Background. Vest chest physiotherapy (VCPT) enhances airway clearance in cystic fibrosis (CF) by an unknown mechanism. Because cilia are sensitive to nitric oxide (NO), we hypothesized that VCPT enhances clearance by changing NO metabolism. Methods. Both normal subjects and stable CF subjects had pre- and post-VCPT airway clearance assessed using nasal saccharin transit time (NSTT) followed by a collection of exhaled breath condensate (EBC) analyzed for NO metabolites ( ). Results. VCPT shorted NSTT by 35% in normal and stable CF subjects with no difference observed between the groups. EBC concentrations decreased 68% in control subjects after VCPT (before = 115 ± 32？μM versus after = 37 ± 17？μM; ). CF subjects had a trend toward lower EBC . Conclusion. We found an association between VCPT-stimulated clearance and exhaled levels in human subjects. We speculate that VCPT stimulates clearance via increased NO metabolism. 1. Introduction Percussive chest physiotherapy (CPT) is the principal treatment that patients use to facilitate clearance of airway secretions with cystic fibrosis (CF) or other causes of bronchiectasis. Patients have historically used various forms of clapping or mechanical percussion to accomplish this. A number of devices, collectively referred to as vest chest physiotherapy (VCPT), are now available that allow patients to perform airway clearance without the aid of a second person to apply the therapy [1]. Several studies demonstrate the superiority of chest physiotherapy over no chest physiotherapy with regard to clinical outcomes [2]. Chest physiotherapy increases mucus clearance as assessed by mucus volume measurements [3]. The mechanism by which percussive chest physiotherapy modalities enhance airway clearance is not known. Clinicians hypothesize that percussion and shaking loosen adherent mucus and biofilms from the airway surface, making it easier for cough clearance to remove them from the airways. Alternatively, a number of investigators have shown that mechanical stimulation of certain tissue types results in increased epithelial cell release of NO [4]. Because mechanical stimulation increases NO release and airway clearance [5], we hypothesized that VCPT alters metabolism of NO, as measured by oxides of nitrogen ( ) release from the human airway, and is associated with enhanced airway clearance. To test these hypotheses, we measured nasal saccharin transit time (NSTT) and in exhaled breath condensate (EBC) in subjects with and without CF, before and after a therapy session with the VCPT. 2. Materials and Methods This study
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