Regional Distribution of Circulating Blood During Submersion Asphyxia in the Duck

Abstract Regional blood flow distribution in ducks was estimated from fractional distribution of Rb 86 CI. A comparison was made between normally breathing ducks and submerged ducks. The data document that conspicuous changes in regional blood flow take place upon submersion. The skin, skeletal muscle, and organs of the gastrointestinal system showed a marked decrease in activity in the submerged condition down to an average of 3.9 % for the gizzard, 29.4 % for skin excised from the thorax and 11.0 % for gastrocnemius muscle. Surprising exceptions to this were displayed by tissues in the cranial part of the animals. Thus both skin and muscle from the head region showed an increase in activity during submersion. The same was true for the excised eye. The esophagus similarly showed an increased activity in the submerged animals. The myocardium from both atria and ventricles showed a striking increase amounting to 4.1 times higher activity in the left ventricular myocardium in the submerged animals. The change in vasomotor constrictor tone taking place upon submersion is thus highly selective and possibly segmentally oriented giving an increase in peripheral resistance to most organs posterior to the heart while the most cranial tissues seem to be subjected to a general decrease in vasoconstrictor tone with an increased blood flow. Activity in the kidneys was markedly consistent and 9.1 % of the value found in normally breathing animals. The adrenals showed an interesting increase in activity on the average as high as 4.9 times the value in normally breathing animals.