Relationship between pressure-volume curve and markers for collagen turn-over in early acute respiratory distress syndrome

Objective: In acute respiratory distress syndrome, the relationships between changes in the elastic behavior of the respiratory system and biological markers of extra-cellular matrix or surfactant turn-over could give some insights into its pathophysiological determinants. Desighn and measurements: In 17 patients with acute respiratory distress syndrome, we assessed the relationship between chord compliance measured on pressure-volume curves obtained at two levels of positive end-expiratory pressure (0 and 10cm H2O) and biological markers of collagen turn-over or surfactant degradation in bronchoalveolar lavage fluid obtained simultaneously in the early phase of the disease (first 4 days). Main results: The compliance of the respiratory system obtained from the pressure-volume curves was significantly correlated with markers for collagen turn-over (type III procollagen peptide and matrix metalloproteinase 2) and with markers of surfactant degradation (type-IIA secretory phospholipase A2). The correlations were stronger when the curve was traced from positive end-expiratory pressure, suggesting that this condition may improve the assessment of tissue mechanics. A logarithmic relationship best described the correlation between compliance and type III procollagen peptide, in agreement with a collagen-dependent model of maximal distension. The marker for surfactant degradation was associated with ongoing alveolar inflammation (cellularity of bronchoalveolar lavage fluid and tumor necrosis factor-alpha concentration). Interleukin-10, an anti-inflammatory mediator, showed no correlation with compliance. Conclusion: These preliminary data suggest that a severe reduction in compliance in the early phase of acute respiratory distress syndrome is associated with both collagen deposition and surfactant degradation.