Central cardiovascular responses to submersion asphyxia in the duck

Abstract

Pressure recordings from the central systemic veins, the aorta, the left ventricle, as well as intratracheal pressure, have been obtained during simulated dives of domestic ducks. Upon submersion a conspicuous bradycardia gradually developed. The systemic arterial pressure did not change significantly during the profound bradycardia. There was a distinct increase in the central venous pressure and in the diastolic pressure of the left ventricle. The pressure increase surpassed a concomitant intratracheal pressure rise. The circulation time from the right atrium to the base of the aorta was prolonged four to five times during profound bradycardia. The data suggest that the stroke volume remains unchanged or decreases in spite of an increased filling pressure. The increased transit time through the lungs is suggestive of an increased resistance to flow in the pulmonary bed. The data also indicate an increased resistance to outflow from the larger systemic arteries. It is suggested that a marked change in the activity of the autonomic innervation to the myocardium takes place during submersion.

Onset of and recovery from diving bradycardia in ducks

“…Various authors (Andersen, 1963a, b;Johansen & Aakhus, 1963) have found that the cardiovascular response to submersion can be elicited in the duck by simply covering the head with water. This fact was made use of, and the words 'dive' and 'submersion' as applied to the present investigation mean immersion of the head only into water.…”

Cardiovascular responses to diving in the turtle, Pseudemys scripta

“…On the other hand, Johansen and Aakhus (1963) never observed an in crease in blood pressure during the initial stage of submersion. This, they said, means that the bradycardia of diving cannot be due to increased baroreceptor activity.…”

“…All dives lasted 1-2 minutes. Johansen and Aakhus (1963) reported a fall in mean aortic pressure in ducks for even short dives lasting 40-60 seconds. Butler and Jones (1971) found changes in arterial pressure to be variable in diving ducks; there was either no change or a slight de crease in the systolic, mean, and diastolic pressures.…”

“…However, any fall in mean pressure that does occur is not nearly as great as the reduction in cardiac output which scccmpanies a Give. Tne perioneral vascular resistance musu, znerefore, be increased A substantial increase in central venous pressure during the develop ment of diving bradycardia in ducks has been observed (Johansen and Aakhus, 1963;, as well as a decrease in left ventricular contracti 1 'I ty of birds and m anuria 1 s (r errante and Gpdyke, 1959;B i i x et al, 1976;Gross et al, 1976). This increased venous pressure probaoly pro duces an elevated ventricular filling pressure which may, in turn, pro mote an increased ventricular end-diastolic volume.…”

“…Face immersion with breath-holding reduced the cardiac output and stroke volume in man i !<'h it:"i û'i" ^ 1 1 q a"7 1 cnus seems safe to concl uae zns.z in verieora ûe ai vers rhe carciac output decreases upon diving. There is usually either a decrease or no change in stroke volume with submergence (Johansen and Aakhus, 1963;Eisner et al, 1964;Shelton and Jones, 1955;Murdaugh et al, 1965;Lin, 1974) so that reduction in cardiac output is near pr u^ur uiuiia i uv une : a i i in vue nca» v « a vc.…”