Journal of Asthma, 28(3) 161-177 (1991)
REVIEW ARTICLE
Peak Flow Monitoring
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Guillermo R. Mendoza
Hawthorne Community Medical Group
2990 Sepulveda Boulevard
Los Angeles, Califbrnia 90064
INTRODUCTION
asthma bed days have also increased
noticably during the same period. Despite the
national attention which asthma has attracted over the past years, current pediatric
hospitalization data from the National Center
for Health Statistics has yet to show a significant downward trend in asthma bed days (15).
At least part of the asthma problem may be
a continuing trend of delayed diagnosis of
asthma, with asthma mislabeled as bronchitis, bronchiolitis, or pneumonia (16).
Diagnosis mislabeling appears to be a current
problem in the United Kingdom as well (171,
where asthma-aware health maintenance
organizations tend to hospitalize children
with a diagnosis ratio of 2:l for asthma compared with pneumonia and bronchitis and
bronchiolitis, taken as a group (16).This is
nearly the inverse ratio reported for pediatric
admissions in the United States.
Writing in 1988 in the aftermath of the
New Zealand National Asthma Mortality
Study, Sears comments (18)(Figs. 1-3):
Inexpensive, portable peak flow meters
have been available in this country since
1978.Between 1977 and 1980,the pioneering asthma self-management program Living
with Asthma was developed and tested by
Creer et al. at the National Asthma Center
in Denver. This program strongly emphasized
the importance of peak flow monitoring skills
(1).Since 1978,despite a growing consensus
about the value of peak flow monitoring
(2-131,only a minority of primary care providers in the United States have adopted peak
flow in their ofice practice. Few high-risk
asthma patients in this country have peak
flow meters at home or know how to use them
effectively. From a public health standpoint,
the barriers to implementation are inexplicably at odds with the rapid assimilation
of monitoring in other countries with similar
asthma trends.
To date, the biggest catalyst for change in
asthma care in the United States may be the
discouraging, but well-publicized, rising
trends in asthma mortality (14).Pediatric
The dominant message from all studies of
asthma mortality is that patients die because
161
Copyright 0 1991 by Marcel Dekker, Inc.
162
Age
Ethnicity
Mendoza
the severity of their asthma is underestimated and because the disease is treated
with insufficient and inappropriate therapy.
Previous life-threatening attacks
Psychosocial problems
Inadequate medications (%fold risk)
Failure to use peak flow (%fold risk)
Hospital admission within past 12 months
(12-fold risk)
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Figure 1. Asthma High Risk Factors. Adapted from
Sears MR: Are deaths from asthma really on the rise?
J Respir Dis 8:39-49, 1987.
Discontinuity of medical care/poor compliance
Inadequate follow-up
Delay in seeking help during crisis
Inadequate long-term management
-Overreliance on bronchodilators
-Reluctance to use oral corticosteroid burst
-Failure to use cromolyn/inhaled corticosteroids
chronically
Inadequate monitoring of peak flow, especially
during interval between attacks
Figure 2 . Management deficiencies. Adapted from Sears
MR: Are deaths from asthma really on the rise? JRespir
Dis 8:39-49, 1987.
Develop effective, simple drug regimens
Develop crisis plan to include oral corticosteroids
Provide easy access to medical care
Identify high risk patients for appropriate follow-up
Effective education for patients, families, and
medical providers
Monitor efficacy of treatment with peak flow
Figure 3. How to reduce asthma morbidity and mortality. Adapted from Sears MR: Are deaths from asthma really on the rise? J Respir Dis 8:39-49, 1987.
Identification of these [high-risk] patients,
followed by a detailed assessment of their
asthma, including its patterns, provocative
factors, and optimum management, should
lead not only to control of symptoms, including nocturnal symptoms, but also to normalization of pulmonary function and reduction of airway hyperresponsiveness. This in
turn should result in a reduction in mortality from this disease.
The essential contributions of home peak flow
monitoring are particularly underscored by
Sears (18):
The application of such principles in New
Zealand, helped enormously by the decision
of the government on the recommendations
of the Asthma Task Force to provide peak expiratory flow meters free of charge to patients, has been associated with a recent
downward trend in the asthma mortality
rates, particularly in young people.
If the recent increase in asthma mortality in
the United States is real, and the consensus
view is that it is real, especially in black subjects and among young people, then such
strategies could be used equally effectively
in the United States as in New Zealand.
In January 1991the National Heart, Lung,
and Blood Institute-sponsored National
Asthma Education Program issued a comprehensive Expert Panel Report: Guidelines
for the Diagnosis and Management ofAsthma.
This report adds its support for peak flow
monitoring and other changes in asthma
management in concurrence with a recent
Canadian asthma workshop as well as with
the Mortality Task Force of New Zealand
recommendations in 1988.
The NIH report prominently integrates
peak flow measurement in various sections
of the report including: diagnosis, objective
measures of lung function, treatment overview, as well as detailed management protocols for mild, moderate, and severe asthma
in children and adults.
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Peak Flow Monitoring
Concise peak flow action plans can make
drug regimens more flexible, practical, and
powerful. Determination of peak flow is the
most objective way to teach patients when to
start oral steroids a t home. Phone advice is
unequivocally the quickest and most costeffective way to provide continuity of medical
care. Monitoring peak flow makes 24-h phone
access a reality. Excessive variation in daily
peak flow is a major determinant in the identification of a high-risk patient.
From a health education perspective, peak
flow-based asthma care is a self-regulation
model of self-help. The patient learns to glean
information from the peak flow meter, use
that information to conceptualize a sense of
safety or danger, make plans and evaluate
possible actions, carry out a specific action,
then use the peak flow meter to assess the efficacy of those actions.
OPTIMAL CONTROL OF ASTHMA
A recent Canadian conference report (19)integrates peak flow into a comprehensive
definition of optimal asthma control (see
Fig. 4). This definition combines both timehonored clinical as well as modern, objective
home peak flow criteria for optimal asthma
control.
Minimal symptoms, ideally none
163
The Canadian guidelines base asthma
therapy on reaching a best, not just predicted
peak flow value with less than 20% and ideally < 10% daily peak flow variation. Ideally,
any asthma instability should be mild enough
that 0-agonists would be needed only a t the
beginning and end of the day with complete
restoration of normal peak flow after treatment (Fig. 5).
PEAK FLOW:
FROM THE PATIENT’S PERSPECTIVE
A number of traditional stumbling blocks
in asthma care can be easily diminished with
peak flow monitoring. Most patients have
been victimized by one or more of the following pitfalls of asthma management. However,
they may be reluctant to discuss them openly.
Patients should not feel at fault for failing
to detect symptoms. They should also
understand the limitations of conventional
stethoscope-based office assessments of
asthma.
To find the best airway function during intensive
treatment
To measure the daily variability of PF readings as
a n indicator of the degree of airway
responsiveness
Normal activities of daily living (work, school,
recreational exercise)
To educate the patient about managing his/her
asthma
Inhaled /3-agonist needed not more than twice
daily, ideally none
To keep airway function close to normal at all times
Minimal side effects from medications
Airflow rates normal or near normal at rest
Airflow rates normal after inhaled fl-agonist
Daily variation of
PEFR < 206, ideally < lo6
Figure 4 . Canadian definition of control of asthma. From
Ref. 19.
To determine the severity of an exacerbation and to
detect this early when the patient perceives symptoms poorly
To allow the patient to adjust doses of drugs to maintain normal function with minimal doses of drugs
To identify unknown or suspected trigger factors
Figure 5. Specific peak flow objectives. From Ref. 19.
Mendoza
164
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Symptom misperception by patients and
doctors alike underscores the importance of objective peak flow monitoring
(10,20).
Patients need to understand that nighttime worsening and spontaneous daytime
improvement is a universal feature of
asthma, not an idiosyncrasy for that particular patient. Accordingly, the patient
needs to understand why physicians who
see them only during midday may tend to
underestimate the severity of their
asthma.
Second only to misperception problems,
the night versus day nature of asthma
is the biggest current management
pitfall. If patients see their physician
when the asthma is mild, the daytime
exam (in the absence of a peak flow
meter) almost always biases the physician into making minimal changes, if
any, in the patient’s asthma plan. Even
if a peak flow is done in the office, the
spontaneous midday improvement can
still trick the physician into thinking
t h e patient’s asthma is under
reasonable control.
Many patients are reluctant to see a
physician during the early phase of a
relapse for one of two reasons: fear the
physician will underestimate the
asthma or a reluctance to be labeled a
complainer.
Patients will universally take special
notice if the physician acknowledgesthe
night versus day diurnal rhythm of
asthma. A recent review usefully
describes the underlying causes and implications of a circadian rhythm of
asthma (21).
Together, the pitfalls of misperception
and night versus day are the easiest
ways to close the deal on home monitoring. In essence the physician’s message
is very simple:
Without a peak flow meter at home I can only guess what you are really going through
at night. Guessing means I may over- or
under-medicate you. With a meter a t home,
you can phone me and tell me what happens
at night and save an office visit or two just
for good measure.
Patients are as concerned about overmedication as undermedication. The
physician can make a commitment to adjust medicines in a flexible manner,
depending on the downward and upward
trends of daily peak flow.
Patients are accustomed t o handling
asthma problems with little guidance after
hours. The physician needs to make a commitment to provide continuity of care via
telephone 24 hours a day, either individually or collectively with other
asthma-aware colleagues.
Many patients are virtually resigned to
sporadically chaotic asthma care. The
physician needs to set high standards and
expectations for asthma care.
The physician needs to genuinely demonstrate an open, cooperative style of expertise and comanagement, willing to share
control with the patient.
DETERMINING THE “BEST” PEAK FLOW
Normal or best peak flow for a single subject is easily confused with average peak flow.
The latter is based on nonasthmatic subjects
standardized for age, gender, and height.
Average peak flow values are used to
estimate what a patient should be able to
blow. The best peak flow (which may range
from 80 t o 120% of the average value) is used
for determining peak flow variability and for
devising individual drug action plans.
When a patient is first learning how to use
a peak flow meter, a provisional best peak
flow can be obtained by trial and error in the
office and compared with average values.
Over the long run, regular home monitoring
of peak flow will reveal or confirm the patient’s best peak flow.
Validating the best peak flow benefits from
experienced clinical assessment, ideally coupled with objective spirometry studies in the
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Peak Flow Monitoring
office. Primary care physicians, unfamiliar
with peak flow may have limited immediate
access to airflow data before the patient
leaves the office. A common misconception is
to uncritically define the “best” peak flow as
whatever the patient happens to blow on a
“good” day when the patient feels “ o k and the
chest is “clear” to auscultation.
For a new patient, peak flow should be
routinely determined before and after a bronchodilator (allowing 15-20 minutes or longer
for a significant response). This is important
even for patients who are clear to auscultation. Any improvement based primarily on
the bias of practice needs to be disregarded;
in other words, physicians may need to personally supervise both peak flow maneuvers.
A genuine 1 5 2 0 % increase in peak flow indicates a significant degree of large airway
obstruction. Such a bronchodilator effect
should prompt a thorough clinical reassessment if the patient was seen on a “good” day
and claimed a history of supposedly sporadic
or stable asthma.
Patients seen at midday may have spontaneously normalized to their best peak flow
prior to being seen. Accordingly, the physician needs to take the time of day into account
when evaluating a negative pre- and postbronchodilator peak flow challenge. Not infrequently, a normal midday peak flow may
be followed up at home-revealing significant
late evening or early morning peak flow
dipping-all within 24 h of the initial
consultation.
Finally, patients with chronically undertreated asthma or patients with long-standing
chronic sinusitis may appear not to respond
to bronchodilators in the office. This may be
due to either chronically blunted daily peak
flow variation or to a midday assessment artifact, or both. Usually, these patients present
with significant reductions in their peak flow
regardless of the time of day, not infrequently with little or no obvious clinical signs of
respiratory distress. Small airway pulmonary
studies usually can detect chronic obstruction
ar i si n g from long-standing ai rway
inflammation.
If the patient does not have sinusitis, a n intensive 7-14 day trial of aggressive asthma
165
medications, including oral corticosteroids if
necessary, may be needed before the peak
flow may change. Antibiotic management of
sinusitis should result in upward peak flow
trends within a matter of days. Best peak
flows in either case may not be apparent for
many days, weeks, or even months. Provisional “guesstimates” of best peak may need
to be revised. If the patient is treated appropriately, at some point the improvement
in airflow will reach a limit and the provisional peak flow can be considered the patient’s best peak flow.
Serendipity sometimes plays a role in the
discovery of the best peak flow. After finishing a n oral burst of steroids for a severe relapse, patients may notice that the peak flow
returns to “normal” only to continue to rise
to a n even higher value as the airflow continues to improve. In more subtle ways this
can happen with children in the middle of
their growth spurts as they “suddenly”
outgrow their best peak flow following a
crisis.
Many recent guidelines for peak flow monitoring have suggested twice-a-day monitoring. For routine surveillance it is assumed
that one already knows what the best peak
flow should be. Determining peak flow
variability, requires only knowledge of how
low the peak flow drops. Since the dip in peak
flow is likely to occur near breakfast time or
bedtime, twice-daily day monitoring makes
good sense. If the peak flow is within 10%(or
whatever the determined tolerance limit is for
that patient), the peak flow will almost
always self-correct by midday.
Twice-a-day monitoring is insufficient in
two general situations: first, the physician
isn’t sure what the best peak flow actually is.
second, the patient discovers during routine
testing that the trough level of peak flow in
the morning is below 90%. For very different
reasons, in both cases it is important to
recheck the peak flow at midday. In the first
case, the best peak flow will be missed if not
checked at midday and may change from
week to week. In the second case, the
midday peak flow gives one a better sense of
the level of airway inflammation-i.e., the
morning peak flow may be low because of
Mend oza
166
bronchospasm, swelling, or both. Bronchospasm usually dissipates during the day with
treatment but airway edema may not.
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INFLAMMATION, AIRWAY
REACTIVITY, A N D DAILY PEAK
FLOW VARIABILITY
If histamine or methacholine bronchoprovocation is the gold standard for assessing airway reactivity, daily peak flow variation
should be considered the silver standard. Certainly from a public health standpoint, monitoring peak flow trends is the easiest and
least expensive way t o both achieve and document a very high standard of asthma control.
Diurnal variation in peak flow and airway
reactivity were first linked together in studies
done by Hargreave’s group and reported by
Ryan et al. in 1982 (22). In these studies the
lower the PC2,,: (1) the lower the morning
peak flow; (2)the greater the response of peak
flow to albuterol; and (3)the greater the daily
variability of peak flow.
Moreover, peak flow was abnormal in all
subjects with moderate or severe airway
responsiveness (PC20 < 2 mg/ml) and normal
in all subjects with normal airway responsiveness (PC20> 21 mg/ml). In patients with
mild hyperresponsiveness (PC20 between 2
and 21 mg/ml), about half of the asthmatics
had abnormal peak flows.
The data mean that clinical screening with
peak flow may miss some subjects with mildly reactive airways. They also mean that
management should be aimed not only at
reducing peak flow variability, but at keeping the peak flow as steady as possible each
and every day. In practical terms, the patient’s peak flow will likely become normal
before the airway reactivity gets back to normal. Hence asthma medications should empirically continue until the peak flow has remained stable for weeks or months at a time.
Alternatively in selected cases, the physician
may wish to determine the patient’s PCzoas
a n end point in treatment.
The study also concluded that diurnal variation of peak flow was likely to be abnormal
if the diurnal fluctuation in peak flow was
greater than 12% or if the response to
albuterol in the morning was greater than
10%. Twenty percent variation had been considered the lower limit of normal by Hetzel
and Clark in 1980 (23). Ryan et al. suggest
that the stricter 12% figure could have
reflected milder patients or patients who were
more stable at the time of the study.
Two airflow assessments were not considered a s sensitive as diurnal variation of
peak flow: (1)measurement of FEVl pre- and
postbronchodilator; (2) estimation of diurnal
peak flow variation without using a
bronchodilator.
Moderate or severe increases in responsiveness were sometimes associated with
FEVl which was within 10% of maximum.
Presumably the second limitation could be
corrected by using the patient’s best peak flow
when determining variation. (Catch 22-in a
new patient, you may not know the patient’s
best peak flow.)
The effects of long-term aggressive asthma
management on airway reactivity were only
recently reported by Woolcock et al. in 1988
[241. In this study, subjects in the study group
were instructed in home peak flow monitoring and given a n aggressive asthma action
plan based on peak flow variation. Several
findings were reported:
All subjects in the study group became
asymptomatic over a n average of 19
months, compared to negligible reductions
in symptom scores in the control group.
The average peak flow variability in the
study group fell from 106 to 29%.
Average FEVl for the study group increased
from 77 to 93% of predicted; in the control
group the average baseline FEVl was 88%
at the beginning and 87% at the end of the
study.
There was a 10- to 100-fold improvement in
PD20in all subjects in the study group; no
significant change in PDzo in the control
group.
During the study, 7 of 13subjects in the study
group were sufficiently stable to allow for
reductions in their doses of inhaled
beclomethasone. Four of the seven stayed
Peak Flow Monitoring
off beclomethasone until the conclusion of
the study (3 months) on either prn
0-agonists or cromolyn. The other three
subjects had shortlived remissions and
relapsed shortly after t a p e r i n g
beclomethasone.
Some subjects in the study group reached
their best PD2,, within 6 months. Other
subjects continued to improve over 15
months.
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Peak flow variation correlated well with
PD2,, for individual subjects in the study
group over the duration of the study.
The authors theorized that the clinical improvements seen in the study group could
have been due to several factors, all linked
in one way or another to the use of a peak flow
meter: (1) better compliance, (2) improvements in perception, and (3) encouragement.
Finally Woolcock et al. noted the significant
implications of monitoring diurnal peak flow
variability: (1)peak flow variability can be
used as a “reliable guide” to determining airway reactivity; (2) peak flow is useful in
designing asthma management action plans;
(3) monitoring peak flow is a valuable source
of reinforcement for the patient.
Ultratwitchy Peak Flow: What level of
Significance?
For most patients, early morning peak flows
rise slowly and gradually to a maximal level
by midday. However, a number of patients experience very brittle early morning peak flow
levels. Such patients wake up blowing at one
level of peak flow, yet spontaneously in less
than 1 hour and without any 0-agonists
therapy, may improve to a significantly
higher peak flow.
Anecdotally, patients with very twitchy early morning peak flows seem to have past
clinical patterns of brittle asthma as well.
One can only wonder what endogenous factors must be operative to allow such rapid
shifts in airway obstruction. The question remains: do you count the very early morning
peak flow or the not-so-early morning peak
flow in determining their daily peak flow
167
variability? If the very early morning peak
flow dip is significant, how much effort should
be made to keep the very early peak flow
within lo%?At the very least, such patients
need to report early morning peak flow values
consistently; since the physician may not be
aware of the early morning lability in peak
flow.
Peak Flow Variability and Small Airways
At the risk of oversimplifying matters,
whatever keeps the peak flow very stable
tends t o keep the FEVl stable as well.
Ferguson’s (25) report of a reasonable correlation between peak flow and FEF25-75has
been cited for its advocacy of regular home
monitoring.
However, the study also showed certain
discordances between “normal” peak flow
trends and small airways. That is, normal
peak flow trends were sometimes disappointingly associated with abnormal values of
FEF25-75.It should be noted that normal
peak flow variability was defined as <25%
of the patient’s predicted or best peak flow.
Given the tighter standard of 10%peak flow
variability, there should be significantly less
discordance between peak flow and FEF25-75.
EDUCATING THE PATIENT ABOUT
MANAGING HlSlHER ASTHMA
Home peak flow monitoring should become
a n integral part of any modern asthma selfmanagement program. The implementation
of monitoring may be elaborate or simple.
Ideally, it should not be expensive or require
multiple visits. Group sessions may be the
focus for learning or the patient may go home
with self-paced materials. Education may
even be reduced to its most elemental form,
face-to-face teaching between physician and
patient with refresher courses anytime the
patient calls for help. Above all, the education is a two-way street. Physicians
themselves learn more about the daily intricacies of asthma when patients keep track
of peak flow trends.
In a self-management workshop in 1983,
Mendoza
168
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Thoresen and Kirmil-Gray reviewed a
number of self-management programs. Many
of the programs had different strengths but
Living with Asthma received especially high
marks for combining (26):
careful teaching of cognitive and analytic
skills, including behavior analysis, problem
solving, and self-monitoring. In addition, the
close link between assessment procedures
and treatment techniques is commendable.
Several of the measures used to assess
change probably served as interventions by
helping children and parents become more
aware of behavior patterns and providing information that could be used in treatment.
For example, daily assessment of pulmonary
functioning by use of peak flow meters provided important physiologic information that
children and parents used to help them
decide when and how to intervene and
whether their interventions were effective.
Fortunately, one bonus of peak flow monitoring is that patients can learn to perceive
symptoms. Such patients can become better
predictors of peak flow than their physicians
(27). If this is true, it should then be possible
to trust stable, experienced patients to
monitor their peak flow less formally and
more selectively. Possible some subjects may
become aware of inflammtory changes in
their airways before the airway reactivity or
peak flow has a chance to change.
Once the best peak flow is confirmed, once
or twice daily monitoring may suffice, provided the values remain near 90% of best.
Any breakfast or bedtime peak flow near 90%
is a reasonable guarantee that the peak flow
will remain within normal limits for the rest
of the day. However, if the early morning
peak flow drops below 90%, the midday peak
flow varies according to the relative level of
airway inflammation. At early stages of an
asthma relapse, the midday best peak flow
may still be normal. At later stages of a
relapse, the midday peak flow will begin to
drop significantly below the best level.
After the patient has been stable, the question of monitoring frequency needs to be addressed. Depending on the asthma severity,
the coping style of the patient/parent, and
physician, the monitoring may be useful
either on a daily or a prn basis-or something
in between. Selective vigilance is a comfortable term for prn vigilance. To be successful
it presupposes the patient can feel transitional changes in airflow. The aware patient
can then become more vigilant and check
peak flows until the problem is solved. To be
sure, patients do make mistakes shifting from
selective to active vigilance, but they can
learn from these mistakes as well. The bottom line is that while the monitoring issue
can be handled in differernt ways for different
patients, peak flow should be maintained as
stable as possible each and every day.
KEEPING THE PEAK FLOW CLOSE TO
“NORMAL” AT ALL TIMES
Invariably, viral infections, sinusitis, and
allergic triggers will eventually take their toll
on asthma. If the patient is prepared, and
responds with an appropriate pharmacologic
counterpunch, peak flow should remain close
t o normal most of the time. If the peak flow
cannot be easily rescued by 0-agonists back
to a near-normal level, then something needs
t o be changed.
To oversimplify what must be a complicated
situation, an irreversible dip in peak flow
means the airway inflammation has progressed to a point where swelling, not bronchospasm, is the rate-limiting obstructive
feature. At the very least, this concept has
proved to be very helpful in handling daily
asthma problems.
Debugging a Sluggish Peak Flow
If the patient is new or has never used a
peak flow meter at home, and the problem appears to be chronic-the differential diagnosis
needs to include undertreated asthma. That
is, the problem probably has been ongoing for
some time and airway swelling and mucous
plugging drops the peak flow in the way that
0-agonists alone cannot match.
If the patient is a n experienced selfmanager, the gradual development of a sluggish peak flow over several days is usually a
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Peak Flow Monitoring
very different matter. A recent viral upper
respiratory tract infection, plus one or more
classic signs of sinusitis usually indicate
bacterial sinus infection. If the diagnosis of
sinusitis is certain, it should be feasible to
defer making long-term changes in baseline
asthma medicines.
Given a likelihood of sinusitis, once antibiotics are started, the peak flow and other
clinical signs can be followed closely over the
next 72 h. If the diagnosis of sinusitis is accurate and the choice of antibiotic is ideal, the
peak flow and clinical signs should respond
within 24-48 h. If the peak flow does not rise,
then either the diagnosis or the choice of drug
needs to be re-evaluated.
Sometimes one can be misled by unsuspected chronic sinusitis into attributing a low
and unresponsive peak flow t o severe, uncomplicated asthma. However, in this case,
oral bursts of corticosteroids are usually
minimally effective in raising the peak flow
24 hours later. In practice, this clinical pattern is common enough t o attribute oral corticosteroid failures to sinusitis until proven
otherwise. In retrospect, these steroid “failures” are often the result of a poor history, a
hurried assessment, or inadequate peak flow
monitoring-or a combination of all. Sinus infections usually do not cause precipitous falls
in peak flow overnight, at least not in the way
some viral infections do.
DETERMINING SEVERITY OF
EXACERBAT10NS, ESPECIALLY AT
EARLY STAGES O F ASTHMA
This used to be the major peak flow
monitoring objective. That is, in the days
when we did not understand the concept of
airway inflammation and the need for adjusting inhaled corticosteroids, the peak flow
meter was a n overly simplistic bronchospasm
surveillance device. The meter warned patients when to get “serious” about taking their
daily or as-needed medicines. If they complied, we would assure them they would get
well and stay well. If they did not comply, we
warned them that asthma crises were to be
expected.
169
Perhaps the reason that peak flow meters
failed to catch on when they first were introduced is that we were using them for the
wrong reason. Perhaps as physicians we had
a n unrealistic sense of knowing what the patient needed-namely, that compliance was
the rate-limiting step in their bronchodilatorbiased management. Today, given our better
understanding of the pathogenesis of asthma,
adequacy of therapy has become as important
a factor as compliance in determining treatment outcome.
FAClLlTATlNG FLEX1B LE
LEVELS O F MEDICATION
Case History
A 45-year-old 62-inch tall nonallergic
female with a history of brittle and severe
asthma was seen recently for a second opinion
on her asthma management. She had improved significantly over the past 3 months,
but was still having some nighttime awakening with wheezing. Her peak flow at midday
in the office was 440 by mini-Wright and her
complete PFTs pre- and postbronchodilator
was comparable: FVC 2.66 L (97% predicted);
FEVl 2.12 L (92%); PEF 6.55 L/s (131%);
FEF25-75 1.96 L/s (78%).
Her previous daily medications included
seven sometimes redundant medications:
prednisone 5 mg qod with a history of multiple bursts in the past 6 months; sustained
release theophylline 400 mg tid; albuterol
tablets 4 mg tid as well as a n albuterol inhaler 1-2 puffs tid or prn; ipratropium
bromide 1-2 puffs tid; cromolyn sodium inhaler 2 puffs qid; beclomethasone 2 puffs qid.
The patient was unfamiliar with aerosol
chambers or peak flow monitoring.
Spirometry had not been done in the past 12
months.
Within 24 hours of monitoring, her pre- and
postbronchodilator peak flows were 260 and
340, and she regained a level of 420 by midday. Her beclomethasone was intensified but
simplified to 8 puffs bid. Within 14 days, the
patient completely stopped the following
three-drug regimen: albuterol 4 mg tablets,
Mendoza
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170
ipratropium bromide, and cromolyn sodium,
and reduced the dose of theophylline from 400
to 200 mg tid. She also discontinued the qod
prednisone prematurely. The aerosol 0agonists were reduced to strictly prn usage,
in effect bid.
By the end of 14 days of peak flow monitoring, her daily flows varied from 390 to 450.
During the next two weeks she attempted to
taper the midday theophylline dose, but her
peak flows became unstable and she restored
the previous schedule of 200 mg tid.
Subsequently, it was revealed that she had
prematurely reduced her beclomethasone to
4 puffs bid.
The preceding case illustrates the consequences of an asthma plan which either intentionally or inadvertently required an excessive and inappropriate level of medication.
The asthma action plan was unwritten,
unclear, and very cumbersome.
Unlike the chronic management of diabetes
or epilepsy, the fallout from inflexible, overmedication in asthma is not always apparent
to the patient. In this case the patient did not
complain of any significant side effects prospectively or retrospectively after discontinuing and tapering 90% of her medications. The
patient expressed concern that she was taking too much medication, but she was afraid
to accept blame for relapse if the medicines
were reduced.
IDENTIFYING UNKNOWN OR
SUSPECTED TRl GGER FACTORS
The need for diagnostic peak flow monitoring is clearly understandable for work-related
asthma problems. Daily peak flow trend
charts may be more sensitive to diagnosing
work-related asthma than single FEVl
measurements in the office (28).To a surprising degree, patients and parents may discover
a number of environmental irritants by applying simple deductive reasoning to peak
flow trends.
In divorced families, joint custody of a child
with asthma is a frequent source of conflicts
about smoking, environmental issues, and
management compliance. The peak flow
meter should be introduced to both parents
and extended family members at the onset.
Otherwise, the noncustodial parent/family or
the parent not involved in the initial consultation will be at a disadvantage with regard to
peak flow implementation.
WHO SHOULD KEEP A PEAK FLOW
METER AT HOME?
To anwer a question with a question-Who
should keep a bathroom scale or a thermometer at home? We live in a society with
countless appliances and devices without
which we would feel deprived. Just to name
a few, consider speedometers, oil pressure
gauges, tire gauges for our cars; gauges to tell
us when the fire extinguisher or propane tank
for the barbecue is empty; electronic and
digital control panels for virtually every
modern appliance in our house.
Even in the health care business a patient
can readily buy devices, test kits, and equipment at the local drug store to check their
blood pressure, blood glucose, find out if they
are pregnant, or monitor their pulse during
a workout. Why then should a patient with
asthma have to search for a peak flow meter?
Keep in mind that the cost of even the most
expensive peak flow meter is less than a one
month supply of virtually any asthma
medicine. From the perspective of a managed
care medical system or health insurance
group, providing meters to patients (and
teaching medical providers and patients alike
how to use them) at a discounted cost, or even
free, may be the cheapest form of asthma
self-insurance.
PEAK FLOW IN THE EMERGENCY ROOM
The value of pulmonary function tests, including peak expiratory flow, has been
studied in the emergency room setting by
numerous investigators. The studies have examined the influence of pulmonary functions
on the decision to admit or discharge patients
with asthma as well as the likelihood of
relapse following discharge. Some of the
171
Peak Flow Monitoring
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studies accepted existing clinical variables for
determining hospitalization; the question was
whether peak flow could predict that outcome
more quickly and expedite management.
Some studies concluded that peak flow
could not well predict who should be
hospitalized or discharged (29-31). Other
studies have concluded the opposite; namely
that peak flow should be a major criteria in
the decision to admit or discharge (32-36).
One would be well advised to review these
studies in detail before formulating a detailed
algorithm for asthma care in the physician’s
office or emergency room.
THE NIH EXPERT PANEL GUIDELINES
The Expert Panel has developed a very comprehensive set of guidelines for the management of asthma at home as well as in the office, emergency room, and hospital. The
measurement of airflow obstruction is an integral part of all the action plans at every
level of management. In many respects this
emphasis on objective pulmonary measures
differs from past studies. Peak flow becomes
less a gatekeeper for discharge and admission
and more a determinant for medical management. The emphasis is on what needs to be
done. Whether the patient stays in the
emergency department, goes home, or gets admitted becomes secondarily negotiable.
A patient presents to an emergency room
with a very low peak flow which improves
to some slightly higher level. By some peak
flow criteria the patient should be started on
corticosteroids and possibly admitted.
However, the patient appears to improve
clinically, goes home without a steroid burst
and does not return or get hospitalized over
the next several days.
Did the peak flow fail to predict the disposition correctly or did the patient go home with
inadequate treatment? What happened to the
patient’s airways at home without steroids?
Did they really get better or did they continue
to smolder for weeks at a time? The bottom
line is that we need to look beyond the
short-term outcome of a single episode. The
NIH guidelines provide a unified assessment
and management approach to immediate, intermediate, and long-term asthma outcomes.
A REVIEW OF PEAK FLOW
ACTION PLANS
Until recently, most clinical selfmanagement studies have omitted details of
their asthma management plans. With varying nuances, all of the action plans described
below deal with specific criteria for:
Defining normal or “best” peak flow
Objective parameters for short-term intensification of inhaled corticosteroids
The specific peak flow level which should
prompt a short-term oral burst of
corticosteroids
Both the Australian plan (see Fig. 6) and
Canadian plan (see Fig. 7) base decision making on post-P-agonist peak flow levels. Conversely, both the Southhampton plan (see
Fig. 8) and Los Angeles plan (see Fig. 9) base
decision making in the morning with prebronchodilator peak flow levels.
All of the action plans, regardless of their
differences, are likely to facilitate excellent
asthma management, especially when compared with asthma plans based on subjective
perceptions of asthma. However, the difference between basing action on pre- or post0-agonist is noteworthy and undoubtedly will
be a matter of continuing discussion and
study in the future.
PR E- VERSUS POST-P-AGONI ST-BAS ED
DECISION MAKING
Pre- and post-P-agonist-baseddecision making are both linked to the concept of airway
hyperresponsiveness and daily variation of
peak flow. As stable patients become
unstable, the first indication of change is the
modest and highly reversible drop in the
early morning peak flow. Mild bronchospasm
Mendoza
172
If during a whole day, your readings, including those
after sprays, do not reach:
Peak flow measured every morning, or more frequently if unstable
80% Double your usual number of doses of
beclomethasone until you can blow at least
96% and take your inhaled bronchodilator, no
less than every four hours during the day. If
after 24 hours there has been no improvement
or if your peak expiratory flow is less than:
Peak flow >70% potential normal value, continue “maintenance regimen” of
70% Take 50 mg of prednisone (and all your sprays)
until you can blow at least 96%. Ring your
doctor if the values do not improve.
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If a t any time during the day, after your spray,
your flow rate does not reach:
60% Take 50 mg of prednisone immediately and
bronchodilator spray up to each 10 minutes
if necessary and seek help.
Figure 6 . The Australian peak flow guidelines. From
Woolcock A, Rubinfeld AR, Seale JP,Landau LL, Antic
R, Mitchell C, REA HH, Zimmerman l? Asthma management plan, 1989. Med J Australia 151:650-653,1989.
readily responds to bronchodilators at such
early stages of asthma, but less easily as the
level of inflammation progresses. Whether
this is simply due to greater intensity of bronchospasm or airway swelling or both is not
always apparent at the event. The bottom line
is that unresponsive low peak flow requires
a change in management.
If, for 24 hours, PEFR after inhaled /3-agonist is:
<85% of best result, increase the dose of
inhaled corticosteroid twofold or fourfold until
readings are within 10% of the best result
< 60% of best result, take prednisone, 20 to
50 mg daily, until readings are again within
10% of the best result
< 50% of best result, take an additional 25 to
50 mg of prednisone and seek medical treatment at a specified medical facility
Figure 7 . The Canadian Conference Report peak flow
guidelines. From Ref. 19.
inhaled beta sympathomimetic, twice daily
and as required
inhaled beclomethasone diproprionate twice
daily
Peak flow <70% potential normal value
double dose of beclomethasone diproprionate
for number of days required to achieve
previous baseline
continue this increased dose for same number
of days
return to previous dose of maintenance
program
Peak flow <50% potential normal value
start oral prednisolone 40 mg daily and contact general practitioner
continue this dose for the number of days required to achieve previous baseline
reduce oral prednisolone to 20 mg daily for
same number of days
stop prednisolone
Peak flow < 150-120 I/min
contact general practitioner urgently or, if he
is unavailable,
contact ambulance service or, if it is
unavailable,
go directly to hospital
Figure 8. The Southhampton peak flow guidelines. From
Ref. 37.
There may be legitimate situations when
mild early signs of airway inflammation can
be treated with P-agonist alone without need
for further medical intervention unless the
peak flow cannot be restored to a specified
level. Accordingly, there may also be times
when the risk of status asthmaticus is so high
that the patient should be encouraged to
utilize pre-0-agonist peak flow values as an
immediate indication for steroids, not waiting
for post-P-agonist peak flow values to determine the proximity of the patient to
respiratory failure (Fig. 10).
Peak Flow Monitoring
Peak flow measured every morning prior to medications, or more frequently if unstable and compared
to best peak flow. If early morning peak flow is:
90-100% Green Zone Plan
Continue with maintenance regimen which consists
of either:
Peak Flow Alert #1:
Ideally, the patient should have a sense of
when the asthma is relapsing for three
reasons:
-
Cromolyn 4-8 puffs bid or
Beclomethasone/Triamcinalone 4-8 puffs bid
or Flunisolide 2-4 puffs bid
P-agonist optional a t rest, recommended
pre-exercise
-
Confer with practitioner for possible reductions in
medicines if stability steadily maintained for 2-3
months
-
(a)
(b)
(c)
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173
70-90% High Yelbw Zone Plan
Continue with maintenance regimen as above but
supplement with aerosolized 0-agonist q4-6 hr or
pin to keep peak flow in Green Zone
Notify practitioner if peak flow does not return to
Green Zone or keeps falling into this zone day after
day.
50-70% Low Yelbw Zone Plan
Supplement maintenance plan from above by:
(a)
Increasing inhaled corticosteroid or cromolyn
resuming a P-agonist would make the
patient feel better without delay
if the peak flow is low and the patient
is not aware, the concept of selective
vigilance is in trouble.
any fall in peak flow should be easily
correctable; otherwise a non-correctable
fall in peak flow is a warning that a #2
alert status may develop
Biggest mistakes at this stage-no perception
of change in airway reactivity and drifting
levels of compliance
Peak Flow Alert #2:
The patient needs to know when to intensify
inhaled corticosteroids [ 11 (or consider starting them if the asthma is becoming a daily
process).
two- or fourfold until peak flow trends remain
(b)
in Green Zone
Anticipate need for intensifying P-agonist
therapy by increasing doses, increasing the
dosing frequency, or shifting to a nebulizer as
directed in separate instructions
Notify practitioner if peak flow does not return to at
least the High Yellow Zone by midday, or if the peak
flow continues to drop into this zone 2 days in a row
<50% Red Zone
Plan
Contact practitioner at once and daily until stable.
Continue aggressive maintenance plan from Low
Yellow Zone Plan and supplement with:
(a)
(b)
Oral prednisone/prednisolone at 20 mg twice
daily or 1-1.5 mg/kg/day if under 60 pounds
Anticipate need for very aggressive use of
aerosolized P-agonists as directed in separate
instructions
Figure 9. The Los Angeles peak flow guidelines.
Biggest mistake at this stage-overreliance on
P-agonists with either no access to or without
intensifying inhaled corticosteroids
Peak Flow Alert #3:
The patient needs to know when to start an
oral burst of steroids.
Biggest mistake at this stage-continued overreliance on P-agonist with either n o access to
or without intensifyng inhaled corticosteroids
and no access to or failure to start oral
steroids.
Figure 10. Peak Flow Alerts #1,2,3. For patients on daily
cromolyn sodium it is plausible, but as yet unproven, that
a parallel strategy of “bursts” of extra cromolyn sodium
could be useful.
Mendoza
174
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PEAK FLOW ALERT #1:
STARTING BRONCHODILATORS
The Los Angeles guidelines were designed
to encourage patients to accept a step-care
system of asthma management (11).In that
spirit, if the peak flow was very stable, the
use of P-agonist inhalers was treated as an option, not as a daily necessity. From a pharmacologic standpoint this is probably a minor
concession. However, from a n educational
and psychological standpoint, the patient’s
control of the 0-agonist has proven to be a
valuable reinforcement for self-monitoring.
Many physicians routinely recommend Pagonists prior to using a n inhaler of either
cromolyn or any inhaled corticosteroids.
However, if the peak flow is 90-loo%,
pretreatment is seldom necessary to prevent
coughing, especially if the patient uses a n
aerosol chamber.
PEAK FLOW ALERT #2:
INTENSIFYING INHALED STEROIDS
The Australian plan calls for doubling of
beclomethasone if the post-0-agonist peak
flow falls below 80%. In the Canadian plan
the post level is set at 85%. In contrast, the
Southampton and Los Angeles plans suggest
intensification of inhaled corticosteroids at a
pre-0-agonist level of 70%. What difference
would these plans make in any single patient?-perhaps none. In many, if not most
cases, the peak flow trend would satisfy either
pre- or postcriteria within the cycle of a day
or two with comparable efficacy.
PEAK FLOW ALERT #3:
STEROID BURST DECISIONS: PREVERSUS POSTBRONCHODI LATOR
GUIDELINES
Selecting guidelines for starting a n oral
burst of steroids tends to be problematic and
open to second guessing. There are obvious
concerns for starting steroids too early, too
often, or too late. The four guidelines
reviewed offer very different approaches to
starting steroids.
The Australian and Canadian guidelines
are predicated not on how low the peak flow
falls at night or upon awakening, but on how
low it is after a 0-agonist treatment. In other
words, regardless of the extent of the initial
peak flow dip, if the recovery with 0-agonists
is adequate, the steroid would be deferred. If
the post-0-agonist peak flow fails to reach 70%
and 60%, respectively, the patient self-starts
the steroid burst. In contrast, the Southampton and Los Angeles guidelines are based on
how low the peak flow drops (50% in both
cases), regardless of the recovery after intensive 0-agonists.
How can these pre- versus post-based
guidelines all be successful if they are based
on such different principles? Is it possible the
prebronchodilator c 50% rule commits patients to a burst of steroids when the asthma
episode could have remitted spontaneously?
Is it possible also that some patients may find
themselves in difficulty if, despite precipitous
falls in peak flow below 50%, steroids are
deferred until the airways fail to respond to
bronchodilators, that is, peak flow does not
reach 60-70% pstbronchodilator? Should the
guidelines be combined for maximal
sensitivity?
The data from Woolcock’s 19-month study
would tend to support the postbronchodilatorbased oral steroid strategy. Beasley’s selfmanagement study in Southampton, using
prebronchodilator peak flow values, also
showed substantial improvement in a number
of different parameters (37). It is entirely
possible that most patients who get into
serious trouble will fulfill the criteria for
starting steroids of any guidelines within the
same general time frame.
With the exception of one near-fatal aspirin
reaction, I have never seen asthma progress
to status asthmaticus and hospitalization provided the patient followed the 50%guideline
explicitly. That is, the patient is aware of the
first ever dip below 50% and calls for advice
and/or self-starts a burst of oral steroids
within 6-12 h of the < 50%dip. Patients who
start the steroids early almost always enjoy
a prompt and relatively uneventful
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Peak Flow Monitoring
stabilization within a matter of 12-24 h.
Bursts beyond 4 days are becoming unusual
and immediate relapses are extremely rare,
probably because all the patients also intensify their daily inhaled corticosteroids.
From personal experiences in a managed
care health system of more than 100,000total
members, very few peak flow monitoring
patients have been sufficiently noncompliant
to become hospitalized. In those hospitalized
cases, oral corticosteroids were delayed
beyond 12-24h of the peak flow falling below
50% or failing to attain 60-70% postbronchodilator. In cases where the patient failed the
50% rule but called as soon as the peak flow
failed to reach 60-70%, no delay has resulted
in hospitalization. However, a number of such
cases were complicated by hectic evenings in
the emergency mom or home, waiting for the
steroids to begin to work.
In all candor, the incidence of nonreported
~ 5 0 %
incidents may be biased by selective
patient self-reporting and recall. It is difficult
to know how many times patients may
uneventfully go below 50% and successfully
defer starting steroids. Until clinical studies
assess the differences between the pre- and
post-0-agonists features of these guidelines,
the decision will have to rest on the individual
physician. Each physician caring for asthma
patients would be advised to thoroughly
review the details of each guideline and sift
out what appears to be different and similar.
By trial and error, guidelines should evolve
which are successful within the context of the
physician’s management style and the
asthma population.
In summary, delayed awareness of a Peak
Flow Level #1 Alert status may result in
nothing more than nuisance level asthma.
However, if the patient does not notice change
until Level #2,then shehe begins to seriously jeopardize their asthma management.
Needless to say, errors at Level #3 are serious
and potentially critical.
The ability of some patients to tolerate and
even sleep through Level 1 alerts is legendary. These patients start using bronchodilators at Level 2, when they should
really be increasing the dose of the inhaled
corticosteroid. Fortunately, with time most
175
monitoring patients do improve their
perception of Level 1 alerts.
PICKING THE BEST
PEAK FLOW GUIDELINE
Given the range of patients’ airway reactivity, varying expert opinion of what constitutes
optimal control of reactivity and patients’ coping styles, no single guideline can possibly
satisfy every physician for every case. Good
guidelines can be successful with some patients all of the time, and some patients none
of the time, yet with most of the patients most
of the time.
Reaction time is as relevant to asthma
step-care management as driving a car.
Patients need to perceive danger at a
distance, think about what to do and then
apply the brakes and take some evasive
maneuver. In any clinical practice, some
patients become instinctively adept at
avoiding crises while others may need to
learn one step at a time.
Guidelines can be relatively permissive or
strict. Some physicians can make loose
guidelines work well (i.e., relatively permissive ranges of “normal” peak flow
variability), often because they find ways of
teaching patients to read between the lines
of the guidelines and react appropriately.
Other physicians may feel they can achieve
excellent clinical results with only the most
stringent guidelines.
The key word is individualization. Make the
guidelines fit the patient as well as your own
sense of management. At the same time teach
patients in a manner which is consistent with
the way the guidelines should be followed. At
every opportunity show the patient how the
guideline would have handled a specific
question. Allow the guidelines to be
sufficiently flexible to encompass a variety of
common clinical situations. Be willing to
change your approach or specific tolerance
limits if the best patients keep making the
same kinds of mistakes. Be open to your
colleagues’ guidelines even if they are very
different from yours-he or she may be on to
something medically or educationally useful.
Mendoza
176
Good guidelines stand the test of time and
keep getting better with tinkering and
experience.
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THE FUTURE OF
PEAK FLOW MONITORING
Given the proven ability of children to
undertake significant self-care responsibilities, Lewis and Lewis have reviewed the
significant progress of general and asthma
self-management programs over several
years. Numerous studies have shown unequivocal cost-effective reductions in emergency room visits and hospitalizations for
asthma. However, the authors have noted a
disappointing level of asthma self-care implementation into clinical practice, even in
health maintenence organizations. The major resistance t~ implementation, according to
the authors, continues to be the reluctance of
physicians to share power with parents and
children (38).
In 1983,just before the current asthma mortality crisis was discovered, Mullen and
Mullen outline issues and strategies for implementation of asthma self-management
education in medical settings (39). The
authors warned that medical providers would
be reluctant to see the relative advantages of
asthma self-management and proposed a
variety of incentives for implementation.
Over the past few years, many implementation factors have begun to fall into place.
The asthma mortality epidemic has catalyzed
a renewed interest in self-management programs culminating in the N M Expert Panel
Report. The Asthma Education Program
should serve to influence a number of
standard-setting bodies to raise professional
awareness of the asthma problem. In turn,
this should effect change in technical asthma
care standards for the primary care practitioner and specialist alike.
Concerning the role of the asthma consumer, Mullen and Mullen noted that:
“Parents of children with asthma do not tend
to be organized or viewed as a market in and
of themselves” (39).
Writing in 1983,the authors did not foresee
the emergence of the asthma self-help movement later in the decade. Today such patient
advocacy groups as Mothers of Asthmatics,
Inc., the Asthma and Allergy Foundation of
America, the American Lung Association,
and a network of local patient‘parent support
groups have become essential partners with
physicians and other health care professionals in determining the future directions
of asthma care.
NOTE ADDED IN PROOF
An international consensus statement
about the diagnosis and management of
childhood asthma, including assessment of
peak expiratory flow, was developed in London in December 1988 (40).
The National Asthma Education Program
Expert Panel Report “Guidelines for the
Diagnosis and Management of Asthma” is
available from the NHLBI Information
Center, 4733 Bethesda Avenue, Suite 530,
Bethesda, MD 20814-4820.
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