Inspiratory and expiratory muscle
aids are devices and techniques that involve the manual
or mechanical application of forces to the body or intermittent
pressure changes to the airway to assist inspiratory
or expiratory muscle function. The most important inspiratory
aid is to receive air under pressure when one inhales
(intermittent positive pressure ventilation or IPPV).
The most important expiratory aid is to have a negative
pressure (vacuum) applied to the airway via the nose
and mouth when one coughs along with a manual thrust
to the belly to further increase cough flows.
No one should receive supplemental oxygen, bronchodilators,
or other medications as an alternative to normalizing
blood oxygen levels by normalizing lung ventilation.
Using oxygen rather than assisted ventilation results
in worsening of carbon dioxide retention and inevitably
results in respiratory failure.
Maintaining Lung Range-of-Motion
Lungs become stiff if not expanded regularly. The
vital capacity is the deepest breath that one can
blow into a measuring device called a spirometer.
If the vital capacity is 500 ml but the predicted
capacity is 5000 ml then without assistance one can
only expand about 10% of one's lungs and the rest
closes down and for children does not grow properly.
Use of incentive spirometry or deep breathing is useless
because it does not expand the lungs more than about
10%. Mobilization of the lungs to prevent chest wall
contractures and lung restriction can only be achieved
by providing regular deep volumes of air (insufflations)
or overnight deep breaths (IPPV).
A person's maximum insufflation capacity (MIC) is
determined by giving the person the largest volume
of air that he or she can hold with the throat closed.
This is usually done by teaching the person to stack
volumes of air consecutively delivered from a manual
resuscitator. The person holds the stacked air with
the throat (glottis) closed until no more air can
be held. Patients who learn glossopharyngeal (frog)
breathing can often air stack to the MIC without mechanical
assistance.
The primary objectives in using air stacking or in
providing maximum insufflations as lung and chest
wall range-of-motion are to: increase the MIC, to
maximize cough flows, to maintain or improve lung
elasticity, to prevent or eliminate atelectasis, and
to master noninvasive ventilation (noninvasive IPPV).
The ability to air stack means that one can use noninvasive
ventilation and assisted coughing to prevent pneumonia,
respiratory failure, or the need to ever undergo tracheostomy.
Air stacking can also increase voice volume, facilitate
eating, and promote lung growth in children.
Since anyone who can air stack is also able to use
noninvasive IPPV, if such a patient is intubated for
respiratory failure, he or she can be extubated directly
to continuous noninvasive IPPV whether or not able
to breathe independently. (see intensive care protocols).
Noninvasive IPPV
IPPV can be noninvasively delivered via mouth pieces,
nasal, and oral-nasal interfaces for nocturnal ventilatory
assistance . Many people with no ability to breathe
on their own and no upper limb function keep simple
Respironics (Murrysville, PA) 15 mm or 22 mm angled
mouth pieces near their mouths and grab them between
their teeth as needed to receive mouth piece IPPV
during daytime hours. Mouth piece IPPV is the most
important method of daytime ventilatory support. Some
people keep the mouth piece between their teeth all
day. Most prefer to have the mouth piece held near
the mouth. A metal clamp attached to a wheelchair
can be used for this purpose or the mouth piece can
be fixed onto motorized wheelchair controls, most
often, sip and puff, chin, or tongue controls. The
ventilator is set for much greater than normal tidal
volumes, often from 1000 to 2000 ml. The person grabs
the mouth piece with his mouth and supplements or
substitutes for inadequate breath volumes. The person
varies the volume of air taken from ventilator cycle
to ventilator cycle and breath to breath to vary speech
volume and cough flows as well as to air stack to
fully expand the lungs.
To use mouth piece IPPV effectively and conveniently,
adequate neck rotation and oral motor function are
necessary to grab the mouth piece and receive IPPV
without insufflation leakage. Since the low pressure
alarms of volume-cycled ventilators can often not
be turned off, to prevent their sounding during routine
daytime IPPV when not every delivered volume is received
by the patient, a flexed mouth piece for IPPV or an
in-line regenerative humidifier can be used. These
create 2 or 3 cm H2O back pressure which is adequate
to prevent the low pressure alarm from sounding.
The lipseal can provide an essentially closed system
of noninvasive ventilatory support when using mouth
piece IPPV during sleep. Lipseal IPPV is delivered
during sleep with little loss of air out of the mouth
and with virtually no risk of the mouth piece falling
out of the mouth. Orthodontic bite plates and custom
fabricated acrylic lipseals can also increase comfort
and effectiveness. Typically high ventilator insufflation
volumes of 1000 to 2000 ml compensate for air leakage
out of the nose during sleep.
Because people prefer to use mouth piece IPPV or
the intermittent abdominal pressure ventilator for
daytime use, nasal IPPV (or the noninvasive delivery
of IPPV via a nasal interface "CPAP mask")
is most practical only for nocturnal use. Daytime
nasal IPPV is indicated for those who can not grab
or retain a mouth piece because of oral muscle weakness,
inadequate jaw opening, or insufficient neck movement.
Twenty-four hour nasal IPPV can, nevertheless, be
a viable and desirable alternative to tracheostomy
even for some people with severe lip and mouth muscle
weakness.
Most people prefer to use IPPV via a nasal rather
than oral interface during sleep. Whether using nocturnal
nasal or lipseal IPPV in a regimen of 24 hour noninvasive
IPPV, and despite the maintenance of normal daytime
alveolar ventilation, about 3% of people with no ability
to breathe on their own have episodes of excessive
air loss during sleep. These often result in arousals
with shortness of breath. The person may also complain
of recurrence of morning headaches, fatigue, and perhaps
nightmares and anxiety. The nasal ventilation user
should usually be switched to lipseal IPPV and lipseal
IPPV users can have their systems "closed"
by having their nostrils clipped or plugged with cotton
kept in by covering the nostrils by a bandaid during
sleep. Another practical solution is to set the ventilator's
low pressure alarm at a level that, by its sounding,
stimulates the sleeper sufficiently to shorten periods
of air leaking during sleep. Commonly, a low pressure
alarm setting of 10 to 20 cm H2O pressure is used
for this purpose and the user develops sleep reflexes
to prevent prolonged air leakage.
There are now numerous commercially available nasal
interfaces (CPAP masks). These include the Monark
and gel masks from Respironics Inc., Murrysville,
CO, the ResCare Inc. (San Diego) Sullivan mask, the
SleepNet (Manchester, N.H.) Phantomtm and IQtm Nasal
Masks, and Mallincrodt interfaces (Pleasanton, CA).
Each interface design applies pressure differently
to the paranasal area. One can not predict which model
will be most effective and preferred by any particular
user. Skin pressure and insufflation leakage into
the eyes are common complaints with several of these
generic models. Such difficulties resulted in the
fabrication of interfaces that mold themselves to
facial tissues and of other custom molded interface
designs . People must be offered trials using various
nasal interfaces and are encouraged to choose between
them. Interface use is evaluated for comfort and seal
around the nose. No one should be offered and expected
to use only one nasal interface anymore. Alternating
IPPV interfaces nightly alternates skin pressure sites,
minimizes discomfort, and is to be encouraged.
People whose blood carbon dioxide levels increasing
during the day causing their blood oxygen levels to
decrease below 95% need to use noninvasive IPPV, usually
mouth piece IPPV, for periods of time during daytime
hours. Failure to maintain normal lung ventilation
during daytime hours will result in inadequate nocturnal
benefit from the use of noninvasive IPPV. For patients
not wishing to switch to lipseal IPPV for nocturnal
aid despite excessive air leakage out of the mouth,
a chin strap or plugged lipseal can be used to decrease
mouth leakage. In the presence of nasal congestion
people either use decongestants to permit nasal IPPV
or they switch to mouth piece and lipseal IPPV, or
on rare occasions, temporary use of a body ventilator
like a portable iron lung. Most often the person continues
nasal IPPV using decongestants.
Because of the need for air stacking, people over
5 years old whose MICs exceed their vital capacities
need to use volume cycled portable ventilators rather
than pressure cycled machines like BiPAP because the
latter can not provide optimally deep breaths or permit
users to stack breaths.
In summary, noninvasive IPPV can be used for up to
full-time ventilatory support for the great majority
of people with no ability to breathe on their own
provided that they have mouth muscle function sufficient
for speaking.
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