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Pulmonary Funtion Tests BY:-Abhishek Verma J R IIPG Department of General MedicineRohilkhand Medical College And Hospital

Pulmonary Function TestsThe term encompasses a wide variety of objective tests to assess lung function.Provide objective and standardized measurements for assessing the presence and severity of respiratory dysfunction.Evaluates one or more major aspects of the respiratory system:Lung volumesAirway functionGas exchangevide valuable clinical information.

Includes..SpirometryBronchial provocation testsStatic lung volumesCarbon monoxide diffusing capacityAlveolar arterial oxygen gradientExercise testingBed side PFTs

IndicationsDetect disease Evaluate extent and monitor course of diseaseEvaluate treatmentMeasure effects of exposuresAssess risk for surgical procedures

Contraindications Hemoptysis of unknown originPneumothoraxUnstable angina pectoris Recent myocardial infarctionThoracic aneurysms Abdominal aneurysmsCerebral aneurysmsRecent eye surgery (increased intraocular pressure during forced expiration) Recent abdominal or thoracic surgical proceduresHistory of syncope associated with forced exhalation

SpirometrySpirometry is a medical test that measures the volume of air an individual inhales or exhales as a function of time.Measurement of the pattern of air movement into and out of the lungs during controlled ventilatory maneuvers.Often done as a maximal expiratory maneuver.

Indications:1. Symptoms and clinical signs Dyspnea with or without or wheezing Chest pain or orthopnea Cough for a longer time with or without phlegm production Cyanosis Decreased or unusual breath sounds 2. Abnormal chest x-ray (e.g. Hyperinflation) 3. Abnormal blood gases (hypoxemia, hypercapnia) 4. Abnormal laboratory findings (e.g. polycythemia) 5. Monitoring of known pulmonary diseases

Contd..6. Assessing severity or progression of disease (e.g. asthma, COPD) 7. To screen individuals at risk of having pulmonary disease (eg. Smokers ,Individuals in occupations with exposures to injurious subs.)8. Assess prognosis (after ttt, lung transplant ...etc.)9. Assess health status before beginning strenuous physical activity

Contraindications for spirometry1. Acute disorders affecting test performance (e.g. vomiting, nausea, vertigo) 2. Hemoptysis of unknown origin (FVC maneuver may aggravate underlying condition.) 3. Pneumothorax 4. Recent abdominal or thoracic surgery 5. Recent eye surgery (increases in intraocular pressure during spirometry) 6. Recent myocardial infarction or unstable angina 7. Thoracic, abdominal, or cerebral aneurysms (risk of rupture because of increased thoracic pressure)

Terminology & InterpretationForced vital capacity (FVC):Total volume of air that can be exhaled forcefully from TLCThe majority of FVC can be exhaled in 60% Normal40-60% Mild obstruction20-40% Moderate obstruction are not measured by gas dilution technique, but measured by body plethysmograph

N2 WASH OUT METHODFollowing a maximal expiration (RV) or normal expiration (FRC), Pt. inspires 100% O2 and then expires it into spirometer ( free of N2) over next few minutes (usually 6-7 min.), till all the N2 is washed out of the lungs. N2 conc. of spirometer is calculated followed by total vol.of AIR exhaled. As air has 80% N2 so actual FRC/RV is calculated.

TESTS FOR GAS EXCHANGE FUNCTION1) ALVEOLAR-ARTERIAL O2 TENSION GRADIENT:Sensitive indicator of detecting regional V/Q inequalityNormal value in young adult at room air = 8 mmhg to upto 25 mmhg in 8th decade (d/t decrease in PaO2)Abnormal high values at room air is seen in asymptomatic smokers & chr. Bronchitis (min. symptoms) PAO2 = PIO2 PaCo2 R

Contd..2) DYSPNOEA DIFFENRENTIATION INDEX (DDI):To differentiate dyspnoea due to resp/ cardiac diseases DDI = PEFR x PaCO2 1000DDI- Lower in resp. pathology

Contd..3) DIFFUSING CAPACITY OF LUNG (DL): defined as the rate at which gas enters into bld. divided by its driving pressureDRIVING PRESSURE: gradient b/w alveoli & end capillary tensions.Ficks law of diffusion : Vgas = A x D x (P1-P2) TD= diffusion coeff= solubility MW

Contd..DL IS MEASURED BY USING CO, because:High affinity for Hb which is approx. 200 times that of O2 , so does not rapidly build up in plasmaUnder normal condition it has low blood concentration 0Therefore, pulmonary concentration0

SINGLE BREATH TEST USING COPt inspires a dilute mixture of CO and hold the breath for 10 secs.CO taken up is determined by infrared analysis: DlCO = CO ml/min/mmhg PACO PcCON range 20- 30 ml/min./mmhg.DLO2 = DLCO x 1.23

Diffusing Capacity Decreased DLCO (120-140% predicted)

Asthma (or normal)

Pulmonary hemorrhage

Polycythemia

Left to right shunt

TESTS FOR CARDIOPLULMONARY INTERACTIONSReflects gas exchange, ventilation, tissue O2, CO.QUALITATIVE- history, exam, ABG, stair climbing testQUANTITATIVE- 6 minute walk test

1) STAIR CLIMBING TEST:If able to climb 3 flights of stairs without stopping/dypnoea at his/her own pace- ed morbidity & mortalityIf not able to climb 2 flights high risk2) 6 MINUTE WALK TEST:Gold standardCardiopulmonary reserve is measured by estimating max. O2 uptake during exerciseModified if pt. cant walk bicycle/ arm exercisesIf pt. is able to walk for >2000 feet during 6 min pd,VO2 max > 15 ml/kg/minIf 1080 feet in 1 min : VO2 of 12ml/kg/minSimultaneously oximetry is done & if Spo2 falls >4%- high risk

BED SIDE PFTSabrasez breath holding test:Ask the patient to take a full but not too deep breath & hold it as long as possible. >25 SEC.-NORMAL Cardiopulmonary Reserve (CPR) 15-25 SEC- LIMITED CPR 60 L/minFEV1 > 1.6LMODIFIED MATCH TEST: DISTANCE MBC 9 >150 L/MIN. 6 >60 L/MIN. 3 > 40 L/MIN.

4) COUGH TEST: DEEP BREATH F/BY COUGH ABILITY TO COUGH STRENGTH EFFECTIVENESSINADEQUATE COUGH IF: FVC 6 SEC RES. LUNG DIS.- < 3 SEC

6) WRIGHT PEAK FLOW METER: Measures PEFR (Peak Expiratory Flow Rate) N MALES- 450-700 L/MIN. FEMALES- 350-500 L/MIN.