Floatation Test (Hydrostatic Test)
Introduction
- Hydrostatic test is a test done to confirm whether the lungs tested are from a respired newborn or not.
Principle
- If the newborn has respired after birth, the air that has entered the lungs shall remain within the lungs as residual air, which cannot be removed even after death, renders the lung lighter and makes it float in water giving positive result.
Procedure
The procedure of the test includes following steps:
- Put each lung separately into a jar of water, see whether it sinks or floats.
- Cut each into 10 to 12 pieces observe the blood exuding. Test each of them for buoyancy.
- Pick up the floating pieces, and press firmly under water. Observe the nature of bubbles streaming up. Note whether they continue to float or not.
Note: Fix a few lung pieces for histopathological examination.
Interpretation
- If the entire lung floats, it means that the child had not only respired but respiration had been completely established.
- In the absence of putrefaction this test itself is conclusive.
- If some pieces float but others sink, the child has of course respired but for a very short period and ineffectively. Yet it is a live born child.
- If all pieces sink, the child never respired and is stillborn.
Fallacies
- Putrefaction: An unrespired lung may float due to gases of decomposition.
- Oedema lungs, congenital syphilis, pneumonia, lung collapse, etc.: These conditions can make a respired lung sink in water. But unaffected areas may give a clue to respiration having been established if that is the case.
