A conscious victim will hold his or her breath (see Apnea) and will try to access air, often resulting in panic, including rapid body movement. This uses up more oxygen in the blood stream and reduces the time to unconsciousness. The victim can voluntarily hold his or her breath for some time, but the breathing reflex will increase until the victim will try to breathe, even when submerged. The breathing reflex in the human body is weakly related to the amount of oxygen in the blood but strongly related to the amount of carbon dioxide. During apnea, the oxygen in the body is used by the cells, and excreted as carbon dioxide. Thus, the level of oxygen in the blood decreases, and the level of carbon dioxide increases. Increasing carbon dioxide levels lead to a stronger and stronger breathing reflex, up to the breath-hold breakpoint, at which the victim can no longer voluntarily hold his or her breath.
Cardiac arrest and death
The brain cannot survive long without oxygen and the continued lack of oxygen in the blood combined with the cardiac arrest will lead to the deterioration of brain cells causing first brain damage and eventually brain death from which recovery is generally considered impossible. A lack of oxygen or chemical changes in the lungs may cause the heart to stop beating; this cardiac arrest stops the flow of blood and thus stops the transport of oxygen to the brain. Cardiac arrest used to be the traditional point of death but at this point there is still a chance of recovery. The brain will die after approximately six minutes without oxygen but special conditions may prolong this (see 'cold water drowning' below). Freshwater contains less salt than blood and will therefore be absorbed into the blood stream by osmosis. In experiments this was shown to change the blood chemistry and led to cardiac arrest in 2 to 3 minutes. Through osmosis water will leave the blood stream and enter the lungs thickening the blood. In experiments the thicker blood requires more work from the heart leading to cardiac arrest in 8 to 10 minutes. After death, rigor mortis will set in and remains for about two days, depending on many factors including water temperature.
Pediatric Drowning: A 20-Year Review of Autopsied Cases: Demographic Features
Abstract - Somers, Gino R. MD, PhD; Chiasson, David A. MD; Smith, Charles R. MD
Drowning is a significant cause of childhood mortality in the developed world. Males and preschool-aged children are overrepresented in most series of pediatric drowning. To obtain a better understanding of age- and gender-related factors, a retrospective review of autopsy records over a 20-year period (1984-2003) for cases of drowning (exclusive of bathtub drownings) was performed. Sixty-three consecutive cases of drowning were identified in 45 males and 18 females (ratio 2.5; P = 0.0007). The ages ranged from 9 months to 17 years, and most cases occurred in the 0- to 4-year age group (57%). Boys tended to be older than girls (5 years 9 months versus 4 years 4 months; P = 0.2133). Sites of drowning were open water (48%) and pools (44%), with children drowning in open water being significantly older than those drowning in pools (6 years 6 months versus 4 years 6 months; P = 0.0462). Most boys drowned in open water (53%), whereas most girls drowned in pools (50%). Resuscitation was attempted after the drowning episode in 84% of cases, with children aged 4 years or less having significantly higher rates than older children (P = 0.0346). The present study highlights differences in the pattern of drowning according to age and sex and may aid in developing targeted educational and preventative campaigns.
DROWNING FACTS:
•Adults need to be within two feet of a child under the age of five when near water •Drowning victims do not wave their arms around and make lots of noise. Drowning is known as the silent killer •Drowning can take place in as little as 10 seconds •Water wings, arm floaters and inflatable rings or tubes are not effective flotation devices for children •A lifejacket is the best floating device •90 per cent of people who drown while boating were not wearing a lifejacket and alcohol was involved in about one third of the drowning victims •Drowning is the third leading cause of accidental death among Canadians under 60 years of age and the second leading cause of death for children under the age of 10 •Men are four times more likely to drown than women
