External examination and autopsy findings are often non-specific, and the available laboratory tests are often inconclusive or controversial. The purpose of an investigation is generally to distinguish whether the death was due to immersion or whether the body was immersed postmortem. The mechanism in acute drowning is hypoxemia and irreversible cerebral anoxia due to submersion in liquid.Drowning would be considered a possible cause of death if the body was recovered from a body of water, near a fluid that could plausibly have caused drowning, or found with the head immersed in a fluid. A medical diagnosis of death by drowning is generally made after other possible causes of death have been excluded by a complete autopsy and toxicology tests. Indications of drowning are seldom completely unambiguous and may include bloody froth in the airway, water in the stomach, cerebral edema and petrous or mastoid hemorrhage. Some evidence of immersion may be unrelated to the cause of death, and lacerations and abrasions may have occurred before or after immersion or death.Diatoms should normally never be present in human tissue unless water was aspirated. Their presence in tissues such as bone marrow suggests drowning; however, they are present in soil and the atmosphere, and samples may easily be contaminated. An absence of diatoms does not rule out drowning, as they are not always present in water. A match of diatom shells to those found in the water may provide supporting evidence of the place of death.
This alternation is repeated until vital signs are re-established, the rescuers are unable to continue, or advanced life support is available.For babies (very small sized infants), the procedure is slightly modified. In each sequence of rescue breaths (the 5 initial breaths, and the further series of 2 breaths), the rescuers mouth covers the babys mouth and nose simultaneously (because a babys face is too small). Besides, the intercalated series of 30 chest compressions are applied by pressing with only two fingers (due to the body of the babies is more fragile) on the chest bone (approximately on the lower part). Attempts to actively expel water from the airway by abdominal thrusts, Heimlich maneuver or positioning head downwards should be avoided as there is no obstruction by solids, and they delay the start of ventilation and increase the risk of vomiting, with a significantly increased risk of death, as the aspiration of stomach contents is a common complication of resuscitation efforts.Treatment for hypothermia may also be necessary. However, in those who are unconscious, it is recommended their temperature not be increased above 34 degrees C. Because of the diving reflex, people submerged in cold water and apparently drowned may revive after a relatively long period of immersion. Rescuers retrieving a child from water significantly below body temperature should attempt resuscitation even after protracted immersion.