| The importance of a pneumothorax
is determined not by its size, but by its physiologic effect. An otherwise
healthy person can tolerate a unilateral totally collapsed lung without
problem whereas a person with an underlying lung disease may have extreme
problems with a very small pneumothorax. A trauma patient, however, is a
special case because even a small pneumothorax can quickly become life
threatening when a patient is placed on mechanical ventilation or given
general anesthesia. Thus, pneumothoraces must be looked for meticulously
and the clinical service alerted, even if the patient is not symptomatic.
Generally, 15-38% of blunt trauma patients and 18-19% of penetrating
trauma patients will have pneumothoraces. Free air in the pleural space
will travel to the least dependent portion of the chest. In an upright
person, this will be at the apex of the lung and is usually easily
identified when compared to the adjacent lung. One sometimes confusing
pattern is that of a skin fold trapped between the persons chest and the
film cassette. This can usually be differentiated from a true pneumothorax
by looking for the absence of lung markings beyond the edge of the
presumed lung, (not seen with a skin fold), and by looking for a thin
white line at the lung edge. This white line is the pleural margin and
would not be seen with a skin fold. Although an apical pneumothorax is
generally easy to see, many trauma patients cannot be placed in an upright
position and are studied supine. Thus the least dependent part of the
chest is not the apex, but rather the base of the chest at the level of
the diaphragms. Signs of free air in this location include the Òdeep
sulcusÓ sign where the costophrenic sulcus is significantly lower than on
the contralateral side, hyperlucency of the lung base due to the free air,
and unusually clear definition of the diaphragm and cardiac apex. Although
CT is much more sensitive for pneumothoraces than plain radiography, it is
rarely used solely to look for free air. However, if a patient is to also
have a head or abdomen CT, limited cuts through the chest can quickly
demonstrate the presence or absence of free air of a suspected
pneumothorax. |
Free blood in the chest is seen in 23-51% of
blunt trauma victims and 64-82% of penetrating trauma victims. Usually it
comes from cut or torn low pressure pulmonary vessels and thoracic veins.
Radiography plays a limited role as the fluid is usually clinically
suspected by the presence of decreased breath sounds, dullness to
percussion on physical exam and possible hypotension. Placing a chest tube
is not only diagnostic but in most cases is also the only needed therapy
as the bleeding will resolve on its own. Ten to 15% of patients with
traumatic hemothorax will need a thoracotomy because of massive initial
hemothorax (>1000ml) or because of continued heavy bleeding. Again,
though, this will be clear clinically and radiographs add little to
clinical management. |
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