H E M O D Y N A M I C AND HORMONAL C H A N G E S I N D U C E D B Y N O I S E

L e n n a r t AndrBn , L e n n a r t Hansson , M a r t i n B j o r k m a n ,

A n d e r s J o n s s o n and K a r l O l o f B o r g

From t h e D e p a r t m e n t o f M e d i c i n e , O s t r a H o s p i t a l ,

I n s t i t u t e o f O c c u p a t i o n a l M e d i c i n e , S a h l g r e n s k a H o s p i t a l ,

D e p a r t m e n t o f H y g i e n e , U n i v e r s i t y o f G o t e b o r g , and

H a s s l e A B , G o t e b o r g , Sweden

Abstract . Eighteen hea l thy male vo lun teers with normal hear ing

were exposed t o i n d u s t r i a l no i se a t d i f f e r e n t sound l e v e l s (75,

85 and 95 dB A) i n a no ise l abo ra to ry . Blood pressure, hea r t

r a t e , s t roke volume and ca rd iac ou tpu t were recorded with non-

i nvas i ve techniques. Adrenal ine and noradrena l ine concen t ra t i on

i n venous plasma were analyzed be fore and du r ing no ise exposure.

The mean r e s t i n g b lood pressure o f t h e whole group was 120/70 mm

Hg. Dur ing no ise s t i m u l a t i o n d i a s t o l i c b lood pressure inc reased

(12.276, p < 0.001) as d i d mean a r t e r i a l pressure (6.6%, p < 0.001)

and t o t a l p e r i p h e r a l res i s tance (12.7%, p < 0.001). Stroke volume

(7.3%, p 4 0.001) and ca rd iac ou tpu t (5.0%, p 4 0.01) were bo th

reduced a t 95 dB A.

Heart r a t e and s y s t o l i c blood. pressure d i d n o t change s i g n i f i c a n t -

l y , A t 75 and 85 dB A t he re were s i m i l a r b u t smal le r changes i n

the hernodynamic parameters.

There were no changes i n adrena l ine and noradrena l ine i n plasma

du r ing maximal no i se exposure.

The no ise induced hemodynamic changes remained 5 minutes a f t e r t h e

no ise s t i m u l a t i o n was stopped b u t had disappeared a f t e r 10 minutes

o f r e s t .

13

I t h a s b e e n known f o r s e v e r a l d e c a d e s t h a t n o i s e c a n

c a u s e t e m p o r a r y b l o o d p r e s s u r e i n c r e m e n t s i n a n i m a l s ,

e .g . d i f f e r e n t s t r a i n s o f r a t s . I n 1 9 4 8 Y e a k e l e t a l .

( 1 ) showed t h a t d a i l y n o i s e e x p o s u r e t o r a t s f o r s e v e r a l

m o n t h s r e s u l t e d i n a b l o o d p r e s s u r e i n c r e a s e w h i c h

r e m a i n e d f o r f o u r m o n t h s a f t e r t h e n o i s e s t i m u l a t i o n

h a d s t o p p e d . F u r t h e r m o r e , t h e y showed t h a t i f t h e

a n i m a l was r e e x p o s e d t o n o i s e , t h e b l o o d p r e s s u r e i n c r e -

men t came f a s t e r t h a n d u r i n g t h e i n i t i a l e x p o s u r e , i n d i -

c a t i n g a mechan ism o f s e n s i t a t i o n i n t h e a n i m a l .

S e v e r a l s t u d i e s h a v e shown t h a t d i f f e r e n t s t r e s s

s t i m u l i , e .g . n o i s e , c a n p r o d u c e t e m p o r a r y b l o o d p r e s s u r e

i n c r e m e n t s i n S H R - r a t s a n d t h a t t h e s e s t i m u l i a c c e l e r a t e

t h e d e v e l o p m e n t o f p e r m a n e n t h y p e r t e n s i o n ( 2 , 4 -71 , J o n s s o n

a n d Hansson h a v e shown t h a t i n d u s t r i a l w o r k e r s w i t h a

s e v e r e n o i s e i n d u c e d h e a r i n g i m p a r m e n t ( d e f i n e d a s m o r e

t h a n 65 d 8 A h e a r i n g l o s s a t t h e f r e q u e n c i e s 3000 , 4000

o r 6 0 0 0 H Z ) , h a d s i g n i f i c a n t l y h i g h e r b l o o d p r e s s u r e com-

p a r e d t o a n a g e - m a t c h e d c o n t r o l g r o u p w i t h n o r m a l h e a r i n g

( d e f i n e d a s l e s s t h a n 20 dB h e a r i n g l o s s a t a n y f r e q u e n c y ) ;

8 . F u r t h e r m o r e , i n t h e g r o u p w i t h n o i s e i n d u c e d h e a r i n g

l o s s t h e r e were s i g n i f i c a n t l y m o r e h y p e r t e n s i v e s c o m p a r e d

w i t h t h e c o n t r o l g r o u p ( 8 ) . T h i s made u s i n t e r e s t e d i n

f u r t h e r e v a l u a t i o n s o f t h e e f f e c t o f n o i s e o n b l o o d p r e s s u r e

and o t h e r hemodynamic v a r i a b l e s . T h u s , t h e a i m o f t h e p r e s e n t

s t u d y was t o i n v e s t i g a t e t h e hemodynamic a n d h o r m o n a l

e f f e c t s o f a c u t e n o i s e s t i m u l a t i o n i n man.

P A T I E N T S AND METHODS

E i g h t e e n m a l e h e a l t h y v o l u n t e e r s w i t h n o r m a l h e a r i n g ( a u d i o -

m e t r y ) p a r t i c i p a t e d i n t h e i n v e s t i g a t i o n . T h e i r mean a g e

was 26 y e a r s , r a n g e 23 -31 . They w e r e s t u d i e d i n t h e a f t e r -

n o o n u n d e r s t r i c t l y s t a n d a r d i z e d c o n d i t i o n s i n a n o i s e

l a b o r a t o r y . F o l l o w i n g 20 m i n u t e s ' r e s t i n t h e s u p i n e p o s i t i o n ,

a t a s o u n d l e v e l o f 4 0 dB A n o i s e s t i m u l a t i o n s t a r t e d . The

p a t i e n t s were d i v i d e d i n t o t w o g r o u p s . The f i r s t g r o u p ( n = 8 )

was e x p o s e d t o i n c r e a s i n g n o i s e l e v e l s i n 1 0 - m i n u t e p e r i o d s ,

s t a r t i n g w i t h 75 dB A f o l l o w e d b y 85 dB A a n d 95 dB A . The

o t h e r g r o u p ( n = 1 0 ) was e x p o s e d d i r e c t l y t o 95 dB A f o r 2 0

m i n u t e s . T h e r e w e r e a l s o i n t e r m i t t e n t b r i e f s o u n d d i s t u r b a n c e s 14

w i t h s o u n d l e v e l s u p t o 1 0 5 dB A . The h e m o d y n a m i c p a r a m e t e r s

were r e c o r d e d s e v e r a l t i m e s b e f o r e , d u r i n g a n d a f t e r t h e

n o i s e s t i m u l a t i o n . A d r e n a l i n e a n d n o r a d r e n a l i n e i n v e n o u s

p l a s m a were s t u d i e d a f t e r 2 0 m i n u t e s ' r e s t i n t h e s u p i n e

p o s i t i o n a n d a f t e r 5 m i n u t e s o f n o i s e e x p o s u r e a t 9 5 dB A .

The s u b j e c t i v e e x p e r i e n c e o f t h e n o i s e d i s t u r b a n c e w a s

r e g i s t e r e d i n a q u e s t i o n n a i r e . The i n v e s t i g a t i o n was e n d e d

by a r e s t i n g p e r i o d a t 40 dB A .

B l o o d p r e s s u r e w a s m e a s u r e d i n d i r e c t l y w i t h a n a u t o m a t i c

b l o o d p r e s s u r e r e c o r d e r ( B o s c h B o s o m a t ) . T h e r e was a v e r y

g o o d c o r r e l a t i o n ( r = 0 . 9 3 , p L 0 . 0 0 1 ) b e t w e e n s i m u l t a n e o u s l y

r e c o r d e d b l o o d p r e s s u r e s w i t h a m e r c u r y m a n o m e t e r a n d t h e

a u t o m a t i c b l o o d p r e s s u r e r e c o r d e r . D i a s t o l i c b l o o d p r e s s u r e

was m e a s u r e d a t t h e d i s a p p e a r e n c e o f t h e K o r o t k o f f s o u n d s

( p h a s e V ) . H e a r t r a t e a n d s t r o k e v o l u m e were r e c o r d e d n o n -

i n v a s i v e l y w i t h i m p e d a n c e c a r d i o g r a p h y ( 9 ) . I t s c o r r e l a t i o n

w i t h d y e - d i l u t i o n t e c h n i q u e ( C a r d i o - G r e e n ) w a s r = 0 . 8 9 ,

p c 0 . 0 0 1 ( 1 3 ) . I t i s known t o b e a t l e a s t a s r e l i a b l e a s t h e d y e d i l u t i o n t e c h n i q u e i n a s s e s s i n g c h a n g e s i n s t r o k e

v o l u m e i n t h e s a m e p e r s o n ( 1 0 - 1 2 ) .

T o t a l p e r i p h e r a l r e s i s t a n c e w a s c a l c u l a t e d a s t h e q u o t i e n t

o f mean a r t e r i a l b l o o d p r e s s u r e a n d c a r d i a c o u t p u t . T h e

b l o o d s a m p l e s f o r c a t e c h o l a m i n e a n a l y s i s ( 1 3 ) were t a k e n

f r o m a c a n n u l a i n s e r t e d i n a n a n t e c u b i t a l v e i n 1 0 m i n u t e s

b e f o r e t h e r e s t i n g p e r i o d s t a r t e d .

RESULTS

A t 9 5 dB A t h e r e were h i g h l y s i g n i f i c a n t i n c r e m e n t s i n

d i a s t o l i c b l o o d p r e s s u r e ( 1 2 . 2 % , p < 0 . 0 0 1 ) , mean a r t e r i a l

p r e s s u r e ( 6 . 6 % , p c 0 . 0 0 1 a n d t o t a l p e r i p h e r a l r e s i s t a n c e ( 1 2 . 7 % , p 4 0 . 0 0 1 ) ; F i g . 1 .

The s t r o k e v o l u m e d e c r e a s e d s i g n i f i c a n t l y (7 .376, p < 0 . 0 0 1 )

a s d i d t h e c a r d i a c o u t p u t (5 .076, p C. 0 . 0 1 ) . Hear t r a t e a n d

s y s t o l i c b l o o d p r e s s u r e d i d n o t c h a n g e s i g n i f i c a n t l y .

A t 7 5 dB A t h e r e were s t a t i s t i c a l l y s i g n i f i c a n t i n c r e m e n t s

i n d i a s t o l i c b l o o d p r e s s u r e (5.076, p < 0 . 0 5 ) , mean a r t e r i a l p r e s s u r e ( 3 . 2 % , p C 0 . 0 5 ) a n d t o t a l p e r i p h e r a l r e s i s t a n c e

1 5

1 6

15 --

Hernodynamic Changes Induced by Noise (n=18)

95 (dBA) TPR

SBP

DBP

I I sv co n P<OOOl

Fig. 1 . Hernodynamic changes i n 18 h e a l t h y s u b j e c t s caused

by n o i s e s t i m u l a t i o n a t 95 dB A .

( l l . l % , p < 0 . 0 5 ) . Hear t r a t e (3 .276 , n .s .1 , s t r o k e v o l u m e

( 3 . 6 % , n . s . 1 , s y s t o l i c b l o o d p r e s s u r e i n c r e a s e d (1 .176 ,

n . s . ) arid c a r d i a c o u t p u t (6 .276 , n . s . ) d i d n o t c h a n g e s i g -

n i f i c a n t l y . A t 85 dB A t h e r e were c h a n g e s s i m i l a r t o t h o s e a t 7 5 dB A ,

a l t h o u g h t h e y were l e s s p r o n o u n c e d .

T h e r e were n o s i g n i f i c a n t d i f f e r e n c e s a t 9 5 dB A b e t w e e n

t h e g r o u p w h i c h w a s e x p o s e d t o a s t e p - w i s e i n c r e a s e i n

n o i s e a n d t h e g r o u p w h i c h was d i r e c t l y s t i m u l a t e d w i t h 9 5

dB A .

Loud s h o r t i n t e r m i t t e n t n o i s e ( 1 0 5 dB A) d i d n o t a c c e n t u a t e

t h e h e m o d y n a r n i c r e s p o n s e e l i c i t e d by c o n t i n u o u s n o i s e a t

9 5 d 8 A . T h e r e was n o c o r r e l a t i o n b e t w e e n s u b j e c t i v e l y e x p e r i e n c e d

d i s t u r b a n c e and o b j e c t i v e l y r e c o r d e d hemodynamic c h a n g e s .

The hemodynamic c h a n g e s w e r e s t i l l p r e s e n t 5 m i n u t e s

a f t e r t h e n o i s e s t i m u l a t i o n was s t o p p e d b u t t h e y h a d d i s -

a p p e a r e d a f t e r 1 0 m i n u t e s o f q u i e t r e s t a t 4 0 dB A .

T h e r e were n o s i g n i f i c a n t c h a n g e s i n a d r e n a l i n e o r n o r -

a d r e n a l i n e c o n c e n t r a t i o n i n p l a s m a d u r i n g m a x i m a l n o i s e

s t i m u l a t i o n ( 9 5 d8 A ) , n o r w e r e t h e r e a n y c o r r e l a t i o n s

b e t w e e n t h e c h a n g e i n hemodynamic p a r a m e t e r s and t h e c a t e -

c h o l a m i n e c o n c e n t r a t i o n s .

DISCUSSION

A c u t e n o i s e e x p o s u r e c a u s e d a t e m p o r a r y b l o o d p r e s s u r e

i n c r e a s e i n n o r m a l v o l u n t e e r s . The b l o o d p r e s s u r e i n c r e a s e

was a s s o c i a t e d w i t h an i n c r e a s e d t o n u s i n t h e r e s i s t a n c e

v e s s e l s , i n d i c a t e d b y t h e r i s e i n r e s i s t a n c e . T h i s was

r e v e r s i b l e when t h e n o i s e s t i m u l a t i o n was s t o p p e d . The

d e c r e a s e i n s t r o k e v o l u m e a n d c a r d i a c o u t p u t c o u l d b e

s e c o n d a r y t o b a r o r e c e p t o r r e f l e x a c t i v i t y . We d i d n o t f i n d

a l i n e a r r e l a t i o n s h i p b e t w e e n n o i s e l e v e l a n d b l o o d p r e s s u r e

i n c r e a s e s i n c e a l l hemodynamic c h a n g e s , w i t h t h e e x c e p t i o n

o f t h o s e r e g a r d i n g s t r o k e v o l u m e a n d c a r d i a c o u t p u t w e r e

l e s s p r o n o u n c e d a t 85 dB A c o m p a r e d w i t h 75 dB A .

T h e r e c o u l d be s e v e r a l d i f f e r e n t r e a s o n s f o r t h i s . The

a b r u p t change i n s o u n d l e v e l f r o m t h e v e r y q u i e t 4 0 dB A

t o 75 d8 i s a p r o p o r t i o n a l l y g r e a t e r c h a n g e i n n o i s e

l e v e l t h a n t h e c h a n g e f r o m 75 dB A t o 85 d8 A .

A n o t h e r p o s s i b l e e x p l a n a t i o n c o u l d b e t h a t t h e i n i t i a l

hemodynamic c h a n g e s a t 75 dB A m i g h t b e s e c o n d a r y t o a com-

b i n a t i o n o f t h e n o i s e e x p o s u r e and e x p e c t a n c y " s t r e s s " .

T h e r e a r e d i f f e r e n t o p i n i o n s r e g a r d i n g c h r o n i c n o i s e

e x p o s u r e and i t s p o s s i b l e a s s o c i a t i o n w i t h p e r m a n e n t h y p e r -

t e n s i o n i n man ( 8 , 1 4 - 1 5 ) .

S e v e r a l f a c t o r s c o u l d m o d i f y t h e c a r d i o v a s c u l a r r e s p o n s e

t o n o i s e i n man a s w e l l a s i n a n i m a l s . R e p e a t e d d a i l y e x p o s u r e

t o n o i s e f o r l o n g p e r i o d s c o u l d c o n c e i v a b l y c r e a t e a p e r m a n e n t

h y p e r t e n s i o n i n man due t o s t r u c t u r a l c h a n g e s i n t h e r e s i s t a n c e

v e s s e l s i n a n a l o g y w i t h f i n d i n g s i n a n i m a l s t u d i e s ( 7 ) .

1 7

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