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886 Archives of Disease in Childhood, 1984, 59
the delivery room and neonatal intensive care unit for patient
cooperation, and Mrs M J Rigby for secretarial work.
DWB was funded by St Joseph's Hospital Foundation.
References
Bowen F, Johnson L, Papodopoulous M, Peckman G, Nerrman N, Ritchie W. A prospective analysis of perinatal-neonatal
factors associated with intracranial hemorrhage. Proceedings of
2nd Special Ross Laboratories Conference otn Perinatal Intracranial Hemorrhage. Washington: 1982.
2 Kosmetatos N, Dinter C, Williams ML, Lourie H, Berne AS.
Intracranial hemorrhage in the premature: its predictive features and outcome. Ain J Dis Child 19801:134:855-9.
3 Setzer ES, Webb IB, Wassenaar JW et al. Platelet dysfunction
4
and coagulopathy in intraventricular hemorrhage in the premature infant. J Pediatr 1982;100:599-605.
Sykes GS, Johnson P, Ashworth F, et al. Do Apgars inidcate
asphyxia? Lancet 1982;i:494-6.
5ubowitz LMS, Lubowltz V, Goldberg C. Clinical assessment
of gestational age in the newborn infant. J Pediatr 1970;77:1-10.
Beverley DW, Chance GW, Coates CF. Intraventricular
haemorrhage-timing of occurrencc and relationship to perinatal events. Br J Obstet Gyvnaecol 1984; in press.
Correspondence to Dr D W Beverley. Department of Paediatrics,
Clarendon Wing, Leeds General Infirmary, Leeds.
Received 2 April 1984
Heat shield reduces water loss
C W FITCH AND S B KORONES
Departments of Paediatrics and Obstetrics and Gynaecology, University of Tennessee, USA
SUMMARY A heat shield covered by polyvinyl chloride film greatly reduced insensible water loss and
radiant energy requirements in 12 preterm infants
on a radiant cradle. Measured transmittance of
radiant energy emitted by the radiant heater was
impeded minimally by various thin film plastics but
was blocked significantly by Perspex.
The principal objective of a heat shield for infants
on radiant warmer beds is reduction of insensible
water loss, but a shield should neither impede
transmittance of radiant energy appreciably nor
impair patient visibility and accessibility. A shield
used in our nursery fulfills these objectives. The
effect on insensible water loss and radiant energy
requirements was assessed by this study. We also
measured transmittance of radiant energy through
five common plastic materials.
Patients and methods
The shield is in two sections which telescope to
adjust for length. The Perspex walls are 4 mm thick
and measure 13 cm (high) x 22 cm (wide) x 35 cm
(long) for each section; the top is covered by a thin
film of polyvinyl chloride. Small semicircular openings along the bottom permit passage of apparatus
(Figure).
Twelve well preterm infants were studied. Their
birthweight was mean (SD) 1-33 (0-2) kg (range 0-92
to 1-65 kg) and their gestational age was mean (SD),
33 (1-3) weeks (range 30 to 34 weeks). At the time
:Wb.JW
::
.:
Figure Preterm neonate enclosed in heat shield on radiant
cradle. The cover (polyvinyl chloride film) does not touch
the skin, and the telescoping sections permit easy adjustment
for infant's size. Openings along bottom margin allow
passage of ventilator coninectionis and support apparatus.
of the study their ages ranged from 8 to 76 days
(mean 29-8 days) and weights from 1-38 to 1-72 kg
(mean (SD), 1-51 (0-11) kg). Infants were studied
on the same radiant warmer (Cavitron KDC Model
IW-IOA) placed away from outside walls and
windows. Each infant was studied for two consecutive 90 minute intervals, one shielded (period I) and
one unshielded (period II). The heat source, a metal
clad quartz tube, emits radiant energy around a
peak wave length of 3 [tm. It was proportionally
servocontrolled to maintain abdominal skin temperature at 36-0 to 36-5°C. Abdominal skin and rectal
temperature and air temperatures inside and outside
the shield were monitored continuously by thermis-
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Heat shield reduces water loss 887
tors (Yellow Springs Instrument Co) appropriately
placed and shielded. Radiant energy was monitored
by a thermopile (Model 21-330, Barnes Engineering
Co). Temperatures and radiant energy were recorded graphically by a modified monitor (Model
512, Corometrics Medical Systems, Inc). Radiant
energy was determined for each infant during each
period by the average of three planimetric measurements of area beneath the recorded curve. Results
were expressed as mw/cm2/hour, representing the
mean radiant energy required to maintain skin
temperature during the specified interval. In four
infants, relative humidity was measured inside and
outside the shield and vapour pressure calculated.
Change in weight was determined by an electronic scale (Potter Baby Scale, Model 62). Thermal
stability, resolution, and repeatability of the scale
under typical study conditions, with and without the
shield in place, were evaluated carefully before in
vivo measurements. Thus, we were aware of potential thermal effects on scale stability and for each
study period allowed sufficient time for thermal
equilibration and stabilisation of the scale. Calibration of the scale and other recording devices was
verified at the beginning and end of each period.
Weight change and cardiorespiratory rates were
recorded by a research nurse at 15 minute intervals.
Data were discarded when, during any 15 minute
interval, the baby voided or defecated. The baby
was dried and a new 15 minute interval was initiated
after resetting the scale at zero. In this manner, 90
minutes of observation were accumulated for each
period. As reported by others,'- weight loss (g) was
equated with insensible water loss (ml/kg/hour).
Statistical significance of differences between study
environments was determined by paired Student's
quartz heater described above. To ensure comparable measurements, constant peak radiant output
was maintained. The unobstructed radiant energy received by the thermopile recorded a straight line
representing 100% transmittance. Each plastic
material was then interposed between the thermopile and heat source, immediately resulting in a
steady lower level of radiant energy received by the
thermopile; removal of the material produced a
prompt return to the original line of maximal
transmittance. The average decline (three measurements) in radiant energy induced by the interposed
plastic was measured from recorded curves and
expressed as per cent impedance for each material
studied. Plastics tested were polyethylene, polyvinyl
chloride-polyvinylidene, polyvinyl chloride, polyvinylidene, a double layered 'bubbled' material of
polyethylene coated with polyvinylidene and 4 mm
thick Perspex.
Results
Mean values of measurements for each study period
shown in the Table. Skin and rectal temperatures and cardiorespiratory rates were not influenced significantly by the presence or absence of
shielding. Shielding, however, produced a warmer
proximal ambience of higher vapour pressure; insensible water losses and radiant energy requirements were reduced significantly.
Measurements of radiant transmittance showed
85% blockage by Perspex, and an average of 14%
blockage by single layer plastic films; the double
layered 'bubble blanket' blocked approximately
32% of radiant emissions.
are
t test.
Discussion
Measurements of radiant transmittance through
plastics were made with the thermopile placed in the
centre of an empty radiant cradle, 5 cm above the
mattress. The radiant source was the same tubular
In the group of infants studied, the shield reduced
insensible water loss by 5 l'o and radiant energy
requirements by 59%M0. Baumgart et a13 reported
Table Summary of temperatures, ambient conditions, radiant energy, insensible water loss, and vital signs for infants in
each study period (mean (SD))
Study
period
Skin
Rectal
(abd()
1 wiih shicli
11. [lo sYlicId
ahd =hdominal.
Ambient
in
Amnbient
Radiant
eniergv
Insetisible
water loss
(mlAkglh)
(mnmHg)
(niw nIl2)
129'28
(2 (.(8')
8 77
(2'97)
(0
RespiratorY
rate
(per mnin)
Heart
rate
(per inn)
out
1.62
36.9
3(09
'26-
(0(3)
(0-3)
(1I1)
(()19)
362'
372'
(()-2)
28.7
(1*7)
277)9
(I I)
9 '1(4
'140)
( S
3A45
(I1-072)
<(O-(H)I
<)11101
<(0-0t
<(0(XII
<0)1(11
(0) 3)
P v.aluc
Vapour
pressure
Temperature (IC)
68
sS)
())()
44
14'
(7)
(7)
45
148
(7)
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888 Archives of Disease in Childhood, 1984, 59
similar results using a blanket of plastic film placed
directly upon the infant. They also measured a
significant reduction in air turbulence near the baby.
The rapidity with which radiant heat requirements
diminished in response to the blanket suggested that
the immediate and perhaps major effect of such
shielding is abrupt reduction of air turbulence and
resultant convective and evaporative heat losses. A
greenhouse effect is unlikely because ambient
temperature and radiant energy requirements would
change more gradually. Air turbulence is greater
over open radiant cradles3 than within incubators,
and this may contribute to the greater insensible
water loss associated with radiant heaters. We did
not measure air velocity, but we assume a reduced
turbulence because the shield provided virtually
complete enclosure. Reduced turbulence and raised
ambient vapour pressure under the shield should
decrease convective and evaporative heat losses. By
reducing insensible water loss to levels reported for
incubators, 5 ' the shield may eliminate a major
objection to the protracted use of radiant warmers.
We used a plastic film cover (polyvinyl chloride)
for the shield because Indyk6 suggested that polyvinyl chloride-polyvinylidene film did not block
transmittance of radiant energy significantly while
Perspex did. Our study of five plastic materials has
confirmed and extended his observations. The thin
film plastics that we tested should not interfere with
warming.
Wc thank our dcdicatcd rcscarch nurscs and Jiamcs E Waidc.
biomedical cnginccr, whosc scrvices wcrc indispensablc.
References
Fanaroff AA. Waild M. Gruber HS. Klatus MI. Insensibic waitcr
loss in low birth weight infatnts. Pediatrics 1972:50:236-45.
2 Wu PKY. Hodgman JE. Insensibic watcr loss in pretcrm
infants: chaingcs with postnatail dcvclopmcnt aind non-ionizing
radiant cncrgy. Peditilrics 1974:54:704-12.
Baumgart S. Englc WD. Fox WW. Polin RA. Effcct of hcat
shiciding on convcctivc aind cvatporaitivc hcat losscs aind on
raidiaint hcat trainsfcr in the prcmalturc infaint. J Pedai(tr
1981I99:948-56.
4 Hey EN. Mount LE. lcait losscs from ba.bics in incuba.tors.
Arc/i Dis Clhild 1967:;42:75-82.
5 Bcil EF. Wcinstcin MR. Oh W. Hcat bahlancc in premature
infants: comparative cffccts of convcctivcly hcatcd incubattor
and radiant wairmcr with aind without plastic heat shicid. J
Pedi(ilr 1980):96:460)-5.
Indyk L. A daingcrous situattion cncountcred in the administration of oxygen to an infaint in a ba.by wairmcr. Pediatrics
1971:47:6(3-5.
Correspondence to Dr C W Fitch, Newborn Center, 853 Jefferson
Avenue, Room 301, Memphis, TN 38163, USA.
Rcceived 29 Mairch 1984
Traumatic perforation of the hypopharynx-an unusual
form of abuse
H P McDOWELL AND D W FIELDING
Department of Paediatrics, West Cheshire Maternity Hospital, Chester
SUMMARY Two infants presented with extensive
interstitial emphysema of the neck as a result of
non-accidental trauma to the pharynx. The clinical
presentation, diagnosis, and management of this
unusual form of child abuse is discussed.
The variations in the clinical presentation of child
abuse are legion. We describe two infants with
erythematous swelling of the neck after nonaccidental traumatic perforation of the hypopharynx
complicated by haemorrhage, infection, and massive interstitial emphysema.
Case reports
Case 1. A 4 month old boy presented with a 24 hour
history of feeding difficulty, coughing, and the
production of bloodstained sputum. Examination
showed respiratory distress, head retraction, pyrexia, and a rapidly progressing erythematous swelling of the anterolateral aspects of the neck over
which crepitus could be felt. A linear abrasion was
found on the soft palate; direct laryngoscopy
showed fresh blood in the oropharynx and a
haemorrhagic sloughing lesion on the posterior
pharyngeal wall. Radiological examination showed
extensive interstitial emphysema of the neck and
three healing lower rib fractures, evidence of
probable previous abuse.
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Heat shield reduces water loss.
C W Fitch and S B Korones
Arch Dis Child 1984 59: 886-888
doi: 10.1136/adc.59.9.886
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