NOISE IN INFANT INCUBATORS AND IN NEONATAL INTENSIVE CARE
UNITS
A P Ca alho [1] and L F Pe ei a [2]
[1] Acous ical Lab., Dep. o Ci il Eng., College o Eng., U. Po o, R. B agas, P-
4099 Po o Codex, Po ugal, Tel/ ax: 351-2-2041931/40, ca [email p o ec ed]
[2] Sain An hony Gen. Hospi al, P-4050 Po o, Po ugal, [email p o ec ed]
1. INTRODUCTION
In Po ugal, he numbe o child en bo n ali e was in 1996 o abou 110,000.
Nea 10% o 15% o hese need in ensi e neona al ca e wha ep esen s abou
14,000 newbo n child en equi ing a s ay wi hin an Neona al In ensi e Ca e Uni
(NICU), an en i onmen usually noisy.
Rega ding noise, he possible damage o he cochlea in newbo n child en
caused by he exposu e o high le el p essu e le els has been s udied [1,2]. By
p e iously held s udies [3,4,5] i is known ha he cochlea o some newbo n
animals can be mo e ulne able o excessi e audi o y s imula ion han adul
cochleas. Fo his eason, i is usual o sugges he hypo hesis ha he human
newbo n can also p esen a educ ion in he ole ance o noise ega ding ha o
he adul [6].
Howe e , a hypo hesis ha has been s udied is ha noise wi hin he e us
in au e ine en i onmen can be loude han he no mal alues in he ex e io . I
so, he high sound le els wi hin he incuba o s would no be so unsa e as
expec ed. By measu ing he sound le els in he u e us o p egnan women and
close o he e us, a e aged alues we e egis e ed [15], co ec ed o he
en i onmen impedance misma ch, o abou 95 dB (± 2.5 dB s anda d de ia ion)
bu wi h maximum alues in he low equency bands (≤ 250 Hz). These sound
p essu e le els a e associa ed wi h he u bulen blood low and muscle
mo emen .
Du ing he las h ee decades, s udies ha e been published e alua ing and
s a ing ha newbo n child en a e exposed in he incuba o s o loud sound
p essu e le els [2,6,7]. The goal o his esea ch is o con inue hese s udies,
ega ding he si ua ion in Po ugal and o b ie ly analyze he possible changes in
iden ical si ua ions in o he coun ies in he las 30 yea s.
2. STUDY DESCRIPTION
INTERNOISE 98 Ch is chu ch New Zealand 16-18 No embe
The goal o his s udy was o cha ac e ize he acous ic en i onmen in wo
si ua ions: wi hin Neona al In ensi e Ca e Uni s (NICU) and in he incuba o s
(wi hin hese NICU). Th ee hospi als in he u ban a ea o Po o (second la ges
Po uguese own) we e selec ed: V. N. Gaia Hospi al wi h wo NICU ooms (la ge
egional uni buil in he 1970's); Ma osinhos Hospi al ( e y la ge egional hospi al
buil in 1997) and he Po o S . John Hospi al ( e y la ge gene al and uni e si y
hospi al buil in he 1960's). The selec ion o hese hospi als was done by logis ic
easons and also o been ep esen a i e o he Po uguese hospi als wi h
NICU's. Nine incuba o s and ou NICU's we e e alua ed (Table 1).
The measu emen s we e held du ing day ime on June 10, 1997. The
equipmen used was a
2231
-
B&K
sound le el me e (SLM) wi h a 1/3 oc a e il e
se model 1625. The measu emen s in he incuba o s we e done placing he
mic ophone (a ached o he SLM) a ew cen ime e s om he in an 's head. In all
cases excep o incuba o 6 he in an was p esen du ing he measu emen s.
Fo he measu emen s in he NICU's he SLM was placed in he middle o he
oom a a heigh o abou 1.4 m and a om windows and doo s. In any case
was he noise o opening/closing he incuba o s doo s included in he e alua ion.
The assessed noise is only he ep esen a i e o he no mal sound en i onmen
wi hin hese places bu wi h occasional sounding wa ning ala ms in he
su ounding incuba o s.
The pa ame e s used we e he sound p essu e le els
L
(dB) in he equency
bands 20 Hz o 20 kHz, he global sound p essu e le els
L
(dB) and he noise
c i e ion cu es (
NC-noise c i e ia
[11],
NR-noise a ing
[12],
RC- oom c i e ia
[13]
and
NCB-balanced noise c i e ia
[13]). The e alua ions we e done using he
equi alen con inuous sound p essu e le els (
Leq
) du ing each measu ing ime (a
ew minu es).
Table 1. Incuba o s analyzed.
INCUB. BRAND-MODEL-BUILDER PLACE
INFANT
1
Ai Shields-
142 MK2-
Vicke s Médical
V.N.Gaia H. oom 1 wi h in an
2
D äge -
8000 SC-
D äge we k
" wi h in an
3
Ameda-
Ameca e-
Ameda Egnell
" wi h in an
4
Ai Shields-
142-
Vicke s Médical
V.N.Gaia oom 2 wi h in an
5
Ai Shields-
C450-
Vicke s Médical
Ma osinhos H. wi h in an
6
Ohmeda-
Ca eplus-
Boc hea h Ca e
" wi hou in an
7
Ai Shields-
C2 HS/1C-
Vicke s Médical
Po o S . John H. wi h in an
8
Ai Shields-
C200-
Vicke s Médical
" wi h in an
9
Ai Shields-
C100-
Vicke s Médical
" wi h in an
3. RESULTS
Table 2 p esen s he summa y o he a e aged esul s ound o
Leq
and o he
noise c i e ion cu es
NC
,
NR
,
RC
and
NCB
in 4 NICU's and in 9 incuba o s.
Table 2. Mean alues o Leq (dB and dBA) and noise c i e ion cu es.
PLACE Leq (dB) Leq (dBA) NC NR (1) RC NCB
V. N. Gaia Hospi al - NICU #1 76.7 71.1 68 70 64 63
INTERNOISE 98 Ch is chu ch New Zealand 16-18 No embe
V. N. Gaia Hospi al - NICU #2 73.0 62.2 56 58 57 55
Ma osinhos Hospi al (2) 67.8 53.2 49 50 47 45
Po o S . John Hospi al 69.3 73.0 68 71 68 66
a e age o NICU's 72 65 60 62 59 57
Incuba o 1 78.5 68.1 67 65 61 59
Incuba o 2 76.0 61.7 59 58 56 54
Incuba o 3 74.2 61.4 58 59 55 51
Incuba o 4 71.6 58.0 57 55 49 47
Incuba o 5 84.8 59.5 60 56 49 47
Incuba o 6 68.7 56.3 57 55 45 41
Incuba o 7 70.9 56.1 58 52 49 47
Incuba o 8 68.1 55.5 52 54 49 48
Incuba o 9 76.9 61.0 64 60 52 48
a e age o Incuba o s 73 58 59 57 52 49
(1) no using he co ec ions p esen ed in [12] (2) he alues exp ess he s ill educed ac i i y o
his new hospi al and he be e quali y o he acili ies.
4. LEGISLATION AND IDEAL VALUES
Rega ding in e io acous ical com o he Po uguese Noise Code
(
Regulamen o Ge al sob e o Ruído
, DL 251/87) s a es only ha in hospi al
a eas occupied by pa ien s, he
L
50
o equipmen noise should be less han 35
dB(A). This alue is possibly exceeded in all he e alua ed si ua ions. As
equi emen s o acous ic com o ega ding Noise C i e ion Cu es, he
e e ence alues shown in Table 3 can be used as ideal alues [13,14].
Table 3. Ideal uppe limi alues o noise c i e ion cu es
RC
[13] and
NC
[14].
PLACES IN HOSPITALS
RC NC
p i a e ooms, auma uni s, ope a ing ooms, e c. 25-35 -
public a eas, co ido s, e c. 30-40 -
(gene al) - 25-35
5. ANALYSIS
As s a ed abo e, he e alua ed si ua ions do no each, in any o he cases, he
ideal alues (noise c i e ion cu es) and appea o be in disag eemen wi h he
essence o he legisla i e noise code ules (wi h alidi y since 01.01.1988).
The measu ed alues indica e acous ical en i onmen s jus a li le loude in
he NICU's han wi hin he incuba o s. This e eals ha one o he bes ways o
dec ease he sound le els close o he in an s mus also deal wi h he educ ion
o sound le els in he NICU's and namely by dec easing (o elimina ing) he
sound o he wa ning ala ms used in moni o ing; inc easing he o al sound
abso p ion in he oom, by changing he cha ac e is ics o he loo co e ings
and ceilings; diminishing (o elimina ing) all he speech in he NICU's and
damping he impac s p oduced by he opening/closing o he doo s o he
incuba o o o he shel es usually a ailable below he incuba o .
I seems o be a small bu posi i e e olu ion owa ds quie e en i onmen s
shown in he measu ed alues when compa ed wi h he ones a ailable in he
INTERNOISE 98 Ch is chu ch New Zealand 16-18 No embe
li e a u e o simila si ua ions a wo o h ee decades ago (Table 4).
No wi hs anding being his analysis e y es ic i e due o he pa icula ly small
da a base used, ha posi i e e olu ion seems o exis especially o he
acous ical condi ions exis en in he incuba o s g aded by i s maximum
NC
alues ha appea o ha e educed abou 14 o 16 dB. Wi hin he NICU's i
does no seem o be any g ea change in he las h ee decades. Simila ly
a o able is he dec ease (o abou 11 o 15 dB) in he sound p essu e le els in
he low equencies (125 Hz) bu wi hou signi ican change in he las 20 yea s
o i s maximum alues. The
Leq
(dBA) do no appea o ha e g ea ly changed
in he las wo decades.
Table 4. Sho his o ical analysis wi h a ailable da a (incuba o s and NICU's).
DATE/PLACE NC
(NICU) NC
(incub.) L @125Hz
(dB) (inc.) Leq (dB)
(incub.) Leq (dBA)
(incub.)
1968 Chicago -EUA [7] 55-65 55-83 64-86 67-86 (1) 50-69 (1)
1978 Vande bil -EUA [2] na na 66-72 74-80 52-58
1997 Po o -Po ugal 49-68 52-67 53-71 68-78 56-68
na - no a ailable (1) calcula ed om a ailable alues in [7].
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INTERNOISE 98 Ch is chu ch New Zealand 16-18 No embe