Final answer:
The cause of death for an individual found floating in a lake without exterior injuries could be drowning. Drowning occurs silently and involves respiratory impairment, leading to hypoxia and potential cardiac arrest. Immediate CPR upon rescue can increase survival chances if administered swiftly.
Step-by-step explanation:
If someone is found floating in a lake with no signs of exterior injury, the cause of death might be drowning, which is defined as respiratory impairment from being in or under a liquid. Since drowning can occur quietly without obvious signs of distress, this might explain why the individual lacks exterior injuries. The mechanism of drowning involves the inability to breathe under water, leading to hypoxia and eventually cardiac arrest if the person is not removed from the water and resuscitated quickly.
Drowning does not typically cause visible injuries as other forms of trauma might. Instead, the hallmark feature is the inability to breathe through the liquid, and any associated symptoms would be internal such as fluid in the lungs or damage to the brain due to lack of oxygen. It's crucial to understand that drowning victims can't always call for help as muscular spasms seal their airway, preventing the passage of both air and water, meaning they may appear deceptively calm on the surface of the water.
Sometimes, environmental hazards such as an outgassing event, like the one at Lake Nyos, can also contribute to drowning if it displaces oxygen around the water surface. However, this is a rare incident. More common causes of drowning include swimming ability, panic in the water, or being unable to reach the surface for air.
In the event of finding someone unconscious in water, immediate CPR should be administered. The earlier CPR is started, the better the chances of recovery, especially if there is no water in the lungs and the airway had been sealed by the laryngeal spasm characteristic of drowning.