Shiferaw D, Jackson W, Burke JM, Morjaria JB, Morice AH. European Respiratory Journal. 2012 Sept;40:1685.
OBJECTIVES: To assess pharyngeal gaseous pH in patients who failed to respond to NF.
RESULTS: Total of 22 patients (18 female) with a mean age of 45 (range 22-72) constituted the study population. All of these patients continued to have troublesome cough evidenced by a high Hull Cough Hypersensitivity Score with a mean score of 39(range 25-66), normal < 12.15(68%) of these patients had an abnormal airway pH study with a mean upright Ryan score of 145 (range 17.72-573.46), normal < 9.41. All of the 7 patients who had 24 hour oesophageal pH monitoring had a normal DeMeester score with a mean of 3.47(range0.5-11.7), normal < 14.72.Out of the 7 with normal DeMeester 5 had an abnormal airway PH with a mean Ryan score of 175.28 (range 17.5-573.46).
CONCLUSION: The data suggest that NF eliminated significant acid liquid reflux. A significant proportion of patients continued to have airway gaseous reflux as evidenced by a positive Ryan score. This implies that the aetiology of chronic cough lies in impaction of gaseous reflux in the pharynx and upper airways rather than the liquid reflux detected on conventional testing.