Transcript TL-esitelmä työpaikka-PEF

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
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pocket-size spirometres
(FEV1, FVC, PEF)
– Oneflow
– Microplus
– Vitalograph
Use 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.
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Repeated diurnal variation (calculated
from the mean value!) >20% (>60 l/min)
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effect of bronchodilating drug >15% (>60
l/min)
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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
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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
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Follow-up of bronchial asthma
– full medication, PEF in the morning and evening, also after
bronchodilating medicine
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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
Contraindications

severe or moderate asthma symptoms

severe/anaphylactic symptoms at work
PEF surveillance at work and at home
suspicion of occupational asthma /
medication
 preferably
without continuous
medication, no inhaled steroids
 if needed, short-acting sympathomimetic
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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
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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
Making graphs 1.
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Is the follow-up carried out properly, in the
actual exposure conditions?
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The best of the parallel blowings marked
down
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are parallel blowings reliable?
learning effect during 1-2 first days?
occasional diverging values?
morning measurements at same time?
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"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
Making graphs 2
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Plotting of graphs
– Manual
1. The daily highest and lowest values are marked down
Note: the work day begins from the first blowing at work.
2. Plot different graphs from the highest and the lowest
values
3. Mark the days off, notes on exposure, symptoms,
medication
– Computer program
OASYS( 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 protected])
– Both programs count the diurnal variations. OASYS
Findings
Is there:
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a decrease in PEF level during the work
days?
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an increase in PEF level during days off?
PEF surveillance
Car painter, diisocyanate (HDI) exposure,
PEF follow-up points to occupational asthma
PEF surveillance
Foreman, enzyme production
(Keuhkosairaudet, Duodecim 2000)
--- highest PEF, — lowest PEF,
X enzyme exposure,  day off
PEF-surveillance
(OASYS graph)
xxxxxxxxxxxxxxxxxxxxx
Mould exposure, water-damaged workplace, PEF surveillance points to occupational asthma.
PEF level falls during work
days
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Similar PEF variation during work days,
no variation during days off
- immediate-type asthmatic reaction,
recovery during days off
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Gradually decreasing PEF values during
work days, recovery during days off
- longlasting delayed asthmatic reaction.
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PEF variation only on some work days,
not during days off
- variable exposure
PEF level rises during days
off
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Recovery already during the first day off
- immediate asthatic reaction?
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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
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Labile asthma, insufficient
medication
– occupational asthma?
– non-occupational asthma?
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Enhanching of the treatment
– new PEF surveillance ?
– other investigations for occupational asthma
Low PEF level?
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small diurnal variation
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not much difference between work days and
days off
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sick leave and follow-up, is PEF level rising?
500
450
400
350
300
250
200
150
sick leave - - - - - - - - - - - - - - - - -
100
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Interpretation
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An experienced physician's estimation and
impression from the graphs
considering
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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
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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
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PEF follow-up / validation
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without medication:
specificity 77-100%
sensitivity 77-87%
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with medication sensitivity 42%
Causes of failure
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Poor blowing technique, unequal parallel
measurements
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Exposure at work place not adequate, the
suspected agent not used?
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Patient on inhaled steroids
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Only few measurements
Improving of PEF surveillance
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Training of the personal
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Good training of the patients / checking and
encouragement during follow-up
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Check exposure
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PEF follow-up immediately when (occupational) asthma is
suspected
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Only bronchodilating medicine, if needed, during the
follow-up
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Measurements every 2 hours when awake
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Future: pocket-size recording devices
Conclusion
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Serial PEF measurements - a handy basic
investigation when occupational asthma is
suspected
– in occupational health care, in lung clinics
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Requires patient collaboration, good
training!
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Carry out immediately, when you suspect
(occupational) asthma in a worker with
exposure to sensitizing agents. Plot a graph!
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Attach also the patients own markings to
the referral,
Literature
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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