Spirometry
Content Indication Indications in occupational medicine Contraindications Confounding factors Complications Type of spirometer Lung volumes & Lung capacities Spirometric values Hygiene & infection control Spirometry steps Reference values Interpretation
Pulmonary function tests Spirometry Post bronchodilator spirometry Bronchial challenge test Diffusing capacity of lung (DLCO) Arterial blood gas (ABG) Static lung volumes (TLC, RV ) Resistance & compliance of lung
Definition of spirometry A physiological test for measuring volumes inhaled or exhaled by an individual as a function of time
Indication Not a screening test for general population Diagnostic Monitoring Impairment evaluation
Indication (diagnostic) Evaluation of symptoms and signs Measuring the effect of dis. on pulmonary function Screening individuals at risk for pulmonary dis. Assess preoperative risk
Indication (monitoring) Assess therapeutic intervention Monitor people exposed to injurious agents
Indications in occupational medicine Primary prevention (Pre-employment) employment) physical demands of a job require a certain level of cardiopulmonary fitness, eg, heavy manual labor or firefighting Respirator use can impose a significant burden on the cardiopulmonary systems, eg, use of a selfcontained breathing apparatus, or prolonged use of certain negative-pressure masks under conditions of heavy physical exertion and/or heat stress
Secondary prevention Medical surveillance programs & periodic evaluation OSHA : asbestos, cadmium, coke oven emissions, or cotton dust respirator-wearers exposed to benzene, formaldehyde methylene chloride Silicosis Spirometry detect large changes over a short time or smaller changes cumulated over a longer observation period, it is not sensitive to small, short-term term changes Tertiary prevention Follow-up spirometry Workers compensation setting
Contraindications Active hemoptysis Pneumothorax Unstable Cardiovascular status (6 w) Cerebral/Thoracic/Abdominal aneurysm Recent eye surgery Acute disorder that may interfere with performance (e.g, vomiting) Thoracic or abdominal surgery( 3 w) Recent CVA or pulmonary emboli Respiratory distress
Confounding factors Common cold (3 days ego) Severe respiratory infection (3w) Smoking( 1hr) Heavy food (1hr) Bronchodilator use
Complications Chest pain Syncope, dizziness Increased ICP Paroxysmal coughing Nosocomial infection Bronchospasm
Type of spirometer Volumetric spirometer Flow-type spirometer
Spirometry standards ATS (American Thoracic Society) ERS (European Respiratory Society)
Lung volumes TV :The: volume of air inhaled & exhaled at each breath during normal quiet breathing IRV: The maximum amount of air that can be inhaled after a normal inhalation ERV: The volume of air that can be forcefully expired following a normal quiet expiration RV: The volume of air remaining in the lungs after a forceful expiration
Lung capacities TLC: The total volume of the lungs VC:The maximum amount of air that can be exhaled after the fullest inspiration possible IC :The : maximum of air that can be inhale after end tidal position FRC: The amount of air remaining in the lungs after a normal quiet expiration
Lung volumes VC IC TLC ERV RV RV
Spirometric values FVC FEV 1 FEV 1 /FVC FEV t FEF 25-75 PEF FVC (forced vital capacity) (forced expiratory volume in 1 s) (forced expiratory volume in t s) (maximum midexpiratory flow) PEF (peak expiratory flow) VT curve FV curve
Normal values depends on: Age Height Kyphoscoliosis arm span (H=arm span/1.06) Gender Race Caucasian
Hygiene & infection control Hand washing Gloves Disposable mouth piece & nose clip Disinfection or sterilization of reusable mouth piece Extra precautions for patient with known transmissible infection
Spirometry steps Equipment performance criteria Equipment validation Quality control Subject maneuvers Measurements procedures Acceptability Repeatability interpretation
Equipment validation Calibration: daily if for screening every 4hr
calibratio n
Subject maneuvers FVC maneuver Closed circuit Open circuit Well-fitting Sitting or standing Nose clip Procedure 1. Inhale 2. Exhale
maneuver evaluation Start of test criteria - Extrapolation volume (EV < -Time-to-PEF < 0.120 s End of test criteria (EV < 5% of FVCor 150 ml) - the subject cannot or should not continue - exhalation at least 6s (in children <10 yrs: at least 3s) - volume-time curve show no change in volume (<0.025025 lit) for at least 1s In obstruction or older subjects more than 6s exhalation (till 15s)
a b c
Acceptability Start of test criteria End of test criteria Cough especially during first second Valsalva maneuver (glottis closure) Leak from the mouth Obstruction of the mouthpiece Extra breath during the maneuver
Acceptable spirogram
G rainbow
Reproducibility At least three acceptable maneuvers Maximum difference between the largest and next largest FVC and FEV 1 = 150ml or 5% (If FVC <1lit, this value is 100ml)
Reproducibility
Flow chart of criteria Perform FVC Acceptability criteria 3 acceptable maneuvers Repeatability criteria Largest FVC and largest FEV1 Maneuver with largest FVC + FEV1 for other indices
Reference values Knudson (male/ female) NHANES III (race difference) ACOEM recommends that the NHANES III equations be considered for general use in the occupational setting ERS ATS
Predicted value & lower limit of normal (LLN) LLN : fifth percentile, the point below which 5% of normal subjects fall. LLN calculated in this way affect by age sex, height & race
LLN FEV 1 and FVC = 80% FEV 1 /FVC = 70-75% FEF 25-75 = 50-60%
Interpretation
A. Normal: both the FVC and the FEV 1 /VC ratio are normal. K nee
B.Obstructive : FEV1/FVC, FEV1 TLC & RV or NL
The severity of the abnormality is graded: - % Pred FEV 1 > 100 = May be a physiological variant - % Pred FEV 1 < 80 and > 70 = Mild - % Pred FEV 1 < 70 and > 60 = Moderate - % Pred FEV 1 < 60 and > 50 = Moderately severe - % Pred FEV 1 < 50 and > 35 Severe - % Pred FEV 1 < 34 = Very severe
C. Restrictive: FEV1/FVC or NL FVC & FEV1, TLC & RV
The severity of the abnormality might be graded as follows: - % Pred FVC < LLN and > 70 = mild - % Pred FVC < 70 and > 60 - % Pred FVC < 60 and > 50 Moderately severe - % Pred FVC < 50 and > 34 = Moderate = = Severe - % Pred FVC < 34 = Very severe
D.Mixed pattern: FEV1, FVC, FEV1/FVC< LLN
VC VC VC RV Obstructive RV Normal RV Restrictive
Upper airway obx
Early small airway obx FV curve :upward concavity FVC, FEV1, FEV1/FVC :NL FEF 25-75??? ATS states that FEF25-75% should not be used to diagnose small airway disease or to assess respiratory impairment
Probably normal spirogram Only FEF 25-75 No small airway disease (ATS) If FEV1/FVC is borderline airway obx Only FEV1/FVC FEV1> 100% Normal FVC>100%
Non-specific ventilatory pattern FEV1/FVC NL FEV1 < LLN FVC< LLN TLC, RV, DLCO NL Obesity Normal variant Occult asthma Early stage of parenchymal disease
Spirogram with restrictive pattern Spirogram with mixed pattern Spirogram with obstructive pattern
Case 1 A 71 yrs male Height :175,weight :88 FVC:45% FEV1: 31% FEV1/ FVC :53 53% FEF25-75 :15%
Case 2 A 36 yrs female Height :162,weight :83 FVC:89% FEV1: 94% FEV1/ FVC :89 89% FEF25-75 :131% TLC :92%
Case 3 A 29 yrs female Height :165,weight :109 FVC:78% FEV1: 79% FEV1/ FVC :86 86% FEF25-75 :85% TLC :82%
Case 4 A 43 yrs female Height :167,weight :61 FVC:33% FEV1: 17% FEV1/ FVC :42 42% TLC :114% RV/TLC :103%
Case 5 A 30 yrs male Height :186,weight :68 FVC:19% FEV1: 21% FEV1/ FVC :93 93% FEF25-75% :48% TLC :28%
Case 6 A 30 yrs male Height :175,weight :70 FVC: 88% FEV1: 69% FEV1/ FVC :66 66% FEF25-75 :38% VEXT : 90
Case 7 A 29 yrs male Height :179,weight :83 FVC: 104% FEV1: 84% FEV1/ FVC :67 67% FEF25-75 :51% VEXT : 120
Case 8 A 26 yrs male Height :177,weight :67 FVC: 97% FEV1: 77% FEV1/ FVC :66 66% FEF25-75 :48% VEXT : 60
Post bronchodilator spirometry (reversibility testing) Short-acting inhaled drugs should not be used within 4h of testing Long-acting should be stopped for 12h prior test Smoking should be avoided for 1h Salbutamol 400 µg (4 puffs) at 30 10 min and up to 15 min 30s s intervals Ipratropium bromide 160 µg (4 puffs) 30 min later
Positive reversibility testing Percent change from baseline & absolute change in FEV1 and/or FVC : >12% AND 200 CC
A 24 yrs male Height :170,weight :82 FVC:80% FEV1: 70% FEV1/ FVC :69 69% FEF25-75 :50%
pre post %change FVC 4 4.26 +7 FEV1 2.91 3.32 32 +14 FEV1/ FVC 72.8 77.9 +7 FEF25-75 2.32 3.09 +31
Case 7 A 70 yrs male Height :172,weight :65 pre %pred post %chg FVC 3.13 83 3.52 +12 FEV1 2.02 70 2.49 +23 FEV1/ FVC 64.5
Case 26 A 28 yrs male Height :192,weight :92 pre %pred post %chg FVC 5.68 95 5.81 +2 FEV1 4.02 81 4.28 +6 FEV1/ FVC 68.2
Change in spirometric indices over time In occupational setting, changes over time in pulmonary function should be examined for two reasons: (1) to evaluate a worker's response to treatment in the clinical setting (2) to screen healthy workers for excessive loss of function over time.
Change in spirometric indices over time NIOSH :(0.85.baseline value) (expected decline over time) FEV1 FVC male female male female 30 ml/yr 25 ml/yr 25 ml/yr 25 ml/yr
Significant change in periodic spirometry (ATS) > 15% of FEV1 or FVC over one year > 5% of FEV1 or FVC over one working shift (8 am- 4 pm) > 25-30% of PEF over one working shift
Bronchial provocation test Specific: emergency hospital available Nonspecific : out patient Purpose : detection hyper reactive airways
Methacholine challenge test (MCT) Most agent for BCT: methacholine Immediate response More useful in excluding a dx of asthma Excellent sensitivity
MCT is also positive in: Allergic rhinitis Sarcoidosis (50 50%) COPD CF
Data presentation PC20 provocative concentration causing a 20% fall in FEV1