Abstract
Recent research suggested an important role for pulmonary extracellular adenosine triphosphate (ATP) in the development of ventilation-induced lung injury. This injury is induced by mechanical deformation of alveolar epithelial cells, which in turn release ATP to the extracellular space. Measuring extracellular ATP in exhaled breath condensate (EBC) may be a non-invasive biomarker for alveolar deformation. Here, we study the feasibility of bedside ATP measurement in EBC. We measured ATP levels in EBC in ten subjects before and after an exercise test, which increases respiratory parameters and alveolar deformation. EBC lactate concentrations were measured as a dilution marker. We found a significant increase in ATP levels in EBC (before 73 RLU [IQR 50–209] versus after 112 RLU [IQR 86–203]; p value 0.047), and the EBC ATP-to-EBC lactate ratio increased as well (p value 0.037). We present evidence that bedside measurement of ATP in EBC is feasible and that ATP levels in EBC increase after exercise. Future research should measure ATP levels in EBC during mechanical ventilation as a potential biomarker for alveolar deformation.
Highlights
We suggested an important role for pulmonary extracellular adenosine triphosphate (ATP) in the development of ventilation-induced lung injury or acute respiratory distress syndrome (ARDS) [1]
We found a significant increase in ATP levels in exhaled breath condensate (EBC) after the exercise test as compared to before exercise
ATP levels in EBC increased after exercise, whereas lactate concentrations in EBC remained similar
Summary
We suggested an important role for pulmonary extracellular adenosine triphosphate (ATP) in the development of ventilation-induced lung injury or acute respiratory distress syndrome (ARDS) [1]. At this moment, there is no clinically applicable method to detect extracellular ATP in the lungs. Stretch of the alveolar epithelial type I (AT I) cells results in the extracellular release of ATP [5,6,7]. A nanomolar increase in extracellular ATP stimulates the alveolar epithelial type II cells to release surfactant in the alveolar space [7, 9,10,11]. Extracellular ATP is converted by the CD39 and CD73 enzymes to adenosine and inosine [3, 4]
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