Effect of acute haemorrhage and autotransfusion on respiration in the pig.

The effect of haemorrhage and transfusion of blood on minute ventilation, VE, in eight anaesthetized pigs was studied by bleeding the animals from the jugular vein and retransfusion of the same quantity of blood. Bleeding the pig from the jugular vein at approximately 50 ml/min, during 2 min, decreased V/ by 8.4 +/- 5.6 per cent of the pre-bleeding control valve (p = 0.0004) and when the same quantity of blood was retransfused the VE increased by 11.8 +/- 12.4 per cent (p=0.03). The possible mechanisms are discussed. We conclude that: a) mechanoreceptors localized in pulmonary circulation play an important role in the VE response during the first seconds of venous haemorrhage and venous transfusion, b) autotransfusion from moving legs and its effect on pulmonary mechanoreceptors may explain in part hyperpnoea at the onset of muscular exercise.