PULMONARY FUNCTION TESTS.ppt

1、PULMONARY FUNCTION TESTS,Lung Volumes and Capacities,PFT tracings have: Four Lung volumes: tidal volume, inspiratory reserve volume, expiratory reserve volume, and residual volume Five capacities:, inspiratory capacity, expiratory capacity, vital capacity, functional residual capacity, and total lun

2、g capacity,Addition of 2 or more volumes comprise a capacity.,Lung Volumes,Tidal Volume (TV): volume of air inhaled or exhaled with each breath during quiet breathing (6-8 ml/kg) Inspiratory Reserve Volume (IRV): maximum volume of air inhaled from the end-inspiratory tidal position.(1900-3300ml) Exp

3、iratory Reserve Volume (ERV): maximum volume of air that can be exhaled from resting end-expiratory tidal position.( 700-1000ml).,Lung Volumes,Residual Volume (RV): Volume of air remaining in lungs after maximium exhalation (20-25 ml/kg) (1700-2100ml) Indirectly measured (FRC-ERV) It can not be meas

4、ured by spirometry,Lung Capacities,Total Lung Capacity (TLC): Sum of all volume compartments or volume of air in lungs after maximum inspiration (4-6 L) Vital Capacity (VC): TLC minus RV or maximum volume of air exhaled from maximal inspiratory level. (60-70 ml/kg) (3100-4800ml) Inspiratory Capacity

5、 (IC): Sum of IRV and TV or the maximum volume of air that can be inhaled from the end-expiratory tidal position. (2400-3800ml). Expiratory Capacity (EC): TV+ ERV,Lung Capacities (cont.),Functional Residual Capacity (FRC): Sum of RV and ERV or the volume of air in the lungs at end-expiratory tidal p

6、osition.(30-35 ml/kg) (2300-3300ml). Measured with multiple-breath closed-circuit helium dilution, multiple-breath open-circuit nitrogen washout, or body plethysmography. It can not be measured by spirometry),VOLUMES, CAPACITIES AND THEIR CLINICAL SIGNIFICANCE,TIDAL VOLUME (TV): VOLUME OF AIR INHALE

7、D/EXHALED IN EACH BREATH DURING QUIET RESPIRATION. N 6-8 ml/kg. TV FALLS WITH DECREASE IN COMPLIANCE, DECREASED VENTILATORY MUSCLE STRENGTH. INSPIRATORY RESERVE VOLUME (IRV): MAX. VOL. OF AIR WHICH CAN BE INSPIRED AFTER A NORMAL TIDAL INSPIRATION i.e. FROM END INSPIRATION PT. N- 1900 ml- 3300 ml.,CO

8、NTINUED,3) EXPIRATORY RESERVE VOLUME (ERV): MAX. VOLUME OF AIR WHICH CAN BE EXPIRED AFTER A NORMAL TIDAL EXPIRATION i.e. FROM END EXPIRATION PT. N- 700 ml 1000 ml 4) INSPIRATORY CAPACITY (IC) : MAX. VOL. OF AIR WHICH CAN BE INSPIRED AFTER A NORMAL TIDAL EXPIRATION. IC = IRV + TV N-2400 ml 3800 ml.,C

9、ONTINUED.,4) VITAL CAPACITY: COINED BY JOHN HUTCHINSON. MAX. VOL. OF AIR EXPIRED AFTER A MAX. INSPIRATION . MEASURED WITH VITALOGRAPH VC= TV+ERV+IRV N- 3.1-4.8L. OR 60-70 ml/kg VC IS COSIDERED ABNORMAL IF 80% OF PREDICTED VALUE,FACTORS INFLUENCING VC,PHYSIOLOGICAL : physical dimensions- directly pro

10、portional to ht. SEX more in males : large chest size, more muscle power, more BSA. AGE decreases with increasing age STRENGTH OF RESPIRATORY MUSCLES POSTURE decreases in supine position PREGNANCY- unchanged or increases by 10% ( increase in AP diameter In pregnancy),CONTINUED,PATHOLOGICAL: DISEASE

11、OF RESPIRATORY MUSCLES ABDOMINAL CONDITION : pain, dis. and splinting,FACTORS DECREASING VITAL CAPACITY,Alteration in muscle power- d/t drugs, n-m dis., cerebral tumours. Pulmonary diseases pneumonia, chronic bronchitis, asthma, fibrosis, emphysema, pulmonary edema,. Space occupying lesions in chest

12、- tumours, pleural/pericardial effusion, kyphoscoliosis Abdominal tumours, ascites.,5) Depression of respiration : opioids/ volatile agents 6) Abdominal splinting abdominal binders, tight bandages, hip spica. 7)Abdominal pain decreases by 50% flow plotted as function of volume Classic spirogram-volu

13、me as a function of time,Normal Flow-Volume Curve and Spirogram,Spirometry Interpretation: So what constitutes normal?,Normal values vary and depend on: Height Age Gender Ethnicity,Acceptable and Unacceptable Spirograms (from ATS, 1994),Measurements Obtained from the FVC Curve,FEV1-the volume exhale

14、d during the first second of the FVC maneuver FEF 25-75%-the mean expiratory flow during the middle half of the FVC maneuver; reflects flow through the small (2 mm in diameter) airways FEV1/FVC-the ratio of FEV1 to FVC X 100 (expressed as a percent); an important value because a reduction of this ra

15、tio from expected values is specific for obstructive rather than restrictive diseases,Spirometry Interpretation: Obstructive vs. Restrictive Defect,Obstructive Disorders Characterized by a limitation of expiratory airflow so that airways cannot empty as rapidly compared to normal (such as through na

16、rrowed airways from bronchospasm, inflammation, etc.) Examples: Asthma Emphysema Cystic Fibrosis,Restrictive Disorders Characterized by reduced lung volumes/decreased lung compliance Examples: Interstitial Fibrosis Scoliosis Obesity Lung Resection Neuromuscular diseases Cystic Fibrosis,Normal vs. Ob

17、structive vs. Restrictive,(Hyatt, 2003),Spirometry Interpretation: Obstructive vs. Restrictive Defect,Obstructive Disorders FVC nl or FEV1 FEF25-75% FEV1/FVC TLC nl or ,Restrictive Disorders FVC FEV1 FEF 25-75% nl to FEV1/FVC nl to TLC ,Spirometry Interpretation: What do the numbers mean?,FVC Interp

18、retation of % predicted: 80-120% Normal 70-79%Mild reduction 50%-69% Moderate reduction 50% Severe reduction,FEV1 Interpretation of % predicted: 75% Normal 60%-75% Mild obstruction 50-59% Moderate obstruction 60 y.o. subtract 5,Spirometry Interpretation: What do the numbers mean?,FEF 25-75% Interpre

19、tation of % predicted: 79% Normal 60-79%Mild obstruction 40-59%Moderate obstruction 40% Severe obstruction,FEV1/FVC Interpretation of absolute value: 80 or higherNormal 79 or lowerAbnormal,What about lung volumes and obstructive and restrictive disease?,(From Ruppel, 2003),MEASUREMENTS OF VOLUMES,TL

20、C, RV, FRC MEASURED USING Nitrogen washout method Inert gas (helium) dilution method Total body plethysmography,CONTINUED.,1) HELIUM DILUTION METHOD: Patient breathes in and out of a spirometer filled with 10% helium and 90% o2, till conc. In spirometer and lung becomes same (equilibirium). As no he

21、lium is lost; (as he is insoluble in blood) C1 X V1 = C2 ( V1 + V2) V2 = V1 ( C1 C2) C2 V1= VOL. OF SPIROMETER V2= FRC C1= Conc.of He in the spirometer before equilibrium C2 = Conc, of He in the spirometer after equilibrium,CONTINUED,2) TOTAL BODY PLETHYSMOGRAPHY: Subject sits in an air tight box. A

22、t the end of normal exhalation shuttle of mouthpiece closed and pt. is asked to make resp. efforts. As subject inhales expands gas volume in the lung so lung vol. increases and box pressure rises and box vol. decreases. BOYLES LAW: PV = CONSTANT (at constant temp.) For Box p1v1 = p2 (v1- v) For Subj

23、ect p3 x v2 =p4 (v2 - v) P1- initial box pr. P2- final box pr. V1- initial box vol. v- change in box vol. P3- initial mouth pr., p4- final mouth pr. V2- FRC,CONTINUED,DIFFERENCE BETWEEN THE TWO METHODS: In healthy people there is very little difference. Gas dilution technique measures only the commu

24、nicating gas volume. Thus, Gas trapped behind closed airways Gas in pneumothorax = are not measured by gas dilution technique, but measured by body plethysmograph,CONTINUED,3) N2 WASH OUT METHOD: Following a maximal expiration (RV) or normal expiration (FRC), Pt. inspires 100% O2 and then expires it

25、 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. E.g. Total vol. collected = 50 L (as N2 makes 80% of FRC o

26、n room air) Measured N2 = 5% vol. of N2 in bag = 50 x .05 = 2.5L 2.5 L = X L .80 FRC 1 FRC X = 3.125 l (THIS IS PTS FRC),PROBLEMS WITH N2 WASH OUT METHOD,Atelectasis may result from washout of nitrogen from poorly ventilated lung zones (obstructed areas) Elimination of hypoxic drive in CO2 retainers

27、 is possible Underestimates FRC due to underventilation of areas with trapped gas,MEASUREMENT OF DYNAMIC LUNG VOLUMES,TIMED EXPIRED SPIROGRAMS,FORCED VITAL CAPACITY (FVC),Max vol. Of air which can be expired out as forcefully and rapidly as possible, following a maximal inspiration to TLC. Exhaled v

28、olume is recorded with respect to time. Indirectly reflects flow resistance property of airways. Normal healthy subjects have VC = FVC. Prior instruction to patients, practice attempts as it needs patient cooperation and effect. Exhalation should take at least 4 sec and should not be interrupted by

29、cough, glottic closure or mechanical obstruction.,FORCED VITAL CAPACITY IN 1 SEC. (FEV1),Forced expired vol. In 1 sec during fvc maneuver. Expressed as an absolute value or % of fvc. N- FEV1 (1 SEC)- 75-85% OF FVC FEV2 (2 SEC)- 94% OF FVC FEV3 (3 SEC)- 97% OF FVC,CONTINUED,CLINICAL RANGE (FEV1),3 -

30、4.5 L 1.5 2.5 L 1 L 0.8 L 0.5 L,PATIENT GROUP,NORMAL ADULT MILD MOD.OBSTRUCTION HANDICAPPED DISABILITY SEVERE EMPHYSEMA,CONTINUED,FEV1 Decreased in both obstructive as in malignancy or tracheomalacia,TESTS FOR GAS EXCHANGE FUNCTION,1) ALVEOLAR-ARTERIAL O2 TENSION GRADIENT: Sensitive indicator of det

31、ecting regional V/Q inequality N value in young adult at room air = 8 mmhg to upto 25 mmhg in 8th decade (d/t decrease in PaO2) AbN high values at room air is seen in asymptomatic smokers & chr. Bronchitis (min. symptoms) PAO2 = PIO2 PaCo2 R,CONTINUED.,2) DYSPNEA DIFFENRENTIATION INDEX (DDI): To d/f

32、 dyspnea due to resp/ cardiac ds DDI = PEFR x PaCO2 1000 DDI- Lower in resp. pathology,CONTINUED,3) DIFFUSING CAPACITY OF LUNG: defined as the rate at which gas enters into bld. divided by its driving pr. DRIVING PR: gradient b/w alveoli & end capillary tensions. Ficks law of diffusion : Vgas = A x

33、D x (P1-P2) T D= diffusion coeff= solubility MW,CONTINUED.,DL IS MEASURED BY USING CO, COZ: High affinity for Hb which is approx. 200 times that of O2 , so does not rapidly build up in plasma Under N condition it has low bld conc 0 Therefore, pulm conc.0,SINGLE BREATH TEST USING CO,Pt inspires a dil

34、ute mixture of CO and hold the breath for 10 secs. CO taken up is determined by infrared analysis: DlCO = CO ml/min/mmhg PACO PcCO N range 20- 30 ml/min./mmhg. DLO2 = DLCO x 1.23,DLCO decreases in- Emphysema, lung resection, pul. Embolism, anaemia Pulmonary fibrosis, sarcoidosis- increased thickness

35、 DLCO increases in: (Cond. Which increase pulm, bld flow) Supine position Exercise Obesity L-R shunt,TESTS FOR CARDIOPLULMONARY INTERACTIONS,Reflects gas exchange, ventilation, tissue O2, CO. QUALITATIVE- history, exam, ABG, stair climbing test QUANTITATIVE- 6 minute walk test,CONTINUED.,1) STAIR CL

36、IMBING TEST: If able to climb 3 flights of stairs without stopping/dypnoea at his/her own pace- ed morbidity & mortality If not able to climb 2 flights high risk 2) 6 MINUTE WALK TEST: Gold standard C.P. reserve is measured by estimating max. O2 uptake during exercise Modified if pt. cant walk bicycle/ arm exercises I