frequency linear probe or curvilinear probe can be used. In the absence of pleural adhesions in the normal lung the parietal and visceral pleurae are opposed and slide on each other during respiration. When there is no air sitting between the two pleural surfaces (i.e. when there is no pneumothorax), this lung sliding can be seen between the shadows of two anterior ribs with ultrasound. The probe should be placed on the anterior chest wall perpendicular to the ribs. Two to three intercostal spaces should be scanned usually in the midclavicular line.
Signs in a normal lung when there is no pneumothorax:
Signs indicating presence of a pneumothorax:
Regarding management of a patient presenting with a first episode of primary spontaneous pneumothorax, which ONE of the following statements is TRUE?
Answer: B: The aim of providing supplemental oxygen to patients with spontaneous pneumothoraces is to accelerate the rate of absorption of air from the pleural cavity. 100% oxygen as a treatment should be provided to patients with small primary pneumothoraces who are admitted to hospital for observation alone. Supplemental oxygen reduces the alveolar partial pressure of nitrogen creating a nitrogen gradient between the pleural space and the alveoli. This increases the air absorption from the pneumothorax into the alveoli. By providing 100% oxygen, the usual 1–2% per day of air absorption can be increased by fourfold. Oxygen has no effect in preventing the rare complication of reexpansion pulmonary oedema.
For small primary pneumothoraces chest tube drainage is not necessary. Even for large primary pneumothoraces it has not shown to be more effective than aspiration. Success rate for aspiration is said to be 45–71%. The success rate of aspiration reduces:
Regarding the selection of an appropriately sized intercostal catheter or tube when treating a spontaneous pneumothorax, which ONE of the statements is TRUE?
Answer: A: The intercostal catheter or tube size should be determined on the basis of the anticipated amount of air leak from the lung. If a large air leak is anticipated a relatively larger catheter or tube should be used to prevent development of a tension pneumothorax. Tension may develop in spite of the presence of a catheter/tube that is inadequate comparative to the amount of air leak. Aspiration of >4 L of air suggests a large air leak from the lung. A large air leak can also be expected from a secondary spontaneous pneumothorax and from a patient who is going to be mechanically ventilated. The following catheter sizes are generally acceptable.
Between 2 and 7% of spontaneous pneumothoraces have associated blood in the thoracic cavity (haemopneumothorax). If this is expected or visible on imaging, a large tube (24F–36F) should be used. French tube size represents the diameter of the tube. 1 French means a diameter of one-third of a millimetre (1/3 mm). For example, 24F = a diameter of 8 mm.
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