Also, fresh water drowning differs from salt water drowning in terms of the mechanism for causing suffocation. Only a small amount of either kind of water is needed to damage the lungs and interfere with the body's ability to breathe. If fresh water is inhaled, it passes from the lungs to the bloodstream and destroys red blood cells. If salt water is inhaled, the salt causes fluid from the body to enter the lung tissue displacing the air.
Nature of inhaled fluid
- fresh water: water quickly absorbed into circulation. May cause haemolysis. Surfactant denatured
- chlorine and soap in fresh water does not appear to be of any adverse consequence for lungs
- sea water: hypertonic fluid promotes rapid fluxes of water and plasma proteins into alveoli and interstitium, dilutes or washes out surfactant and disrupts alveolar-capillary membrane
- both fresh and salt water produce an inflammatory reaction in alveolar-capillary membrane leading to an outpouring of plasma-rich fluid into alveoli. Inhaled gastric contents may contribute to this reaction
- fresh water results in a greater increase in alveolar surface tension than salt water near drowning
- fluid fluxes through lungs can lead to hyper/hypovolaemia. Latter is more common, even in fresh water drowning. Changes rarely sufficient to be life-threatening