Spectroscopic approach to capillary-alveolar membrane damage induced acute lung injury

Acute (or adult) respiratory distress syndrome (ARDS) is often associated with a high mortality rate in the critical care population. The term acute lung injury (ALI), a primitive phase of ARDS, was introduced by the European and American consensus groups to provide early diagnoses of ARDS. The pathophysiological characterization of ALI/ARDS - an increased pulmonary capillary-alveolar membrane barrier permeability - is generally not included in current intensive care unit diagnosis criteria.

To apply the infrared (IR) spectroscopic technique, in combination with the administration of hydroxyethyl starch (HES), to patients with ALI and ARDS.

This retrospective study involved 67 patients from the intensive care unit at the Health Sciences Centre, University of Manitoba, Winnipeg, Manitoba. The methodology was based on the IR spectroscopic determination of HES in patient's bronchial washing fluid. Exaggerated infiltration of HES into the alveolar space was taken as evidence of damage to the pulmonary capillary-alveolar membrane, which in turn provided a diagnosis of ALI/ARDS.

The accuracy of determining pulmonary HES leakage in severe lung injury (Partial pressure of arterial oxygen/fraction of inspired oxygen [PaO2/FiO2] less than 100 mmHg [n=10]), was 100%. The subgroups with PaO2/FiO2 between 100 and 200 mmHg (n=23), and PaO2/FiO2 between 200 and 300 mmHg (n=22), 56.5% and 77.3%, respectively, showed IR positive for HES leakage.

The proposed IR bronchial washing assay is very sensitive in determining the pulmonary HES leakage in severe lung injury. It is also suitable for evaluating pulmonary leakage at an early phase of the injury, a fact that is particularly important for supportive treatment. The method is advantageous because no radioactive tracers are employed, little sample preparation is required, and it is rapid and minimally invasive, making it convenient to use in the critical care environment.