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142
LETTERS
TO
THE
EDITOR
Continuous Positive Airway Pressure in Hyaline Membrane Disease
To THE EDIToR:
It is possible to employ the isolette
incuba-tor-respirator for application of a constant
neg-ative pressure (CNP) without the modification described by Vidyasagar.1
The solenoid valve is blocked in “up
posi-tion” by a simple mechanical procedure which is easily reversible. Tank is employed in “incu-bator position.” The motor driven vacuum is
then acting continuously and creates CNP.
Several applications of this method envi-sioned by us have been practiced on 20 infants.
1. It is a useful adjunct at oxygen therapy
in hyaline membrane disease (HMD) . Our
re-sults on gas equilibrium are identical to results
of the authors.
2. We have observed favorable results with
conjoint utilization CNP and intermittent
posi-tive pressure ventilation (IPPV) , when that alone does not sufficiently raise Pao2.
3. When diagnosis between HMD and aspi-ration syndrome of the premature infant is
doubtful, CNP aids diagnosis because a
con-stant and spectacular effect on Pao2 is found in
HMD
and a deleterious effect quickly observed in aspiration syndrome.F 57-Thionville, France
CLAUDE MARCHAL
PHILIPPE LEVEAU
YvES GENET H#{244}pital Bel-Air
REFERENCE
1. Vidyasagar, D., and Chernick, V. : Continuous
positive transpulmonary pressure in hyaline membrane disease: A simple device.
PEDI-ATRICS, 48:296, 1971.
To THE EDITOR:
The paper by Doctors Vidyasagar and
Cher-nick’ on the achievement of continuous posi-tive transpulmonary pressure using continuous
negative chest wall pressure contains a
sugges-tion for modification of the Air-Shields
Isolette-Respirator to permit its use in this fashion. They suggest the insertion of a switch into the electrical circuit to activate the solenoid valve
and thereby permit continuous evacuation of
air from the body compartment. While this
modification is effective, it is not necessary to do so in order to achieve continuous negative
pressure (CNP).
We have utilized the isolette-respirator for
similar purposes2 with encouraging blood gas
responses without any structural alterations in
the existing equipment. When the vacuum
mo-tor is turned on and the “expiratory vacuum”
control turned fully clockwise to the closed
po-sition, a continuous negative pressure can be
obtained. The amount of this can be regulated
by the “vacuum” control which varies the mo-tor speed. Figure 1 shows the position of these
controls. No override switch or modification of
the respirator is necessary. The valve operated by the solenoid does not remain closed when not electrically activated. A vacuum applied
via a connection from the pump to the top of
the valve stem opens the valve to a mid-way
position shown in Figure 2. Air is then drawn
through the “intake port” that communicates
with the atmosphere and from the patient com-partment. When the expiratory vacuum control is closed, communication with the surrounding
atmosphere is obstructed and air is evacuated
by the pump from the body compartment of the respirator. The body compartment is in
complete communication with the atmosphere
LETTERS TO THE EDITOR 143
. .
-Fic. 1. Position of controls of isolette-respirator.
the open position. A vacuum of up to 15 m
1120 can be so obtained, provided there are no
leaks at gaskets within the respirator or at the
collar around the infant’s neck.
In their report, cooling was encountered in
one infant, resulting in the abandonment of CNP and exclusion from the study. With this
respirator, cooling is due to leakage of cold air
at the iris collar across the body of the infant.
This can be prevented by positioning the infant
and adjusting the collar so that it fits snugly
and provides a seal on the infant’s shoulders.
The accompanying editorial comment in the
same issue of the Journal’ suggests the use of
an additional radiant heater. In our experience
with this respirator,5 radiant heat is neither
necessary, nor will it suffice to warm tile infant when there is a large leak present. \Vhat is
nec-essary is to close off the leak.
\Ve have found the technique here described of obtaining continuous positive airway
pres-sure very sensitive to small air leaks. This can be frustrating when it is an internal gasket that is leaking, l)Ut it is a good safety feature if the
leak is at tile 1115 collar to neck junction. A
rela-tivelv smaller volume of air will enter because
of the lower maximum pressure obtainable via
tllis method, the danger of cooling is less and
the fall in presstire alerts personnel to look for
the leak and readjust the infant’s position and the collar.
\Ve hope these 1)OiIltS may be helpful to
any-one planning to undertake this approach to the
TWf---_:_T____-_
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EXPIRATORY
VACUUM rr
CONTROL ,
J-1
I
I
Fic. 2. Isolette-respirator where a vacuum applied
via a connection from the pump to the top of tile valve stem opens the valve to a mid-way position.
management of infants with hyaline membrane disease.
EUGENE \V. OUTERBHIDGE, M.D.
DIETrucil W. ROLOFF, M.D.
LEO STERN, M.D.
Department of Newborn Medicine The Montreal Children’s Hospital
2.300 Tupper Street
Montreal 108, Quebec, Canada
REFERENCES
1. Vidyasagar, D., and Chernick, V. : Continuous positive transpulmonary pressure in hyalinc
membrane disease: A simple device.
Pr.ni-ATRICS, 48:297, 1971.
2. Outerbridge, E. W., Roloff, D. W., and Stern, L.: Improved oxygenation following simultaneous
use of negative and positive pressure
respira-tors. (Abst. ). Proceedings of the Society for
Pediatric Researcil, Atlantic
City,
p. 310,1971.
3. Stern, L. : Description and utilization of the neg-ative pressure apparatus. Biol. Neonatorum,
16:24, 1970.
4. Oliver, T. K., Jr. : Positive transpulmonary air-way pressure. PEDIATRICS, 48: 175, 1971.
144 LETTERS TO THE EDITOR
Beaudry, P. H. : Negative pressure artificial respiration: Use in treatment of respiratory
failure of the newborn. Canad. Med. Ass. J.,
102:595, 1970.
EDIToR’s NOTE : On the two letters above,
Doctors Chernick and Vidyasagar comment as
follows:
We are aware that a continuous negative
pressure may be obtained with the Air-Shields incubator-respirator without the use of an
over-ride switch. The method suggested by
Outer-bridge, et al was used on the two machines we
have but produced maximum pressures of only
3 to 5 cm of water. It is possible to modify the
expiratory vacuum control to produce higher
pressures. However, if the highest pressure
ob-tamable is only 15 cm of water this would be
inadequate since we have had two infants who
required higher pressures. The major
disadvan-tage of the method of Outerbridge, et al. is that
at high pressures the vacuum motor is exces-sively noisy, since it must be run at high speed.
Furthermore the lifetime of the motor may be
reduced because of overheating due to
insuffi-cient air flow through the pump. It is possible
to mechanically displace the solenoid valve as
suggested by Marchal, et al.; indeed in our first
patient treated with CNP we used a tongue
blade! We still maintain that the investment of
a $2.00 switch and 30 minutes time is
worth-while.
We agree that cooling in the infant is due to
the leak of air into the body compartment! Oc-casionally it is not as easy to correct the leak as suggested by Outerbridge, et al. and we have successfully maintained good body
tempera-ture control using a radiant heater.
Marchal, et al. have indicated favorable
re-sults with 20 infants with hyaline membrane disease and we look forward to seeing their
data. The suggestion that CNP may be used di-agnostically is not physiologically sound. CNP
theoretically should be efficacious in any
situa-tion associated with a loss of lung volume whether it be hyaline membrane disease, aspi-ration pneumonia, or post-operative atelectasis.
One certainly would not use this method in
pa-tients with meconium aspiration associated with expiratory airway obstruction and in-creased lung volumes.
Our experience with this method of
produc-ing a continuous positive transpulmonary
pres-sure has been most gratifying; 36 of 49 infants
with severe hyaline membrane disease have
survived.’ It seems a small point to argue
about minor differences between methods. We
would like to suggest that the use of a
contin-uous positive transpulmonary pressure by any
method is the most important adjunct to the
treatment of hyaline membrane disease
intro-duced in the past decade; its use by any
method is highly recommended.
V.
CHERNICK,M.D.
D.
VIDYASAGAR,M.D.
Children’s Hospital of Winnipeg
Winnipeg 3, Manitoba
REFERENCE
1. Vidyasagar, D., and Chernick, V.: Continuous
negative chest wall pressure in hyaline
mem-brane disease. (Abst. ). Proceedings of the
Society for Pediatric Research, Atlantic City,
p. 13, 1971.
Radiant Heaters and Other Hazards in the Delivery Room
To THE EDITOR:
In the May issue of PEDIATRICS,’ Dr. Alex
Robertson pointed out the unhappy fact that no effective radiant warmer now available
meets standards of safety sufficient for use in
delivery rooms where flammable anesthetics
are administered. His unhappiness had to do
with the manufacturers. Dr. T. K. Oliver
re-sponded on behalf of the Committee on Fetus
and Newborn to the effect that it is important
to provide neonates with a suitable
environ-ment in the delivery room and suggested that
the problem of unacceptable heating devices
vis-a-vis flammable anesthetics can be obviated
by discontinuing the use of flammable
anes-thetics or permanently mounting the heating
units at a height of 60 in. or more.
Frankly, Dr. Oliver’s reply seemed weak and
unsatisfactory. The hedge of placing
unap-proved electrical devices above the 60-in. level
in Class 1, Group C hazardous areas is
unac-ceptable because, in the event of a malfunction
which produces sparks, the sparks might easily
fall to below the 60-in. level.
It is apparent that as of now there is but one
avenue available to resolve the problem,
namely that of removing the hazardous gases
from the delivery rooms.
If the goal of parturient women,
