PULMONARY FUNCTION TESTS Effort dependent tests Forced expiratory

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) - Sa. O 2 during exercise

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

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

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

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%

Obstructive Restrictive PEFR FEV 1 FVC FEV 1/FVC ratio FEV 1 response to 2 -agonist Normal(Asthma) (COPD) < 75% > 15% (Asthma) <15% (COPD) Normal > 75% No response

BRONCHIAL CHALLENGE TESTING • Exercise • Methacholine/Histamine - marker of airway hyperreactivity - concentration to produce 20% FEV 1 • Allergens/Chemicals - early and late responses - diagnosis of occupational asthma

EXERCISE TESTING • FEV 1 or PEF post exercise - Asthma • Sa. O 2 during exercise in interstitial lung disease - to monitor treatment response • Differentiate cardiac vs respiratory dyspnoea - heart rate vs oxygen uptake vs ventilatory rate

STATIC LUNG VOLUMES • Effort independent test • Helium dilution / N 2 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

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

SUMMARY OF LUNG FUNCTION PATTERNS Parameter PEFR FEV 1 FVC FEV 1/FVC% Gas transfer (TLCO) FEV 1 response to 2 -agonist Obstructive Restrictive Normal in asthma Reduced in COPD <75% >75% in Emphysema Normal in Asthma > 15% in asthma < 15% in COPD No response