Diagnostic
Services
Desert Pulmonary
& Sleep Consultants
Diagnostic
Center performs
medical tests
for breathing
and sleep:
SLEEP STUDIES:
PULMONARY
STUDIES:
Polysomnography
Polysomnography
is the medical
term for a sleep
study.
The
purpose of the
test is to
determine what,
if anything, is
abnormal with a
person’s sleep.
In order
to monitor the
sleep, small
metal cups
connected to
wires are
affixed to the
patient’s scalp,
face and chin.
These
cups (called
electrodes)
conduct signals
from the body to
a series of
filters and
amplifiers, and
a computer then
displays graphic
waves that
represent these
body signals.
Technologists
with years of
training are
able to
interpret these
signals to
determine if you
are awake,
drowsy, or in
dreaming or deep
sleep.
The
signals are
monitored
throughout the
study (which
typically takes
7 to 8 hours),
and the
technologist
(either during
the study or
after it is
completed) will
mark the sleep
“stage” every
thirty seconds
on the recording
as well as any
disruptions from
normal sleep.
At the
same time,
several
different
sensors monitor
your
breathing.
A small
wire or tube
placed in front
of the nose
senses air
movement, while
elastic belts
around the
stomach and
chest sense
expansion,
indicating
breathing
effort.
A tiny
flat microphone
or vibration
sensor taped to
the neck detects
snoring, and a
plastic finger
clip or wrap
around the
finger
determines
oxygen levels by
measuring light
absorbed by the
blood vessels.
Small
sticky plastic
patches are
placed below the
shoulders and on
the ribcage to
monitor heart
rate and rhythm
(EKG).
Another
set of patches
is placed on
each of the
lower legs to
detect muscle
twitches or
foot/leg
movements.
All of
these sensors
are amplified,
filtered and
displayed the
same as those
for detecting
sleep.
A video
camera and
microphone/speaker
is also
installed so the
technologist can
observe your
movements and
communicate with
you.
The
technologist
will examine the
signals from
every one of
these monitors
throughout the
study and mark
or notate
anything out of
the ordinary.
(The
sensors and
electrodes are
attached in such
a manner that
you can still
move around, and
even get up
without removing
everything, but
it is best to
ask the
technologist to
assist you to
prevent injury
or equipment
damage.)
It is
important to
understand that
a polysomnogram
is a medical
procedure, and
you will
probably not
experience a
completely
normal night’s
sleep.
The
technologists
and physicians
recognize this,
and are only
looking for
things that are
irregular – they
have studied
many people
without sleep
problems and
know what is
“normal” for the
sleep
laboratory.
Once the
study is
completed, the
technologist
will prepare a
summary of the
findings.
A
physician
trained and
certified in
sleep medicine
will then review
the entire study
and the
technologist’s
notes and
summary before
making a final
diagnosis.
This
physician will
also recommend
treatment if any
is necessary,
but it is
usually up to
your own doctor
to actually
provide this
treatment.
Polysomnography
is almost always
covered by
private
insurance, as
long as your
doctor has
documented an
appropriate need
for testing.
This
might include
obstructive
sleep apnea,
nocturnal
hypoventilation
(insufficient
breathing), low
oxygen levels at
night,
narcolepsy,
unexplained
daytime
sleepiness,
violent or
excessive body
movements while
asleep,
nocturnal chest
pain or
arrhythmias
(unusual heart
rhythms), or
waking up
choking or
gasping.
The
procedure is
usually not
covered to test
for insomnia,
sleep talking or
nightmares.
CPAP
CPAP
stands for
Continuous
Positive Airway
Pressure.
It is the
most effective
treatment for
obstructed
breathing during
sleep.
Small
amounts of air
are applied to
the nose by a
mask strapped
over the head or
a forked tube in
the nostrils.
The air
is supplied
through a
plastic hose
connected to a
book-sized
blower at the
bedside.
The air
does not contain
any more oxygen
than normal air,
but it is at
slightly higher
pressure (about
1/30th
that of an
aquarium pump.)
For those
who cannot
breathe through
their mouth, or
can only breathe
through nose and
mouth, larger
masks are
available.
Since
breathing
control is very
sensitive, it is
important to
determine the
correct amount
of pressure to
relieve the
obstruction.
Too
little, and the
airway will
close off,
resulting in
lower oxygen
levels, heart
strain and other
serious
complications.
Too much
pressure can
affect the
body’s chemical
sensors and
actually produce
more pauses in
breathing.
The
technologist
will generally
start the
pressure at the
lowest
comfortable
setting and
increase it
gradually while
you are asleep.
Besides
correcting
oxygen levels
and breathing
pauses, the
optimum pressure
will help
restore normal
sleep patterns
and decrease
disruptions.
This
technique may
require some
trial and error,
so it is
important that
the technologist
has adequate
time to perform
this procedure.
Once the
ideal pressure
has been
determined (and
reviewed by a
doctor), a
prescription can
be written for a
home device to
be used while
sleeping.
A large
number of mask
types are
readily
available, and
they are all
interchangeable
with any
machine.
Your own
doctor can help
you find a
company that
provides and
maintains these
devices.
Bilevel PAP
Bilevel
PAP (Positive
Airway Pressure)
is similar to
CPAP.
It uses
the same masks
and hoses, and
the machines
look similar as
well.
With
bilevel PAP, the
pressure you
breathe in is
higher than the
pressure when
you exhale.
There are
essentially two
different
reasons to use
bilevel PAP
instead of CPAP:
Some
people may find
that the
pressure
required to keep
the airway open
makes it
difficult to
exhale.
As long
as the pressure
is high enough
while breathing
in, a lower
pressure can be
used while
exhaling.
A bilevel
Pap machine
allows the two
pressures to be
different.
The more common
use of the
bilevel PAP
machine is in
treating
non-obstructive
breathing
disorders.
By
breathing in
more pressure
than you exhale,
it is sometimes
possible to
regulate the
depth and
frequency of
breathing.
In
addition, these
devices often
have other
settings to help
control the size
and regularity
of each breath,
both inspiration
and expiration.
The
bilevel PAP
machines are not
for everyone:
they are many
times more
expensive than
CPAP, and they
are unnecessary
if breathing is
primarily
obstructive and
the pressure is
well tolerated
(which is
usually the
case.)
A bilevel
study is
conducted the
same way as a
CPAP study, but
it is typically
much more
difficult to
find the correct
settings.
Patience,
adequate time
and a very
experienced
technologist are
necessary to
find optimal
pressure
settings.
Oft
times, more than
one study may be
necessary to
provide
sufficient time
and exposure to
all body
positions and
stages of sleep.
In some
patients,
bilevel PAP
alone may not be
sufficient to
treat all
nighttime
breathing
problems.
Your
physician may
need to order
additional
therapies to
manage your
breathing.
Split
Night
In
order to save
time (and often
money), a
split-night
study is
sometimes
ordered.
The first
half of the test
is the same as a
normal
polysomnogram
(see above).
If
significant
obstructive
breathing
(apnea) is noted
during this
time, a mask is
applied to the
nose and the
test continues
as a CPAP study
(see above).
Under
ideal
conditions, this
takes the place
of two separate
tests.
In
reality,
however, this
test is often
inconclusive.
Regulations
require that you
sleep for at
least two hours
before the CPAP
is applied, and
demonstrate a
large number of
obstructed
breathing events
before beginning
treatment.
Because
of the strange
environment and
the anxiety
sometimes
associated with
testing, it may
take longer than
usual to fall
asleep, or you
may awaken for
some time.
As a
result, it may
take a number of
hours before two
hours of sleep
have occurred.
This
leaves less time
to perform the
CPAP procedure.
After
being awakened
to begin the
CPAP procedure,
it may take some
time to adjust
and return to
sleep, further
limiting the
ability to find
an adequate
pressure.
In
addition, the
breathing events
may only occur
later in the
night, during
specific stages
of sleep, or
only in certain
body positions,
usually while
flat on your
back.
It may
take the entire
study before
sufficient data
has been
documented to
qualify for
treatment.
Because
of this, many
“split-night”
patients have to
return to the
sleep center for
a second night
of (CPAP)
therapy anyway.
MSLT (Multiple
Sleep Latency
Test)
The
MSLT is a test
for excessive
sleepiness.
If left
alone in a dark,
comfortable,
quiet bed long
enough, anybody
will fall
asleep.
A well
rested person,
however, will
usually take a
significant
amount of time
(more than 15 to
20 minutes)
before
succumbing.
After spending
the night in the
sleep lab and
undergoing a
polysomnogram to
rule out any
obvious sleep
disturbance, the
MSLT patient
awakens as usual
and goes about
their morning
routine
(breakfast,
usual
medications, get
dressed, etc.).
About an
hour later, the
patient is asked
to get back into
bed (some of the
sensors are left
in place or
reattached.)
The
lights are
turned out and
the patient is
instructed to
try to nap.
A short
time later, the
patient is asked
if they think
they fell
asleep.
Their
perception is
recorded, as is
the brain
activity during
the test.
The
patient is then
asked to get up
and resume
normal
activities.
(Caffeinated
coffee and other
stimulants are
sometimes
prohibited
during this
test.)
This
procedure is
repeated every
two hours for
four or five
trials
(depending on
the length and
depth of the
patient’s
sleep.)
After the
final trial, the
sensors are
removed and the
patient is free
to leave.
The
entire procedure
takes nine or
more hours to
complete.
Falling
asleep on one or
more naps is not
unusual, but the
sleepier you
are, the quicker
and more often
you will fall
asleep.
The
technologist is
also looking at
the depth (or
stage) of sleep
or wake every
thirty seconds.
Dreaming
sleep (REM)
during these
short trials is
unusual, and may
signify a
disorder such as
narcolepsy.
(Note:
You may
experience
dreams during
sleep, but not
be in REM sleep.
The brain
waves can
distinguish the
difference.)
MWT (Maintenance
of Wakefulness
Test)
The MWT
is designed to
test the ability
of a person to
stay awake when
all stimulation
has been
removed.
The test
is conducted by
attaching the
same sensors
used for the
MSLT test
(above).
The
patient is then
asked to sit in
a comfortable
lounger or sit
up in bed.
The
lights are
dimmed the door
is closed.
The
patient is then
asked to remain
awake without
any stimulation
for forty
minutes (no
reading,
television,
singing to
yourself,
wiggling your
feet, etc.)
The trial
ends when the
patient falls
asleep or after
forty minutes.
The
patient is then
free to resume
normal
activities.
This is
repeated every
two hours four a
total of four
trials.
Complete
Pulmonary
Function Test
(PFT)
A
Complete
Pulmonary
Function Test is
actually a
series of
breathing tests
conducted at one
visit.
The
separate tests
may vary
depending on
your diagnosis,
but are
typically:
Spirometry
Spirometry
measures the
amount of air a
person can
breathe in and
out as well as
the speed of air
movement to and
from the lungs.
Several
different
maneuvers are
performed:
The Forced Vital
Capacity (FVC)
requires you to
take a deep
breath and blow
into a tube as
hard and long as
you can (like
blowing a
trumpet.)
This is a
sensitive test
for obstructive
lung disease
like asthma or
emphysema.
The
Maximal
Voluntary
Ventilation
(MVV) requires
you to huff and
puff through a
mouthpiece,
breathing as
much as you can
for about 10
seconds.
This
procedure
measures lung
flexibility and
muscle strength.
These
procedures are
usually repeated
several times
after a short
rest, to assure
consistency and
accuracy.
Lung
Volumes
The amount of
air that your
lungs can hold
cannot be
measured by
blowing out.
Instead,
it is measured
indirectly by
one of two
methods:
Body Box
(Plethysmograph)
– In this
procedure, you
sit in a
Plexiglas box
about the size
of a telephone
booth and
breathe in and
out through a
small
mouthpiece.
On the
technologist’s
prompt, you pant
like a puppy for
2 or 3 seconds
while the box is
closed.
With the
help of data
from the
spirometry test
(above), the
instrument
instantly
calculates your
lung volume.
The
Nitrogen Washout
Test uses
simpler
equipment, but
gives the same
results.
By
breathing pure
oxygen through a
mouthpiece, all
the nitrogen in
your lungs
(normal air is
78% nitrogen) is
replaced with
oxygen.
The
system measures
the amount of
gas removed and
calculates lung
size from this
data.
The test
takes no more
than seven
minutes.
Diffusing
Capacity (DLCO)
The DLCO tests
the ability of
air to cross
through your
lungs into your
blood stream
without drawing
any blood.
After
taking a deep
breath of normal
air mixed with a
tiny bit of
harmless but
rare gas, you
hold your breath
for ten seconds.
When you
exhale, this
test will
determine how
much of the rare
gas passed into
your blood,
indicating how
well oxygen gets
in and carbon
dioxide gets
out.
This test
is very helpful
in
differentiating
emphysema from
other
obstructive
diseases.
Oximetry
An approximation
of your blood’s
oxygen content
can be made with
a small plastic
finger clip that
measures the
absorption of
light through
your fingernail.
Oxygenated blood
is much redder
than
non-oxygenated
blood, and this
device can
instantly
determine the
percentage of
oxygen
saturation in
your blood
stream (it also
determines your
pulse.)
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