Measurement of circulating ICAM-1 in patients with acute lung injury on ventilators in intensive care unit

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Serum levels of circulating inter cellular adhesion molecule-1 (ICAM-1) were measured by usign a sandwich-type Enzyme Linked Immunosorbent Assay (ELISA) kit (R&D System Inc). cICAM-1 was detected in the serum of fifteen normal healthy volunteers with an age range of 20 to 56 years, who had an average level of 172.4 ng/ml and a range of 92.59 ng/ml to 305.32 ng/ml. A significant elevation of cICAM-1 levels was observed (P < 0.0006) in patients with acute lung injury as compared with the normal. The trends of the patients' cICAM-1 were determined by sequential measurements during their stay in ICU. Seven patients demonstrated a rising trend of serum cICAM-1. The remaining patient showed a falling trend, with a marked elevation (>1300 ng/ml) of cICAM-1 level on the day of admission into ICU. The cICAM-1 levels of the eight patients were correlated with two clinical parameters: ratio of arterial oxygenation to inspired oxygen fraction (PF ratio), and pressure adjusted heart rate. Despite a poor correlation of cICAM-1 levels with the PF ratio, cICAM-1 levels were elevated to at least 400 ± 20 ng/ml, when the PF ratio was low (<300). The infection pattern in these patients were also analyzed by bacteriological investigations done on clinical samples. The measurements of cICAM-1 levels may be important in understanding the pathophysiology of critically ill patients with acute lung injury. Further studies on the immunological mechanism and modulation of the injurious inflammatory response may benefit critically ill patients with the development of effective immunotherapy.