Someone in the list would like to know what means "non invasive
ventilation". I would like to try to resume as briefly as I could the types
of ventilatory support that can be used at home:
1.-Invasively: Trough a tracheostomy, a surgical intervention (minor
surgery) performing an orifice (the exact term is "stoma") in the upper
part of the trachea. In the stoma a canulae is inserted to provide a
connection to the ventilator. You can find lot of information in links you
have in the vent-users page to other webs specifically dedicated to
tracheostomies. Nowadays this mode of ventilation can be considered the
"gold standard" in terms of efficacy. Nevertheless there are problems and
complications related to tracheostomies. This is the reason to search for
other forms of ventilatory support in a noninvasively way...
2.-Noninvasively:
a) Negative pressure ventilation: Applying a negative pressure around the
thorax would force the air into the lungs, aspirating it. Thatīs what the
iron lung does. The iron lung is the oldest device used for chronic
ventilatory support and a lot of people used it in the past and itīs still
used nowadays. But itīs cumbersome and different models have been
developed, like the Porta-Lung, smaller and "relatively" portable. The
shell is another extended type of negative pressure ventilation. Itīs a
shell made in fiberglass or similar material that covers the anterior and
lateral parts of the thorax. Usually there are different sizes of shells to
provide the more accurate fit to the thorax. The shell is then connected to
a pump that at the frequency you have stablished generates a negative
pressure (that you can regulate) to provide inspiration. Expiration is
passively though there are negative pressure ventilators capables of create
a possitive pressure to force expiration. In this list thereīs a person
whose child uses a Hayek oscilator, a shell-type negative pressure device.
Finally we have the poncho-wrap that is derived from the shell. The shell
is complemented in this case with a wrap that covers arms and legs, fitting
to ankles and wrists. The system is also connected to a pump.
b) Possitive pressure noninvasive ventilation: You use a possitive
pressure ventilator (like when you ventilate trough a trach) but without
disrupting the physiological airway. For this proposal we can use a nose
mask that can be made to measure in silycone and that must be well fitted
to the nose to avoid leaks of air around the mask. Part of the inspired air
can be delivered to the stomach but this usually doesnīt cause important
problems. One of the principal problems with this type of ventilation are
oral leaks trough the mouth during the sleep. Other form is using a mouth
piece that can be also made to measure. The patient bites the mouthpiece to
mantein it in place. There are vent-users that combine this two types, for
example, mouthpiece during the day and nose mask by night. Other persons
use noninvasive positive pressure by day and negative pressure by night.
There are also problems related to this forms of ventilatory support but
thatīs another story...
c) Abdominal ventilation, abdominal belt (Neumobelt is a commercial name):
An inflatable belt is adjusted to the abdomen and connected to a positive
pressure generator (it can be a simple ventilator). Regularly it creates
positive pressure, pushing the abdominal wall, forcing the diaphragm to go
up (sitting position is needed in this case) so helping expiration. When
thereīs no more pressure, diaphragm recovers itīs original position going
down so helping inspiration. This is a complement to other types of
ventilatory support and itīs necessary to be seated to use it.
d) Rocking bed: A bed that oscilate the position up and down. In this case
the diaphragm is passively displaced by the effect of gravity producing
inspiration and expiration.
There are more things related to noninvasive ventilatory support like the
problem with bronchial secretions. We could talk about manual assisted
cough, electrical stimulation of the muscles of the abdomen to assist
cough, the use of the Emerson In-exsufflator, vibration of the thorax by
means of external high frequency oscilation (the Hayek oscilator can do
that), etc., etc. but I think itīs enough for the moment and I donīt want
to be overwhelming.
One thing I think itīs important talking of noninvasive ventilation is
that you need a cooperative patient, plain of consciencie. But, really (and
this is a question for all of you) without consciencie I wonder if
ventilatory support is ethical. Life is possible without moving your legs
and your arms but moving your mind where life force is...but what happens
when mind fails?...
Well, I get a lot of information and ideas from this list. I admire the
work of people like James Lubin and the enthusiastic participation of a lot
of persons in this list. So I feel obliged to participate and to provide
some aid as far as I can.
Sincerely yours
Dr. Quiroga Ruiz
Intensive Care Unit
Home Mechanical Ventilation Unit
Hospital Central de Asturias
Oviedo
SPAIN