Each year thousands of people drown; more than one fifth of them are children. While the majority of children under the age of four tend to drown in residential pools, older children and adults tend to drown outside in lakes, rivers, and oceans. Alcohol is often a contributing factor as is the lack of a personal floatation device. For detailed drowning statistics please visit the CDC website.
Contrary to what is often depicted in movies, the act of drowning often goes unnoticed.
There appears to be three three separate actions or body positions people adopt when confronted with the possibility of drowning. Some will progress through all three stages, others will not depending on their swimming ability, injuries, or illnesses.
- Those who have some swimming ability (perhaps due to a floatation device) often call for help and are able to actively aid in their rescue. They may be vertical (treading water) or horizontal (actively swimming).
- Those who are unable to help themselves assume a vertical position in the water with their arms flailing laterally in a futile attempt to keep their head above water; most do not kick with their legs. They will alternately sink below the surface of the water and reappear. Their mouths are not above the surface of the water long enough for them to speak or breathe and they will quickly sink, usually within 30-60 seconds. They are unable to wave, call for help, or actively aid in their rescue.
- Those who are unresponsive float on or below the surface of the water.
Upon submersion in water 85% of drowning victims involuntarily inhale, flooding their lungs with water; 15% will experience an immediate spasm of their larynx that prevents water from entering their lungs. In both cases, due to a systemic loss of oxygen, the victims will quickly become unresponsive, after a few minutes their hearts will stop, and, in most cases, after roughly five more minutes they will suffer permanent brain damage. If not rescued, all drowning victims will die. If rescued, the unresponsive patient who still has a pulse (but not respirations) has an excellent chance for recovery if positive pressure ventilations (PPV) are started immediately. A patient who has no pulse and no respirations may, with immediate CPR, also recover completely.
Mammalian Diving Response
In rare cases, usually associated with cold water and young children, a few victims may also have a complete recovery if rescued within one hour and CPR started immediately. These "lucky" few will have experienced both a laryngospasm and an immediate shell/core response known as the "Mammalian Diving Response" or MDR. An MDR immediately slows their metabolic processes while preventing water from entering their lungs, thus giving protection for up to one hour. Given the potential for an MDR, CPR should be immediately started on all drowning victims recovered within
- Requires immersion in water colder than 68° F (20° C).
- Initiates a laryngospasm that prevents water from entering the victim's lungs.
- Temporarily stops the victim's breathing.
- Slows the victim's pulse.
- Vasoconstricts nonessential vascular beds and shunts blood to coronary and cerebral circulation.
- Lowers the victim's metabolic rate.
- Is more prevalent in very young (infants and toddlers) but may occur at any age.
- Provides resuscitative protection for up to one hour.
If CPR or rescue breathing (PPV) is successful a patient may still die from delayed pulmonary edema within 72 hours of the near drowning incident. Most near drowning patients aspirate greater than 4 ml/kg; aspiration of 1-3 ml/kg fluid leads to significantly impaired gas exchange. During resuscitation aspirated water is absorbed into the microvascular bed surrounding the alveoli where it may wash out the surfactant and stimulate Mast cell degranulation. If Mast cells degranulate, inflammation will occur and plasma will leak into the alveoli, causing pulmonary edema, respiratory distress, and potentially arrest within 72 hours of the event. The amount of central nervous system damage (due to lack of oxygen and corresponding acidosis) will determine the patient's ultimate outcome. If the period of ischemia is limited or the victim rapidly develops core hypothermia (or an MDR) the damage may be limited and the patient may recover with only minor neurologic sequelae. The incidence of pulmonary edema increases with the amount of particulate matter dissolved or suspended in the water (salt, dirt, sand, chemicals, etc.). Delayed infection is also a potential respiratory complication that may result in the patient's death due to bacteria in the aspirated water.
Just as winter snow brings avalanches, spring rain and snow melt bring flooding and high water. Paddling accidents and fatalities rise along with the water. Be sure to plan your paddling adventures carefully: rig-to-flip, dress for cold water and bring additional warm layers, food and water, have adequate floatation for yourself and your boat, brush up on your rescue skills, scout all major rapids, stay alert for log jams, and hit all the "must-make eddies" above mandatory scouts and portages. In addition, pay attention to stream and river crossings when entering the mountains: hikers are not immune to drowning situations. An unexpected fall on slippery rocks next to fast moving water can quickly become a tragedy without a life jacket and friends equipped and trained for rescue. Remember that cold water (hypothermia), debris, and muddy water often play a part in high water drowning fatalities.
If you do find yourself rescuing a fellow adventurer from the water remember that immediate CPR can occasionally be effective in restoring a victim's pulse and/or respirations. In the event that you do successfully resuscitate a drowning victim it is imperative to immediately evacuate the person to the nearest major hospital as life-threatening pulmonary edema can develop within hours of the incident.
Over the next few months I'll present a number of case studies on near drownings to test your assessment and treatment skills. Stay tuned....