This study is being done to find out why some people with mucus dripping down the back of
their throat have a nagging cough while others do not cough.
The objective of the protocol is to determine the pathogenesis of cough in diseases of the
aerodigestive tract. There were over 24 million ambulatory chronic cough visits nationally
in 1991 and over 8,000 visits in 2004 at MCR. Current guidelines for chronic cough are based
on case series and on empirical expert opinions. Studies have implicated mucosal
inflammation, heightened sensitivity of capsaicin cough receptors on peripheral nerves and
elaboration of inflammatory mediators including tussigenic neuropeptides. There are gaps in
our knowledge of what triggers cough in many disease states. For example, postnasal drip
syndrome has been estimated to account for 70% of chronic cough, yet it is known that not
all patients with postnasal drip have chronic cough. Our hypothesis is that there must be
critical factor/s that cause cough in one patient with postnasal drip but not in another.
This study will evaluate whether there exists differences in capsaicin cough sensitivity,
neuropeptides levels and mucosal inflammation in patients with postnasal drip and chronic
cough and compared to its natural control group, subjects with postnasal drip with and
without chronic cough. After standard therapy to eliminate postnasal drip, repeat
measurement of capsaicin sensitivity and nitric oxide levels will be obtained. There is a
critical need to determine the mechanisms underlying cough for better management. The study
results will provide insight and fill gaps in our knowledge and will serve to advance future
work evaluating mechanisms of cough in other disease states including asthma, GERD,
interstitial lung disease and smokers.
Postnasal Drip with chronic cough:
1. Postnasal drip by rhinoscopy
2. Cough by visual analog scale.
3. Patients have to be 18 years old or older.
4. Cough-variant asthma must be excluded by a negative methacholine challenge test
within one year, or documented failure of chronic cough to resolve after
administration of inhaled corticosteroid (> one-month duration). Asthma is defined
by the ATS guidelines.
5. Subjects must have a negative chest radiogram or Chest CT scan within 6 months.
6. No active GERD symptoms (< 7 RSI score) & a stable dose of Proton Pump Inhibitor (4
Eligibility Criteria of Postnasal Drip without cough:
7. Postnasal drip by rhinoscopy
8. No cough by visual analog scale.
9. Patients have to be 18 years old or older.
- Subject Exclusion Criteria for Postnasal Drip with Chronic Cough:
1. Presence of nasal polyposis and/or sinusitis or active GERD symptoms on
2. Current smokers (smoking within the 2 months prior to the study) will be
3. Patients with an upper respiratory tract infection within the preceding 8 weeks.
4. Patients taking angiotensin converting enzyme inhibitors.
5. Patients on leukotriene receptor antagonist and/ or nasal topical
corticosteroids or inhaled corticosteroids. Patient must be off nasal or inhaled
corticosteroid by at least 4 weeks.
Exclusion Criteria: Same for Post Nasal Drip without cough except:
1. A chest radiogram is not necessary in this group.
2. Patients taking leukotriene inhibitors, or using nasal steroid therapy.