Continuous regional blood flow determinations with radioactive krypton85

Summary 1. Krypton 85 dissolved in saline was continuously infused for 30 to 90 minutes into the distal aortas of seven dogs, whose aortic blood flows were maintained at a constant measured level by means of a reservoir and pump. 2. From determinations of the Kr 85 concentration of blood samples drawn distal to the infusion, the blood flow could be calculated by the simple dilution principle. 3. The 122 Kr 85 blood flow determinations averaged 105 per cent ± 7.6 per cent of the measured pump flows. 4. Blood samples, proximal to the infusion, demonstrated that recirculation of the Kr 85 did not exceed 5 per cent after 90 minutes of infusion. 5. The method is a simple and practical one, applicable to a variety of situations.