Ans. is 'a' i.e., Vagal inhibition Types of drowning Drowning is classified as (1) typical and (2) atypical. 1. Typical drowning (wet drowning) Typical drowning refers to obstruction of air passages and lungs by inhalation of water or other fluid. Therefore it is also called wet drowning and findings offluid and froth are present in PM examination. Typical drowning may be :- Fresh water drowning : In fresh water drowning large quantities of water cross the alveolar membrane into circulation causing hypervolaemia and hemodilution. RBCs imbibe water and burst (hemolysis) with liberation of potossium. Therefore, hea is exposed to volume overload, potassium excess, sodium deficit (hyponatremia), and anoxia. Anoxia and hyperkalemia cause ventricular fibrillation and death in 4-5 minutes. Salt water drowning : Hypeonicity of inhaled water causes loss of fluid from circulation into the lungs giving rise fulminating pulmonary edema with progressive hypovolaemia, circulatary shock, and eventually cardiac standstill (asystole) with death in 8-12 minutes. 2. Atypical drowning It refers to drowning in which even after submersion of body in water, little or no water anters respiratory passages and lungs. Hence typical findings of wet drowning in the form of froth and oedema aquosum of lungs are not found. Atypical drowning may be :- Dry drowning : On contact with water, especially cold water, there results intense laryngospasm, so that water does not enter the lungs. Death is due to asphyxia because of laryngospasm. Immersion syndrome (hydrocution/submersion inhibition/vagal inhibition) : Sudden death occurs due to vagal inhibition as a result of (a) sudden impact with cold water, (b) duck diving (falling in water with feet first), and (c) horizontal entry in water with impact on epigastrium. Submersion of unconscious : If person is unconscious since before submersion in water, little or no water enters respiratory passages. It may occur in MI, cerebrovascular accident, hypeension, epilepsy, cerebral aneurysm and in drunk state. Near drowning (secondary drowning syndrome/post immersion syndrome) : In this drowning is survived and death occurs at a later stage after removal from water. Either the person himself comes out of water or he is recovered alive, but due to complications of submersion, he dies at a later stage. It is due to hypoxic encephalopathy and fibrosing alveolitis. The death occurs due to combined effect of cerebral hypoxia, pulmonary edema, aspiration pneumonitis, electrolyte disturbances and metabolic acidosis.