PULMONARY FUNCTION TESTS

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• PULMONARY FUNCTION TESTS
• Effort dependent tests
• - Forced expiratory volumes/flow rates
• Effort independent tests
• - Relaxed vital capacity
• - Helium static lung volume
• Gas diffusion tests
• - CO transfer factor
• - Arterial blood gases (resting)
• - SaO2 during exercise

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• DYNAMIC LUNG VOLUMES (SPIROMETRY)
• Volume (L) vs Time (s) curve
• - Forced expiratory manoeuvre from TLC to RV
• Forced expiratory volume in 1 s FEV1 (L)
• Forced vital capacity FVC (L)
• Forced expiratory ratio FER (FEV1/FVC)

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EXPIRATORY FLOW RATES Flow -volume curve dv/dt
(flow-rate) from volume time curve - Flow rate
(L/s) plotted against forced expiratory volume
(L) - from TLC to RV
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• EXPIRATORY FLOW RATES
• Shape of expiratory flow-volume curve
• Volume dependent expiratory airway closure
• - asthma, chronic bronchitis
• Pressure dependent expiratory airway closure
• - emphysema

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• EXPIRATORY FLOW RATES
• From flow-volume curve
• Peak expiratory flow rate (PEFR)
• - expressed in L/min (L/s x 60)
• - also measurable with simple linear peak flow
  meter
• Forced expiratory flow rate (FEFR) at a of FVC
• - FEFR 50, FEFR 75

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Obstructive Restrictive PEFR ?
Normal FEV1 ? ? ? FVC
Normal(Asthma) ?

?(COPD) FEV1/FVC ratio lt 75
gt 75 FEV1 response
gt 15 (Asthma) to ?2-agonist
lt15 (COPD) No response
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• BRONCHIAL CHALLENGE TESTING
• Exercise
• Methacholine/Histamine
• - marker of airway hyperreactivity
• - concentration to produce 20 ? FEV1
• Allergens/Chemicals
• - early and late responses
• - diagnosis of occupational asthma

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• EXERCISE TESTING
• ?FEV1 or ?PEF post exercise - Asthma
• ?SaO2 during exercise in interstitial lung
  disease
• - to monitor treatment response
• Differentiate cardiac vs respiratory dyspnoea
• - heart rate vs oxygen uptake vs ventilatory
  rate

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• STATIC LUNG VOLUMES
• Effort independent test
• Helium dilution / N2 washout functional
  residual capacity
• (RV FRC - ERV) (TLC VC RV)
• ?TLC in hyperinflation (Emphysema)
• ?TLC in restrictive lung disease
• Gas trapping in COPD
• (RV/TLC) (RVC - FVC/RVC)
• TLC adds little to RVC and FVC

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• TRANSFER FACTOR (DIFFUSION CAPACITY)
• CO diffusion across alveolar-capillary barrier
• TLCO - total lung transfer for CO
• ?TLCO Anaemia, Emphysema, Int lung disease,
  Pulmonary oedema, Pulmonary emboli
• To monitor treatment response in In lung disease

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SUMMARY OF LUNG FUNCTION PATTERNS Parameter Obst
ructive Restrictive PEFR ? Normal FEV1 ?
? FVC Normal in asthma
? Reduced in COPD FEV1/FVC
lt75 gt75 Gas transfer (TLCO) ? in
Emphysema Normal in Asthma FEV1 response to
? 2-agonist gt 15 in asthma No response lt
15 in COPD
?