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PULMONARY FUNCTION TESTS Effort dependent tests - Forced expiratory volumes/flow rates

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) - SaO 2 during exercise.

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PULMONARY FUNCTION TESTS Effort dependent tests - Forced expiratory volumes/flow rates

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  1. 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

  2. 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%)

  3. 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

  4. EXPIRATORY FLOW RATES • Shape of expiratory flow-volume curve: • Volume dependent expiratory airway closure • - asthma, chronic bronchitis • Pressure dependent expiratory airway closure • - emphysema

  5. 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%

  6. Obstructive Restrictive PEFR  Normal FEV1    FVC Normal(Asthma)  (COPD) FEV1/FVC ratio < 75% > 75% FEV1 response > 15% (Asthma) to 2-agonist <15% (COPD) No response

  7. 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

  8. 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

  9. 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

  10. 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

  11. SUMMARY OF LUNG FUNCTION PATTERNS Parameter Obstructive Restrictive PEFR  Normal FEV1   FVC Normal in asthma  Reduced in COPD FEV1/FVC% <75% >75% Gas transfer (TLCO)  in Emphysema Normal in Asthma FEV1 response to 2-agonist > 15% in asthma No response < 15% in COPD 

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