MEASUREMENT OF THE PULMONARY VASCULAR GRANULOCYTE POOL

We have developed a technique for measuring the pulmonary granulocyte pool (PGP) as a fraction of the whole body total blood granulocyte poo l (TBGP). The technique ''captures'' a dose of Tc-99m-labeled granuloc ytes in a region of interest (ROI) over the lung during first pass by integrating an input time-activity curve from an ROI over the pulmonar y artery, superior vena cava, or right ventricle. The ratio of the est imated first-pass count rate and the count rate in the same lung ROI a fter equilibration of the cells between the circulating and pulmonary pools (15-30 min) represents the PGP/TBGP. The technique was validated in eight subjects by using Tc-99m-labeled macroaggregated human serum albumin. With corrections for background and injected doses, the rati os of first-pass granulocyte-to-macroaggregated human serum albumin co unt rates given by the three input ROIs were close to unity [superior vena cava 0.98 +/- 0.079 (SD), right ventricle 1.01 +/- 0.070, and pul monary artery 0.97 +/- 0.073]. Significant increases in PGP/T'BGP were demonstrated in systemic inflammation. Thus, in patients with inflamm atory bowel disease, it was 0.22 +/- 0.07 (n = 7) compared with 0.08 /- 0.01 (n = 5) in control subjects. It was also elevated in patients with systemic vasculitis (0.34 +/- 0.07:, n = 5), in transplant recipi ents (0.33 +/- 0.08; n = 5), and In patients with osteomyelitis (0.15 +/- 0.06; n = 4). We conclude that this is a valid technique for quant ifying the PGP that is expanded in several conditions associated with systemic inflammation.