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Haematocrit, plasma volume and viscosity were not notably different at rest in fifteen diabetics from those in ten controls. After moderate exercise, plasma volume was reduced and haematocrit was increased significantly more than those in controls. In the diabetic subgroups based on varying degrees of dermal angiopathy, no significant differences were demonstrated. In circulatory steady state during exercise the diabetics responded with a marked increase of systolic blood pressure. The amount of filtrate from the vascular bed to the interstitial tissues was not correlated to increasing systolic pressure. The difference in work intensity between the groups is not of such an order that it can be assumed to influence haematocrit or plasma volume. These findings may indicate increasing permeability of the capillary walls because of changes characteristic of diabetic microangiopathy.

Infrared thermography revealed characteristic abnormalities in the emission patterns over the hands and feet of 16 young diabetics with or without manifest vascular complications. Infrared thermography seems to be a method well suited for further studies of circulation and metabolism in the hands and feet of diabetics.

The rheology of blood cells studied intravascularly, and the relation between blood cells and endothelium was analyzed in vivo by high resolution, vital microscopy in four diabetic patients with varying duration of the disease. In a dipedicled, tubed skin-flap a titanium chamber with optics was implanted. A thin layer of tissue in this chamber was observed microscopically over a period of up to 4 months. Microvascular structure and function were analyzed under normal flow conditions as well as in various test situations with reduced or completely blocked flow in lipaemia and when slight local tissue trauma was added. It was found, contrary to what has hitherto been considered in the literature, that there is no aggregation of blood cells in diabetes, unless the metabolic balance is heavily upset as in acidosis. The rheology of the various types of blood cells is normal even in long-standing diabetes.