APPENDIX C: MEDICAL DEFINITIONS AND TERMINOLOGY

WORLD HEALTH ORGANIZATION DEFINITIONS 1,2

1. Immersion: “some portion of the body is covered in water” (i.e. head is out of the water).

2.Submersion: “during submersion, the entire body, including the airway, is under water” (i.e. head is in the water).

3.Submersion injuries: “water-related conditions that do not involve the airway and respiratory systems.

4. Drowning: “the process of experiencing respiratory impairment from submersion/immersion in liquid.” The drowning process begins with respiratory impairment as the person’s airway goes below the surface of the liquid (submersion) or water splashes over the face while being completely in a liquid (immersion).1-3 Subdivided into 3 categories:

- Fatal drowning: “person dies at any time as a result of submersion/immersion with respiratory impairment.”
- Non-fatal drowning with morbidity: “person is injured at any time as a result of submersion/immersion with respiratory impairment but survives.”
- Non-fatal drowning without morbidity: “person survives uninjured from submersion/immersion event with respiratory impairment but survives.”

5. Water rescue: “submersion or immersion incident without evidence of respiratory impairment.”1-4

6. Shallow water blackout: “hyperventilating to decrease hypercapnic drive to breathe and prolong ability to stay under water such that hypoxemia results in unconsciousness.” The compulsion to breathe from hypercapnia (acidosis) is physiologically more potent than hypoxemia (except when subverted by hyperventilation – e. lowering CO2).5

7. Asphyxia: “a condition where breathing stops and both hypoxia and hypercapnia occur simultaneously due to: (1) the absence of gas to breathe; (2) the airway being completely obstructed; (3) respiratory muscles being paralyzed; or (4) respiratory center failing to send impulses to ” Running out of compressed air is a common cause of asphyxia in SCUBA diving.1,5,6

8. Drowning after shallow water diving: Diving into shallow water makes concussion, head injury, and cervical spine (C-spine) injury more common, so rescuer must balance C-spine precautions against time of extraction (normally in drowning C-spine precautions are not required because the risk is < 0.5%). Also consider drug/alcohol impairment.1,69.

9. Warm water drowning: Unplanned submersion → panic and violent struggle → gulping / swallowing of air and water → breath holding until hypoxia leads to unconsciousness → gag reflex relaxing resulting in passive influx of water → drowning if PFD does not keep airway out of the water.1

10. Cold water drowning: Impacts every organ system similar to complex trauma. Sudden immersion in cold water ( < 91.4°F/33 °C) causes panic, reflexive gasp for air and rapid breathing making:1-5, 8-10

- Inhalation/aspiration of water is more likely.
- Core temperature drop causing arrhythmias, confusion, incapacitation (diminished strength and coordination) increasing the chance of drowning.
- Water conduct heat away from the body 25 times faster than air leading to immersion hypothermia – impaired meaningful movement usually precedes.1,6,8

TERMS NOT TO USE

Terms NOT to use as they do not have diagnostic or therapeutic distinctions (although still widely used by medical professionals and the lay public, so important to be familiar with them).1,4,5,7,8,11

1. Wet drowning: “Fluid is aspirated into the lungs.” Aspiration of water occurs in only 80-90% of cases and does not change the treatment or management.

2. Dry drowning: “Fluid is not aspirated; death is due to laryngospasm and glottis closure.” Asphyxia still occurs secondary to laryngospasm occurring in 10-20% of cases, but no change in management. Difference is only relevant at autopsy.

3. Secondary drowning/Delayed onset of respiratory distress: Varied definitions with death occurring from 1-72 hours after initial resuscitation due to acute respiratory distress syndrome (ARDS). Fifteen percent of victims conscious at initial resuscitation subsequently die from ARDS.

4. Near drowning: “Suffocation by submersion in a liquid with at least temporary survival. Death from near drowning occurs after 24 hours.” Caused confusion because it had 20 different published definitions, most commonly if the person is rescued at any time, thus interrupting the process of drowning.

5. Immersion syndrome: “Sudden death immediately following submersion in very cold water” thought to be caused by vagal nerve stimulation resulting in overwhelming bradycardia.

6. Active drowning: Witnessed drowning.

7. Passive drowning: Unwitnessed drowning.

8. Fresh water vs. saltwater drowning: Typical human aspiration during drowning is 4 mL/kg. To change blood volume requires 8mL/kg, or to alter electrolytes require 22 mL/kg. Therefore, not clinically significant, and instead focus remains on hypoxemia, acidosis, and pulmonary injury rather than electrolyte or volume status.

- Freshwater: Hypervolemia (in animal models only, not humans, so no clinical relevance).
- Saltwater: Hypovolemia with hypernatremia (in animal models only, not humans, so no clinical relevance).

REFERENCES

1. Auerbach’s Wilderness Medicine, 7th Edition, Paul S. Auerbach, Drowning and Submersion Injuries (Chapter 69) (2016).
2. Global report on drowning: preventing a leading killer, World Health Organization (2002).
3. Wilderness Medical Society Practice Guidelines for the Prevention and treatment of Drowning 27, 236-251 (2016).
4. Szpilman, D. et al. Drowning. New England Journal of Medicine. 366(22):2102-2110.
5. US Navy Diving Manual, Rev 7, Commander Naval Sea Systems Command (2016) Drowning/Near-drowning (Chapter 3-5.4).
6. NOLS Wilderness Medicine, 6th Edition, Tod Schimelpfenig, Drowning and Cold-Water Immersion (Chapter 14) (2007).
7. Global report on drowning: preventing a leading killer, World Health Organization (2002).
8. GMO Manual A Medical Reference for the Operational Medical Officer 4th Edition, LT Denis Ashley, Submersion injuries.
9. S. Search and Rescue Task Force, Cold Water Survival.
10. American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular. Circulation 2010;122:S768–S786.
11. Prevention and Treatment of Drowning, Mott & Latimer.