CP

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Author:
jessiekate22
ID:
169364
Filename:
CP
Updated:
2012-09-13 19:55:27
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Pulmonary function testing spirometry
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PFT
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  1. Lung volumes
  2. what is pulmonary function testing?
    - to understand what is happening int he lungs
  3. How is a pulmonary function test performed?
    - spirometry
  4. What is TLC? Total lung capacity?
    - total amount of gas contained in the lung at full inspiration
  5. WHat is FRC?
    • - volume of gas ramining in the lung at the end of a normal expiration
    • - the frc is the point (lung volume) at which all these forces are in equilibrium
  6. What is RV? residule volume
    - volume of gas ramining in the lung at the end of a maximal expiration
  7. What is tidal volume?
    - voume of gas inspired or expired during a normal breath
  8. What is the VC? vital capacity
    - maximal amount that can be expired aftera  full inspiration
  9. What is FRC affected by?
    • - height
    • - lung, chest wall and abdominal pathology (basically elasticity)
    • - gravity
    • - position
  10. What is the significance of FRC?
    • - prevents closure of the small airways and alveoli during expiration
    • - reduces WOB- efficient
    • - allows for continuous gas exchange during inspiration and expiration
  11. What is closing volume?
    - is volume at which small airways start to close
  12. What happens if the closing capacity increases above the FRC?
    then the small airway collapse is likely to occur during breathing - alveolar collapse- blood directed to non ventilated alvolie (V/Q mismatch) - hypoxaemia
  13. What reduces FRC?
    • - age
    • - obestity
    • - post surgery
    • - anaesthesia
    • - restricitve lung disease
    • - increased abdominal pressure
  14. What are measurements of static lung volumes?
    • -measurement of volume of gas in the lung at fixed points during the breathing cycle
    • - lab based
    • - most commonly measured
    • - TLC
    • - RV
    • - FRC

    • - total body plethysmography- pt inside a closed pressure box and inspired and expires against a closed shutter- thoracic volumes can be worked out by pressure changes
    • - helium dilution- a marker gas is used to measure RV or FRC, gas is rebreathed through a closed circuit and the final concentraion is used to calculate the accessible volume of the lung
  15. What does it mean if TLC and FRC are greater than 120% of predocted
    - hyperinflation
  16. What does it mean if RV is greater than the 120% of predicted?
    - gas trapping
  17. What does it mean if TLC, RV and FRC are < 80% predicted?
    - restrictive pattern
  18. What is vital capacity?
    - max expired air after full inspiration
  19. What is spirometry?
    • - involves the measurement of forced expiration from TLC
    • - provides a great deal of infomration
    • -pts readings are compared to age and height match to normal values
    • - identifying pathology
    • - assessing extent of respiratory compromise
    • - monitoring lung disease
  20. What are the measures that are commonly taken through spirometry
    • - FVC- forced vital capacity
    • - VC- slow (unforced) vital capacity
    • - FEV1- forced vital capacity in one second
    • - MMEFR (FER 25-75%)
  21. Spirometry- FEV1
    • - the volume of gas that can be forcefully expired in the first second
    • - FEV1 is a measurement of the flow rate at which air can beblwon out of the lungs
  22. How can FEV1 be reduced?
    • - narrowing of the airways
    • - loss of expiratory power
    • - inadequate expiratory effort
    • - inadequate inspiratory volume
  23. Spirometry FEV1 reported as
    • - as an actual volume (eg 1.0L)
    • - as a % redicted (eg 40% pred)
    • - as a % of FVC (ratio)
  24. FEV1- is after one sec
    -FVC- is the highest point
  25. Spirometry- VC
    -FVC- the total colume of gas that be forcefully expired from TLC. Measure of the accessible lung volume (apart from RV)

    • - VC (slow vital capacity)
    • - used if the pts airways have a tendency to collapse during forceful expiration eg emphysema (COPD)
    • - in this situation VC is more acurate than FVC
  26. How can FVC be reduced?
    • - factors that reduce inspiratory volume- ie not enough volume to start
    • - factors that limit airflow- airway obstruction, loss of lung elasticity
  27. What is the FEV1/FVC ratio?
    - an adult with normal respiratory system functioning can blow out at least 75% of FVC in the first second of forced expiration
  28. What 2 groups lung disease may be categorised?
    • -restrictive pattern
    • - obstructive patterns
  29. How can we tell through spirometry if a condition is obstructive?
    • - low FEV1
    • - FVC- normal, increase or decreased
    • - FEV1/FVC ration <75%
  30. How can you tell through spirometry if a condition is restricitive?
    • - all lung volumes are reduced
    • - FEV1 and FVC are down
    • - FEV1/FVC may be preserved or sometimes elevated
  31. What is maximum mid expiratory flow rate? (MMEFR)
    • - maximum mid expiratory flow rate
    • - forced expiratory flow- 25-75%
    • - detects obstructive changes in small airways- often the first sign of obstructive lung disease
  32. What are the safety precautions of spirometry?
    • - due to being a forced technique- can generate high intrathoracic and abdominal pressure
    • - unstable heart- IHD, angina, arythmias
    • - AAA
    • - hernias
    • - paroxysmal coughing
    • - very unstable airways
  33. When must you stop spirometry?
    • - dizzy/ faint
    • - angina
    • - increase SOB
    • - coughing
    • - pain in thorax
  34. What is peak expiratory flow rate?
    PEFR- effort dependent measurement which gives info about the calibre of airways
  35. SEE NOTES ABOUT FLOW VOLUME LOOPS
  36. What is diffusing capacity for carbon monoxide?
    • - DLCO
    • - the measurement of diffusing capacity for carbon monoxide is made when ever a diffusion problem is suspected
    • - a reduced DLCO indicates a limitation to diffuse eg pulmonary interstitial fibrosis
  37. FRC
    CC= CV+ RV
    if CC increases above FRC or FRC falls below CC collapse will occur

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