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Tallinn IX/2003. Serial Peak Expiratory Flow (PEF) measurements in the diagnostics of occupational asthma. H. Keskinen MD Finnish Institute of Occupational Health. PEF. Peak expiratory flow ( l/min) measures: width of large airways strength and coordination of the breathing muscles.
Tallinn IX/2003 Serial Peak Expiratory Flow (PEF) measurements in the diagnostics of occupational asthma H. Keskinen MD Finnish Institute of Occupational Health
PEF Peak expiratory flow ( l/min) measures: • width of large airways • strength and coordination of the breathing muscles
PEF meters • simple PEF meters • Spira • mini-Wright • Vitalograph • pocket-size spirometres(FEV1, FVC, PEF) • Oneflow • Microplus • VitalographUse same device during the follow-up!The blowing technique is different if the second capacity is measured!
PEF measurements - findings in asthma Always three measurements. Accepted if the difference between the two best is < 20 l/min. The best one is chosen. • Repeated diurnal variation (calculated from the mean value!) >20% (>60 l/min) • effect of bronchodilating drug >15% (>60 l/min) • gradual increase in PEF level after beginning of asthma medication > 20%
The diurnal PEF variation (%) should be calculated from the mean value! > 20% diurnal variation (minimum 60 l/min) is significant highest PEF - lowest PEF x 100 = n % 1/2 x (highest +lowest PEF) example: 450 - 350 x100 = 25% 1/2 x(450+350)
PEF follow up • Diagnostics of bronchial asthma / differential diagnostics with COPD • PEF in the morning and evening (and if symptoms) • 1st week, no drugs, 2nd week before and after bronchodilating drug • 2 weeks before and after bronchodilating drug • Follow-up of bronchial asthma • full medication, PEF in the morning and evening, also after bronchodilating medicine • Occupational asthma suspected / assessment of ability to work • PEF every 2 hours from waking to sleeping at work and during days off • during 3-4 weeks, two periods of days off(Burge since 1982)
Contraindications • severe or moderate asthma symptoms • severe/anaphylactic symptoms at work
PEF surveillance at work and at homesuspicion of occupational asthma / medication • preferably without continuous medication, no inhaled steroids • if needed, short-acting sympathomimetic • if on inhaled steroids, same dosage every day • theophyllines, leukotriene antagonists, same dosage every day • no long-acting sympahtomimetics • (but continued, if ability to work is assessed)
Priming of PEF surveillance • Medication planned • Correct (actual) exposure • training in the use of the PEF meter (short rapid blow) • measurements after 2 hours when awake, 3 weeks, 2 weekends • always 3 blowings (the difference between 2 best < 20 l/min), all written down • training in the use of follow-up forms (blowing results, notes on exposure, symptoms, medications) • informing the occupational health services of the follow-up • well-trained patient - informative PEF surveillance!
Making graphs 1. • Is the follow-up carried out properly, in the actual exposure conditions? • The best of the parallel blowings marked down • are parallel blowings reliable? • learning effect during 1-2 first days? • occasional diverging values? • morning measurements at same time? • "Work day" begins from the first blowing at work and continues to the last blowing at home following morning. Similarly in shift work. • Day off begins from the second blowing after waking up and continues to the first blowing on the next morning.
Making graphs 2 • Plotting of graphs • Manual1. The daily highest and lowest values are marked downNote: the work day begins from the first blowing at work.2. Plot different graphs from the highest and the lowest values3. Mark the days off, notes on exposure, symptoms, medication • Computer programOASYS( available from S. Burge (www.occupationalasthma.com) all values plotted according to the manual) in English Program by Vilkka/GSK, all values plotted (the program itself moves the first morning value at home to the previous day!) in Finnish (for possible translation contact email@example.com) • Both programs count the diurnal variations. OASYS includes also analysis of the grahp.
Findings Is there: • a decrease in PEF level during the work days? • an increase in PEF level during days off?
PEF surveillance Car painter, diisocyanate (HDI) exposure,PEF follow-up points to occupational asthma
--- highest PEF, — lowest PEF,X enzyme exposure, day off PEF surveillance Foreman, enzyme production (Keuhkosairaudet, Duodecim 2000)
PEF-surveillance(OASYS graph) xxxxxxxxxxxxxxxxxxxxx Mould exposure, water-damaged workplace, PEF surveillance points to occupational asthma.
PEF level falls during work days • Similar PEF variation during work days, no variation during days off - immediate-type asthmatic reaction, recovery during days off • Gradually decreasing PEF values during work days, recovery during days off - longlasting delayed asthmatic reaction. • PEF variation only on some work days, not during days off - variable exposure
PEF level rises during days off • Recovery already during the first day off - immediate asthatic reaction? • Recovery not before the second day off or even on the following morning- delayed asthmatic reaction worsens during the work week
Marked diurnal PEF variation during work days and also during days off • Labile asthma, insufficient medication • occupational asthma? • non-occupational asthma? • Enhanching of the treatment • new PEF surveillance ? • other investigations for occupational asthma
Low PEF level? • small diurnal variation • not much difference between work days and days off • sick leave and follow-up, is PEF level rising? sick leave - - - - - - - - - - - - - - - - -
Interpretation • An experienced physician's estimation and impression from the graphsconsidering • timing of exposure • medication • reliability of the measurements • respiratory infections • Can the patient have occupational asthma?yes / maybe / no (Eur Respir J 1997)
PEF follow-up, interpretation If • PEF-surveillance positive for occupational asthma • PEF monitoring does not relate symptoms to specific agent, challenge tests needed (exception: clear demonstration of specific sensitization/ baker with flour allergy!) If • the result is negative, but the history points to occupational asthma, does not exclude occupational asthma, further investigations needed (challenge tests) IF • PEF-surveillance does not point to occupational asthma • exposure has been adequate • no inhaled steroids during the measurement • the history does not point to occupational asthma occupational asthma is not probable, follow-up
PEF follow-up / validation • without medication: specificity 77-100% sensitivity 77-87% • with medication sensitivity 42%
Causes of failure • Poor blowing technique, unequal parallel measurements • Exposure at work place not adequate, the suspected agent not used? • Patient on inhaled steroids • Only few measurements
Improving of PEF surveillance • Training of the personal • Good training of the patients / checking and encouragement during follow-up • Check exposure • PEF follow-up immediately when (occupational) asthma is suspected • Only bronchodilating medicine, if needed, during the follow-up • Measurements every 2 hours when awake • Future: pocket-size recording devices
Conclusion • Serial PEF measurements - a handy basic investigation when occupational asthma is suspected • in occupational health care, in lung clinics • Requires patient collaboration, good training! • Carry out immediately, when you suspect (occupational) asthma in a worker with exposure to sensitizing agents. Plot a graph! • Attach also the patients own markings to the referral,
Literature • Eur Respir J 1997;10:Suppl • Burge S, Moscato G. Physiological Assessment: Serial Measurements of Lung Function. Kirjassa Asthma in the Workplace, toim. Bernstein IL ym. Marcel Dekker Inc, 1999:193-210. • www.occupationalasthma.com