Chronic Cough — Full Text

A cough lasting over 2 weeks that hasn’t begun to improve won’t be a virus.  Over 3 weeks and into 4, without having begun to get better at all, we surely call it “Chronic.”  The possibilities are listed below, and then our thought process for diagnosis. Covid-19 isn’t a concern, because it doesn’t last that long, and isn’t contagious beyond 10-14 days.

Causes of Chronic Cough

Not From the LungLung Diseases
Allergic Rhinitis (Allergies; Hay Fever) #
Chronic Sinusitis
Esophageal Reflux (Heartburn) #
Hypertension medication (“ACE-Inhibitors”)

  #  =  Conditions which can sometimes go away & then recur  [as opposed to an ongoing “cough”]
Asthma #
Post-Viral Bronchospasm
Tuberculosis (TB)
Certain Lung Infections (fungi, etc.)
Chronic Bronchitis #
Heart Failure
Interstitial Lung Disease
Hypersensitivity Pneumonitis #
Uncommon Diseases of Lung or Trachea
Lung Cancer  

All of the Lung Diseases above can occasionally cause shortness of breath (SOB), a potentially-serious symptom.  See link for definition.  If there’s SOB, we know there’s a lung disease, some of which can eventually be fatal; see symptom topic Shortness of Breath.

STEP #1  ––  Rule Out the Common “Not Lung” Conditions, & Consider Asthma

A word about the “treatment trial”: we actually mean a diagnostic trial of therapy, so if treatment helps, we’ve made a Diagnosis!  But to really see if a certain treatment helps, we need to give maximum therapy.  If we only give a low starting dose, & it doesn’t help, we won’t know if it’s Wrong Diagnosis, or Too-Little Treatment.  If the highest-possible-dose works, we can scale back the dose in a few weeks.  If it doesn’t, we’ve pretty much ruled out the diagnosis, & have patient stop the medication.

So now let’s assume we’ve eliminated the first column above (“Not Lung”), and are concerned that our patient’s chronic cough is due to lung disease.  By the way, Chronic Sinusitis is a hard diagnosis.  It causes cough mainly in children (rarely in adults), we only seek it if there are nasal symptoms, medicines for Allergies didn’t work, and Chest X-ray is normal (see below).  We discuss it under symptom topic Nasal Congestion.

STEP #2  —  Get a Chest X-Ray (CXR)

A CXR will find Tuberculosis & pneumonias from uncommon germs, and maybe lung cancer, interstitial lung disease [ILD], and other uncommon conditions.  Immunocompromised persons always need a CXR if they have an ongoing cough.

If the CXR is abnormal, the work-up will depend on what the abnormality looks like.  Tests might include sputum (phlegm) exams, CT scans, pulmonary function tests, bronchoscopy (pulmonologist looking into the lung with an endoscope), even surgical biopsy.  The rest of this discussion deals with patients who have a…


Our diagnosis will depend largely by what we hear, or don’t hear, with our stethoscope. See also Lung Sounds.

Abnormal Lung Sounds

Bronchospasm occurs when the bronchi are narrowed by either bronchial muscle constriction, swelling, and/or mucus.  See Lower Respiratory Tract — Diagram D for a picture-worth-a-whole-bunch-of-words.  How does bronchospasm sound through a stethoscope?

  • Wheezes (long, high-pitched sounds in expiration)
  • Rhonchi (squeaks / gurgles, in inspiration or expiration)
  • Long Expiratory Phase

Problem!  Clinicians all know that wheezes mean bronchospasm.  But some don’t realize that rhonchi do also.  And quite a number fail to appreciate that bronchospasm may declare itself with “clear lungs,” but a long expiratory phase.  Think of how we sound when we breathe normally: a brief breath in, then exhale and pause, before the next breath.

This “exhale + pause” is longer than the breath in, when simply looking at someone from the outside.  But listening with a stethoscope, it’s the opposite: inspiration normally sounds longer than expiration, because the pause sounds silent.  However, with bronchospasm, we hear the sounds of struggled expiration all through the pause. See Lung Sounds by Stethoscope.

If you ever have a chronic cough, and your medical provider tells you, “The lungs are clear,” be sure to ask, “Does inspiration sound longer than expiration?”  If not, suspect Bronchospasm, which is due to one of the following:

Asthma  —  This is what we immediately think of when we hear Bronchospasm.  We virtually clinch the diagnosis if the patient gives a history of other similar episodes in the past.  It’s the most common condition to cause bronchospasm, though there are some other possibilities.  See Lower Respiratory System, Diagram D.

Chronic Bronchitis looks (sounds) just like asthma.  We think of it in a smoker or a farmer.  Initial treatment is the same, except that change in phlegm color & quantity warrants antibiotics.  One difference between treating Asthma and Chronic Bronchitis is that the medications are slightly different.  We diagnose Chronic Bronchitis if a smoker or farmer has:

  • Daily cough with phlegm for at least 3 months, at least 2 years in a row
  • Especially if past exacerbations involved thick green phlegm

So a smoker who seems to have asthma might inquire about other possible medications.  They might also try to stop smoking!!!  See our topic Acute Cough.

Post-Viral Bronchospasm  —  Even after viruses die off, the inflammation they cause can last several weeks or even months.  There’s no way to tell the difference between this and asthma, except for the fact that if it’s from a virus, once it’s over, it won’t come back again.  If the same symptoms recur a few months / years later, it’s Asthma.

When I hear wheezes that sound just like asthma, & the patient had never had a similar illness before, I try to project optimism.  The treatment is the same as for asthma, but I tell the patient that there’s no way to know for sure, so we’ll hope that once symptoms subside & disappear, we can likely stop medication.  One patient with proven Mycoplasma pneumonia got treated and cured of the infection, but wheezed on and off for 3 years, then suddenly it all resolved, never to return.

With Heart Failure we usually hear “Rales” at the bottoms of both lungs.  Rales are “crackles,” heard while breathing in (inspiration).  We’d ask about other symptoms of Heart Failure, especially SOB with exertion, maybe swollen feet. Rarely, we might hear wheezes just like in asthma.  So we try to remember the possibility in a person with lots of risk factors for heart disease (hypertension, diabetes, etc.), but it’s pretty unusual.

Hypersensitivity Pneumonitis causes recurrent bouts of cough, sometimes with fever, maybe an abnormal CXR, but often a normal one.  Lungs usually sound clear; rales are much more common than wheezes.  Any patient who seems to have asthma, but doesn’t respond to treatment, needs a CXR.  We’ll discuss this in depth below.

No Bronchospasm

Anyone with a normal lung exam and cough ≥3 weeks that’s not improving needs a CXR.  More so if we hear rales (“inspiratory crackles”).  The CXR may not make the final diagnosis, but will reveal some abnormality that’ll lead down the path to specialized tests.  It will identify whether any “uncommon  diseases of lung or trachea” (from our Table) may be present.  It’s very good for a lung cancer that causes cough [screening asymptomatic smokers for lung cancer is different].

Therefore, normal-sounding lungs plus a normal CXR is so reassuring that no other work-up is required except in a few cases:

  • A strong smoking history (>30 pack-years), asbestos exposure, or coughing up blood require a CT scan for Lung Cancer.
  • A clear history of new SOB during exertion mandates Pulmonary Function Tests.
  • Voice changes require a referral to Ear-Nose-Throat (ENT) specialist, to look at the larynx with special equipment.
  • Stroke patients, the debilitated, and others who might aspirate food should be evaluated by speech pathologists, and may require CT scan or even bronchoscopy to rule-out a foreign body.
  • Environmental exposures (see link) require a work-up for Hypersensitivity Pneumonitis.

One study found among 84 adults with chronic cough and normal CXRs who didn’t smoke or take ACE-Inhibitors for Hypertension, 99.4 % had a nasal condition (like Allergic Rhinitis), Asthma, and/or Esophageal Reflux (GERD).

So we go for a trial of medication based on best-guess among the above three.  For patients with heartburn, we give Antacid Medication.  For those with nasal symptoms, we treat with Allergy Medications.  We DON’T diagnose “chronic sinusitis,” which can cause a cough in children but not usually adults.  It’s hard to prove, requires a CT Scan, see topic Nasal Congestion.  Making the diagnosis too loosely leads providers to throw around a lot of unnecessary antibiotics.

“Cough Asthma” is medical jargon for a patient who has Asthma but completely normal lung exam, no findings on which to base diagnosis.  One easy maneuver is to perform a Peak Flow test in the clinic, using a small monitor to measure how much air the patient can force out breathing as fast & hard as possible.  Then we give a Nebulized Treatment of albuterol (what’s in common inhalers), and measure Peak Flow again.  If the result improves enough, it’s convincing.

However, some asthmatics only cough during or after exertion (“exercise-induced asthma).  This may be identified by formal pulmonary function tests, but only if including the uncommonly-ordered “methacholine challenge”.  An easier way is to prescribe an albuterol inhaler, which the patient should use 15 minutes before exercise.  If that prevents coughing spells, we pretty much have a diagnosis.

Pertussis comes to mind if a patient has a new cough for several weeks.  Wheezing is uncommon, but possible.  However, by 2 weeks of illness, treatment only helps prevent transmission, not improve symptoms.  And most transmission happens during the first two weeks of cough, & the prodrome before.  See the specific section of Acute Cough.  Pertussis (occasionally called “100 day cough”) can last up to 3 months, but not much longer.

I hate Hypersensitivity Pneumonitis (HP), one of those conditions which lacks easy diagnosis until irreversible damage has occurred.  It’s an environmental disease of the lung alveoli (not the bronchi; see Diagram —  Lower Respiratory Tract), caused by something inhaled.  It may seem like asthma in terms of intermittent coughing episodes, but requires completely different management.

HP is common among farmers [“farmer’s lung”], especially in humid climates, & perhaps also common among bird fanciers [“pigeon breeder’s lung” — people who keep birds, not just “fancy” them].  Outbreaks of HP have occurred among office workers [“humidifier lung”], lifeguards [“lifeguard lung”], & autoworkers.  There are long lists of irritants such as “mushroom worker’s lung,” “paprika slicer’s lung,” “sauna taker’s lung,” “mummy handler’s lung,” “bible printer’s lung,” etc…..  The problem is, these substances don’t just “irritate” the lung, like with asthma, but cause long-term damage that often won’t get better.

The key to diagnosis of HP depends on a history of jobs and hobbies.  Recurrent symptoms of cough, SOB, fatigue, fever, and/or nausea begin 4-8 hours after being exposed, and go away in 12 hours to several days after the exposure is gone.  Rales on lung exam add likelihood, wheezes are rare. 

The CXR is usually normal until late in the course; commercial lab tests are unreliable.  Weight loss is an ominous sign.  If you have symptoms fitting the above pattern, ask your health care provider for a list of possible environmental causes, in case one matches.

A specific type of chest CT scan (“high-resolution chest CT”) may point to the diagnosis, but may also be normal at a point where treatment is still successful.  Farmers who don’t easily respond to asthma inhalers, and other patients with specific exposure risks, should see a pulmonologist.  This lung specialist may know a lab that can concoct a custom-made brew of the patient’s actual exposure and run immunologic tests.

One last comment about the chronic cough — if symptoms are progressively getting worse, especially if there’s any sort of SOB involved, or weight loss, we need to be aggressive in our work-up, including CT scans, Pulmonary Function Tests, and referral to a Pulmonologist. Occasional people, depending on initial test results, may need biopsies.

See also our topic Acute Cough.

See also Chronic Cough for the clinician’s condensed thought-process when face-to-face with a patient.

Leave a Reply

%d bloggers like this: