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Thorax
1990;45:728-732
Jet
and
ultrasonic
nebuliser
output:
use
of
a
new
method
for
direct
measurement
of
aerosol
output
J
H
Dennis,
S
C
Stenton,
J
R
Beach,
A
J
Avery,
E
H
Walters,
D
J
Hendrick
Chest
Unit,
Newcastle
General
Hospital,
and
Newcastle
upon
Tyne
University
Department
of
Medicine
J
H
Dennis
S
C
Stenton
J
R
Beach
A
J
Avery
E
H
Walters
D
J
Hendrick
University
Department
of
Environmental
and
Occupational
Medicine
J
H
Dennis
University
Department
of
Statistics
A
J
Avery
Newcastle
upon
Tyne
Address
for
reprint
requests:
Mr
J
H
Dennis,
Chest
Unit,
Newcastle
General
Hospital,
Newcastle
upon
Tyne
NE4
6BE.
Accepted
II
July
1990
Abstract
Output
from
jet
nebulisers
is
calibrated
traditionally
by
weighing
them
before
and
after
nebulisation,
but
the
assump-
tion
that
the
weight
difference
is
a
close
measure
of
aerosol
generation
could
be
invalidated
by
the
concomitant
process
of
evaporation.
A
method
has
been
developed
for
measuring
aerosol
output
directly
by
using
a
solute
(fluoride)
tracer
and
aerosol
impaction,
and
this
has
been
compared
with
the
traditional
weight
loss
method
for
two
Wright,
six
Turbo,
and
four
Micro-Cirrus
jet
nebu-
lisers
and
two
Microinhaler
ultrasonic
nebulisers.
The
weight
loss
method
overestimated
true
aerosol
output
for
all
jet
nebulisers.
The
mean
aerosol
content,
expressed
as
a
percentage
of
the
total
weight
loss,
varied
from
as
little
as
15%
for
the
Wright
jet
nebulisers
to
54%
(range
45-61%)
for
the
Turbo
and
Micro-Cirrus
jet
nebulisers
under
the
operating
conditions
used.
In
contrast,
there
was
no
discrepancy
between
weight
loss
and
aerosol
output
for
the
ultrasonic
nebulisers.
These
findings,
along
with
evidence
of
both
concentrating
and
cool-
ing
effects
from
jet
nebulisation,
con-
firm
that
total
output
from
jet
nebu-
lisers
contains
two
distinct
fractions;
vapour
and
aerosol.
The
vapour
fraction,
but
not
the
aerosol
fraction,
was
greatly
influenced
by
reservoir
temperature
within
the
nebuliser;
so
the
ratio
of
aerosol
output
to
total
weight
loss
varied
considerably
with
temperature.
It
is
concluded
that
weight
loss
is
an
in-
appropriate
method
of
calibrating
jet
nebuliser
aerosol
output,
and
that
this
should
be
measured
directly.
Jet
nebulisers
are
widely
used
in
respiratory
medicine
in
preference
to
ultrasonic
nebu-
lisers
because
they
are
traditional,
economical,
and
efficient
in
producing
respirable
aerosols.
They
are
used
therapeutically
to
deliver
bronchodilators,
antimicrobials,
mucolytic
drugs,
and
local
anaesthetics
to
the
airways
and
gas
exchanging
tissues.
Diagnostically,
they
are
used
in
inhalation
provocation
tests
to
deliver
drugs,
allergens,
and
industrial
chemicals-for
example,
in
the
measurement
of
non-specific
bronchial
responsiveness
and
in
the
investigation
of
occupational
or
environmental
causes
of
asthma
and
alveolitis.
For
diagnostic
purposes
precision
of
dose
delivery,
through
accurate
nebuliser
calibra-
tion,
is
critical
if
threshold
values
and
dose-
response
relationships
are
to
be
defined.
The
mechanism
of
jet
nebulisation
is
well
understood.'
Compressed
air
is
forced
through
a
narrow
orifice
within
the
nebuliser
and
negative
pressure
is
created
by
the
expan-
ding
jet,
which
draws
liquid
up
a
feeder
tube
by
the
Bernoulli
effect.
The
liquid
then
enters
the
air
stream
and
is
broken
up
by
air
turbu-
lence
within
the
jet
itself
and
by
impaction
on
interior
surfaces
within
the
nebuliser.
Baffle
structures
within
the
nebuliser
filter
all
but
a
small
proportion
of
respirable
aerosols
back
to
a
common
reservoir.
The
total
mass
of
re-
leased
aerosol
defines
the
available
dose
of
solute,
and
the
size
distribution
dictates
its
potential
deposition
in
the
respiratory
tract.23
The
present
investigation
is
primarily
con-
cerned
with
measurement
of
aerosol
mass.
Nebuliser
output
is
conveniently
calibrated
by
weighing
the
nebuliser
unit
before
and
after
activation.48
This
assumes
that
no
solvent
is
lost
during
nebulisation
by
the
con-
comitant
process
of
evaporation-an
assump-
tion
known
to
be
incorrect.""
To
investigate
the
importance
of
this
potential
limitation
to
the
weight
loss
method
of
calibration
we
have
developed
a
method
for
direct
measurement
of
aerosol
output
using
a
chemical
(fluoride)
tracer.
We
have
compared
this
with
the
traditional
method
of
calibration
by
weight
loss
in
several
types
of
jet
nebuliser
and
one
type
of
ultrasonic
nebuliser.
In
addition,
we
have
used
this
new
technique
to
investigate
the
effect
of
reservoir
temperature
and
air
flow
rate
on
jet
nebuliser
output.
Methods
NEBULISERS
Three
types
of
jet
nebuliser
were
chosen
for
study,
two
Wright
(Aerosol
Medicals
Ltd,
Colchester),
four
Micro-Cirrus
(Intersurgical,
Twickenham),
and
six
Turbo
(Medic
Aid,
Pagham)
nebulisers.
Two
Microinhaler
ultrasonic
nebulisers
(Vestric,
Runcorn)
were
also
examined.
Measurements
of
weight
loss
and
aerosol
output
were
determined
in
parallel
four
to
seven
times.
MEASUREMENT
OF
TOTAL
OUTPUT
BY
GRAVIMETRIC
ANALYSIS
Before
and
after
each
activation
period,
during
which
aerosol
was
collected
as
described
below,
jet
nebulisers
(the
nebuliser
itself,
nebuliser
reservoir,
and
fitted
T
piece)
were
disconnec-
ted
and
weighed
on
a
Mettler
analytical
balance
728
group.bmj.com on January 13, 2017 - Published by http://thorax.bmj.com/Downloaded from
Jet
and
ultrasonic
nebuliser
output:
use
of
a
new
methodfor
direct
measurement
of
aerosol
output
(model
H6GD,
Gallen
Camp,
Loughborough)
to
the
nearest
0.01
mg.
For
measurement
of
weight
loss
from
the
Microinhaler
ultrasonic
nebuliser
the
reservoir
container
(a
20
ml
glass
vial)
was
removed
and
weighed
in
a
similar
way.
The
time
taken
to
weigh
an
individual
nebuliser
unit
was
about
30
seconds.
From
a
separate
study
of
repeatability
of
weighings
it
was
found
that
the
95%
confidence
interval
for
the
difference
of
a
pair
of
weighings
was
+0-89
mg.'6
MEASUREMENT
OF
AEROSOL
OUTPUT
BY
FLUORIDE
TRACER
METHOD
Aerosol
generation
and
preparation
of
solute
tracer
Fresh
solutions
of
1
-00%
w/v
sodium
fluoride
(BDH
Chemicals
Ltd,
Blyth)
were
prepared
in
distilled
water
(10-0
g/l),
and
5
ml
aliquots
were
placed
in
each
nebuliser.
Compressed
air
(British
Oxygen
Company
medical
grade)
was
driven
through
the
Turbo
and
Micro-Cirrus
nebulisers
from
a
pressure
of
20
lb/in2
(138
kPa),
which
resulted
in
a
flow
rate
of
7-5
1/min.
For
the
Wright
nebuliser
a
flow
rate
of
8-0
1/
min
was
used.
A
2-00
second
nebulisation
through
the
Micro-Cirrus
and
Turbo
nebul-
isers
was
directed
by
a
locally
designed,
microprocessor
controlled
dosimeter.'7
For
the
Wright
jet
nebulisers
we
used
three
minutes
of
continuous
nebulisation.
The
ultrasonic
nebul-
isers
were
manually
activated
in
short
bursts
of
0.5-5
0
seconds.
Collection
of
aerosol
output
During
activation
of
nebulisers
ambient
air
was
drawn
at
15
1/min
through
a
fitted
T
piece
over
the
nebulisers
by
a
modified
(reversed
flow)
MiniNeb
Compressor
(Bard Ltd,
Sunder-
land).
This
entrained
and
impacted
aerosols
on
to
a
25
mm
Whatman
glass
fibre
(GF/A)
filter
(BDH
Chemicals
Ltd)
held
within
a
metal
cassette
positioned
5
cm
from
the
nebuliser
head
(fig
1).
Aerosols
from
the
ultrasonic
nebulisers
were
similarly
impacted
on
to
37
1
tr
.to
vacuum
pump
Glass
fibre
filter
onto
which
NaF
laden
aerosols
impact
jet
nebuliser
reservoir
containing
1
%
w/v
NaF
mm
GF/A
filters,
through
which
air
was
drawn
at
25
1/min.
A
higher
flow
rate
and
larger
filter
were
used
for
the
ultrasonic
nebulisers
because
the
filter
could
not
be
positioned
as
close
to
the
source
of
nebulisation.
After
aerosol
collection
GF/A
filters
were
removed
and
stored
for
later
analysis.
For
flow
rates
of
15
1/min
and
above
and
for
aerosols
having
a
mass
median
diameter
of
0
3
gm
or
more
the
collection
efficiency
of
GF/A
filters
exceeds
99
9%.18
When
a
second
filter
was
placed
in
series
we
detected
no
aerosol
breakthrough.
Analysis
of
aerosol
output
Total
ionic
strength
adjustment
buffer
(TISAB;
BDH
Chemicals
Ltd)
was
prepared
as
a
50%
solution
in
distilled
water,
and
20
ml
were
added
to
each
Whatman
filter
within
25
ml
plastic
Universal
bottles.
The
bottles
were
then
sealed
and
fluoride
was
allowed
to
desorb
overnight.
The
recovery
of
fluoride
from
filters
was
complete
(>
98%)
and
no
fluoride
was
detected
in
unused
filters.
Fluoride
analysis
followed
well
established
protocols.'9
Fluoride
standards
were
prepared
by
microlitre
injec-
tions
of
5
0,
10-0,
and
15-0
pl
of
1
00%
sodium
fluoride
into
20
ml
aliquots
of
50%
TISAB
buffer,
resulting
in
5-95E-5M,
1
19E'M,
and
1
*78E'M
fluoride
solutions.
Both
standard
and
test
solutions
were
equilibrated
to
25°C
in
a
water
bath.
Fluoride
concentrations
within
the
buffered
solutions
were
then
measured
electro-
chemically
with
a
fluoride
specific
ion
electrode
(Corning
Ltd,
Halstead)
on
a
Corning
255
pH/
ion
meter
with
a
calomel
reference
electrode.
This
electrochemical
system
had
a
log-linear
relation
between
concentration
and
activity
(mV)
from
10-'M
to
10'M
F.
All
solutions
were
continually
agitated
during
analysis
with
an
electromagnetic
stirrer.
An
internal
two
point
calibration
was
established
with
the
5
and
15
pl
fluoride
standards
and
its
accuracy
was
checked
with
the
10
p1
standard.
The
standard
curve
was
used
to
quantify
all
test
solutions
and
reported
directly
the
microlitre
quantity
of
aerosol
fluoride
impacted
on
and
desorbed
from
the
test
filters.
The
error
of
fluoride
determination
was
within
+
2%.
Given
that
the
concentration
of
the
chemical
tracer
used
in
this
method
is
only
1%
(w/v
as
sodium
fluoride),
the
density
of
the
solution
is
virtually
unity,
allowing
direct
comparison
of
weight
loss
and
aerosol
output-that
is,
1
mg
=
1
pl.
CONCENTRATION
AND
TEMPERATURE
CHANGES
WITHIN
NEBULISER
SOLUTIONS
For
investigating
the
effect
of
jet
nebulisation
on
reservoir
concentration
and
temperature
in
a
Wright
jet
nebuliser
we
used
5
ml
of
1
-00%
sodium
fluoride
solution
and
an
air
flow
rate
of
8
0
1/min.
Temperature
was
monitored
with
a
thermocouple
(±
0-1°C),
which
lay
in
the
reservoir
solution.
At
time
0
and
at
roughly
three
minute
intervals
the
reservoir
tem-
perature
was
recorded
and
nebulisation
was
interrupted
for
30
seconds
so
that
three
10
pl
aliquots
of
the
reservoir
solution
could
be
removed
for
fluoride
analysis.
A
similar
inves-
tigation
was
made
with
an
ultrasonic
nebuliser
except
that
reservoir
temperatures
and
concen-
'.
.
i
I;
,
...
compressed
air
Figure
1
Schematic
representation
of
method
of
aerosol
collection.
A
glassfibrefilter
is
held
in
front
of
the
nebuliser.
Fluoride
laden
aerosols
emittedfrom
the
nebuliser
during
activation
are
entrained
in
an
airstream
and
impact
on
the
filter.
The
quantity
of
fluoride
on
the
filter
is
subsequently
desorbed
and
measured
electrochemically.
729
group.bmj.com on January 13, 2017 - Published by http://thorax.bmj.com/Downloaded from
Dennis,
Stenton,
Beach,
Avery,
Walters,
Hendrick
trations
were
measured
before
and
after
the
period
of
nebulisation
only.
EFFECT
OF
TEMPERATURE
ON
WEIGHT
LOSS
AND
AEROSOL
OUTPUT
The
effect
of
temperature
on
jet
nebuliser
weight
loss
and
aerosol
output
was
investigated
in
a
dosimeter
driven
Turbo
nebuliser.
Separate
sodium
fluoride
solutions
(1
00%,
5ml)
were
warmed
to
400C
or
cooled
to
5°C
and
allowed
to
equilibrate
to
ambient
temperature
(21°C)
for
15
minutes.
Temperature
was
measured
continuously
with
a
thermocouple.
At
0-5-2
minute
intervals
reservoir
tem-
perature
was
recorded
and
the
nebuliser
was
activated
for
2-0
seconds
at
a
flow
rate
of
7-5
1/
min.
Output
was
determined
by
both
the
weight
loss
and
the
fluoride
tracer
methods
at
each
temperature
point.
EFFECT
OF
AIR
FLOW
RATE
ON
JET
NEBULISER
OUTPUT
A
Wright
jet
nebuliser
was
filled
with
fresh
5
ml
solutions
of
1
00%
sodium
fluoride
and
activated
for
periods
of
20
seconds
at
flow
rates
of
3,
5,
7,
9,
and
11
1/min.
Weight
loss
and
aerosol
outputs
were
determined
in
triplicate
for
each
flow
rate.
In
a
similar
but
more
prolonged
experiment
using
an
airflow
rate
of
4.5
1/min
the
nebuliser
was
activated
until
at
least
half
of
the
reservoir
solution
(10
ml
of
1
-00%
sodium
fluoride)
had
dissipated;
during
this
period
any
aerosol
emitted
was
captured
on
a
GF/A
filter.
Results
MEASUREMENT
OF
NEBULISER
OUTPUT
The
mean
weight
loss
from
the
nebulisers
under
the
operating
conditions
used
ranged
from
356
mg
with
a
Wright
nebuliser
to
9
3
mg
with
a
Micro
Cirrus
nebuliser
(table).
Weight
loss
substantially
overestimated
aerosol
output
for
all
jet
nebulisers.
Mean
aerosol
output
expressed
as
a
proportion
of
total
weight
loss
varied
from
as
little
as
15%
for
the
Wright
jet
nebuliser
to
54%
(range
45-61%)
for
Turbo
and
Micro-Cirrus
jet
nebulisers.
No
significant
difference
between
total
weight
loss
and
aerosol
output
was
noted
for
the
ultrasonic
nebulisers.
EFFECT
OF
NEBULISATION
ON
CONCENTRATION
AND
TEMPERATURE
OF
JET
NEBULISER
SOLUTIONS
Activation
of
a
Wright
nebuliser
for
35
minutes
dissipated
3-6
ml
of
the
5.0
ml
reservoir
solu-
tion.
The
concentration
of
fluoride
increased
from
1-00%
to
3-01%
and
the
reservoir
tem-
perature
fell
from
22°C
to
9°C
(fig
2).
Activa-
tion
of
the
ultrasonic
nebuliser
for
six
minutes
dissipated
4
0
ml
of
an
original
5
0
ml
solution
but
had
no
appreciable
effect
on
the
reservoir
concentration
of
fluoride
(before
1-00%,
after
1.01%)
or
temperature
(before
22°C,
after
23°C).
EFFECT
OF
RESERVOIR
TEMPERATURE
ON
JET
NEBULISER
OUTPUT
The
total
weight
loss
from
the
Turbo
jet
nebuliser
increased
substantially
with
the
tem-
perature
of
the
reservoir
solution
(fig
3),
weight
loss
approximately
tripling
over
the
tem-
perature
range
5-40TC.
Over
the
range
5-35°C
the
increase
was
approximately
linear
(inter-
cept
9
5;
slope
0-58;
Fl,24
=
188,
p
<
00001).
By
contrast,
the
change
in
aerosol
output,
though
statistically
significant
(intercept
8-8,
slope
0
083;
F,
24
=
114,
p
<
0
00
1),
was
only
13
fold
over
this
temperature
range,
and
negligible
over
the
normal
range
of
operating
temperatures
(10-25°C).
EFFECT
OF
AIR
FLOW
RATE
ON
JET
NEBULISER
OUTPUT
Mean
weight
loss
increased
approximately
lin-
early
with
airflow
rate
through
a
Wright
nebul-
iser
(fig
4).
For
aerosol
output,
however,
there
was
a
threshold
flow
rate,
near
7
1/min,
below
which
aerosol
output
was
negligible.
At
higher
Mean
composition
of
nebuliser
output
for
the
different
models
Mean
(SD)
Mean
(SD)
Mean
vapour
Mean
(SD)
No
of
aerosol
weight
loss
content
aerosolfraction
Nebulisation
deter-
output
(AO)
(WL)
(WL-AO)
(AO/WL)
time
(s)
minations
(mg)
(mg)
(mg)
(%)
JET
NEBULISERS
Wright
1
180
6
52-0(4-6)
356-0(14-2)
306-0
14-6(1-0)
Wright2
180
4
48-0(5-2)
320-0(15
9)
272-0
14
3(1-0)
Turbo
1
2-00
5
6
4(0-2)
14-2(0-6)
7-8
45-0(1-9)
Turbo
2
2
00
5
7-4
(0-1)
14-4
(1-0)
7
0
51-2
(3
9)
Turbo
3
2-00
5
10-1
(0
2)
18-7
(0
7)
8-6
54
0
(2-4)
Turbo4
200
5
11-4(0-3)
20-1
(1-2)
8-7
56-8(3-1)
Turbo
5
200
5
11-8
(0-3)
20-5(1-1)
8-7
57-7(39)
Turbo
6
2-00
5
12
0
(0
6)
21-2
(0-8)
9-2
56-4
(5
5)
Micro-Cirrus
1
2-00
4
5-1
(0
3)
9'3
(0-5)
4-2
54-2
(1-7)
Micro-Cirrus
2
200
4
56(0-1)
11-0
(0.4)
5-4
50-8
(2.2)
Micro-Cirrus
3
2
00
4
6-2
(0-2)
11-7
(0-5)
5-5
53-0
(2
6)
Micro-Cirrus
4
2
00
4
6-9
(0-2)
11-4
(0-3)
4-5
61-2
(2
9)
Nebulisation
No
of
Aerosol
Weight
Aerosolfraction
time
deter-
output
loss
(s,range)
minations
(mg,
range)
(mg,
range)
(mg,
range)
(%,
mean
(SD))
ULTRASONIC
NEBULISERS*
Microinhaler
1
0
5-5
5
8-66-123
94-115-0
849-107
97
5
(9
2)
Microinhaler
2
05-5
7
18-0
-82-2
16-5-
85-0
939-109
99-8
(5-1)
*Ultrasonic
nebulisation
time
was
controlled
by
a
manual
trigger
and
ranged
from
about
0-5
to
5
seconds.
730
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Jet
and
ultrasonic
nebuliser
output:
use
of
a
new
methodfor
direct
measurement
of
aerosol
output
20
10
0
cu
z
ON-
c
0
4.
CA
0
L.
0
en
(I)
0)
10
20
30
0
nebulisation
time
(min)
Figure
2
Effect
of
nebulisation
on
temperature
(°C)
and
concentration
(%NaF)
the
reservoir
solution
of
a
Wright
jet
nebuliser;
4
ml
of
an
original
5
ml
solution
wa.
nebulised
over
35
minutes
at
aflow
rate
of
8-0
I/min.
flow
rates
aerosol
output
increased
sub
tially.
With
an
air
flow
rate
of
4-5
1/min
155
utes'
activation
reduced
an
initial
10-0376
1
00%
sodium
fluoride
solution
to
4-4045
the
Wright
nebuliser.
The
reservoir
so
fluoride
concentration
increased
to
2-
implying
that
essentially
all
the
original
so
fluoride
solute
was
still
present
in
the
rese
(calculated
initial
content
=
10-0
mg/r
10
0376
ml
=
100-4
mg;
calculated
final
20
-
0
.
weight
aerosol
0
0
0
Z°
0
0
0
0
0
U
0
o
0
0
0
0
(P
8°0
.
.
m
IV=
so
.
.
20
reservoir
temperature
(C)
Figure
3
Effect
of
reservoir
temperature
(°C)
on
weight
(mg)
and
aerosol
(mg)
from
a
Turbojet
nebuliser.
Temperature
within
the
reservoir
solution
was
monitorei
with
a
thermocouple.
At
selected
intervals
the
nebuliser
was
activatedfor
2.00
secoi
and
measurements
of
weight
loss
and
aerosol
output
were
made.
of
stan-
min-
ml
of
ml
in
nebuliser
output
(mg/s)
61
4
2-
0
O
weight
loss
*
aerosol
output
0
0
0
0
0
.
.
4
8
1
2
air
flow
rate
(I/min)
Figure
4
Effect
of
airflow
rate
(I/min)
on
rate
of
weight
loss
(mg/s)
and
aerosol
output
(mg/s)
from
a
Wright
jet nebuliser.
Simultaneous
measurements
of
weight
loss
and
aerosol
output
over
20
second
activation
periods
at
flow
rates
of
3,
6,
9,
and
11
1/min
were
made
in
triplicate,from
which
mean
values
were
calculated.
tent
=
22-9
mg/ml
x
4
4045
ml
=
100
9
mg).
In
parallel,
only
0-292
mg
sodium
fluoride
was
recovered
as
aerosol
from
the
GF/A
filter,
which
corresponds
to
less
than
0
3%
of
the
available
solute.
idium
Discussion
29%,
It
is
widely
recognised
that
solutions
in
the
idium
reservoir
of
jet
nebulisers
concentrate
and
cool
~rvoir
during
use
owing
to
evaporation
of
solvent,"'5
nl
x
and
we
have
found
these
effects
in
the
reservoir
con-
solution
of
a
Wright
jet
nebuliser.
The
corollary-that
the
weight
loss
overestimates
the
amount
of
solute
nebulised-has
not
been
fully
investigated.
This
could
exert
an
impor-
tant
confounding
influence
when
jet
nebulisers
0
calibrated
by
weight
loss
are
used
to
determine
threshold
levels
and
dose-response
relation-
ships
from
inhalation
provocation
tests.
Evaporation
of
solvent
would
not
be
expec-
ted
from
ultrasonic
nebulisation
and
we
detec-
ted
neither
concentrating
nor
cooling
effects
within
ultrasonic
nebuliser
reservoirs.
Nor
did
we
find
differences
between
aerosol
output
measured
by
the
fluoride
tracer
method
and
weight
loss.
This
close
agreement
validates
the
fluoride
tracer
method
as
a
means
of
collecting
and
measuring
true
aerosol
output.
The
princi-
*
ples
of
using
chemical
tracers
and
aerosol
impaction
have
been
successfully
applied
in
similar
systems.20
21
By
contrast,
there
were
substantial
differences
between
total
weight
loss
and
aerosol
output
for
all
the
jet
nebulisers
tested,
total
weight
loss
being
as
much
as
six
times
aerosol
output
in
the
case
of
the
Wright
4
nebuliser.
40
°
These
results,
supported
by
the
findings
on
concentration
and
cooling
effects,
suggest
that
the
process
of
jet
nebulisation
releases
appreciable
amounts
of
water
vapour.
On
dUtput
entering
the
nebuliser
compressed
air
is
almost
ids
completely
dry.
Within
the
high
velocity
air
turbulence
of
the
nebuliser
jet,
air
may
be
0
C)
0
%-0.
o
c0
L.
L.
(I)
0
&n
40
-
E
0.
4.'
0
(I)
._
0
n3
0
i
I
731
group.bmj.com on January 13, 2017 - Published by http://thorax.bmj.com/Downloaded from
Dennis,
Stenton,
Beach,
Avery,
Walters,
Hendrick
expected
to
become
saturated
with
water
vapour.
This
alone
did
not
fully
account
for
all
the
differences
observed
between
total
weight
loss
and
aerosol
output.
Compressed
air
driven
through
the
Micro-Cirrus
and
Turbo
jet
nebulisers
from
our
dosimeter
per
2-0
second
nebulisation
acquired
a
mean
volume
of
250
ml
when
expanded
to
atmospheric
pressure
and
a
mean
temperature
of
16°C.
Under
these
condi-
tions
it
could
theoretically
absorb
some
48
,ul
of
water
vapour
before
saturation
occurs
(psy-
chometric
chart).
Whereas
this
agrees
closely
with
the
mean
vapour
loss
measured
from
the
Micro-Cirrus
jet
nebuliser
of
4-9
(range
4-2-
5
5)l
ul,
higher
vapour
losses
were
noted
from
the
Turbo
nebuliser
(mean
8-3,
range
7-0-9-2
pl).
These
may
be
attributed
to
the
Turbo
nebuliser
design,
which
causes
additional
los-
ses
to
ambient
air
drawn
through
the
nebuliser
during
activation.
The
temperature
of
the
reservoir
solution
strongly
influenced
the
amount
of
weight
loss
but
not
aerosol
output,
implying
that
tem-
perature
exerted
a
major
effect
on
vapour
generation.
The
weak
but
significant
effect
of
reservoir
temperature
on
aerosol
output
is
likely
to
be
due
to
temperature
dependent
changes
in
surface
tension
and
viscosity.
Because
jet
nebuliser
temperature
decreases
during
nebulisation
the
relation
between
weight
loss
and
aerosol
output
will
vary
during
use.
This
means
that
measurements
of
weight
loss
cannot
readily
be
adjusted
to
provide
an
accurate
estimate
of
aerosol
output.
Like
other
investigators
we
found
that
weight
loss
from
the
Wright
jet
nebuliser
was
directly
related
to
airflow
rate.22
23
Aerosol
output,
however,
showed
no
relation
to
air
flow
rate
until
a
threshold
flow
around
7
1/min
was
reached.
That
this
threshold
flow
rate
exists
was
confirmed
by
the
prolonged
use
of
the
Wright
nebuliser
at
a
flow
rate
of
4-5
1/mim.
From
this
we
measured
a
negligible
aerosol
output
by
the
fluoride
tracer
method,
and
recovered
essentially
all
the
original
solute
in
the
concentrated
solution
at
the
end
of
nebul-
isation.
Our
findings
reinforce
recent
observations
of
other
investigators.
O'Callagan
et
al
collected
the
output
of
nebulised
sodium
cromoglycate
from
three
brands
of
jet
nebuliser
in
a
multi-
stage
liquid
impinger
and
compared
the
aerosol
content
as
assayed
by
spectrophotometric
means
with
the
observed
weight
loss.
"
They
concluded
that
drug
output
calculated
from
weight
loss
may
result
in
overestimation
of
the
true
drug
output
by
as
much
as
50%.
Cockcroft
et
al
measured
sodium
concentration
changes
in
saline
solutions
of
Wright
jet
nebuliser
reservoirs
before
and
after
nebulisation,
and
calculated
that
aerosol
output
was
about
a
quarter
of
that
predicted
by
weight
loss.'5
We
conclude
that
use
of
the
gravimetric
method
to
determine
aerosol
output
from
jet
(but
not
ultrasonic)
nebulisers
is
inappropriate,
and
that
direct
measurement
(by
the
fluoride
tracer
method,
for
example)
should
be
used.
JHD
was
supported
in
part
by
the
Asthma
Research
Council
and
JRB
by
the
Newcastle
Health
Authority
Research
Committee.
1
Mercer
TT.
Production
and
characterisation
of
aerosols.
Arch
Intern
Med
1973;131:39-50.
2
Tillery
MI,
Wood
GO,
Ettinger
HJ.
Generation
and
characterisation
of
aerosols
and
vapours
for
inhalation
experiments.
Environ
Health
Perspec
1976;16:25-40.
3
Clay
MM,
Pavia
D,
Newman
SP,
Clarke
SW.
Factors
influencing
the
size
distribution
of
aerosols
from
jet
nebulisers.
Thorax
1983;38:755-9.
4
Cockroft
DW,
Killian
DN,
Mellon
JJA,
Hargreave
FE.
Bronchial
reactivity
to
inhaled
histamine:
a
method
and
clinical
survey.
Clin
Allergy
1977;7:235-43.
5
Nieminen
MM,
Holli
H,
Lahdensuo
A,
Muittari
A,
Karvonen
J.
Aerosol
deposition
in
automatic
dosimeter
nebulization.
Eur
J
Respir
Dis
1987;71:145-52.
6
Newman
SP,
Pellow
PGD,
Clarke
SW.
In
vitro
comparison
of
DeVilbiss
jet
and
ultrasonic
nebulizers.
Chest
1987;
92:991-4.
7
Tsanakas
JN,
Wilson
AJ,
Boon
AW.
Evaluation
of
nebulisers
for
bronchial
challenge
tests.
Arch
Dis
Child
1987;62:506-8.
8
Kongerud
J,
Soyseth
V,
Johansen
B.
Room
temperature
influences
output
from
the
Wright
jet
nebulizer.
Eur
Respir
J
1989;2:681-4.
9
Wright
BM.
A
new
nebuliser.
Lancet
1958;ii:24-5.
10
Clay
MM,
Pavia
D,
Newman
SP,
Lennard-Jones
T,
Clarke
SW.
Assessment
of
jet
nebulisers
for
lung
aerosol
therapy.
Lancet
1983;ii:592-4.
11
Wood
JA,
Wilson
RSE,
Bray
C.
Changes
in
salbutamol
concentration
in
the
reservoir
solution
of
a
jet
nebulizer.
Br
J
Dis
Chest
1986;80:
164-9.
12
Clay
MM,
Clarke
SW.
Wastage
of
drug
from
nebulisers:
a
review.
J
R
Soc
Med
1987;80:38-9.
13
Schoni
MH,
Kraemer
R.
Osmolality
changes
in
nebulizer
solutions.
Eur
Respir
J
1989;2:887-92.
14
O'Callaghan
C,
Clarke
AR,
Milner
AD.
Inaccurate
calcu-
lation
of
drug
output
from
nebulisers.
Eur
J
Pediatr
1989;
148:473-4.
15
Cockroft
DW,
Hurst
TS,
Gore
BP.
Importance
of
evaporative
water
losses
during
standardized
nebulized
inhalation
provocation
tests.
Chest
1989;96:505-8.
16
Bland
MS,
Altman
DG.
Statistical
methods
for
assessing
agreement
between
two
methods
of
clinical
measurement.
Lancet
1986;i:307-10.
17
Connolly
MJ,
Avery
AJ,
Walters
EH,
Hendrick
DJ.
The
relationship
between
bronchial
responsiveness
to
metha-
choline
and
bronchial
responsiveness
to
histamine
in
asthmatic
subjects.
Pulmon
Pharm
1988;1:53-8.
18
Cotes
JC,
Steel
J.
Environmental
monitoring.
Work-related
lung
disorders.
Oxford:
Blackwell,
1987:23-48.
19
Crosby
NT,
Dennis
ALM,
Stevens
JG.
An
evaluation
of
some
methods
for
the
determination
of
fluoride
in
potable
waters
and
other
aqueous
solutions.
Analyst
1968;93:
643-52.
20
Donna
E,
Danta
I,
Kim
CS,
Waner
A.
Relationship
between
deposition
of
and
responsiveness
to
inhaled
methacholine
in
normal
and
asymptomatic
subjects.
J
Allergy
Clin
Immunol
1989;83:456-61.
21
Kim
CS,
Lewars
GG,
Eldridge
MA,
Sackner
MA.
Deposi-
tion
of
aerosol
particles
in
a
straight
tube
with
an
abrupt
obstruction.
J
Aerosol
Sci
1984;15:167-76.
22
Ryan
G,
Dolovich
MB,
Obminski
G,
et
al.
Standardization
of
inhalation
provocation
tests:
influence
of
nebulizer
output,
particle
size,
and
method
of
inhalation.
J
Allergy
Clin
Immunol
1981;67:156-61.
23
Hickey
AJ,
Byron
PR.
Effect
of
solution
flow
rate
on
the
output
of
two
modified
commercially
available
jet
nebulizers.
J
Pharm
Sci
1987;76:338-40.
732
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aerosol output.
new method for direct measurement of
Jet and ultrasonic nebuliser output: use of a
Hendrick
J H Dennis, S C Stenton, J R Beach, A J Avery, E H Walters and D J
doi: 10.1136/thx.45.10.728
1990 45: 728-732 Thorax
http://thorax.bmj.com/content/45/10/728
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