Pulmonary Function & Spirometry

Question 1

Define: transpulmonary pressure

Answer 1

P_transpulmonary = P_alveolar - P_pleural

Question 2

What portion of the airway has the highest resistance?

Answer 2

medium-sized bronchi

Question 3

Describe the compliance (relative to normal) seen in:

1. Emphysema
2. Fibrosis

Answer 3

1. more compliant
2. less compliant

Question 4

Describe the basic indications for administering pulmonary functional tests (PFTs), such as spirometry

Answer 4

Diagnostic: symptoms, signs, or abnormal lab tests consistent with pulmonary disease

Track or assess prognosis of disease or therapies

Screen for pulmonary disease in high-risk patients, such as smokers, occupational exposures, preoperative risk, disability

Question 5

Define: FEV₁

Answer 5

The volume expired in the first second during maximal forced expiration

Question 6

Abnormalities in the expiratory portion of the spirometry flow-volume loop is indicative of dysfunction in what region of the respiratory system?

Abnormalities in the inspiratory loop?

Answer 6

Intra-thoracic (i.e. lower airways)

Extra-thoracic (i.e. upper airways)

Question 7

A ‘scalloped’ expiratory curve is indicative of what?

A normal-shaped expiratory curve with a markedly lower TLC is indicative of what?

Answer 7

Obstructive lung disease

Restrictive lung disease

Question 8

Both asthma and a mass in the upper lung could lead to abnormalities in the inspiratory portion of the flow-volume loop. How could you tell them apart via physical exam?

Answer 8

Auscultation: Asthma is wide-spread, whereas a mass is localized.

Question 9

Define: FVC

Answer 9

Forced Vital Capacity - total expiratory volume of a patient following a maximal inspiration (starting at total lung capacity)

Question 10

1. What defines an abnormal FEV1/FVC ratio?
   
   • What is the normal range of ratios?
2. What demographic factors influence a patient’s predicted ratio?
3. A low ratio indicates what?
4. A not low ratio is seen in what?

Answer 10

1. Anything not close to 100% (below the 95% CI) for a patient’s predicted value is abnormal
   
   • Normal ratios are between .70 and .87, depending on pt demographics
2. Factors:
   
   • Age
   • Sex
   • Height
   • Race
     
     • African Americans have longer legs & shorter torso for their height, which decreases the expected ratio
3. Low = Obstructive process
4. Not Low = Normal, or restrictive proccess (look at other metrics)

Question 11

What two conditions must be met for a spirometry test to be considered normal?

Answer 11

• FEV1/FVC ratio is normal (**near 100%, **within 95% CI of predicted)

AND

• FVC (VC) is normal (>= 80% of predicted)

Question 12

Name the degree of airway obstruction based on the percent of predicted FEV1:

• >99%
• 70-99%
• 60-69%
• 50-59%
• 34-49%
• <34%

Answer 12

\>99% = Physiological variant
70-99% = **Mild**
60-69% = **Moderate**
50-59% = **Moderately Severe**
34-49% = **Severe**
\<34% = **Very Severe**

Question 13

1. Your patient demonstrates a low FEV1/FVC ratio, indicating obstructive pumonary disease. You suspect asthma or COPD. What is a useful next test to perform?
2. Briefly, a positive result to this test indicates what?
3. What is a significant positive result in this test?

Answer 13

1. Bronchodilator response
2. Reversibility of obstruction
3. FVC OR FEV1:
   
   • Must increase by 12% AND 200mL

Question 14

What types of diseases / conditions cause obstruction within:

1. the large conducting airways?
2. the peripheral airways?
3. the pulmonary parenchyma?

Answer 14

1. tumors & foreign bodies
2. asthma, chronic bronchitis, cystic fibrosis
3. emphysematous changes from cigarette smoking

Question 15

1. Your patient has a normal FEV1/FVC ratio but a decreased FVC. You suspect ________ pulmonary disease.
2. What other metric should you always obtain if able in order to confirm this?
3. Describe the grading of this metric.

Answer 15

1. Restrictive
2. Obtain lung volumes - reduced TLC is the true hallmark of a restrictive pulmonary defect
3. Grading:
   
   • 70% to LLN (lower limit of normal) = Mild
   • 60-69% = Moderate
   • <60% = Moderatey Severe

Question 16

In the diagnosis of restrictive pulmonary disease:

If you cannot obtain lung volumes (patient unable to complete the test accurately due to symptoms, etc.), what should you grade on to asses restriction?

Answer 16

Grade on **percent of predicted FVC. **Grading scale similar to that of FEV1 for obstructive disease:

**\>80%** = Normal
70-79% = **Mild**
60-69% = **Moderate**
50-59% = **Moderately** **Severe**
34-49% = **Severe**
\<34% = **Very Severe**

Question 17

Define: FEF₅₀ and FIF₅₀

What is the FEF₅₀/FIF₅₀ ratio used to differentiate, and how?

Answer 17

FEF₅₀ = the flow** rate** at the 50% point of a forced expiration

FIF₅₀ = the flow rate at the 50% point of a forced inspiration

The ratio is used to differentiate intrathoracic from extrathoracic obstruction.

FEF₅₀/FIF₅₀ > 1 = extrathoracic obstruction

FEF50/FIF50 = 1 = normal

FEF50/FIF50 < 1 = intrathoracic obstruction (slides say <1 may also be normal, so perhaps further tests are needed)

Question 18

What should you look for as criteria of good spirograms?

Answer 18

• Acceptability
  
  • Free from artifacts: cough, early termination, hesitation at any point along the loop
  • 6sec of exhalation and/or a plateau in the loop
• Repeatability
  
  • Start with 3 spirograms
    
    • Are the two largest FVCs and two largest FEV1s within 0.2L of each other?
  • Do a maximum of 8 tests if more are needed (fatigue sets in after this)