Solid state pulsed coagulating diathermy instrumen

Lim, A. J.

Petty, P. G.

Stahl, R.

English

NASA Technical Reports Server

( 1 )  
A SOLID STATE PULSED COAGULATING DIATHERMY INSTRUMENT 
(2) 
P. G. Petty, A. J. L i m ,  R. Stahl .. 
Space B iology Laboratory 
B ra in  Research I n s t i t u t e  
Univers l ty  o f  C a l i f o r n i a  
Los Angeles, Cal i f o r n l a  
("This study was supported by Grant I-PO7-FR00257 from the 
National I n s t i t u t e s  o f  Health, and by Grant NsG 237-62 from the 
National Aeronautics and Space Administration. 
(*)Address from January 21st, 1967: 
Department o f  Neurological Surgery 
Royal Melbourne Hospital 
Melbourne, Aus t ra l i a  
c 1 .  
https://ntrs.nasa.gov/search.jsp?R=19680015818 2020-03-12T10:26:46+00:00Z
Address all correspondance to: 
Dr. Peter Petty 
Department of Neurological Surgery 
Royal Melbourne Hospital 
Melbourne, Australia 
A SOLID STATE PULSED COAGULATING DIATHERMY INSTRUMENT 
1 The spark gap diathermy introduced by Cushing and Bovle i n  1928 
won ready acceptance throughout the surgical  world, and has come t o  
p lay an essent ia l  r o l e  i n  haemostasis i n  a l l  branches of surgery. The 
f a c t  t ha t  present day instruments are b a s i c a l l y  unchanged from the 
o r i g i n a l  design a t t e s t s  t o  the soundness o f  t h a t  design f o r  achieving 
i t s  intended purpose. However the advance I n  e lec t ron i c  technology, 
p a r t i c u l a r l y  i n  the f i e l d  o f  semfconductors, has prompted a reconsi- 
derat ion of the design of coagulating diathermy instruments. 
THE INSTRUMENT 
An instrument has been designed and b u i l t  t o  provide square wave 
pulses through an i s o l a t i n g  transformer. The c i r c u i t  is shown i n  Fig. 1 ,  
and i s  simple, inexpensive, and re l iab le,  The power supply i s  conven- 
t i o n a l ,  w l t h  f u l l  wave r e c t i f i c a t i o n  from e i t h e r  tap of the transformer 
prov id ing +20 o r  4 0  v o l t s  D.C. selected by switch S 
as a coarse power contro l .  
provide the h igh peak energy required. During i n i t i a l  invest igat ions 
a va r iab le  transformer was placed i n  the primary c i r c u i t  to  provide 
adjustable voltages. The pulse r e p e t i t i o n  frequency i s  f i x e d  by the 
un l j unc t i on  t r a n s i s t o r  re laxa t i on  o s c i l l a t o r ,  Q The frequency i s  
determined by R 
1 
va r ied  by changing R 1  and/or C . 
1 
a s tab le  frequency over a wide temperature and voltage range. 
T r igge r ing  of the monostable mu l t i v i b ra to r  i s  through con t ro l  switch 
( f o o t  pedal), S3, which passes the 2 v o l t  pulse from Q,. 
c o n t r o l  swOtch a t  t h i s  low current-low voltage point i n  tne c i r c u i t .  d i i  
danger t o  the operator i s  obviated. 
which funct ions 
2' 
The large value of capacitance i s  used t o  
1' 
and C1, shown fo r  a frequency o f  250 H t  which may be 
The un i j unc t i on  t r a n s i s t o r  provides 
By p lac ing the 
The monostable mu l t i v i b ra to r ,  Q and Q determines the pulse width 
2 3' 
and dr ives the output stage, Q,+ and Q 
by R2, R 3  and C 2  and i s  adjustable from approximately 20 t o  80 microseconds. 
This  adjustment i s  used as a f i n e  power control .  
Output i s  through a 1 : l O  step-up pulse transformer which provides 
The pulse width i s  determined 5' 
a h igh degree o f  e l e c t r i c a l  i s o l a t i o n  and the r e q u i s i t e  pulse amplitude. 
Series r e s i s t o r  R4 l i m i t s  the output current and protects  the c i r c u i t  
against the overload which would otherwise occur when the output i s  
shorted, 
prov id ing a useful  i n d i c a t i o n  that  the instrument i s  operating. 
V lb ra t i on  i n  t h e  output transformer produces an audible note, 
The forceps f o r  b i p o l a r  coagulation were made by separating 
the blades o f  a p a i r  o f  Gerald forceps a t  t h e i r  junct ion,  then r e j o i n i n g  
them w i t h  a sheet o f  3 nun. nylon interposed, using two nylon nuts and 
b o l t s ,  
tub ing shrunk over the whole junction. 
One w i re  was then attached t o  each blade, and p o l y o l e f i n  
The whole instrument f i t s  i n  a cabinet 4X5X6 inches overal l .  
RESULTS 
The b i p o l a r  conf igurat ion has been u t i l i z e d  f o r  the diathermy 
forceps i n  t h i s  i n i t i a l  phase of development o f  the instrument, as the 
power required I s  much lower than wi th  unipo lar  coagulation. 2,s 
The a b i l i t y  t o  ob ta in  haernostasis and coagulate t i ssue  w i t h  t h i s  
instrument has been tested i n  l i v i n g  t i ssue  o f  anaesthetized cats and 
ra ts .  Pa r t i cu la r  a t t e n t i o n  has been pa id  t o  haemstasis i n  braIn. The 
3. 
e f f e c t s  were compared w i t h  ltordinaryll coagulat ion w i t h  a Bovie u n i t  and 
were considered sa t i s fac to ry  only i f  coagulat ion was a t  least  as good 
as wi th  tha t  instrument. 
Each o f  the parameters of voltage, pulse width, and r e p e t i t i o n  ra te  
was var ied i n  turn. 
On hundred and f i f t y  v o l t s  was the minfmum vol tage a t  whfch coagu- 
l a t i o n  would occur, but  i t  was inconveniently slow a t  t h i s  level. Two 
hundred v o l t s  provided e f f i c i e n t  and steady coagulat ion o f  brain,  small 
and large (up t o  3 mm.) a r t e r i e s  and veins, and small I1bitesi1 of muscle. 
Four hundred v o l t s  provided good haemostasis i n  large I t b i t es t1  o f  muscle 
and was sa t i s fac to ry  f o r  coagulation on the surface o f  the b r a i n  but 
was less sa t l s fac to ry  for coagulat ion o f  vessels than was 200 vo l t s .  
The reason for  t h i s  is t ha t  a t  200 v o l t s  "white coagulation" occurred, 
but a t  400 v o l t s  I1fulgurat ion1l  -- sparking causing charr ing and burning -- 
was the predominant e f fec t .  
been discussed recent ly  by M i t che l l  and Lumb. 6,7 The voltages speci f ied 
These d i f f e r e n t  types o f  coagulat ion have 
e are the open c i r c u i t  voltages (measured wi th  a Tektronix 532 o s c i l l o s -  
cope w i t h  type D d i f f e r e n t i a l  p lug- in  ampl i f ier)  across the -&he 
vol tage drops, dur ing coagulation, by an amount dependent upon the impe- 
dance o f  the t i ssue  and the value of  the ser ies load resistance. Tissue 
impedance i s  o f  the order o f  200 ohms, but var ies w i t h  the type o f  
t lssue, s ize o f  the "blte,It and stage of coagulation. Figure 2 show 
the  voltage waveform appearing across t issue dur ing coagulation. 
The r e p e t i t i o n  r a t e  was varied i n  the range from 100 HZ t o  20 ';I!z. 
4. 
A t  each r e p e t i t i o n  r a t e  the pulse width was var ied i n  the range 1 pec.  
t o  80 psec. 
any r e p e t i t i o n  r a t e  o r  pulse width, and approximately the same as w i t h  
a Bovle instrument. Our i n i t i a l  premise was tha t  the duty cyc le  ( the  
r a t i o  o f  pulse width t o  pulse spacing) would be the  most important f ac to r  
w i t h  regard t o  these parameters, but t h i s  was found not  to  be true. 
Rather, each parameter manifested a separate and la rge ly  independent 
e f f e c t  . 
The s t imu la t ing  e f f e c t  was found t o  be equal ly  marked a t  
Repet i t ion  ra te  a f fec ted  mainly the q u a l i t y  of the  coagulum, h igh 
rates (500 Hz and higher)  causing s t ick iness w i t h  consequent adherence 
o f  t i ssues  and tear ing  on withdrawal o f  the forceps. Lower r e p e t i t i o n  
ra tes  (250 Hz and lower) provided cleaner haemostasis and coagulation, 
and for  t h i s  reason a f i x e d  r e p e t i t i o n  r a t e  o f  250 Hz has been adopted 
I n  the  present design. 
Pulse width a f fec ted  the r a t e  o f  coagulat ion v i r t u a l l y  independently 
o f  r e p e t i t i o n  rate. 
values, the shorter t ime being appropriate fo r  very small vessels, the 
longer t ime f o r  bigger vessels. 
obtainable a t  200V w i t h  the output transformer used. 
maximum o f  100 psec. as the waveform degraded under load (Fig. 2). Even 
wider pulses s t i l l  would probably be necessary If monopolar coagulat ion 
were t o  be performed i n  t h i s  way. 
Pulses o f  between 40 and 80 psec. were p r a c t i c a l  
Eighty psec. was the widest pulse 
This  widened t o  a 
Pulse width v a r i a t i o n  was u t i l i z e d  as the  method of power cont--c* 
s ince t h i s  provided a smooth gradation o f  power wi thout  v a r i a t i o n  i -  
5. 
qual i ty .  
by switching the voltage level. 
Change i n  q u a l i t y  of coagulat lon (as stated above) was provided 
Instantaneous power was calculated by measurlng the vol tage drop 
across the ser ies load r e s i s t o r  w i t h  the oscfl loscope and from th is ,  
Instantaneous current dur ing coagulation was calculated. This var ied 
w i t h  condttlons, but was approximately 1 amp. Thus the t o t a l  Instan- 
taneous power a t  200 v o l t s  was 200 watts (ha l f  o f  t h i s  being d iss ipated 
i n  the ser les load). 
4 watts, because no current flowed during the In te rva l s  between pulses. 
The average output power however was approximately 
Grounding of the instrument is t o  the negative side o f  the power 
supply. 
b i p o l a r  coagulation.) 
(Grounding e i t h e r  side o f  the output would ser ious ly  impair 
The EKG was monltored dur ing coagulation, and no in ter ference w i t h  
the t race occurred, even when pectoral muscles were coagulated, To 
t e s t  f o r  rad lo and T,V. interference, the Instrument was operated 
adjacent to, and from the same power po int ,  as a domestic t e l e v i s l o n  
receiver  and domestic AM radio. There was no e f f e c t  on e i t h e r  recelver. 
D I SCUSS I ON 
The operating parameters of t h e  present Instrument he lp t o  c l a r i f y  
t h e  mode o f  ac t i on  o f  spark gap machines. 
produce a damped t r a i n  o f  waves which we have observed (on a Bovle 
instrument under t y p i c a l  neurosurgical condit ions) to  have a fundamental 
frequency o f  about 3 MHz, a peak t o  peak maximum voltage of about 1200, 
a du ra t i on  ( for  the t r a l n )  o f  about 5 ysec. and a r e p e t i t i o n  r a t e  o f  120 Hz. 
These l a t t e r  instruments 
6.. 
(The r e p e t i t i o n  r a t e  w i th  a 50 Hz main supply would be 100 Hz.) 
Most previous authors’ ,3,4,6,7 have pointed out the importance o f  
the damped waveform fo r  achieving good coagulation, but  have not always 
emphasized tha t  the duty cyc le  I s  extremely low. 
The present instrument also produces short pulses o f  h igh energy 
w l t h  a low (250 Hz) r e p e t t t i o n  rate, but  w i t h  a very d i f f e r e n t  waveform. 
The coagulat ion obtained i n  th is  way appears t o  be i n  every way s im i la r  
t o  tha t  obtained w i th  spark gap machines and we therefore fee l  j u s t i f i e d  
i n  concluding tha t  the actual waveform I s  less important than the mode 
of energy input, which i s  b r i e f  high energy pulses separated by r e l a t i v e l y  
long inac t i ve  periods. With t h i s  type o f  energy Input, an extremely 
rap id  r i s e  i n  temperature would occur a t  the forceps t i p s  a t  the t i m e  
of the  pulse, the r e l a t i v e l y  long quiescent i n te rva l  would permit  heat 
t ranspor t  mechanisms (conduction and blood perfusion) t o  maintain 
adequate coo l ing  o f  even very c losely  adjacent t issue. 
The peak power i n  the pulses o f  the present instrument 1s 200 watts, 
but  w i t h  a 2% maximum duty cycle, the t o t a l  average power is only  4 watts. 
Th ls  I s  considerably less than spark gap instruments, r e f l e c t i n g  a higher 
e f f i c i ency  o f  the present c i r c u i t r y .  However, the power output of t h i s  
instrument I n  i t s  present form i s  inadequate f o r  monopolar coagulation, 
which requires a t  least  5 t imes more power than the b ipo la r  conf igurat ion,  5 
The elimination of the spark gap removes the f i r e  danger from the 
instrument I t s e l f ,  but as sparking w i l l  s t i l l  occur a t  the forceps t i ps ,  
t h i s  danger can never be t o t a l l y  eliminated. 
7. 
The absence of interference w i th  other e lec t ron i c  devices is a 
valuable asset of t h i s  instrument. Spark gap instruments generate 
energy I n  a broad frequency band up t o  5 MHz’ and high voltages e x i s t  
throughout the c i r c u l t ,  permi t t ing rad ia t i on  from in te rna l  and external  
leads, and r e f l e c t i o n  i n t o  the power l ines.  I n  thTs instrument the 
h igh vol tage (200 t o  400) appears only i n  the secondary of the output 
transformer which is very wel l  iso la ted from ground and the mains supply. 
The main reason for  lack o f  EKG in ter ference is, however, the use 
are thus no currents f lowing o f  t he  b i p o l a r  conf igurat ion,  as there 
through the body towards a remote I n d i f f e r e n t  electrode. 
SUMMARY 
A s o l i d  s ta te  pulsed coagulating diathermy instrument is described. 
The operat ing parameters o f  t h i s  instrument have been invest igated f o r  
b i p o l a r  coagulation. 
The advantages o f  t h i s  instrument over spark gap instruments 
are lower power requirement, smaller physical  size, lessened f i r e  
danger and e l im lna t i on  o f  EKG interference (when used w i t h  the b i p o l a r  
conf i gurat ion). 
The authors w i s h  t o  acknowledge the discussion one o f  us (P.G.P.) 
had w i t h  Mr .  J. B lacket t  o f  the Matburn Company, London, when he pointed 
out  the very short duty cyc le  of  spark gap instruments, and the p o s s i b i l i t y  
of u t i l i z i n g  s o l i d  s ta te  devices to replace spark gaps. 
8. 
RE FERE NC E S 
. 
1. Cushlng, H, Electrosurgery as an a id  t o  the  removal o f  i n t rac ran ia l  
tumours. (With a p r e l  Iminary note on a new surgical-current generator 
by W.T. Bovle, Ph.D., Chicaga,) Surq. Gyn. Obstets., 1928, 3:751-790. 
2. Greenwood, J. Jr. Two point  o r  i n te rpo la r  coagulation. Review a f t e r  
a twelve year per iod w i t h  notes on addi t ion o f  a sucher t i p .  
Neurosurq., 1955, 12: 196-197. 
J. 
3. Kel ly ,  A,, Ward, G.E. Electrosurgery. PhiladelDhia: W.B. Saunders 
@., 1932. 
4. McLean, A.J. The Bovle e lect rosurg lca l  current  generator. Some 
underlying p r i n c i p l e s  and resul ts.  Arch. Surq., 1929, 18: 1863-1873. 
5. Malls, T. B ipo lar  coagulation. Neurosurqical News (Codman and 
Shurt l e f f )  , Fa1 1 1966: 9-1 1 . 
6. M i t che l l ,  J.P., Lumb, G.N. The p r i n c i p l e s  o f  surg ica l  diathermy 
and i t s  l im i ta t i ons .  B r i t .  J, Surg., 1962, %:314-320. 
7. M i t che l l ,  J.P., Lumb, G.N. A handbook o f  surg ica l  dlathermy. 
B r l s t o l :  John Wright and Sons, Ltd., 1966. 
I .  
9. 
CAPT I O N S  FOR F IGURES 
Fig, 1. The c i r c u i t  o f  the instrument i n  i t s  present form. 
Fig. 2. The waveform appearing across t l ssue dur ing coagulation, 
The g r i d  represents 1 cm, squares on the  face of a Tektronix 
532 osci l loscope, using a type D p lug- in  un i t ,  w i t h  d i f f e ren -  
t i a l  input. 
a. A s ing le  pulse. Cal ibrat ion:  v e r t i c a l  10V/cm. Hor izontal  
50 C;sec./cm. 
b. Three separate pulses. Cal ibrat ion:  v e r t i c a l  10V/cm. 
Hor izontal  1 msec./crn. 


A Solid State Pulsed Coagulating Diathermy Instrument

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