Ultrasonography has been shown to have high sensitivity (95%),
specificity (100%), and diagnostic effectiveness (98%) for pneumothorax
when compared with CT as a standard. It is useful for
detecting small collections not seen on plain films and the extent of
the air collection can be estimated by tracking the presence of the
‘sliding lung sign’ over the chest wall. Experience in the use of
ultrasound for this indication is required to be confident in its application.
It is difficult or impossible to visualize pleural structures
with ultrasound through surgical emphysema.