Pulmonary Function Studies: Review

1
Pulmonary Function Studies Review

• By Elizabeth Kelley Buzbee AAS, RRT-NPS, RCP
• Lone Star college Systems- Kingwood

2

• Identify the indications for PFT

3
answer

• according to the AARC CPG, PFT need to be done
  to
• 1 diagnosis restrictive defects,
• 2 to differentiate between restrictive and
  obstructive defects,
• 3 assess the patients response to
  interventions
• 4 pre-op assessment of patients at risk for
  pulmonary limitations
• 5 evaluate pulmonary disability
• 6 Quantify air trapping is it getting worse,
  better

4

• What are the hazards of PFT?

5
answer

• According to the AARC CPG, the relative
  contraindications include
• 1 untreated pneumothorax
• 2 hemoptysis
• 3 unstable hemodynamics
• 4 aneurysms.
• If persons have claustrophobia, upper body
  paralysis or cast that makes the body box
  impossible, this single test may be deferred.

6

• Identify this type of pulmonary function study

7
answer

• This is a flow volume loop used to find both
  obstructive and restrictive defects.
• The shape of the curve can give the RCP
  information about where an obstruction is
  located intra-thoracic large airway, large fixed
  or small airways

8

• Read the FVC of the blue tracing and compare it
  to the normal one

9
answer

• The FVC of the blue tracing on the flow volume
  loop is 200 ml the line starts at 100 so we need
  to subtract that from the end point
• The FVC of the normal flow volume loop is 600 ml.
• The percent of predicted is 200/600 or 33 of
  predicted
• There is very severe derangement of the FVC
  values

10

• Is the blue tracing consistent with a restrictive
  defect or an obstructive defect?

11
answer

• The blue tracing is 33 of predicted which
  demonstrates a very severe restrictive defect.

12

• Identify the peak inspiratory flow rate of the
  blue tracing
• Identify the peak expiratory flow rate of the
  blue tracing

13
answer

• the peak inspiratory flow rate of the blue
  tracing is about 65 LPM
• The peak expiratory flow rate is also about 65 LPM

14

• Compare the blue tracing of the PIFR to the
  normal one
• Compare the blue tracing of the PEFR to the
  normal one

15
answer

• PIFR is about 80 LPM so 65/80 81 predicted or
  normal
• PEFR is about 100 LPM so 65/100 is 65 of
  predicted which is consistent with mild airway
  obstruction

16

• Discuss the clinical significance of VT that is
  50 of predicted.

17
answer

• A VT by itself is not too helpful we could have
  a restrictive defect or an obstructive one.
• The most use we get out of this value is during
  weaning parameters.

18

• Discuss the clinical significance of a FEV1 that
  is 45 of predicted

19
answer

• A FEV1 that is 45 of predicted implies that
  there is a severe obstructive defect, but we need
  to see the FVC also
• If both are down, we may have restrictive defect
• If FVC is ok, but there is a lower FEV1 then it
  is clear we have obstruction
• Calculate the FEV1/FVC. A normal person should be
  able to exhale 70 of his FVC in the first second

20

• Discuss the clinical significance of a FEV1/FVC
  that is higher than normal.

21
answer

• The person with a FEV1/ FVC that is high may have
  a normal exhaled flow, but have a low FVC due to
  a restrictive defect.

22

• Discuss the clinical significance of an elevated
  FRC.

23
answer

• High FRC implies that there is air trapping which
  is associated with obstructive defects

24

• Discuss the clinical significance of a TLC that
  is 135 of predicted

25
answer

• TLC that is elevated shows significant
  hyperinflation if the FRC is also higher than
  normal

26

• If a persons RV is increased what problems does
  this imply?

27
answer

• An elevated RV implies that there is air-trapping
  associated with obstructive defects such as
  asthma, COPD or emphysema

28

• How do we ask a patient to perform the flow
  volume loop?

29
answer

• We ask him to perform a FVC into the computer
  which will display the graphics
• We ask him to inhale as deeply as possible from
  the end expiratory of a normal breath then exhale
  as completely and as quickly as possible

30

• What is the function of the MVV?

31
answer

• The MVV is used to monitor the ability of a
  patient to maintain rapid and deep breaths over a
  period of time
• The person with significant obstruction cannot do
  this because he will start to air trap
• The person with restrictive defect will have
  problems getting a big enough VT with each
  breath---the most important diagnostic benefit of
  looking at the MVV is assessing the patient for
  his ability to tolerate pulmonary rehabilitation

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• How do we measure a value like the RV that cannot
  leave the body?

33
answer

• To collect the value of the RC which is needed to
  calculate the FRC, we need to measure this volume
  indirectly by helium dilution studies or by N2
  washout over several minutes

34

• What is the function of the single breath N2
  washout study

35
answer

• In the single-breath N2 washout study we are
  looking at gas distribution which is directly
  related to the level of airway obstruction

36

• What is the significance of having a higher TGV
  by body box than TLC by helium dilution

37
answer

• If the body box results in a higher volume than
  the helium dilution, it is because there are
  airways that have not been exposed to the other
  airwaythey are completely obstructed

38

• What circumstances can result in decreased
  diffusion of Carbon monoxide during diffusion
  studies?

39
answer

• Any disorder that results in hypoxemia can result
  in diffusion defect.
• If there are no s/s of restrictive or obstructive
  defects on PFT, but there is diffusion, we worry
  about disorders such as pulmonary emboli.

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Case study 1

• Your patient is a 45 YO Asian male who presents
  with episodes of SOB associated with weather
  changes and increased activity.
• He is tested in the Pulmonary function lab
• you see the following
• FVC - 63 predicted
• Slow VC - 88 predicted
• What does this imply?

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answer

• If the slow VC is higher than the forced VC, we
  may have an obstructive defect without a
  restrictive componant

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• He also has this
• IC 89 predicted
• FRC- 136 predicted
• PEFR 65 predicted
• PIFR 91 predicted

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answer

• IC 89 predicted- this is WNL and shows that
  there is no restrictive defect
• FRC- 136 predicted- this shows that there is no
  restrictive defect. But that there is obstructive
  defect associated with air trapping
• PEFR 65 predicted- the peak flow is decreased
  showing mild obstructive defect
• PIFR 91 predicted is WNL there is no upper
  airway obstruction

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• He has the following data
• FEV1 62 predicted
• FEV1/FVC 67 predicted
• FEV 25-75 65 predicted
• MVV 54 of predicted

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answer

• FEV1 62 predicted implies that there is
  moderate obstructive defect
• FEV1/FVC 67 predicted supports this obstructive
  defect
• FEV 25-75 65 predicted- mild obstruction in
  the smaller airway
• MVV 54 of predicted shows that this patient
  would have poor exercise tolerance, but could
  undergo pulmonary rehab

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• What is your overall impression of this patient?

47
answer

• This patient has several indices for
  mild-moderate obstructive defect with air
  trapping
• This patient has no evidence of restrictive defect

48
Case study 2

• Your patient is a 58 YO LAF who presents with the
  following s/s She is in considerable respiratory
  distress at rest with RR 25 BPM, HR 109 with
  sinus tachycardia. Systemic BP is 156/99. She
  is afebrile at this time, but has recurrent
  pneumonias over the last few years. On 12-lead
  EKG we see right axis deviation.

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• She has the following PFT
• FVC - 49 predicted
• Slow VC - 49 predicted
• IC 50 predicted
• FRC- 45 predicted

50
answer

• FVC - 49 predicted implies there is might be
  a severe restrictive or obstructive defect
• Slow VC - 49 predicted supports a severe
  restrictive defect
• IC 50 predicted implies moderate restrictive
  defect
• FRC- 45 predicted implies there is severe
  restrictive defect

51
answer

• The patient has the following parameters on PFT
• PEFR 88 predicted before and after BD no
  obstructive defect
• PIFR 95 predicted no obstructive defect
• FEV1 120 predicted WNL no obstructive
  defect
• FEV1/FVC 145 predicted implies there is
  restrictive defect
• FEV 25-75 98 predicted no obstruction in
  the small airways
• MVV unable to complete

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• What is your overall impression of this patient?

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answer

• This patient has moderate-severe restrictive
  defect with no obstruction