Case Study Number 2

Learning Objectives:

Form a differential diagnosis for ‘shortness of breath’ and be able to differentiate causes based on patient history and physical exam.
Interpret Pulmonary Function Tests and FEV1/FVC ratio in the setting of restrictive and obstructive lung disease.
List the causes of pulmonary fibrosis and know how these present on PFT and CT scans.

Case Study:

A 60-year old Caucasian male with a past medical history of well-controlled hypertension, hyperlipidemia, well-controlled diabetes mellitus type II, 45 pack-year history of smoking, comes to your office stating “Doc, I’ve been having some trouble breathing.”

1. Create a differential diagnosis based on the information provided so far. List the differential by organ system.

Based just on this 60 year-old patient's presentation of controlled hypertension and Type II diabetes, hyperlipidemia, 45 pack-per-year smoking history, and dyspnea, the following could be potential (differential) diagnoses:

Cardiac -- CAD, CHF, Arrythmia, MI 

Pulmonary -- Pneumonia, COPD, Asthma, Emphysema, Pulmonary Fibrosis 

Non-CP -- Infection, Metabolic Acidosis, Neuromuscular (Guillan Barre)

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Seeing as you plan on graduating first in your class and landing a spot in dermatology at Stanford University (think of the sun and palms trees), you ask a perfect open-ended question, such as “Tell me more about your breathing difficulties.” The patient states that there his shortness of breath has been slowly getting worse over the past few years. He is not very dyspneic at rest, but upon exertion, he becomes very short of breath and has to stop his activities. As he is farmer in central Illinois, this has become a very large problem for him. Most of his work is strenuous and if he cannot farm, he will have no source of income. He has had a “hacking cough” over the past year or so that his PCP has been unable to find a cause for. The patient reports that there are no aggravating or relieving factors besides activity and rest, respectively. He also acknowledges that there is no correlation between shortness of breath and time of day. He denies fever, chills, night sweats, or weight loss. The patient denies chest pain, orthopnea, or paroxysmal nocturnal dyspnea. The patient denies a productive cough. He also denies trauma to the chest or back. He denies any headaches, dizziness, syncope, visual changes, hearing changes, changes in muscle strength/tone, and difficulty walking. He denies any changes in bowel or urinary habits.

On physical exam

General: Patient is in no acute distress. He is alert and oriented x 3.

Skin: No apparent lacerations or bruises. No spider angiomatas noted.

HEENT: Head is normocephalic and atraumatic. Extraocular movements intact (EOMI). Pupils equally round and reactive to light (PERRL). Visual acuity 20/20 with corrective lenses. Ear canals patent and non-erythematous. Tympanic membranes pearly gray with no pus or air-fluid level visible.

Cardiac: Regular rate and rhythm. S1/S2 heart sound present. No murmurs, rubs, or gallops. PMI located in the 5th intercostal space in the mid-axillary line. No JVD noted.

Pulmonary: Chest expands symmetrically on inspiration. Chest wall non-tender to palpation. Resonant to percussion in all lung fields. Normal fremitus in all lung fields. Airways clear to auscultation. Diaphragmatic excursion symmetric.

Gastrointestinal: A 8cm scar is located in the lower right quadrant. Normal bounds sounds in all four quadrants. No renal, aortic, or iliac bruits noted on auscultation. No tenderness to palpation.

Musculoskeletal: Muscle strength rated as 5/5 in all muscle groups.

Neurological: Cranial nerves II-XII in tact. Reflexes 2+ in all extremities.

Medications: Lisinopril, Hydrochlorothiazide, Atorvastatin, Metformin, Aspirin, Albuterol

2. What are the top 3 diagnoses you are considering? Provide evidence for each diagnosis from history and physical exam. List tests you would want to conduct.

a. Obstructive Disease: Chronic Obstructive Pulmonary Disease. COPD is a common result of long-term smoking in patients of older age; furthermore, hyperlipidemia, diabetes, and hypertension have been known to exacerbate COPD. Quick to become short of breath. It should also be noted that the patient is using albuterol - albuterol can relieve the symptoms of COPD to a certain extent, so he may have progressed from an albuterol-sensitive form.

b. Restrictive Disease: Pulmonary Fibrosis. Dyspnea upon exertion (exercise) and hacking coughs are common symptoms of pulmonary fibrosis, and certain environmental factors he may be exposed to as a farmer, such as animal droppings and grain particles, have the potential to aggrevate and damage his lungs. No apparent barrel-chest of COPD; lung exam was clear with no wheezing or other sounds that tend to indicate airway obstruction. More common in males over 50.

c. Obstructive Disease: Asthma. Quick to become short of breath, aggravating particles from farming, and hacking coughs can indicate a tendency towards developing asthma. When the number of packs smoked per year is relatively low, as 45/yr may be considered compared to a pack/day smoker, adults may develop asthma rather than COPD. No apparent barrel-chest of COPD. COPD may also involve heart issues - right ventricle hypertrophy due to extra work from perceived lack of oxygen - but our patient had a normal heart exam.

A PFT test demonstrating lung volumes and flow rate ratios would help in differentiating between obstructive (larger lung volumes (TLC, RV, FRC), low FEV1/FVC) and restrictive (small lung volumes (TLC, RV, FRC), normal or high FEV1/FVC). Radiographs (X-ray, CT) could be immensely telling - enlarged lung spaces may suggest COPD or another obstructive disorder; highly fibrotic lungs would indicate a restrictive lung disease, pulmonary fibrosis, as being the likely situation.

If we are to want to differentiate between the two obstructive diseases suggested, COPD and Asthma: A bronchoprovocation test can be used to see if asthma is the issue (reversibility in such tests tends to indicate asthma over COPD), and can also be used to test if there are particular stimuli - in this case, it seems that exercise is at least part of it - for it in a controlled environment. Another option is to have the do a nitric oxide exhalation (eNO) test - NO is an indicator of inflammation of the lungs, generally seen in asthma. 16ppbillion or greater in a breath suggests asthma, less than that suggests COPD.

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3. As part of your work-up, you had ordered a pulmonary function test, which is displayed below. His FEV1/FVC is 0.91. Does the patient have normal lung function, a restrictive lung pattern, or an obstructive lung pattern?

An FEV1/FVC ratio of .75 or greater in a patient with lung disease is indicative of being normal or of a restrictive disease, such as pulmonary fibrosis. FEV1 values of 80% or lower can indicate different degrees of airway obstruction - according to this, he has over 100% expected FEV1 (the amount of air expelled forcefully from the lungs in one second), suggesting no airway obstruction and likely no obstructive disease.

In restrictive lung disease, the curves look similar to normal but tend to be smaller - especially volume-wise (x-axis) due to the decreased volume the lungs are able to hold in such disease states, as shown by the comparative curves above. COPD and other obstructive diseases will show a curve which has an overall TLC of being similar or larger than the normal, even though the amount breathed out will be small since much of the air is trapped in the lungs. Our patient's PFT most resembles a normal curve, but our x-axis indicates that we are only looking at a vital capacity of 4L overall, thus establishing that this is a restrictive curve.

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4. Based on the graph above, what other abnormality would you expect on this patient’s PFTs?

Based on the graph above, which indicates a restrictive disease, we would also expect to see the pulmonary function tests show that there is decreased oxygen delivery to the blood if this is the case of a scarring restrictive disease such as pulmonary fibrosis. Pulmonary fibrosis can also lead to a decrease in dead space - testing for this would help confirm the diagnosis. A-a (ABG) blood tests and exercise testing on the lungs would help further reveal useful information.

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5. Because of his PFT, you order a high resolution CT scan of his lungs to get a better picture of the patient’s lungs. What is the final diagnosis?

The patient's CT scan, taken at the level of the heart, provides the main conformation of what our final diagnosis is. Compare this to a normal CT scan of the lungs, here:

In our patient, we see comparably heavy reticulation of the lung space, as well as the potential development of "honeycomb cysts," noted by dark pockets particularly near and along the sides of the lung. Another feature seen in pulmonary fibrosis patients is "traction bronchiectasis," where bronchi(oles) can be seen as perpetually dilated due to the surrounding fibrosis pulling on them and keeping them open. This diffuse state suggests pulmonary fibrosis.

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6.  What are the causes of pulmonary fibrosis?

Pulmonary fibrosis is often considered "idiopathic" in that the specific cause of the disease is not known in many patients; however, it is known that cigarette smoking is a major contributor to the development of the disease. Other risk factors include infection by certain viruses and pneumonia/tuberculosis causing pathogens, gastroesophageal reflux disease (acid from the GI system falls into and damages the lungs), certain medications (particularly chemotherapy drugs, some antibiotics and heart medications), radiographic injury, and exposure to pollutants, bacteria, fumes, animal particles, and other irritants. Genetics may also contribute.

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SOURCES USED:

Lectures

Texts: Boron & Boulpaep, J.B. West 

Websites: http://www.nhlbi.nih.gov/health/health-topics/topics/lft, http://www.coalitionforpf.org/lets-talk-about-idiopathic-pulmonary-fibrosis-comprehensive-information-for-patients-and-caregivers/ , http://www.mayoclinic.org/diseases-conditions/pulmonary-fibrosis/basics/tests-diagnosis/con-20029091 , https://lunginstitute.com/blog/obstructive-and-restrictive-lung-diseases/, https://www.nlm.nih.gov/medlineplus/druginfo/meds/a682145.html , https://lunginstitute.com/blog/the-relationship-between-copd-and-heart-problems/