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. Design 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 10 cm 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-α 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. Presented in part at the 2003 meeting of the European Society of Intensive Care Medicine.