Describe the signs of live birth with the hydrostatic test and its fallacies.

External Signs of Respiration

The Lungs and the Hydrostatic Test

• The hydrostatic (floatation, RAYGAT’S) test — performed in a large vessel of cold water → Step 1 — the whole thoracic viscera together (lungs, heart and thymus) are placed in water and observed → Step 2 — the lungs separated from the heart and thymus → Step 3 — each lung separately → Step 4 — the lungs cut into 12 to 20 small pieces, each tested → Step 5 — each piece squeezed firmly under water between the fingers, or rolled with a roller, to expel gas, and retested.
• putrefactive gas is expelled and the piece then sinks
• genuine respired air is held within the alveoli and the piece continues to float → Interpretation — floating at every stage, including after compression, indicates respiration has occurred

Fallacies of the Hydrostatic Test

• The consequence is that the test must never stand alone. It is one element among several, and a report resting on it alone will not survive cross-examination — particularly since the bodies in these cases are usually decomposed

Other Tests of Live Birth

• Breslau’S second life test (the stomach-bowel test) — a child that has breathed also swallows air, so the stomach and intestine contain air and float in water. The stomach and duodenum are ligated at both ends before removal. Its additional value is in timing survival: air reaches the stomach and duodenum within about 1 to 2 hours, the small intestine by about 6 hours, and the large intestine by about 12 hours
• WREDIN’S test (the middle ear test) — the middle ear of a fetus contains a gelatinous plug, which is replaced by air after respiration is established. The middle ear is protected from putrefaction, which is its advantage
• Presence of milk in the stomach — proves not only live birth but survival long enough to have been fed, and is conclusive
• Fodere’s test (absolute lung weight, rising from about 30 g to about 60 g) and Ploucquet’s test (the ratio to body weight doubling from 1:70 to 1:35)

Applied Aspects

• Always perform the compression step; without it a putrefied lung floats and the test is positively misleading, and this is the commonest technical failure in these autopsies
• Ask whether resuscitation was attempted before interpreting a positive test; mouth-to-mouth by a panicking mother introduces air and is a recognised false positive
• Use several tests together — the chest shape, the diaphragm level, the lung appearance and weight, the hydrostatic test, the stomach-bowel test and the middle ear — and state the conclusion on their combination
• A negative test in a decomposed body means nothing, and the report should say so rather than concluding stillbirth; this distinction decides whether the charge is murder or concealment of birth
• Use the middle ear in a putrefied body, where it is protected and the lungs are useless
• Milk in the stomach settles the question, and the stomach contents Weigh the lungs and calculate the ratio; a doubling from about one seventieth to one thirty-fifth of body weight is Ploucquet test
• Note the diaphragm level before removing anything; it lies at the fourth rib before respiration and the sixth or seventh after
• Compare chest and abdominal circumference; the chest is smaller before respiration and larger after, and both are measured in seconds
• Ligate the stomach and duodenum before removal for the second life test, or the swallowed air escapes and the finding is lost
• Air in the large bowel indicates about twelve hours of survival, which converts a question of live birth into one of how long the child lived
• Vagitus uterinus is recognised — a cry before complete birth — showing that a cry alone does not establish separate existence
• The lungs of a premature child may sink despite respiration, and this is the commonest false negative in Indian practice
• Report the tests together and reason from the whole; no single test establishes live birth, and a report resting on one will not survive
• Artificial respiration by a panicking mother introduces air and is a recognised false positive; ask before interpreting the test
• Hyaline membrane disease and pneumonia make the lung dense, so it sinks although the child breathed — a false negative of real importance
• Freezing and thawing makes a lung float, which matters where a body has been refrigerated before autopsy
• Wredin test uses the middle ear, which is protected from putrefaction and answers the question when the lungs cannot
• Squeeze every piece under water; putrefactive gas escapes and the piece sinks, while respired air is held in the alveoli and it floats
• Test the viscera in five stages — together, lungs alone, each lung, pieces, and compressed pieces — and record each result
• Milk in the stomach is conclusive of live birth and of survival long enough to be fed, so the contents are always examined
• Respired lung is mottled pink, crepitant and rounded at the margins, and unrespired lung is liver-like, uniform and sharp-edged
• Fodere test uses the absolute lung weight, rising from about thirty grams to about sixty after respiration
• The lungs of a live-born child overlap the heart, and those of a stillborn lie back in the vertebral gutters
• Record the result of every stage separately; a report saying only that the test was positive cannot be examined by anyone else
• Should always be examined and preserved