Distribution of facial and nasal blood flow in the cold loaded dog

Abstract

1. 1 Electromagnetic flow measurements and the tracer microspheres technique were combined to measure total blood flow of the internal maxillary artery (IMA-FLOW) and its flow distribution to the arteriovenous anastomoses (AVA-FLOW) and the capillaries (CAP-FLOW) of the left and right side of the nose and forehead regions together with perfusion pressure (PP) in 9 anaesthetized dogs at blood temperatures ( blood ) of 38, 36 and 34°C. 2. 2 Decrease of T blood to 34°C by internal and external body cooling induced shivering and a significant decrease of IMA-FLOW on either side without any significant effect on PP. The reduction of IMA-FLOW resulted from decreases of CAP-FLOW and of AVA-FLOW. 3. 3 There was an extreme differentiation in CAP-FLOW of the different vascular compartments under normothermic and hypothermic conditions. Lowering T blood produced reductions of CAP-FLOW mainly in those tissues of the face (skin, lips, nasal plane) and nose (alar folds, nasal cartilages) which are normally affected directly by a cold environment. 4. 4 IMA-FLOW as well as AVA-FLOW were linearly correlated with each other and both were related to PR-IMA ina hyperbolic fashion, while CAP-FLOW did not so clearly indicate such a relationship at normal and at reduced T blood . 5. 5 It is concluded that the adjustment of PR-IMA and thus of IMA-FLOW and AVA-FLOW respectively, is achieved for various requirements solely by small neurogenically induced changes in diameter of the resistance vessels. 6. 6 The fact that CAP-FLOW does not exhibit this clear relationship to PR-IMA suggests additional independent influences, either neurogenic or autoregulatory.