Pulmonary Vascular Permeability during the Adult Respiratory Distress Syndrome: A Positron Emission Tomographic Study

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Abstract
The natural history of change in pulmonary vascular permeability (PVP) during the adult respiratory distress syndrome (ARDS) is unknown. Therefore, we evaluated PVP by measuring the pulmonary transcapillary escape rate (PTCER) for transferrin with positron emission tomography (PET) in 15 ARDS patients, including 5 patients studied within 4 days of onset and 13 patients studied at least 7 days after onset. In 3 patients, studies were performed at both early and late stages. These results were compared to 12 non-smoking adult volunteers. Regional PTCER and extravascular lung density (EVD) were determined from a 1-h PET scan after intravenous injection of gallium-69 citrate, which bindsrapidly to native transferrin. Oxygenation, radiologic score, as well as outcome were recorded for each patient. Mean PTCER was highest during the early phase of ARDS (560 .+-. 275 .+-. 10-4 min-1) although PTCER in the late ARDS patients was also significantly higher than in normals (319 .+-. 187 vs 58 .+-. 33 .times. 10-4 min-1; p < .01). EVD was similar in both early and late ARDS groups (.39 .+-. .08 and .37 .+-. .13 g/ml lung, respectively) and markedly higher than in normals (.22 .+-. .05 g/ml lung, p < 0.01). PTCER decreased in each of the 3 serial adults. The correlation between PTCER and EVD was poor, as were correlations for either PTCER or EVD versus changes in oxygenation, radiologic score, survival, or duration of ventilator dependency. In the late ARDS patients, PTCER was usually elevated even if EVD had returned to normal. We conclude that vascular permeability, as documented by PET, is markedly elevated early in the courses of ARDS and that despite improvement, significant abnormalities can persist even 1 to 2 wk after onset.