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Spectroscopic approach to capillary-alveolar membrane damage: RESULTS AND DISCUSSION (2)

Lung injury

The alveolar HES concentration depends on the levels of circulating HES, as well as on the pulmonary capillary permeability and surface area. IR spectra provide a simple means of grossly estimating the leakage of the pulmonary vasculature. In a patient with no apparent lung injury, the alveolar HES concentration differs markedly from the plasma HES loading (Figure 1). In a healthy lung, only a very low molecular weight fraction of infused HES would be expected to diffuse between the alveolar and intravascu-lar space. Rapid elimination of HES by the kidneys leads to only minor steady-state concentrations of a low molecular weight fraction of HES in the alveolar spaces. Increased pulmonary vascular permeability results in higher molecular weight HES fractions gaining access and penetrating into the alveolar space. As a result, the lung fluid and bronchial washing fluid of an ARDS patient show an accumulation of HES (compare Figures 2B and 1B), which is an indicator of increased pulmonary capillary permeability. An increased pulmonary permeability surface area results in faster intravascular-alveolar HES exchange. Thus, the determination of HES in bronchial washing may be of value in evaluating the progression of ALI/ARDS in a clinical setting. asthma inhalers

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