Pulmonary Function & Spirometry Flashcards Preview

M2 Renal/Respiratory > Pulmonary Function & Spirometry > Flashcards

Flashcards in Pulmonary Function & Spirometry Deck (18):

Define: transpulmonary pressure

P_transpulmonary = P_alveolar - P_pleural


What portion of the airway has the highest resistance?

medium-sized bronchi


Describe the compliance (relative to normal) seen in:

  1. Emphysema
  2. Fibrosis

  1. more compliant
  2. less compliant


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

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


Define: FEV1

The volume expired in the first second during maximal forced expiration


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?

Intra-thoracic (i.e. lower airways)

Extra-thoracic (i.e. upper airways)


A 'scalloped' expiratory curve is indicative of what?

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

Obstructive lung disease

Restrictive lung disease


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?

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


Define: FVC

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


  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. low ratio indicates what?
  4. A not low ratio is seen in what?

  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)


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

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


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


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

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

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


  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?

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


What types of diseases / conditions cause obstruction within:

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

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


  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.

  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


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?

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


Define: FEF50 and FIF50

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

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



What should you look for as criteria of good spirograms?

  • 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)

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