4. Exhaled Breath Condensate (as measure of lung health) There is a growing body of evidence regarding changes in airway lining fluid (ALF) pH in acute and chronic respiratory diseases that are characterized, at least in part, by inflammation. It has been demonstrated that the pH of ALF is low (acidic) in multiple pulmonary inflammatory diseases including asthma28, cystic fibrosis29, pneumonia, and ARDS30-32, and that this pH can be detected continuously, safely and non-invasively in exhaled breath condensate (EBC)33. The pH of EBC may be a safe, non-invasive screening tool for progression of ARDS, and of lung recruitment. It has anecdotally been shown to predict respiratory failure and impending respiratory infection (unpublished data). As seen in Figure 4 (left), the EBC pH is a marker exhibiting rapid turnover and thus may be valuable for real-time monitoring of lung pathology.