Vibration induced cardiovascular changes in anesthetized dog

Dines, J. H.

Roberts, L. B.

English

NASA Technical Reports Server

1 .I 
I 
I .  RF Project .............. G4.5 ....... 
Report No ....................... 1 ....... 
SEMI-ANNUAL .............................................................................................. 
R E P O R T  
BY 
THE OHIO STATE UNIVERSITY 
RESEARCH FOUNDATION 
ENVIRONMENTAL MEDICINE LABORATORY 
1314 KINNEAR RD. 
COLUMBUS, OHIO 43212 
To .... NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
Washington D.C. 20546 
Grant No. NGR 36-008-041 
On. CARDIOVASCXTAI! EFFECTS OF VIBRIITIOK 
Submitted by. Lester B. Roberts and ,John H. Dines 
Department of Preventive Medicine 
'\ 
Hard copy (HC) A fl 
Microfiche (MF) ,a? 
ff 853 July 85 \ 
https://ntrs.nasa.gov/search.jsp?R=19660014368 2020-03-16T19:47:30+00:00Z
. 
SECTION I 
SECTION I1 
TABLE OF CONTENTS 
Studies Malie So Far to Determine the 
Underlying Mechanisn! of Some Cardio- 
vascular Chsnges Brought About by 
Vibration 
P a r t  I Magnetic Tape Recording and Playback 
Technique for:  At Will, Coincident 
Monitoring, and Computer Averaging of 
ECG and Other Similar Repetitive But 
Not Necessarily Periodic Phenomena 
Part I1 Body Vibration and the Electrocardiograph 
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SECTION I 
? * 
STULIES MADE SO FJLR TO DETERMINE TKE UNDERLYING 
I@C"ISM OF SOME CARDIOVASCULAR CHANGES 
BROUGHT ABOUT BY VIBRATION 
During previous investigations described in the accompanying paper, 
an increase in heart rate was found to be an almost constant feature of 
immediate cardiovascular response to the vibration profiles used. This 
increase was seen even when a change in blood pressure would be expected 
to bring about a reflex bradycardia. The question arose whether the vibra- 
tion interferred with normal cardiovascular reflex mechanisms either by its 
direct effect on the baroreceptors, the cardiac centers, or on the heart 
it self. 
A series of experiments was planned to investigate these possibili- 
ties and this report covers the work done so far. 
This series includes experiments on dogs anesthetized with morphine, 
chloralose, and urethan in which left ventricular pressure and dp/dt m a .  
of left ventricular pressure were obtained during vibration at 7 cps and 
1/2-inCh total displacement (horizontally) and further experiments in which, 
in addition, cardiac outputs were measured (using the dye dilution tech- 
nique) together with mean arterial blood pressure measurements from the 
thoracic aorta. 
During all experiments so far, atropine and/or propranolol were used 
to block either the parasympathetic and/or sympathetic pathways, respec- 
tively, to the heart. 
RESULTS 
Results of these experiments so far show that the marked transient 
tachycardia brought about by vibration is accompanied by a drop in peri- 
pheral vascular resistance and an increase in cardiac output. Arterial 
blood pressure rises if the cardiac output more than compensates for the 
fall in peripheral vascular resistance. More often, however, the blood 
pressure shows a transient drop. 
The above changes appear not to be caused by sympathetic efferent 
activity because the transient changes described above are virtually unl 
altered after the administration of propranolol. 
However, atropine abolishes the tachycardia, brought about by vibra- 
tion both when given alone or after propranolol. 
unchanging heart rate, a fall in arterial blood pressure is seen as a 
transient response within 30 seconds of the onset of vibration. 
heart rate remains fixed during vibration when atropine is given alone pro- 
viges further evidence that sympathetic activity to the heart is not stim- 
lated by vibration. 
As a consequence of this 
That the 
1 
Results seem t o  i n d i c a t e  t h a t  changes i n  dp/dt m a x .  of t h e  l e f t  
v e n t r i c l e  t end  t o  fol low t h e  changes i n  h e a r t  r a t e ,  b u t  ve ry  c a r e f u l  
measurements are now being attempted t o  monitor changes i n  both l e f t  
v e n t r i c u l a r  end-d ia s to l i c  pressure and dp/dt max., t oge the r  with mean r' 
p e r i p h e r a l  ar ter ia l  p re s su re .  
COMMENT 
I n t e r e s t  regarding t h e  o r i g i n  of t h e  t achyca rd ia  i s  heightened by the  
f ind ings  r epor t ed  by Glick and Braunwald3 t h a t  a tachycardia  induced by a 
lowered blood p res su re  was mediated v i a  t h e  sympathetic nervous supply t o  
t h e  h e a r t .  I n  t h e i r  experiments t h i s  response t o  hypotension was  blocked 
by p rone tho lo l  ( n e t h a l i d e ) ,  which i s  s a i d  t o  be a beta-adrenergic  block- 
ing agent.  Using propranolol  as a blocking agent and v i b r a t i o n  as a hypo- 
t e n s i v e  agent ,  we a r e  unable t o  confirm t h e  f ind ings  of  these authors .  
Poss ib l e  answers t o  t h e  dilemma produced by the  work of Glick and 
Braunwald a r e  (a)  t h a t  t h e  tachycardia of v i b r a t i o n  i s  e n t i r e l y  mediated 
v i a  t h e  vagus or ( b )  t h a t  pronetholol ,  al though a b e t a  blocking agent ,  
a l s o  has a v a g o l y t i c  e f f e c t .  
ed by some experimenters) .  
t h e s e  quest ions.  
( T h i s  a c t i o n  of p rone tho lo l  has been suggest-  
W e  hope t h a t  f u r t h e r  experiments w i l l  answer 
REFERENCES 
1. Dines, J. H . ,  Sutphen, J. H . ,  Roberts, L .  B . ,  and Ashe, W .  F . ,  Arch. 
Environ. Health,  September 19.5, Vol. 11, pp 323-326. 
2. Hamlin, R .  L . ,  Smith, R . ,  and Smetzer, D .  L . ,  "Sinus Arrhythmia i n  
the  Dog," Am. J .  Phys io l . ,  February 1906, Vol. 210, pp 321-328. 
3. Glick,  G . ,  and Braunwald, E . ,  C i r cu la t ion  Res., A p r i l  1905, Vol. XVI, 
PP 363-375. 
2 
SECTION I1 - PART I 
MAGNETIC TAPE RECORDING AND PLAYRACK TECHNIQUE FOR: AT WILL, COINCIDENT 
MONITORING, AND COMPUTER AVERAGING OF ECG AND OTHER STMILAR REPETITIV2 
BVi NOT NECESSARILY PERIODIC PHENOMENA 
The method descr ibed i s  an extension of the on-l ine method of 
s i g n a l  averaging (random no i se  c a n c e l l a t i o n )  descr ibed by Hon. 1 
Refer  t o  Fig.  1 which r ep resen t s  t h e  t a p e  and head of a four-channel 
instrument  t a p e  recorder  w i th  sepa ra t e  record and p l a y  heads. 
s i g n a l  t o  be  s tud ied  (assume f o r  t h e  p re sen t  one s i g n a l  only)  i s  r e -  
corded on channel one of t h e  t ape  which moves from l e f t  t o  r i g h t  i n  t h e  
f i g u r e .  The recorded s i g n a l ,  on reaching t h e  p l a y  head, i s  reproduced 
and t r a n s m i t t e d  through t h e  jumper wire  connecting channel 1 p l a y  t o  
channel 3 of t h e  record head and t h e r e  recorded, 
s i g n a l s  are recorded on t h e  t a p e  spaced at a . d i s t a n c e  equal  t o  t h e  head 
spacing and t h e r e f o r e  d i sp laced  i n  t ime,  t h e  t ime necessary f o r  t h e  t a p e  
t o  move t h e  head spacing d i s t ance  f o r  t h e  t a p e  speed be ing  used. M u l t i -  
p l e  s i g n a l s  c m  be recorded as i s  i l l u s t r a t e d  i n  t h e  t h i r d  s t r i p  of 
f i g u r e  . 
The 
Thus, two i d e n t i c a l  
If t h e  magnetic t a p e  with s i g n a l s  recorded as above descr ibed i s  
r eve r sed  end f o r  end, as i l l u s t r a t e d  i n  Fig.  2 ,  and played back, 
channel 1 of t h e  t a p e  w i l l  now play back on channel 4 p l ay  of t h e  re- 
co rde r ,  t a p e  channel 3 w i l l  p l a y  back on channel 2 play.  Note t h a t  t h e  
s i g n a l  w i l l  p l a y  backward, i .e . ,  i n  an ECG t h e  T wave w i l l  appear before  
t h e  R wave. 
Any d i s t i n c t i v e  p o s i t i v e  o r  negative po r t ion  of a s i g n a l  can be used 
as a t r i g g e r  for s t a r t i n g  a.n e l e c t r i c a l  event such as t h e  s t a r t i n g  of an 
o s c i l l x c o p e  sweep as i l l u s t r a t e d  i n  t h e  f i g u r e .  If t h e  l ead ing  s i g n a l  
o sc i l l o scope  and t h e  osci l loscope ad jus t ed  t o  t r i g g e r  on a f i x e d  po in t  
of t h e  R wave, t h e  osc i l l o scope  sweep i s  s t a r t e d  when t h e  v e r t i c a l  
s i g n a l  amplitude reaches t h i s  point .  
n a l l y  recorded s i g n a l )  which w i l l  appear a t  recorder  channel 4 ,  i s  
connected t o  t h e  v e r t i c a l  i npu t  it w i l l  appear on t h e  scope screen 
provided t h e  osc i l l o scope  sweep speed i s  g r e a t e r  than t i m e  tl, t h e  time 
f o r  a p o i n t  on t h e  t a p e  t o  move from t h e  record head t o  t h e  p l ay  head 
at  t h e  t a p e  speed be ing  used. By a d j u s t i n g  t h e  sweep speed, t h e  pos i t i on  
adjustment,  and t h e  v e r t i c a l  amplitude t h e  complete s i g n a l ,  or any 
s e l e c t e d  p o r t i o n  of it, can be displayed f o r  s tudy on t h e  osc i l l og raph  
screen.  Reg i s t e r  of s e q u e n t i a l  complexes i s  assured r ega rd le s s  of pu l se  
i n t e r v a l s .  The advantage of t h i s  method of d i s p l a y  i s  t h a t  it permits 
p r e - t r i g g e r  information t o  be s tudied and allows noise  c a n c e l l a t i o n  and 
d e t a i l e d  i n t e r r e l a t e d  physiological  s i g n a l s  t o  be s tudied a t  w i l l .  
f r o m  y e c ~ r r l _ e r  ~ h ~ q ~ e l  2 n l - r r  5 s  n - n n n m + - J  +- + L -  - - -&----- '  L - - 2  C V I I I I L L U L U  bU U i l C  C A ~ . , C L I ~ O L L  l d . L . L ~ ~ ~ ? '  o r  Y--Y 
If t h e  lagging s i g n a l  ( t h e  o r i g i -  
Averaging computers, such as t h e  Mnemontron 400A CAT, which was used 
i n  t h i s  s tudy,  r e q u i r e s  a s i g n a l  and t r i g g e r  as j u s t  described. Figure 3 
shows t h e  equipment and schematic wir ing used f o r  noise  averaging of 
recorded ECG s i g n a l s  recorded before  and during v i b r a t i o n  of t h e  sub jec t .  
3 
I .  
The t r i g g e r  s i g n a l  from recorder  channel 2 i s  f e d  t o  t h e  e x t e r n a l  
t r i g g e r  c i r c u i t  o f  t h e  osc i l loscope ,  t h e  o r i g i n a l  s i g n a l  i s  connected 
from channel 4 of t h e  recorder  t o  t h e  scope v e r t i c a l  ampl i f i e r s ,  thus  
t h e  scope can be used f o r  monitoring as previous ly  descr ibed.  
scope (Tektronix 503) has been modified t o  ob ta in  a square wave output, 
each t ime t h e  scope sweeps. 
a v a i l a b l e  without  modif icat ion.)  
a t ime delay c i r c u i t  ( t h e  i n t e r n a l  delay of t h e  CAT can be used) and 
thence t o  t h e  CAT e x t e r n a l  t r i g g e r .  
d i r e c t l y  sweep by sweep, through s u i t a b l e  ampl i f i e r s  o r  a t t enua to r s  t o  
t h e  CAT. 
The 
(Other model scopes have buch a s i g n a l  
This square wave t r i g g e r  ST i s  f e d  t o  
The s i g n a l s  t o  be averaged a r e  f e d  
. 
Analog information i s  read out  a f t e r  pass ing  through ampl i f i e r  t o  
(AD) a s u i t a b l e  paper recorder .  
s tudy  ana lys i s  (pulse  v e l o c i t i e s ;  see  P a r t  111). 
D i g i t a l  readout DO i s  used f o r  time 
REFERENCES 
1. Hon, E. H., and Lee, S. T. "Noise Reduction i n  F e t a l  E lec t ro-  
cardiography," Am. J. Obstet .  Gynecol. Vol. 87, No. 8, 1086-lOg6 
(December 15, 1$3). 
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Figure 1 
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Figure 2 
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SECTION I1 - PART I1 
BODY VIBRATION AND THE ELECTROCARDIOGRAPH 
PROBLEM 
The fundamental problem is to obtain,if possible, clincally useful 
ECG traces from subjects exposed to vibration intensities within the 
range they can tolerate. 
PROTOCOL 
The research protocol on which we are now working includes: (1) a 
study of the origin and nature of the noise associated with vibration, 
(2) a study of ways to remove the noise in an attempt to recover the 
underlying ECG trace, (3) a study of the traces for evidence of heart 
movement or electrical center shifts, and (4) clinical interpretation 
and evaluation of any real ECG changes elicited by vibration. 
EXPERIMENTAL PROCEDURE 
Multiple ECG traces are recorded on magnetic tape from animals and 
man during nonvibration and various vibration conditions and during gross 
body movement. 
The tracings are examined for noise, random distortion, cyclic dis- 
tortion, clinical readability, and evidence of associated resonance. 
Employing the special recording and playback technique (described 
in Part I) and utilizing computer averaging, attempts are made to remove 
the random noise associated with the recording. 
with the original traces to evaluate the efficiency of noise removal, 
estimate limitations of the method, and suggest development necessary to 
improve the technique. 
The results are compared 
TENTATIVE OBSERVATIONS AND CONCLUSIONS 
1. Generally, acceptable ECG tracings can be obtained during moderate 
vibration by the technique described, providing that an unambiguous trigger 
can be obtained from at least one lead; that the signal noise is sufficiently 
random; and that the recording time is long enough. The limiting factor is 
generally vibration intensity, i.e., the R wave for some lead will stand out 
above the general noise for moderate vibration intensities or a lead can be 
found (not necessarily one of clinical interest) which will give a satis- 
factory trigger wave even under rather severe vibration. 
2. Electrode weight, placement, and anchoring is of obvious import- 
ance. 
a 
u . 
3.  Variations attributable to body build vary in importance with vibra- 
tion intensity and depend on the lead under study. 
4. Wandering ECG base line may be a problem under vibration conditions 
particularly when accompanied by gross body movements. 
ated ac coupling for the trigger signal helps control this variable. 
Moderate exagger- 
5. When the subject's pulse is quite regular and the vibration is 
regular at a fixed frequency and. the two frequencies are harmonically re- 
lated, the vibration signal in the ECG will persist even after many averag- 
ing sweeps, and is displayed as an ECG riding on the vibration wave form. 
0. Additional research is required. 
COMPUTER ANALYSIS 
We have subjected certain of our animal's data to digital computer 
analysis. This analysis was made in order to develop techniques and pro- 
grams for future data handling. Leads I, AVF, and V3 were recorded on 
magnetic tape from an anesthetized dog. Recordings were made using the 
technique described for computer averaging analysis. 
signals for each lead were recorded as reference. Recordings were taken 
before vibration and during vibration at four and fifteen cycles per 
second. Using reverse-tape playback, tape recorder delay circuit, and 
computer of average transients, and average of five sweeps was obtained 
for each lead at each condition. The average data were recovered as a 
digital print-out of 400 points for a one-quarter second portion of ECG 
shown. Thus, each point represented one sixteen-hundredth of a second. 
Cards (IBM) were punched with this data together with a correction factor 
for amplitude. 
Standardization 
The program used for computation is a modification of a program devel- 
oped by Dr. Robert Hamlin and the computer-system programming staff for 
computing vector velocity, vector angles, and vector magnitude. The data 
was recovered from the IBM computer in plotted and digital readout form. 
Vector cardiograms assuming leads 1, AVF, and V3 to be mutually 
orthogonal were calculated and plotted with time markings. Later a 
method of three-point averaging to smooth angle data was programmed. 
The potential value of the combined computer approach to ECG analysis 
of this type is apparent and will, we believe, serve as an important tool 
in future research. We plan to employ this technique extensively. 
9 
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PERSONNEL CZTRRENTLY ASSOCIATED WITH THE PROJECT 
1. L. B. Roberts B.S. Adjunct Professor, Department of 
Preventive Medicine (Co-Principal 
Investigator ) 
2. J. H. Dines 
3. R. L. Hamlin 
4. H. P. Pieper 
5. E. J. Whitehead 
10. R. Molnar 
Investigator ..... 
M.D. Assistant Professor, Department of 
Preventive Medicine 
D.V.M. Ph.D. Associate Professor, 
Department Physiolofy, College of Veterinary 
Medicine, Co-Investigator 
M.D. Associate Professor, Department of 
Physiology, Consultant 
Research Assis-G,ant, Department of Preven- 
tive Medicine 
Senior, Department of Electrical Engineer- 
ing, The Ohio State University 
..Date I g &L If; (4 
.................................................... 1. . . .  
.............. 
Supervisor ........ . . .  Date ..... 
Executive .... : U . . . / % h b  
10 


Cardiovascular Effects of Vibration Semiannual Report, 1 Aug. 1965 - 28 Feb. 1966

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