Distribution of ventilation and perfusion in the sea snake,Pelamis platurus

Summary

• 1) The distributions of ventilation and perfusion in the single elongated lung of the totally aquatic sea snake,Pelamis platurus were studied by observing inspiration and subsequent elimination of¹³³Xe gas and by measuring regional activity of^99mTc labelled macroaggregated albumin introduced into the lung via the posterior vena cava.

• 2) The distributions of the two labels were similar along the lung in snakes floating horizontally (Fig. 6). This indicated a uniformity of ventilation-perfusion ratio throughout the lung that promotes efficient gas exchange. Axial movement of¹³³Xe was slow (Fig. 1) and voluntary mixing of the gas was not observed (Fig. 3). However, head up tilting collapsed the posterior saccular portion of the lung and mixed the gas (Fig. 4).

• 3) Right to left shunts totalled about 50% of the systemic blood flow during voluntary breathing.