Written by Dr. D. Rao

Drowning is a form of asphyxia due to aspiration of fluid into air-passages, caused by submersion in water or other fluid. Complete submersion is not necessary, for submersion of the nose and mouth alone for a sufficient period can cause death from drowning.

Duration of Submersion in Fatal Cases: When a person falls into water, he sinks partly due to the force of the fall, and partly to the specific gravity of the body. Shortly afterwards, he rises to the surface due to the natural buoyancy of the body. In sudden immersion into cold water, the victim may take a deep inhalation of water due to reflex from stimulation of the skin. He may hold his breath for varying periods until the CO2 in his blood and tissues reaches sufficient levels to stimulate the respiratory center. At that time, an inevitable inhalation of water may occur. When he cries for help and struggles, he is likely to inhale water, which produces coughing and drives out large volume of air out of lungs, and leads to disturbance of the rhythm of the breathing. The victim may vomit and aspirate some gastric contents. His struggle increases and again he sinks. If this occurs during inspiration, he will inhale more water. The cerebral hypoxia will continue until it is irreversible and death occurs. With warm water, cerebral anoxia becomes irreversible between 3 to 10 minutes. Consciousness is usually lost within 3 minutes of submersion. The struggle for life with rising and sinking of the body goes on for a variable period, depending on the vitality of a person, until he remains submerged. Convulsive movements then occur, followed by coma or suspended animation and death.

The Mechanism of Drowning: Brouardel carried out experiments with dogs as follows. The four limbs of the dog were fixed to a wooden hoard, and a weight of head was fixed to the lower end. A connula was introduced into the femoral artery to record the blood pressure and heart beats, and a pneumograph attached to the epigastrium for recording respiratory movements. The dog was then lowered into a tub filled with water. The dog’s head was kept about 30cm. below the surface throughout.

The process was divided into five stages.

  1. The stage of surprise lasting for 5 to 10 seconds. The animal inspired once or twice but inactive.
  2. The first stage of respiratory arrest, lasting for about one minute. The dog was violently agitated, fighting against its bonds and obviously trying to reach the surface. The mouth was shut and respiration arrested.
  3. The stage of deep respiration, lasting for about one minute. The dog made some deep inspirations and expelled white foam to the surface. The agitation stopped. The eyes and mouth were open. A few swallowing movements were noted.
  4. The second stage of respiratory arrest, lasting for about one minute. Thoracic movements were not observed. The corneal reflex was lost and pupils were widely dilated.
  5. The stage of terminal gasps, lasting for about 30 seconds. The dog made 3 or 4 respiratory movements. The lips and jaw muscles showed fibrillary contractions. The whole process of drowning of these dogs in fresh water took 3 ½ to 4 minutes. Under identical conditions, sea water is approximately twice as lethal as fresh water. In man, probably the course is similar except rising to the surface once or more. Hypoxic convulsions may occur in the fourth stage.

Kylestra (1965) reported that mice submerged in suitably oxygenated physiological saline solution, could survive for 18 hours. If this medium was replaced by sea water or tap water, the mice succumbed in less than 12 minutes. The volume inhaled is also important. Model (1966) showed that in dogs, if the volume inhaled exceeded 44 ml. Per kg. body weight, the chance of survival was very small. The critical volume of sea water was 22ml. Per kg. In humans, it is believed, similar phenomenon occur in drowning.

Types: Drowning is of four types:

  1. Wet Drowning: in this, water is inhaled into lungs and the victim has severe chest pain. If resuscitated, he has no pleasant recollections.
  2. Dry Drowning: In this type, water does not enter the lungs, but death results from immediate sustained laryngeal spasm due to inrush of water into the nasopharynx or larynx. Thick mucus, foam and froth may develop, producing a plug. This is seen in 10 to 20% cases of immersion. Resuscitated victims have panoramic views of past of life and pleasant dreams without distress.
  3. Secondary Drowning: (post-immersion syndrome or near drowning): In this type, death occurs from within half hour to several days after resuscitation. Electrolyte disturbances and metabolic acidosis occur. Death occurs from cerebral anoxia with irreversible brain damage. Microscopically, the lungs show haemorrhage, desquamative and exudative reaction. Later changes are of inhalation pnemonitis with hyaline membranes in alveolar ducts, and foreign body reaction to inhaled particles, progressing to bronchopneumonia or abscess formation. The loss of the normal surfactant by the inhaled water can result in large areas of atelectasis. Death may occur from cerebral anoxia with irreversible brain damage. Myocardial anoxia may cause delayed heart failure.
  4. Immersion Syndrome (hydrocution or submersion inhibition): Death results from cardiac arrest due to vagal inhibition as a result of
  1. (a) cold water stimulating the nerve endings of the surface of the body,
  2. (b) water striking the epigastrium,
  3. (c) cold water entering ear burns, nasal passages, and the pharynx and larynx which cause stimulation of nerve endings of the mucosa. Falling or diving into the water, feet first, or “duct-diving” by the inexperienced, or diving involving horizontal entry into the water with a consequent blow on the abdomen cause such accident. Alcohol increases such effects, due to the general vasodilatation of skin vessels, and possibly by some central effects on the vasomotor center. This is seen in one to 2% of cases of drowning.
The Pathophysiology of Drowning: The pulmonary alveolar lining is semi-permeable. If water enters the alveoli, an exchange of water takes place through the alveolar lining. The extent and direction of this exchange depends on the difference between the osmotic pressure of the blood and the water.
  1. Drowning in Fresh Water or Brackish Water: In drowning in fresh water (0.6% NaCl), water passes rapidly from the lungs to the blood, leading to haemolysis and dilution of the blood, with an abrupt increase in blood volume. 2.5 liters or more of water may be inhaled and absorbed in three minutes. Fresh water alters or denatures the protective surfactant which lines the alveolar wall, while sea water dilutes or washes it away. The denaturing of surfactant can continue even after a person if successfully resuscitated. Loss or inactivation of pulmonary surfactant and alveolar collapse decrease lung compliance, resulting in severe ventilation perfusion mismatch, with up to 75% of the blood perfusing non-ventilated areas. When water is inhaled, vagal reflexes cause increased peripheral airway resistance with pulmonary vasoconstriction, development of pulmonary hypertension, decreased lung compliance and fall of ventilation perfusion ratios. The conentration of serum electrolytes (sodium and calcium) decreases considerably. The serum potassium increases. The causes rapid overburdening of the heart and produces pulmonary oedema. The oedema fluid contains serum proteins. The heart is subjected to hypoxia, overfilling, sodium deficit and potassium excess. Cardiac arrhythmias leading to ventricular tachycardia and fibrillation occur, probably due to hypoxia and haemodilution. Haemodilution leads to haemolysis, haemoglobinaemia, and haemoglobinuria, marked hyponatraemia and hyperkalaemia. Calcium levels may fall to 2 mEq/L.
  2. Drowning in Sea Water: Due to the high salinity of sea water (usually over 3% NaCl), water is drawn from the blood into the lung tissue, and produces severe pulmonary oedema, and hypenatraemia. This causes haemoconcentration. Simultaneously, in an attempt to re-establish osmotic balance, salts from the water in the lungs pass into the blood stream. Slow death occurs from asphyxia.

Causes of Death: [1] Asphyxia Inhalation of fluid causes obstruction to the air-passages. Circulatory and respiratory failure occurs simultaneously, due to anoxia of both the myocardium and the respiratory center. [2] Ventricular fibrillation, in fresh water drowning death may occur in 3 to 5 minutes from a combination of anoxia, and a disturbed sodium-potassium ratio producing arrhythmias of the heart beat, ventricular tachycardia and fibrillation. [3] Laryngeal spasm may result from inrush of water into the nasopharynx or larynx. [4] Vagal inhibition is due to icy cold water, high emotion or excitement and unexpected immersion. [5] Exhaustion. [6] Injuries: Fracture of skull and fracture-dislocation of cervical vertebrae may occur due to the head striking forcibly against some solid object. Concussion may occur due to striking the head against some hard substance, or the water itself while falling from a height.

Fatal Period: Death usually occurs in 4 to 8 minutes of complete submersion.

DIATOMS: They are microscopic unicellular or colonial algae. They have a complex structure of their cell-walls which are usually strongly impregnated with silica and contain chlorophyll and diatomin, a brown pigment. Diatoms belong to class Bacillariophyceae. Diatom secretes hard siliceous outer box-like skeleton called a frustule. They resist heat and acid. There are about 15,000 species. They vary considerably in size from 2 microns to one mm. in length or diameter. Most species are from 10 to 80 microns in length and if elongated, up to 10 microns in width. Diatoms measuring up to 60 microns in diameter are said to enter the pulmonary circulation during drowning. The diatom skeletons are readily recognizable as radially or axially symmetrical structures. They vary from place to place, and there are seasonal variations at the same place. They occur in cultivated soils and on surface of most rocks. Large numbers of free floating diatoms are found in both fresh water and sea water. Their shape may be circular, triangular, oval, rectangular, linear, crescentric, boat-shaped, etc. They may be demonstrated in human organs by: 1] direct digestion of the material with nitric acid and sulphuric acid, 2] incineration in electrical oven and then dissolving the ashes with nitric acid, 3] direct microscopic examination of the lungs. Water is squeezed out from the lungs, centrifuged and sediment examined, 4] microscopic examination of tissue section, whereby optically empty sections are produced.

The drowning fluid and the particles in it, e.g., diatoms and planktons, pass from the ruptured alveolar wall into lymph channels and pulmonary veins and thus enter the left heart. Only a live body with a circulation could transport diatoms from the lungs to the brain, bone marrow liver and other viscera, and skeletal muscle. They are also found in the bile and rine. The bone marrow is highly suitable and reliable. The bone marrow of long bones, such as the femur, tibia and humerus or sternum is examined for diatoms. The sternum is washed in distilled water. The periosteum is removed from the posterior surface. A piece of rectangular bone is removed with a sharp and clean knife and the marrow is curetted out from the gutter. Kidney, lung, liver or brain is also washed and 1x1 cm. pieces cut from the deeper tissue.

Technique: Five grams of bone marrow or each piece of tissue is put in a separate test tube and covered with five times the volume of concentrated nitric acid, and left at room temperature for one to two days to allow digestion. Alternatively, they can be heated in a water-bath overnight. This process chars, blackens, and destroys organic matter. Diatoms have silica shells and as such are not destroyed, the tube is centrifuged, the supernatant acid poured off and replaced with distilled water. This process is repeated 2 pr 3 times to dilute the acid. The deposit is examined under phase contrast or dark-ground illumination. The number of diatoms found in the tissues is relatively small.

Control samples of about 2 liters water should be obtained from the site of accident for comparison. About 15ml. Of iodine solution is added to this and allowed to settle overnight. The bulk of the water is poured off and the remainder centrifuged to recover diatoms. The finding of similar diatoms in the water and in the body tissues is in favour of drowning.  Recent evidence indicates that diatoms from the alimentary canal may enter the circulatory system and reach the various organs in the body, and occasionally may be found in cases other than drowning. The finding if not absolutely diagnostic, is of the greatest value, especially in cases of putrefaction.

Plasma Specific Gravity:  In drowning, the specific gravity of plasma from the left side of the heart is less than that of the plasma in the right side. In non-drowning cases the reverse is the case.

Dead bodies are commonly found immersed in water and other fluids in all manner of places and circumstances. Such cases prove the most difficult medico-legal problems. The circumstances surrounding each individual case are important. It should be remembered that drowning is not limited to deep water situations like sea, tanks, rivers, lakes, wells, etc., but unconscious person can fall face down in a puddle or ditch and die of immersion. In most cases of drowning, the diagnosis of forensic pathologist is based largely n the history and investigative reports of the case.

Diagnosis: The autopsy diagnosis of drowning can pose problems, because the findings are often minimal, obscure or completely absent. When the findings are negative, cause of death may be given as “consistent with drowning” or even to admit that the cause of death is “undetermined”. The reliable signs of drowning at autopsy are: 1] Fine, white froth at the mouth and nose. 2] The presence of weeds, stones, etc., firmly grasped in the hands, 3] The presence of fine froth in the lungs and air-passages. 4] The voluminous water-logged lungs. 5] The presence of water in the stomach and intestines, and 6] Findings of diatoms in the tissues.

The above signs will not be found, if death occurs due to vagal inhibition. In death from syncope, or when a person is in a state of helplessness from drink or other cause, or when a person receives an injury during fall into the water which prevents him from struggle, the signs will be slight. In dry drowning, the post-mortem appearances are those of asphyxia. A body removed from water undergoes rapid decomposition. If the post-mortem is delayed for a few hours, or if any appreciable delay has occurred before recovery of the body from water, the signs of drowning will not be found to great extent.

If the body remains in water, lividity appears in the head, neck and chest, and putrefaction begins in the same place and produces the appearance of diffuse scalp haemorrhage. The blood becomes more fluid and water is found in gradually increasing quantity in the pleural cavities. In moderately advanced putrefaction the diagnosis is difficult, the only evidence being the presence of water in the pleural cavities due to diffusion of water from the lungs, which finally collapse, and froth in bronchi. In advanced putrefaction the signs are completely absent. Algae get attached to exposed portions of drowned bodies, multiply and from a layer over the skin, which may be seen in 3 to 4 days in summer.

The Circumstances of Drowning: Bodies recovered from water may have died of: 1] natural disease before falling into the water, 2] natural disease, while already in the water, 3] injuries before being thrown into water, 4] injury while in water, 5] drowning. The manner of death cannot be interpreted from an autopsy alone. The findings have to be viewed together with the circumstances.

Accidental Drowning:

  1. Death in the Domestic Bath: A sudden collapse from coronary or cerebrovascular disease may cause loss of consciousness, leading to immersion of head and death. Similarly, epilepsy or a fall producing a disabling head injury may also cause death. Other causes include CO poisoning, alcohol or drug intoxication and electrocution. In such cases, it should be established whether the head was really in the water and if so, whether the water was inhaled. A sample of the bath and tap water should be collected. Bruising of the head is usually seen from falling or being struck. Grip marks (finger-tip bruises) on legs or arms indicate forcible immersion. Natural disease should be excluded at autopsy and the viscera preserved for chemical analysis.
  2. Death of Newborn Infants: In precipitate labour, the baby may fall into lavatory pan or bucket and die. Microscopy of the lungs and examination of the fluid in air-passages may be helpful. Foreign material inhaled into the lung parenchyma or passages may be seen and compared with a sample of fluid from bucket or lavatory pan. Chemical analysis of fluid in the air-passages, e.g., for soap or disinfectant agents present in the fluid in the lavatory or bucket is helpful.

Occasionally, swimmers, fishermen and dockworkers may be drowned accidentally, but it is common in non-swimmers. It also occurs while bathing in tanks, rivers or sea. Women may fall accidentally into a well while drawing water from it. Children may fall in ponds or lakes while playing near their banks. Usually, children die from frowning in shallow water, but adults usually epileptics, o under the influence of drink or drugs, or collapse due to coronary artery disease or dizziness due to hypertension may fall face down into shallow water and die.

Accidental drowning in the swimming pool sometimes results from jumping off the diving board. Impact of the forehead on the floor of the pool may cause hyperextension of the head and loss of consciousness with subsequent inhalation of water. In such cases, haemorrhages are seen in the deep neck muscles in the region of C1 and C2 with or without vertebral fractures.

Hyperventilation Deaths: For swimming for a longer time than normal under the water, the swimmer may hyperventilate before jumping into the water, due to which CO2 tension is very much lowered. While swimming under the water, oxygen is utilized and CO2 is produced, but the CO2 tension does not rise sufficiently to irritate the respiratory center and cause air-hunger, due to its abnormally low starting point. He may suddenly lose consciousness and drown.

Drowning in Skin and Scuba Diving: In skin diving simple mask and fins are used. The hazards are similar to those of swimming. Scuba Diving enables prolonged independent stay under the water. Serious accidents are caused n equipment failure, environmental factors, or human factors, e.g., exhaustion, panic, pre-existing disease, improper use of equipment. Hazards of scuba diving are drowning, barotraumas (pressure changes associated with descent or ascent), bends (Caisson’s disease), acute pulmonary oedema, emphysema, pneumothorax, air embolism, etc. In scuba diving, frequently there is entrapment of air within the lungs on rising from the depths, producing fatal or non-fatal extra-alveolar air syndrome. Air escapes from the alveoli and may result in interstitial emphysema, pnemothorax or air embolism. This is caused by disproportionate expansion of air-containing alveoli, as compared to the adjacent fluid-filled vascular changes during to rapid an ascent.

Suicidal Drowning: In India, drowning is a common method of committing suicide especially amongst women, and more particularly in localities nearby the sea or river or canal. In case of a woman, the body is usually fully dressed. Suicides usually remove some of their outer clothing or shoes before leaping into the water. In a non-swimmer, a naked body suggests suicide. Suicides may drown themselves in very shallow water, or even by putting the head in a pail or cistern. In a body is found with heavy weights attached to it, it must be either homicide or suicide, and with children homicide alone. The nature of the weights, whether they are tied by ligature or fixed in clothing or found in the pockets are important. Sometimes, suicides tie their hands or legs together, and in such case the manner of tying, and the knot of the rope or ligature should be examined to determine whether they could have been made by the suicide himself. Suicidal drowning may be preceded by the swallowing of the poison, cutting the throat or other suicidal attempts. Injuries may be caused during fall, especially if the bodies are found in the wells. Unless there are strong currents, the body will not move very far from its initial position.

Homicidal Drowning: Murder by drowning is very rare, except in the case of infants and children. A person may be pushed into a river or into the sea. Marks of strangulation or throttling or severe violence applied to the head are presumptive of homicide. Bruises are strongly suspicious. Homicidal drowning in shallow water is possible, if the assailants hold the victim’s head in such a position as to cover the nostrils and mouth. Signs of struggle or marks of violence on the body are likely to be found in such cases. If a person is taken unawares or rendered senseless and defenseless by alcohol or hypnotic drugs, and head is submerged in water for 5 to 10 minutes, no marks of violence will be found on the body.

Injuries on Drowning Persons: Wounds may be produced before, at the time of, or after immersion. Before immersion, they may be of accidental, suicidal or homicidal origin. At the time of immersion, the deceased striking hard objects, such as rocks or stone, may produce them. After immersion, injuries may be produced from the striking of the body into rocks, coral or marine structures. As the body floats along the bottom, abrasions may occur on the head, face, backs of the hands, knees and the toes. The body may be hit by ship’s propeller, which may produce often parallel, long and deep cuts and amputation. Aquatic life (fish, crabs, lobsters, eels, crustaceans, etc.) attack and destroy soft parts of the face, i.e., eyelids, lips, nose, ears, penis, scrotum, and also anus. The lesions are circular or oval and punched-out.

Probable Duration of Submersion: Body heat is lost about twice as rapidly in water than in air, and the temperature of the medium is reached in about 14 hours. The time of floatation of body varies greatly. Very obese persons and infants float more readily than thin or heavily-framed persons. The body floats in about 12 to 18 hours in summer, and 18 to 36 hours in winter in India. In cold countries the body floats in about 2 days to one week or more, depending on temperature of the water. The epidermis and nails are loosened and the skin of the hands and feet may be peeled off like glove or stocking in 2 to 4 days. In advanced decomposition, the body usually floats belly up.