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PULMONARY FUNCTION TESTS Dr. Pooja Chopra
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 lung 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.( ml) Expiratory Reserve Volume (ERV): maximum volume of air that can be exhaled from resting end-expiratory tidal position.( ml).
Lung Volumes Residual Volume (RV): – Volume of air remaining in lungs after maximium exhalation (20-25 ml/kg) ( ml) – Indirectly measured (FRC-ERV) – It can not be measured 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) ( ml) Inspiratory Capacity (IC): Sum of IRV and TV or the maximum volume of air that can be inhaled from the end-expiratory tidal position. ( ml). 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 position.(30-35 ml/kg) ( ml). – 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 1)TIDAL VOLUME (TV): VOLUME OF AIR INHALED/EXHALED IN EACH BREATH DURING QUIET RESPIRATION. N – 6-8 ml/kg. TV FALLS WITH DECREASE IN COMPLIANCE, DECREASED VENTILATORY MUSCLE STRENGTH. 2)INSPIRATORY RESERVE VOLUME (IRV): MAX. VOL. OF AIR WHICH CAN BE INSPIRED AFTER A NORMAL TIDAL INSPIRATION i.e. FROM END INSPIRATION PT. N ml ml.
CONTINUED……… 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.
CONTINUED… …….. 4) VITAL CAPACITY: COINED BY JOHN HUTCHINSON. MAX. VOL. OF AIR EXPIRED AFTER A MAX. INSPIRATION. MEASURED WITH VITALOGRAPH VC= TV+ERV+IRV N L. OR ml/kg VC IS COSIDERED ABNORMAL IF ≤ 80% OF PREDICTED VALUE
FACTORS INFLUENCING VC PHYSIOLOGICAL : physical dimensions- directly proportional 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 OF RESPIRATORY MUSCLES ABDOMINAL CONDITION : pain, dis. and splinting
VC CONTINUED……. VC correlates with capability for deep breathing and effective cough. So in post operative period if VC falls below 3 times VC– artificial respiration is needed to maintain airway clear of secretions.
CONTINUED……. 6) TOTAL LUNG CAPACITY : Maximum volume of air attained in lungs after maximal inspiration. N- 4-6 l or ml/kg TLC= VC + RV 7) RESIDUAL VOLUME (RV): Volume of air remaining in the lungs after maximal expiration. N – 2100 ml OR 20 – 25 ml/kg.
CONTINUED…… 8) FUNCTIONAL RESIDUAL CAPACITY (FRC): Volume of air remaining in the lungs after normal tidal expiration, when there is no airflow. N L OR ml/kg. FRC = RV + ERV Decreses under anaesthesia with spontaneous Respiration – decreases by 20% With paralysis – decreases by 16%
FACTORS AFFECTING FRC FRC INCREASES WITH Increased height Erect position (30% more than in supine) Decreased lung recoil (e.g. emphysema) FRC DECREASES WITH Obesity Muscle paralysis (especially in supine) Supine position Restrictive lung disease (e.g. fibrosis, Pregnancy) Anaesthesia FRC does NOT change with age.
FUNCTIONS OF FRC Oxygen store Buffer for maintaining a steady arterial po2 Partial inflation helps prevent atelectasis Minimise the work of breathing Minimise pulmonary vascular resistance Minimised v/q mismatch - only if closing capacity is less than frc Keep airway resistance low (but not minimal
Pulmonary Function Tests The 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.
GOALS To predict the presence of pulmonary dysfunction To know the functional nature of disease (obstructive or restrictive. ) To assess the severity of disease To assess the progression of disease To assess the response to treatment To identify patients at increased risk of morbidity and mortality, undergoing pulmonary resection.
To wean patient from ventilator in icu. Medicolegal- to assess lung impairment as a result of occupational hazard. Epidemiological surveys- to assess the hazards to document incidence of disease To identify patients at perioperative risk of pulmonary complications GOALS, CONTINUED……..
INDICATIONS OF PFT IN PAC TISI GUIDELINES FOR PREOPERATIVE SPIROMETRY Age > 70 yrs. Morbid obesity Thoracic surgery Upper abdominal surgery Smoking history and cough Any pulomonary disease
INDICATIONS FOR PREOPERATIVE SPIROMETRY ACP GUIDELINES FOR PREOPERATIVE SPIROMETRY Lung resection H/o smoking, dyspnoea Cardiac surgery Upper abdominal surgery Lower abdominal surgery Uncharacterized pulmonary disease(defined as history of pulmonary Disease or symptoms and no PFT in last 60 days)
BED SIDE PFT 1)Sabrasez 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) SEC- LIMITED CPR <15 SEC- VERY POOR CPR (Contraindication for elective surgery) SEC ml VC 20 – 25 SEC ml VC SEC ml VC SEC ml VC SEC ml VC
BED SIDE PFT 2) Single breath count: After deep breath, hold it and start counting till the next breath. N COUNT Indicates vital capacity
BED SIDE PFT 3) SCHNEIDER’S MATCH BLOWING TEST: MEASURES Maximum Breathing Capacity. Ask to blow a match stick from a distance of 6” (15 cms) with- Mouth wide open Chin rested/supported No purse lipping No head movement No air movement in the room Mouth and match at the same level
BED SIDE PFT Can not blow out a match – MBC < 60 L/min – FEV1 < 1.6L Able to blow out a match – MBC > 60 L/min – FEV1 > 1.6L MODIFIED MATCH TEST: DISTANCE MBC 9” >150 L/MIN. 6” >60 L/MIN. 3” > 40 L/MIN.
BED SIDE TEST 4) COUGH TEST: DEEP BREATH F/BY COUGH ABILITY TO COUGH STRENGTH EFFECTIVENESS INADEQUATE COUGH IF: FVC<20 ML/KG FEV1 < 15 ML/KG PEFR < 200 L/MIN. VC ~ 3 TIMES TV FOR EFFECTIVE COUGH. A wet productive cough / self propagated paraoxysms of coughing – patient susceptible for pulmonary Complication.
BED SIDE TEST 5) FORCED EXPIRATORY TIME: After deep breath, exhale maximally and forcefully & keep stethoscope over trachea & listen. N FET – 3-5 SECS. OBS.LUNG DIS. - > 6 SEC RES. LUNG DIS.- < 3 SEC
BED SIDE PFT 6) WRIGHT PEAK FLOW METER: Measures PEFR (Peak Expiratory Flow Rate) N – MALES L/MIN. FEMALES L/MIN. <200 L/ MIN. – INADEQUATE COUGH EFFICIENCY. 7) DEBONO WHISTLE BLOWING TEST: MEASURES PEFR. Patient blows down a wide bore tube at the end of which is a whistle, on the side is a hole with adjustable knob. As subject blows → whistle blows, leak hole is gradually increased till the intensity of whistle disappears. At the last position at which the whistle can be blown, the PEFR can be read off the scale.
MEASUREMENT OF TV & MV 8) Wright respirometer : measures tv, mv (15 secs times 4) Simple and rapid Instrument- compact, light and portable. Disadvantage: It under- reads at low flow rates and over- reads at high flow rates. Can be connected to endotracheal tube or face mask Prior explanation to patients needed. Ideally done in sitting pos. MV- instrument record for 1 min. And read directly TV-calculated and dividing MV by counting Respiratory Rate. Accurate measurement in the range of l/min.(±10%) USES: 1)BED SIDE PFT 2) ICU – WEANIG PTS. FROM Ventilation.
BED SIDE PFT 9) MICROSPIROMETERS – MEASURE VC. 10) BED SIDE PULSE OXIMETRY 11) ABG.
CATEGORIZATION OF PFT 2) GAS- EXCHANGE TESTS: A) Alveolar-arterial po2 gradient B) Diffusion capacity C) Gas distribution tests- single breath N 2 test. - Multiple Breath N 2 test - Helium dilution method. - Radio Xe scinitigram. D) ventilation – perfusion tests A) ABG B) single breath CO 2 elimination test C) Shunt equation
CATEGORIZATION OF PFT 3) CARDIOPULMONARY INTERACTION : A) Qualitative tests: - History, examination - Abg - Stair climbing test B) Quantitative tests - 6 min. Walk test (gold standard)
STATIC LUNG VOLUMES AND CAPACITIES SPIROMETRY : CORNERSTONE OF ALL PFTs. John hutchinson – invented spirometer. “Spirometry is a medical test that measures the volume of air an individual inhales or exhales as a function of time.” Measures VC, FVC, FEV1, PEFR. CAN’T MEASURE – FRC, RV, TLC.
PREREQUISITIES Prior explanation to the patient Not to smoke /inhale bronchodilators 6 hrs prior or oral bronchodilators 12hrs prior. Remove any tight clothings/ waist belt/ dentures Pt. Seated comfortably If obese, child < 12 yrs- standing
PREREQUISITES Nose clip to close nostrils. Exp. Effort shld last ≥ 4 secs. Should not be interfered by coughing, glottic closure, mechanical obstruction. 3 acceptable tracings taken & largest value is used.
SPIROMETER Double walled cylinder with water to maintain water tight seal Inverted bell (9 l) attached to pulley which carries a counterweight and pen – moves up and down as volume of bell changes BREATHING ASSEMBLY i.E. Unidirectional breathing valves with mouth piece.
Flow-Volume Curves and Spirograms Two ways to record results of FVC maneuver: – Flow-volume curve---flow meter measures flow rate in L/s upon exhalation; flow plotted as function of volume – Classic spirogram---volume 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 FEV 1 ---the volume exhaled 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 FEV 1 /FVC---the ratio of FEV1 to FVC X 100 (expressed as a percent); an important value because a reduction of this ratio 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 narrowed 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. Obstructive vs. Restrictive (Hyatt, 2003)
Spirometry Interpretation: What do the numbers mean? FVC Interpretation of % predicted: – % 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 – <49% Severe obstruction 60 y.o. subtract 5
Spirometry Interpretation: What do the numbers mean? FEF 25-75% Interpretation of % predicted: – >79% Normal – 60-79%Mild obstruction – 40-59%Moderate obstruction – <40% Severe obstruction FEV1/FVC Interpretation of absolute value: – 80 or higher Normal – 79 or lower Abnormal
What about lung volumes and obstructive and restrictive disease? (From Ruppel, 2003)
MEASUREMENTS OF VOLUMES TLC, 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 helium 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. At 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. BOYLE’S LAW: PV = CONSTANT (at constant temp.) For Box – p1v1 = p2 (v1- ∆v) For Subject – 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 communicating 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 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 on 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 = l (THIS IS PT’S FRC)
PROBLEMS WITH N2 WASH OUT METHOD Atelectasis may result from washout of nitrogen from poorly ventilated lung zones (obstructed areas) Atelectasis may result from washout of nitrogen from poorly ventilated lung zones (obstructed areas) Elimination of hypoxic drive in CO 2 retainers is possible Elimination of hypoxic drive in CO 2 retainers is possible Underestimates FRC due to underventilation of areas with trapped gas Underestimates FRC due to underventilation of areas with trapped gas
MEASUREMENT OF DYNAMIC LUNG VOLUMES TIMED EXPIRED SPIROGRAMS FEF 25–75% = forced expiratory flow during expiration of 25 to 75% of the FVC; FEV 1 = forced expiratory volume in the first second of forced vital capacity maneuver; FVC = forced vital capacity (the maximum amount of air forcibly expired after maximum inspiration).
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 volume 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 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) % OF FVC FEV2 (2 SEC)- 94% OF FVC FEV3 (3 SEC)- 97% OF FVC
CONTINUED…… CLINICAL RANGE (FEV1) 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 & restrictive lung disorders. FEV1/FVC – Reduced in obstructive disorders. NORMAL VALUE IS 75 – 85 % (FEV1/FVC) < 70% OF PREDICTED VALUE – MILD OBST. < 60% OF PREDICTED VALUE – MODERATE OBST. < 50% OF PREDICTED VALUE – SEVERE OBST.
CONTINUED…… DISEASE STATES FVC FEV1 FEV1/FVC 1)OBSTRUCTIVE NORMAL ↓ ↓ 2) STIFF LUNGS ↓ ↓ NORMAL 3 ) RESP. MUSCLE WEAKNESS ↓ ↓ NORMAL
PEAK EXPIRATORY FLOW RATE (PEFR) -It is the max. Flow rate during fvc maneuver in the initial 0.1 sec. -PEFR DETERMINED BY : 1) Function of caliber of airways 2) Expiratory muscle strength 3) Pt’s coordination & effort - Estimated by 1) drawing a tangent to steepest part of FVC spirogram (error prone) 2) average flow during the litre of gas expired after initial 200 ml during fvc maneuver. -.
-Normal value in young adults (<40 yrs)= 500l/min -Measured with pneumotachograph / Wright peak flow meter -Wright peak flow meter - valuable tool in identifying gross pulmonary Disability at bedside. -Less unpleasant & less Exhaustive -Clinical significance - values of <200/l- impaired coughing & hence likelihood of post-op complication
FORCED MID-EXPIRATORY FLOW RATE (FEF25%-75%): Maximum Mid expiratory Flow rate Max. Flow rate during the mid-expiratory part of FVC maneuver. Effort independent Misnomer, as FEF 25-75% decreased by 1) marked reduction in exp. Effort 2)submaximal inspiration b4 maneuver → ↓FVC → ↓ FEF % It may decrease with truly max. Effort as compared to slightly submaximal effort as dynamic airway compression occurs with maximal effort. N value – l/sec. Or 300 l/min. Upto 2l/sec- acceptable. CLINICAL SIGNIFICANCE : SENSITIVE & IST INDICATOR OF OBSTRUCTION OF SMALL DISTAL AIRWAYS
MAXIMUM BREATHING CAPACITY: (MBC/MVV ) MAX. VOLUNTARY VENTILATION Largest volume that can be breathed per minute by voluntary effort, as hard & as fast as possible. N – l/min. Estimate of max. Ventilation available to meet increased physiological demand. Measured for 12 secs – extrapolated for 1 min. MVV = FEV1 X 35
RESPIRATORY MUSCLE STRENGTH Evaluated by measuring max. Static resp. Pressure with anaeroid gauge Pressures are generated against occluded airway during a max. Forced insp/exp. Effort MAX STATIC INSP. PRESSURE: (PIMAX)- Measured when inspiratory muscles are at their optimal length i.e. at RV PI MAX = -125 CM H2O CLINICAL SIGNIFICANCE: IF PI MAX< 25 CM H2O – Inability to take deep breath.
CONTINUED……. MAX. STATIC EXPIRATORY PRESSURE (PEMAX): Measured after full inspiration to TLC N VALUE OF PEMAX IS =200 CM H20 PEMAX < +40 CM H20 – Impaired cough ability Particularly useful in pts with NM Disorders during weaning
PHYSIOLOGICAL DETERMINANTS OF MAX. FLOW RATES 1)DEGREE OF EFFORT- driving pressure generated by muscle contraction (PEmax & PI max) L) 2)ELASTIC RECOIL PRESSURE OF LUNG: (PL) Tendency to recoil or collapse d/t PL PL increases from RV (2-3) to TLC (20-30) Opposed by Pcw (recoil pr. Of chest wall) Prs=Pl + Pcw = 0 at FRC-resting state (Prs-recoil pr.of resp.system) 3) AIRWAY RESISTANCE: (Raw): Determined by the calibre of airways Decreases as lung vol increases (hyperbolic curve) Raw high at RV & low at TLC
Continued…… DISEASE MSL. STRENGTH Raw PL N-M WEAKNESS ↓ N N EMPHYSEMA N N ↓ ASTHMA/BRONCHI TIS N ↑ N PERIPHERAL AIRWAY DIS. N N N
MEASUREMENT OF AIRWAY RESISTANCE 1) Raw- Body plethysmography 2) Forced expiratory maneuvers: Peak expiratory flow (PEF) FEV1 3) Response to bronchodialtors (FEV1)
Spirometry Pre and Post Bronchodilator Obtain a flow-volume loop. Administer a bronchodilator. Obtain the flow-volume loop again a minimum of 15 minutes after administration of the bronchodilator. Calculate percent change (FEV1 most commonly used---so % change FEV 1= [(FEV1 Post-FEV1 Pre)/FEV1 Pre] X 100). Reversibility is with 12% or greater change.
AIRWAY PARTITIONING AND BEHAVIOUUR UPPER (EXTRATHORACIC) Surrounding soft tissue unsupporting Collapses during inspiration Expands during expiration INTRATHORACIC Outer surface exposed to pleural pressure Expands during inspiration Collapses during expiration DISTAL (PULMONARY) Intimately related to lung tissue Collapses as expiration proceeds
FLOW VOLUME LOOPS Do FVC maneuver and then inhale as rapidly and as much as able. This makes an inspiratory curve. The expiratory and inspiratory flow volume curves put together make a flow volume loop.
Flow-Volume Loops (Rudolph and Rudolph, 2003)
How is a flow-volume loop helpful? Helpful in evaluation of air flow limitation on inspiration and expiration In addition to obstructive and restrictive patterns, flow- volume loops can show provide information on upper airway obstruction: – Fixed obstruction: constant airflow limitation on inspiration and expiration—such as in tumor, tracheal stenosis – Variable extrathoracic obstruction: limitation of inspiratory flow, flattened inspiratory loop—such as in vocal cord dysfunction – Variable intrathoracic obstruction: flattening of expiratory limb; as in malignancy or tracheomalacia
TESTS FOR GAS EXCHANGE FUNCTION 1) ALVEOLAR-ARTERIAL O2 TENSION GRADIENT: Sensitive indicator of detecting regional V/Q inequality N value in young adult at room air = 8 mmhg to upto 25 mmhg in 8 th 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 dyspnea due to resp/ cardiac d’s DDI = PEFR x PaCO 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. Fick’s law of diffusion : Vgas = A x D x (P1-P2) T D= diffusion coeff= solubility √MW
CONTINUED……. DL IS MEASURED BY USING CO, COZ: A)High affinity for Hb which is approx. 200 times that of O2, so does not rapidly build up in plasma B)Under N condition it has low bld conc ≈ 0 C)Therefore, pulm conc.≈0
SINGLE BREATH TEST USING CO Pt 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 – PcCO N range ml/min./mmhg. DLO2 = DLCO x 1.23
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 CLIMBING 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. can’t walk – bicycle/ arm exercises -If pt. is able to walk for >2000 feet during 6 min pd, -VO2 max > 15 ml/kg/min -If 1080 feet in 1 min : VO2 of 12ml/kg/min -Simultaneously oximetry is done & if Spo2 falls >4%- high risk
EVALUATION OF PT. FOR LUNG RESECTION GOALS: 1) to identify pts at risk of increased post-op morbidity & mortality 2) to identify pts who need short-term or long term post-op ventilatory support. Lung resection may be f/by – inadequate gas exchange, pulm HTN & incapacitating dyspnoea.
CONTINUED….. Removal of entire lung is likely to be tolerated if pre-op pulm function meets the following criteria: A) FEV1 > 2 L or FEV1/FVC of atleast 50% B) MVV > 50% of predicted value C) RV/ TLC < 50% If any of these criteria is not full filled – go for more invasive & sophisticated, split lung function tests.
CONTINUED…… A predicted post op FEV1 Of atleast 800ml is required to perform pneumonectomy If not- risk of significant resting CO2 retention & dyspnoea is high. IF Sx inevitable – invasive tests : Pulmonary artery occlusion test If after occlusion of pulm artery of segment to be resected is not followed by pulm Htn ( mean pulm art pr > 35 mmhg) AND hypoxemia(PaO2 <45 mmhg) – Assure that remaining lung can accommodate entire C.O.