PFTs Flashcards
What are restrictive disorders?
Extra-airway diseases
Disorders that RESTRICT the ability for the lungs to fill.
What are obstructive disorders?
Airway diseases
Disorders associated withe OBSTRUCTED airflow.
Outline the protocol for a PFT.
Wear nose clip Inhales steadily to TLC Wraps lips round mouthpiece Patient exhales as hard and fast as possible Exhalation continues until RV is reached
Visually inspect performance and volume time curve and repeat if necessary. Look out for:
- Inconsistencies with clinical picture
- Interrupted flow data
What does a flow-volume curve look like for a mild obstructive disease?
Reduced FVC
Indented exhalation curve (called ‘coving’)
What does a flow-volume curve look like for a severe obstructive disease?
Reduced FVC
Indented exhalation curve
Reduced PEFR
What does a flow-volume curve look like for a restrictive disease?
Reduced FVC
Narrower Curve
What does a flow-volume curve look like for a variable extrathoracic obstruction?
Blunted inspiratory curve
What does a flow-volume curve look like for a variable intrathoracic obstruction?
Blunted expiratory curve
What does a flow-volume curve look like for fixed airway obstruction?
Blunted expiratory and inspiratory curve
Are lung volumes most accurately measured when sitting or standing?
Standing
Why is tidal volume easily overestimated?
It has a variable upper point.
Are precision and accuracy the same?
No
What does hyper inflated breathing result in?
Increase rate and decreased TV
Feels uncomfortable and is a lot of effort.
What is the best way to measure PEFR?
Peak flow meters
What is the highest recorder value on a volume-time spirometry curve?
FVC
How do you calculate FEV1 on a volume-time spirometry curve?
Volume at 1 second
How do you calculate PEFR from a volume-time spirometry curve?
Gradient of line (includes error)
How do you calculate FVC from a flow-volume loop spirometry curve?
Width of loop
How do you calculate FEV1 from a flow-volume loop spirometry curve?
Volume indicated by separate marker
How do you calculate PEFR from a flow-volume loop spirometry curve?
Highest point of upper portion of loop
Identify reasons that spirometric PFTs may be undertaken?
Evaluate symptoms (such as breathlessness)
Monitor progression of lung disease over time (e.g. worsening COPD)
Monitor treatment efficacy (e.g. between different bronchodilators)
As a screening tool in the absence of symptoms (e.g. obstructive airway disease)
Which non-disease factors have the greatest influence on healthy lung volumes?
Height
Age
Sex (minor impact)
(Ethnicity also an important determinant)
What factor is decreased in emphysema?
SA for GE
What factor is decreased in COPD?
Partial pressure gradient leading to inadequate ventilation.
What factor is increased in COPD?
Diffusion distance
Increased due to increased interstitial/pulmonary oedema secondary to hypoxia.
What are the major disadvantages of spirometric PFTs?
Heavy reliance on technique and can be rather uncomfortable for patients, reducing their motivation to apply maximum effort.
