A coin test (or a bell metal resonance) is a medical

diagnostic test A medical test is a medical procedure performed to detect, diagnose, or monitor diseases, disease processes, susceptibility, or to determine a course of treatment. Medical tests such as, physical and visual exams, diagnostic imaging, genetic t ...

used to test for a punctured lung. A punctured lung can cause air or

fluid In physics, a fluid is a liquid, gas, or other material that continuously deforms (''flows'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are substances which cannot resist any shea ...

to leak into the

pleural cavity The pleural cavity, pleural space, or interpleural space is the potential space between the pleurae of the pleural sac that surrounds each lung. A small amount of serous pleural fluid is maintained in the pleural cavity to enable lubrication b ...

, leading to, for example,

pneumothorax A pneumothorax is an abnormal collection of air in the pleural space between the lung and the chest wall. Symptoms typically include sudden onset of sharp, one-sided chest pain and shortness of breath. In a minority of cases, a one-way valve ...

hydrothorax Hydrothorax is a type of pleural effusion in which transudate accumulates in the pleural cavity. This condition is most likely to develop secondary to congestive heart failure, following an increase in hydrostatic pressure within the lungs. More ...

. In a coin test, a coin held against the chest is tapped by another coin on the side where the puncture is suspected. A

stethoscope The stethoscope is a medical device for auscultation, or listening to internal sounds of an animal or human body. It typically has a small disc-shaped resonator that is placed against the skin, and one or two tubes connected to two earpieces. ...

is placed on the back to listen to breath sounds and the sound of the coins. If a tinkling sound is heard, it is likely that air or fluid has found its way into the

References

* K. George, Matthew, ''Preparation Manual for Undergraduates of Medicine'' * ''Bellmetal resonance'' in Stedman's Medical Dictionary a
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Physical examination {{Med-diagnostic-stub