Chronic Shortness of Breath (SOB) — Full Text

In both Greek & Medical-Speak, the word is “dyspnea” = difficult breathing.  We’ll stick with the English “Shortness Of Breath,” which gets abbreviated “SOB” all over the country (one reason some clinicians won’t let patients look at their charts).  Please note that our text may be somewhat long.  SOB is a concerning symptom, so completeness seemed important. Scrolling down identifies main sub-topics.  See also Chronic SOB — Summary Approach for a clinician’s nutshell thought process.

Chronic SOB is defined as going on for at least a few weeks, maybe months, possibly getting a little worse bit by bit.  We’ll assume that COUGH does NOT feature prominently (if it does, see our topic Chronic Cough).

This topic deals with “true” SOB.  The term “true” is my invention, not used by clinicians in general.  But I use it here, because some people who say they feel short of breath, really have no problem getting enough oxygen. Reasons include”

  • Nose is all stuffed up
  • A bad coughing spell
  • Stomach-acid reflux (GERD)
  • Frequent need to “sigh”
  • Anxiety, especially with hyperventilation or panic
  • Deconditioning

See our definition “True” Shortness of Breath, which also discusses a common Spanish mistranslation. From now on, “shortness of breath” means the body isn’t getting the oxygen it wants.  Causes have mainly to do with the lungs, heart, and the blood’s ability to circulate.

Causes of Chronic Shortness of Breath

Heart Failure (HF) **
Angina **

xxxxxxxxxNormal SOB
Deconditioning (out-of-shape) **

    ** SOB, with exertion, may come and go
Asthma **
COPD (esp. Emphysema)
Interstitial Lung Disease      

xxxxxxxxxUncommon Causes
Click for List of Rare Causes

Chronic SOB always occurs with exertion, since nobody has SOB at rest for a long time without seeking care.  The above conditions are “common” insofar as they are the most likely diagnoses for patients who complain only of SOB, without prominent cough.

** Asthma (or, if a smoker, COPD) is a common cause, diagnosed by hearing wheezing by stethoscope.  But if we don’t hear wheezes (or even if we do), we consider other possibilities.

** Heart Failure (HF) —  This means that the heart isn’t pumping blood strongly enough. It doesn’t mean “heart attack,” although a previous heart attack can cause chronic HF if enough heart muscle died.  We suspect HF as a cause of chronic SOB based on combination of:

Risk Factors for Heart Failure

Heart Failure Symptoms

  • SOB with exertion
  • SOB when lying flat in bed
  • Sudden SOB wakes you at night
  • Feet swell (usually both feet)

Findings on Physical Exam

  • Rales (crackles) at the bottom of both lungs (heard by stethoscope; see Lung Sounds)
  • Swollen feet
  • Swollen neck veins
  • Certain heart sounds (may also identify cause, like damaged heart valve, Atrial Fibrillation, etc.)

Tests for Heart Failure

  • Blood test for “BNP
  • EKG (sometimes helpful, often not)
  • Chest X-Ray (sometimes helpful, often not)
  • Echocardiogram (best test)

The main diagnostic test for HF is the Echocardiogram (“Echo” for short).  It’s an ultrasound of the heart, doesn’t hurt, not at all dangerous.  The Echo tells us a lot”

  • Estimates the heart strength, reported either in terms of an “ejection fraction” (>55% is normal, <40% is clearly abnormal, <20% heads for transplant), or in terms of function (“severely diminished,” etc.).
  • Determine if the heart’s problem is with each pump, or with relaxing after
  • Tell if there’s a problem pumping blood into the lungs (pulmonary hypertension)

A major error is to simply diagnose HF and treat it, without identifying its cause.  HF is so common, due to old heart attacks (which kill some heart muscle) or long-standing hypertension (which weakens the muscle), that sometimes we forget to consider more unusual causes such as:

  • Anemia (which may itself be due to colon cancer, etc., etc.); diagnose by Complete Blood Count for hemoglobin level
  • Thyroid Diseases (can tell by a simple blood test, the TSH)
  • Amyloidosis (consider if “low voltage” on the EKG, but very rare)
  • Chagas Disease (esp. among immigrants from Latin America); diagnose by “T. cruzi IgG antibody” blood test (Trypanosoma cruzi is the parasite responsible)
  • Cardiomyopathy (“diseased heart muscle”) due to viral infection, alcoholism, etc. etc.

HF on the right-side of the heart suggests lung diseases (see Diagram: The Heart — Anatomy):

So if you or a loved one (or even an enemy) gets diagnosed with “heart failure,” be sure to ask, “Why?  What’s the underlying cause?”

** Angina  —  Blockage of the heart’s coronary arteries (Coronary Artery Disease), that may eventually lead to a full-fledged heart attack.  The word “angina” denotes chest pain, but some patients have mainly SOB at a certain degree of exertion.  People often seek care early on; the main puzzle when a patient comes in with coronary artery blockage after months of chronic symptoms is, “Why’d you wait so long?”  Invariably it’s because the condition is progressing, which makes it more dangerous.

We must always ask patients with Chronic SOB for telltale clues of Coronary Artery Disease:

  • Risk Factors: Hypertension, Smoking, Diabetes, Family History of early heart attack, High Cholesterol, Cocaine / Meth
  • Chest Pain occurring along with the SOB.  Since denial is common, we don’t just inquire about “pain,” but also “pressure,” “heaviness,” squeezing,” or “tightness,” not only in the Chest, but also Left shoulder, upper arm, neck, or lower jaw.
  • Other Symptoms  — “At the same time you have SOB, do you also a) Get nauseous or vomit; b) Get lightheaded; c) Break out into a cold sweat on your forehead?
  • Angina, be it chest pain or just SOB, lasts between 1-5 min. A full-blown heart attack continues on.

If Angina is a possibility, we get an EKG and perform additional work-up (see Diagnosing Coronary Artery Disease).

** Anemia  —  Insufficient red blood cells, which carry oxygen, can cause SOB on its own, but can also cause Heart Failure.  The diagnosis is easy — simply a Complete Blood Count to measure hemoglobin as part of our work-up of SOB (though we would still need to identify the cause of Anemia).

** Asthma (Exercise-Induced)  —  Some asthmatics have their symptoms triggered by exercise, usually vigorous exercise.  The hard part for us is that the lungs sound fine when they’re not exercising.  Exercise-Induced Asthma is most easily diagnosed by successful use of a standard “relief” inhaler (albuterol) shortly before exercise.  We can add a pill to take daily, monteleukast (Singulair®).  If this doesn’t work, & other diagnoses are ruled out, it may be necessary to order spirometry tests after a treadmill session; see Pulmonary Function Tests (PFTs).

** Asthma (Persistent)  —  Asthmatics usually cough, but some don’t.  We can often hear abnormal sounds like wheezes or rhonchi, or maybe just a prolonged expiratory phase, when we listen to the lungs with a stethoscope, but sometimes not (see Lung Sounds).  Symptoms will certainly be worse on exertion, but this is different from exercise acting as a trigger.  See our topic Acute Cough.

Once again, a good clinical history to determine the course of symptoms helps us suspect the diagnosis.  If a patient has had similar episodes in the past, that resolved and recurred, we’re most likely dealing with asthma.  A treatment trial of asthma medication may be diagnostic, although formal Pulmonary Function Testing (PFTs) may be needed, mainly to rule out more serious diseases.

Misdiagnosed Asthma can be due to the rare Heart Failure that just happens to give wheezes instead of the more typical rales; and Hypersensitivity Pneumonitis (see also topic Chronic Cough).

** COPD (Emphysema)  —  COPD stands for “Chronic Obstructive Pulmonary Disease.”  The word “obstructive” is technical, defined by Pulmonary Function Tests.  COPD is subdivided into Chronic Bronchitis & Emphysema, though many people have a combination of both.  As opposed to Chronic Bronchitis, which causes acute episodes of cough and SOB (see Acute Cough), the Emphysema component of COPD does not generate a cough. 

The only symptom of Emphysema is SOB with exertion.  It first occurs at a certain more-extreme level of exertion, then with progressively less and less.  Patients often seek care when the SOB eventually interferes with an important activity of daily living (ADL).  The weekend sports enthusiast may be unable to keep up with friends.  A dynamic executive may find themselves slowing down.  SOB during sex is often the unacceptable ADL infringement.

We might diagnose it by a simple glance at a patient, revealing the classic “barrel-chest” (chest dimensions like a barrel; just as wide front-to-back as side-to-side).  On lung exam we might hear fine wheezes, certainly an abnormally long expiratory phase (breathing out sounds longer by stethoscope than breathing in, a finding often missed by clinicians; see Lung Sounds).  A chest x-ray may show big lungs full of useless air, but diagnosis is best made by Pulmonary Function Tests (PFTs).

If they ever send you for PFTs, be sure they do some of them “before & after bronchodilator.”  That means they test lung function, give an asthma treatment, & test again.  In COPD, the degree of improvement indicates how much is Chronic Bronchitis.  Emphysema doesn’t respond to treatment.

COPD is almost always a smoker’s disease, with the main treatment being STOP!!!  Chronic Bronchitis may then improve, although permanent damage (Emphysema) will merely stay the same.  Unfortunately, studies find that bad PFTs don’t motivate smokers to quit.  A non-smoker with emphysema needs a blood test for alpha-1-antitrypsin (rare genetic condition).

** Interstitial Lung Disease (ILD)  —  This is a broad category of diseases, some treatable with medicines, other with lung transplant.  As opposed to asthma and COPD, which involve the airway (bronchi and bronchioles), ILD affects the cells outside the alveoli (see Diagram — Lower Respiratory System).  Its main symptom is gradual progression of exertional SOB.

Early on, physical exam is usually normal.  Maybe an astute clinician will hear fine rales (crackles) in the lungs, by stethoscope.  A Chest X-ray may be suggestive, but may also be completely normal.  The key to diagnosis is Pulmonary Function Testing (PFTs).  If PFTs are indicative of ILD, the next step is a “High Resolution” CT Scan of the chest (which uses less radiation than a regular CT).

Once we diagnose ILD, then comes the job of sorting through the many possible causes.  They range from environmental or occupational exposures, infections, and inflammatory diseases (like types of arthritis), to that broad category “idiopathic” [medical-speak for “just happens” or “nobody knows”].  Biopsy may be necessary.

** Uncommon Causes  —  As for the less likely etiologies of Chronic SOB (see link for List of Uncommon Causes), we’ll easily find them on either Chest X-ray, Echocardiogram, or Pulmonary Function Tests.  The only tricky one is Chronic Pulmonary Emboli (PE).  Up to 4% of acute PEs, many never identified, develop into a chronic condition.  Chest x-rays are usually normal.

The Echocardiogram may show subtle abnormalities, like pressure build-up in the lungs, or a large right ventricle (heart).  Many clinicians don’t realize that whereas a CT Scan of the chest is the standard test for acute PE, the best for chronic ones is the Ventilation/Perfusion (“V/Q”) Scan.  The “Q,” by the way, is a mathematical symbol for “streamflow”). A subtle clue may be hearing pulsating sounds by stethoscope over the back of the lungs, while a patient holds their breath.

Deconditioning  —  Being plain-old out-of-shape certainly causes Chronic SOB.  We hope patients have enough insight not to seek care for it.  But sometimes a person finds themselves in a new environment (more steps at work, moved to house on hill), and doesn’t make the connection.  Maybe they’ve gained a lot of weight.  Still, unless there’s an obvious explanation, we can’t count on a diagnosis of Deconditioning without ruling out more serious possibilities.

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

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