Pneumothorax - Open
An open pneumothorax occurs when there
is a pneumothorax associated with a chest wall defect,
such that the pneumothorax communicates with the exterior.
During inspiration, when a negative
intra-thoracic pressure is generated, air is entrained
into the chest cavity not through the trachea but through
the hole in the chest wall. This is because the chest
wall defect is much shorter than the trachea, and hence
provides less resistance to flow. Once the size of the
hole is more than 0.75 times the size of the trachea,
air preferentially enters through the thoracic cavity.
This results in inadequate oxygenation
and ventilation, and a progressive build-up of air in
the pleural space. The pneumothorax may tension if a flap
has been created that allows air in, but not out.
Diagnosis should be made clinically
during the primary survey. A wound in the chest wall is
identified that appears to be 'sucking air' into the chest
and may be visibly bubbling - this is diagnostic.
Breathing is rapid, shallow and laboured. There is reduced
expansion of the hemithorax, accompanied by reduced breath
sounds and an increased percussion note. One or all of
these signs may not be appreciated in the noisy trauma
100% oxygen should be delivered via
a facemask. Consideration should be given to intubation
where oxygenation or ventilation is inadequate. Intubation
should not delay placement of a chest tube and closure
of the wound.
The definitive management of the open
pneumothorax is to place an occlusive dressing over the
wound and immediately place an intercostal
Rarely, if a chest drain is not available
and the patient is far from a definitive care facility,
a bandage may be applied over the wound and taped on 3
sides. This, in theory, acts as a flap-valve to allow
air to escape from the pneumothorax during expiration,
but not to enter during inspiration. This dressing may
be difficult to apply to a large wound and it's effect
is very variable. As soon as possible a chest drain should
be placed and the wound closed.