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BackgroundChronic cough is a common problem, frequently caused or exacerbated by acid reflux. Diagnosis of acid reflux cough is haphazard currently, often relying on long therapeutic trials of expensive medications. We tested the hypothesis that the most relevant mechanistic component of acid reflux in chronic cough is when it rises to the level of the airway where acid can potentially be aspirated. We further wished to determine if multi-sample exhaled breath condensate (EBC) pH profiles can identify chronic cough patients likely to respond to proton pump inhibitor therapy.Methods59 subjects were recruited for this study. Initially we examined EBC pH (gas-standardized with Argon) in the setting of 15 experimental pharyngeal acid challenges to determine duration of EBC acidification. Subsequently, we enrolled 22 healthy subjects to determine a normal multi-sample exhaled breath condensate pH profile over 1–3 days. We additionally obtained multi-sample EBC pH profiles in 22 patients with chronic cough. These samples were timed to occur after coughing episodes. Exhaled breath condensate pH was measured after gas standardization.ResultsWe found that exhaled breath condensate pH is substantially reduced for approximately 15 minutes after pharyngeal acid load. Healthy subjects rarely have any low EBC pH values (defined as < 7.4 based on a normative reference range from 404 healthy subjects). Patients with chronic cough who subsequently responded well to proton pump inhibition (n = 8) invariably had one or more cough episodes associated with EBC acidification. No patient who had normal EBC pH with each of their cough episodes reported a clinically relevant response to proton-pump inhibition.ConclusionPatients whose cough responds to proton pump inhibition have transient exhaled breath condensate acidification with coughing episodes, supporting the role of airway acidification in reflux-triggered cough. Multi-sample EBC pH profiles, involving samples collected immediately subsequent to a coughing episode, may be useful appropriately to direct therapy to those patients with cough who have relevant acid reflux.

A simple and cost-effective HPLC method was established for quantification of 5-hydroxyeicosatetraenoic acid (5-HETE) in human lung cancer tissues. 5-HETE from 27 patients' lung cancer tissues were extracted by solid-phase extraction and analyzed on a Waters Symmetry C(18) column (4.6 x 250 mm, 5 microm) with a mobile phase consisting of methanol, 10 mM ammonium acetate, and 1 M acetic acid (70:30:0.1, v:v:v) at a flow rate of 1.0 mL/min. The UV detection wavelength was set at 240 nm. The calibration curve was linear within the concentration range from 10 to 1000 ng/mL (r(2) > 0.999, n = 7), the limit of detection was 1.0 ng/mL and the limit of quantitation was 10.0 ng/mL for a 100 microL injection. The relative error (%) for intra-day accuracy was from 93.14 to 112.50% and the RSD (%) for intra-day precision was from 0.21 to 2.60% over the concentration range 10-1000 ng/mL. By applying this method, amounts of 5-HETE were quantitated in human lung cancer tissues from 27 human subjects. The established HPLC method was validated to be a simple, reliable and cost-effective procedure that can be applied to conduct translational characterization of 5-HETE in human lung cancer tissues.

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