Article Text
Abstract
Background: Acid reflux may aggravate airway disease including asthma and chronic cough. One postulated mechanism concerns a vagally-mediated oesophageal-tracheobronchial reflex with airway sensory nerve activation and tachykinin release.
Aim: To test the hypothesis that patients with airways disease and reflux have higher airway tachykinin levels than those without reflux.
Methods: Thirty-two patients with airways disease (16 with mild asthma and 16 non-asthmatic subjects with chronic cough) underwent 24 h oesophageal pH monitoring. Acid reflux was defined as increased total oesophageal acid exposure (% total time pH <4 of >4.9% at the distal probe). All subjects underwent sputum induction. Differential cell counts and concentrations of substance P (SP), neurokinin A (NKA), albumin and α2-macroglobulin were determined.
Results: SP and NKA levels were significantly higher in patients with reflux than in those without (SP: 1434 (680) pg/ml vs 906 (593) pg/ml, p = 0.026; NKA: 81 (33) pg/ml vs 52 (36) pg/ml, p = 0.03). Significantly higher tachykinin levels were also found in asthmatic patients with reflux than in asthmatic patients without reflux (SP: 1508 (781) pg/ml vs 737 (512) pg/ml, p = 0.035; NKA: median (interquartile range 108 (85–120) pg/ml vs 75 (2–98) pg/ml, p = 0.02). In patients with asthma there was a significant positive correlation between distal oesophageal acid exposure and SP levels (r = 0.59, p = 0.01) and NKA levels (r = 0.56, p = 0.02). Non-significant increases in SP and NKA were measured in patients with cough with reflux (SP: 1534.71 (711) pg/ml vs 1089 (606) pg/ml, p = 0.20; NKA: 56 (43) pg/ml vs 49 (17) pg/ml, p = 0.71). No significant difference in differential cell counts or any other biochemical parameter was noted between study groups.
Conclusion: This study demonstrates increased airway tachykinin levels in patients with asthma and cough patients with coexistent acid reflux. This suggests airway sensory nerve activation in this population.
- FEV1, forced expiratory volume in 1 s
- IQR, interquartile range
- NANC, non-adrenergic non-cholinergic
- NKA, neurokinin A
- N/OFQ, nociceptin/orphanin FQ
- PC20, concentration provoking a fall in FEV1 of less than 20%
- PEF, peak expiratory flow
- SP, substance P
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Footnotes
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Published Online First 24 January 2007
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Funding: None.
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Competing interests: None.