THE SOUTH AFRICAN SOCIETY OF OCCUPATIONAL MEDICINE

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1 THE SOUTH AFRICAN SOCIETY OF OCCUPATIONAL MEDICINE SPIROMETRY IN INDUSTRY SASOM GUIDELINE ISBN: ISBN: by SASOM All rights are reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without the prior permission of the copyright owner.

2 SPIROMETRY IN INDUSTRY 1. INTRODUCTION 1.1 Spirometry is a useful and objective method of assessing the lung function that is required for workers who are exposed to mineral dusts or other airborne pollutants in industry. 1.2 It is commonly used as a screening test to identify the presence of abnormal lung function; grade the extent of the functional impairment; and monitor the progression of the dysfunction. 1.3 In clinical practice, it may further assist in determining the nature of the abnormal function and evaluating the response to intervention with bronchodilators or provocative stimuli. When these tests are used as part of the diagnostic assessment of a patient with a respiratory disorder, it is important that they are used in conjunction with all other clinical and radiological findings. 2. QUALITY CONTROL Quality control in spirometry is essential to produce meaningful results, and meticulous attention must be paid to the following: 2.1 Compliance of equipment with the criteria set in the South African National Standard SANS Daily calibration of the equipment according to the manufacturer s specification and checking for leaks, daily cleaning and regular maintenance all recorded. 2.3 Tester competence, including clear instructions to the client and entry of accurate client data. 2.4 Client understanding and cooperation. 3. PERSONS SPECIFICALLY INDICATED IN INDUSTRY 3.1 Workers who may become exposed to respiratory hazards in the course of their work. Such hazards include irritating chemicals, sensitising agents, dust, moulds and spores (see Appendix A). 3.2 Workers whose occupations will make special demands on their pulmonary function, such as wearing breathing apparatus or respirators; divers and submariners; and a past history of industrial exposure to the above hazards. 3.3 Workers who complain of wheezing or episodic dyspnoea. Serial measurements, particularly before and after a work shift or after a period of absence from work (eg a Monday), may be useful. SASOM Guideline Revision: December 2009 Page 2 of 7

3 4. MEDICAL SURVEILLANCE Periodic medical examinations which may be done annually or more frequently for 4.1 workers who are potentially exposed to the above hazards; and 4.2 grading of functional impairment in patients with pneumoconiosis or any other occupational lung disease. 5. THE EQUIPMENT 5.1 Most spirometers are flow-measuring instruments that generate computerized results, and are programmed to adjust for specific reference values. Lung-function testers should ascertain that the reference values used are appropriate for the population being tested. Guidance can be obtained from the providers. 5.2 Instruments should be calibrated daily with a syringe for volume, temperature, pressure and time, according to the manufacturer s specifications (see Appendix B for minimum standards of spirometers and specifications for computers). 6. THE TECHNIQUE 6.1 The basic measurement is that of an expiratory forced vital capacity (FVC), i.e. the amount of air forcibly exhaled from a full inspiration to a full expiration. From this measurement, the forced expired volume in 1 (one) second (FEV 1) is derived. Most spirometers plot a flowvolume curve which is the graphic representation of the forced vital capacity manoeuvre (expiratory/inspiratory); flow being plotted on the vertical axis and volume on the horizontal axis. 6.2 The technique should be carefully explained to the client since it is essential that the client performs at his or her best. 6.3 The client sits or stands with the head straight and is shown how to close the mouth and lips around the mouthpiece. A nose clip should be used. 6.4 An acceptable FVC test includes the following elements: Maximal inspiration before expiration The commencement of expiration should be abrupt without hesitation Maximum effort must be exerted throughout expiration Maximum expiration should continue until an obvious plateau appears on the tracing and should last longer than six seconds. 6.5 After one or two trial efforts, a series of three efforts should be recorded and the best value of FVC and FEV 1 respectively should be selected. The FVC and FEV 1 in none of the tracings should differ by more than 100 ml from the other two. 6.1 Accurate records must be kept in the client s medical file, and compared with the original baseline graph. 7. INTERPRETATION OF THE TEST 7.1 Normal predicted values Lung volume, as determined by the FVC and FEV 1 is specific for any individual and is a SASOM Guideline Revision: December 2009 Page 3 of 7

4 function of sex, age, height and race (lung volumes of patients of African origin being smaller than those in Caucasians). 7.2 Commonly used values FVC and FEV FVC and FEV 1 both expressed as a percentage of predicted. In convention, any reading above 80% of predicted is considered normal FEV 1 as a percentage of FVC namely FEV 1 /FVC %. In general, values above 75 % are considered normal. 8. PATTERNS OF LUNG-FUNCTION ABNORMALITIES 8.1 Obstructive defects (eg asthma, chronic obstructive airway disorders) produce a reduction in airflow rates and therefore a reduction in FEV 1 and a reduced FEV 1 /FVC ratio. 8.2 Restrictive defects (eg silicosis, asbestosis, lung fibrosis) produce a reduction in lung size and therefore a reduction in FVC, but a normal or even increased. FEV 1 /FVC ratio. 9. GRADING OF IMPAIRMENT CATEGORY OF LUNG IMPAIRMENT: LUNG-FUNCTION ABNORMALITIES Measurement Mild Moderate Severe Normal Obstruct Restrict Obstruct Restrict Obstruct Restrict FVC % predicted 80% and NA 61-79% NA 40-60% NA <50% above FEV 1 % predicted 80% and 60-79% NA 41-59% NA <40% NA above FEV 1 / FVC % 75% and above 69-74% NA 41-59% NA <40% NA Adapted from South African Thoracic Society Standards of Spirometry The table should be used only as a guide, and absolute values must be evaluated in the context of other clinical findings. Serial measurements showing a sustained abnormality are of greatest significance. 9.2 As a general guideline, anyone at initial health evaluation with predicted values for FVC and FEV 1 over 80% and an actual FEV 1 /FVC ratio over 70% could be considered for employment. When considering workers with low normal or subnormal values, it is important to pay particular attention to the presence of pulmonary disease and smoking status. 9.3 All results must be recorded in the client s file. BIBLIOGRAPHY 1. Guild R, Ehrlich RI, Johnston JR, Ross MH (Editors), Handbook of Occupational Health Practice in the South African Mining Industry, Safety in Mines Research Advisory Committee Braamfontein, South African Bureau of Standards, SANS 451 Spirometry. Generation of acceptable and repeatable spirograms. Pretoria, 2008 SASOM Guideline Revision: December 2009 Page 4 of 7

5 3. Van Schalkwyk EM, Schultz C, Joubert JR. White NW, Steward R I, South African Thoracic Society, Standards of Spirometry, Guideline for Office Spirometry in Adults, SAMJ.2004:94 (7) Practical Spirometry, Medical Research Council and Department of Medical Physiology and Biochemistry, University of Stellenbosch, Tygerberg, NOTE The SASOM guidelines are active working documents that are reviewed regularly, or as changes take place in legislation, the work or the workplace. Your inputs and comments are therefore regarded as most valuable. Please send them to info@sasom.org. SASOM Guideline Revision: December 2009 Page 5 of 7

6 APPENDIX A IRRITATING CHEMICALS Sulphur dioxide, nitrogen oxides, fumes of beryllium, cadmium and other heavy metals, chlorine, phosgene, bromine, fluorides, alkalis, acids and other organic hydrocarbons. SENSITISING AGENTS Isocyanates Platinum Nickel Cobalt Vanadium Chromium salts Epoxy resins Acrylic acids or derived salts Fungi or spores Fumes or formaldehyde Proteolytic enzymes Organic dust Substances from animals or insects Amines or diamines Soldering or welding fumes Anhydrides DUSTS Silica, asbestos, coal, cotton, flax, sisal or other organic or inorganic fibrogenic dust. MOULDS AND SPORES Hay, grain, flour, bagasse, feathers and bird droppings. SASOM Guideline Revision: December 2009 Page 6 of 7

7 APPENDIX B THE MINIMUM ACCEPTED STANDARDS FOR SPIROMETERS USED IN MOST CLINICAL SETTINGS ACCORDING TO THE SANS451 (2008) SPIROMETER STANDARDS 1. The spirometer should be able to measure volumes of at least 7 liters with an accuracy of 3% or 50 ml, whichever is the greater. 2. The spirometer should be capable of volume accumulation for at least 30 seconds, time being measured with an accuracy of 1%. 3. Flow should be measured with an accuracy of 5% or 0.2 l/s between the ranges of 0 and l/s in either direction i.e. a dynamic range of - to + l/s. Flow meters should be linear within 2% or 50 ml/s. 4. The resistance of the spirometer and tubing system should be less than 0.1 kpa l/s at a flow of l/s; the inertia of the system should be less than 0.01 kpa l/s². 5. Spirometers used for measuring maximal voluntary ventilation (MVV) should have an amplitude frequency response that is flat (within about 10%) from 0-4 Hz at flow rates up to about 12 l/s. 6. When the results of the tests are displayed on graphs, the scale for flow-volume curves should be 5 ml per cm with a ratio at 2:1 for volume to flow. Should hand measurement be done on volume-time graphs, a minimum scale of 2 cm per sec is required. When a flow-volume loop or curve is plotted or displayed, exhaled flow should be plotted upwards and exhaled volume towards the right. SPECIFICATIONS FOR COMPUTERS 1. The analogue digital converter should be a 12-bit converter. 2. The data sampling rate should be at least 100 Hz. 3. The resolution of the electronic clock should be 40 microseconds. 4. Descriptions of the algorithms used in determining derived values could be provided by the manufacturers of the microprocessor or computer-based spirometer systems. This is especially necessary if interpolation methods are used in determining the start and end of the test, and identifying values at specific points, time or volume, namely FEV1 or FEF The source of reference values should be stated, and the user should be able to select or manually enter reference values best suited to the healthy population from which test subjects are likely to be drawn. 6. Should computerized interpretation of the test results be offered, the criteria for making diagnostic decisions should be made available to the purchaser. 7. It is desirable to display on the screen, and on the final report, both the volume-time and flowvolume recordings of each successive attempt by the patient. 8. It is desirable to be able to select and combine expiratory and inspiratory data from different maneuvers. 9. A hard copy of the results must be provided by the system. 10. It should be possible to store the data on removable computer disks if the spirometer is connected to a computer. SASOM Guideline Revision: December 2009 Page 7 of 7