62
Specialia
d e g e n e r a t i o n in t h e n u c l e u s r e t i c u l a r i s p o n t i s oralis of split b r a i n s t e m cats. T h e increase of W a n d D a n d t h e d e c r e a s e of SS d i d n o t r e a c h s t a t i s t i c a l l y s i g n i f i c a n t values. O u r e x p e r i m e n t s , t h e r e f o r e , s u p p o r t t h e h y p o t h esis t h a t t h e v e n t r o l a t e r a l p o r t i o n of n u c l e u s r e t i c u l a r i s p o n t i s oralis h a s a h y p n o g e n i c f u n c t i o n and, as w a s p r e v i o u s l y r e p o r t e d 2,8, t h i s n u c l e u s h a s a n a c t i v a t i h g function on EEG. R e s u l t s s h o w t h e i m p o r t a n c e of c o n t r o l l i n g e x a c t l y t h e lesions p l a c e d a t t h e level of t h e pons, b e c a u s e little c h a n g e s in t h e l o c a t i o n a n d e x t e n t of lesions p r o d u c e q u i t e d i f f e r e n t m o d i f i c a t i o n s of S~VC. V a r i a t i o n s of S W C d u e to lesions in t h e v e n t r o l a t e r a l a r e a of n u c l e u s r e t i c u -
EXPERIENTIA 34/1
laris p o n t i s oralis are d i f f e r e n t f r o m m o d i f i c a t i o n s f o u n d a f t e r d e s t r u c t i o n of its d o r s o m e d i a l p a r t 10; also m o d i f i c a t i o n s are d i f f e r e n t f r o m t h o s e "found w h e n t h e n u c l e u s r e t i c u l a r i s p o n t i s c a u d a l i s is a f f e c t e d n or w h e n t h e r e are w i d e r lesions a t t h i s level *. I t is imprecise, t h e r e f o r e , t o s p e a k of f i n d i n g s a f t e r lesion in t h e p o n t i n e t e g m e n t u m w i t h o u t d e t e r m i n i n g t h e s t r u c t u r e s i n v o l v e d in t h e lesion.
10 F. Reinoso-Sugrez, Revta esp. Oto-neuro-oftal. Neurocirug. 29, 111 (1971). 11 J. o~. Zarranz and F. Reinso-Su~rez, in: Proc. 25th Int. Cong. Physiol. Sei., vol. 8, p. 315. German Physiol. Soc., Munich 1971.
C o n s t r u c t i o n of a thin f i l m Po2-electrode u s i n g gold paste S. M a k i n o d a 1, S. M i u r a 2 a n d T. K o y a m a
Division o/Physiology, Research Institute o/Applied Electricity, Hokkaido University, Sapporo (Japan), 24 January 1977 Summary. A t h i n film gold e l e c t r o d e for biological o x y g e n m e a s u r e m e n t was c o n s t r u c t e d u s i n g gold paste. T h i s elect r o d e is e a s y t o c o n s t r u c t , h a s h i g h s e n s i t i v i t y a n d is d i s t u r b e d o n l y s l i g h t l y b y b u b b l i n g of t h e s u r r o u n d i n g fluid. As a n a p p l i c a t i o n , t h e e l e c t r o d e was used to m e a s u r e o x y g e n c o n s u m p t i o n of t h e skin a n d yielded a r e a s o n a b l e value. I n t h e m e a s u r e m e n t of biological o x y g e n t e n s i o n , 3 f u n d a m e n t a l p e r f o r m a n c e s are r e q u i r e d for t h e polarog r a p h i c o x y g e n e l e c t r o d e ; i.e. h i g h s e n s i t i v i t y , r a p i d res p o n s e a n d r e s i s t a n c e t o t h e effects b y m o v e m e n t s of s u r r o u n d i n g fluid. T h e s e r e q u i r e m e n t s oppose one a n o t h e r a n d c a n h a r d l y b e r e a l i z e d in 1 electrode : H i g h s e n s i t i v i t y n e e d s a large surface a r e a of t h e a c t i v e electrode, r a p i d r e s p o n s e a n d r e s i s t a n c e t o fluid m o v e m e n t s r e q u i r e a s m a l l e l e c t r o d e surface. T o effect a c o m p r o m i s e of t h e s e r e q u i r e m e n t s , S a i t o a n d M o c h i z u k i 3, Saito 9 i n t r o d u c e d a u l t r a - t h i n film r i n g e l e c t r o d e of s p u t t e r e d p l a t i n u m . T h e c o n s t r u c t i o n of t h i s electrode n e e d s careful c o n t r o l of t h e s p u t t e r i n g a p p a r a t u s , b u t t h e e l a b o r a t e l y constructed electrode often becomes unstable, probably b e c a u s e t h e h e a t e x p a n s i o n of i n s u l a t e d p l a t i n u m film is m a r k e d l y l a r g e r t h a n t h a t of t h e i n s u l a t i n g glass. To a v o i d s u c h difficulties, K i m m i c h a n d K r e u z e r 5 r e c o m -
A
B t"
~u-poste
m e n d e d t o i n s u l a t e a r i n g of a p l a t i n u m foil of a b o u t 3 ~xm t h i c k b y m e a n s of p o l y v i n y l chloride. T h e o x y g e n c u r r e n t of t h e i r electrode, h o w e v e r , is still a f f e c t e d b y fluid m o v e m e n t s , w h e n u t i l i z e d w i t h o u t covering. Therefore, i t seems w o r t h w h i l e t o e x a m i n e a n o t h e r m e t h o d of c o n s t r u c t i o n of t h e t h i n n e r film r i n g electrode. I n t h e p r e s e n t s t u d y , we i n v e s t i g a t e d t h e a p p l i c a b i l i t y of gold p a s t e , w h i c h is used for t h e p a i n t i n g of china, t o t h e c o n s t r u c t i o n of o x y g e n electrode. Construction of the electrode. T h e s t r u c t u r e of t h e e l e c t r o d e is s c h e m a t i c a l l y s h o w n in figure 1, A. A t h i n glass t u b e (OD 2 m m ) is p a i n t e d w i t h d i l u t e d gold p a s t e a n d h e a t e d for 60 m i n a t a t e m p e r a t u r e of 400~ T h i s t u b e is t h e n i n s e r t e d in a n o t h e r glass t u b e w h i c h serves as i n s u l a t i o n . A i r is t h e n r e m o v e d f r o m t h e t u b e s w i t h a v a c u u m p u m p . T h e t u b e is h e a t e d while t h e v a c u u m p u m p is still r u n n i n g , w h i c h causes t h e o u t e r t u b e t o m e l t a n d s h r i n k o n t o t h e i n n e r glass t u b e a n d i n s u l a t e t h e gold film. T h e t i p of t h i s glass t u b e , h a v i n g a n i n s u l a t e d gold film in it, is c u t off a n d p o l i s h e d g e n t l y on artificial l e a t h e r w i t h c e r i u m o x i d e powder, so t h a t a s m o o t h t h i n r i n g of gold film is e x p o s e d o n t h e surface flush w i t h t h e p o l i s h e d c u t e n d of t h e glass t u b e . T h e n a silver wire c o a t e d w i t h silver c h l o r i d e is i n s e r t e d i n t o t h e glass t u b e a n d m o u n t e d in a s u i t a b l e p o s i t i o n a t t h e c u t e n d b y m e a n s of epoxiresin. T h i s Ag-AgC1 wire serves as t h e reference electrode a g a i n s t t h e gold film, w h i c h is c h a r g e d a t -0.7 V. Characteristics and testing o[ the electrode. T h e s e n s i t i v i t y a n d r e p r o d u c i b i l i t y of o x y g e n c u r r e n t of t h i s electrode was t e s t e d in a saline s o l u t i o n b u b b l e d w i t h air a n d n i t r o g e n . T h e o x y g e n c u r r e n t is of t h e o r d e r of 10 -11 A / T o r r a n d its r e s p o n s e t o a l t e r n a t e b u b b l i n g w i t h air a n d n i t r o g e n was r e p r o d u c i b l e w i t h i n a r e l a t i v e e r r o r of 6 % o v e r 7 h. W h e n air b u b b l i n g w a s s t o p p e d , t h e o x y g e n c u r r e n t q u i c k l y d e c r e a s e d b y 5 % of t o t a l c u r r e n t a n d r e m a i n e d a t t h a t level. T h i s m e a n s t h a t t h e d i s t u r b a n c e
I~' Fig. 1, A Schematic illustration of the gold paste electrode. B A microscopic photograph of a part of the gold paste active surface immersed in oil (n= 1.515) and illuminated with a light beam having a suitable incident angle. Olympus oil objective Hi M 100 • and oecular 10 • were used.
1 With leave from the department of gynecology, School of Medicine, Hokkaido University. 2 Glass laboratory. 3 Y. Saito and M. Moehizuki. 6th Int. Conf. med. electro-biol. Engng Tokyo, 600 (1965). 4 Y. Saito, J. appl. Physiol. 23, 979 (1967). 5 H . P . Kimmieh and F. Kreuzer, Prog. Resp. Res. 3, 100 (1969).
15. 1. 1978
of t h e diffusion layer b y t h e w a t e r m o v e m e n t is v e r y small. T h e C-V c u r v e s h o w s a p l a t e a u o v e r t h e r a n g e of - 0 . 3 to - 0 . 8 V. T h e t e m p e r a t u r e d e p e n d e n c y of t h e c u r r e n t was 4 • 10 -14 A / T o r r . ~ o v e r t h e t e m p e r a t u r e r a n g e of 30 to 45~ w h i c h was a r e a s o n a b l e c h a n g e in v i e w of t h e c h a n g e s of 0 2 a b s o r p t i o n a n d diffusion coefficients of saline solution. F i g u r e 1, B s h o w s a p a r t of t h e electrode surface a t a high m a g n i f i c a t i o n b y m e a n s of a m i c r o s c o p e . T h e exp o s e d gold-ring can safely be r e g a r d e d as a s t r a i g h t n a r r o w b a n d h a v i n g t h e w i d t h of 0.2 txm. The 0 2 diffusion l a y e r w h i c h d e v e l o p s on t h i s e l e c t r o d e surface can be expressed by a 2 dimensional partial derivative equation h a v i n g its X a n d Y axes a t r i g h t angles to t h e gold film surface as s h o w n in figure 2. T h e n t h e final solution for t h e o x y g e n diffusion l a y e r a t infinite t i m e is given b y ; P = Po'(1-k), where k = tan
63
Specialia
--1 ( X
+ a ) / Y -- t a n
--1 ( X - -
a)/Y a n d 2a is t h e
w i d t h of n a r r o w b a n d of t h e gold film ring. I3y p u t t i n g k ' = t a n - l k , t h e iso-Po2 line is given b y t h e e q u a t i o n ; X 2 + ( Y - a / k ' ) 2 = (1 + l/k '2)-a s.
I 21a
~A~
The n u m e r i c a l p l o t t i n g of t h i s solution is given in figure 2. T h e f a r t h e s t p o i n t f r o m t h e e l e c t r o d e surface for P = 0.9 9 Po is 19.98 9 a, w h i c h for t h e p r e s e n t elect r o d e is 2 [zm. Application. This electrode m a y be used to m e a s u r e t h e o x y g e n t e n s i o n of t h e skin. T h e e l e c t r o d e t i p is d i p p e d in a s o l u t i o n (10% in acetone) of c e m e d i n e - C | (cellulose solved in a c e t o n e - e t h a n o l - i s o p r o p a n o l m i x t u r e , C e m e d i n e Co, Tokyo) a n d is d r i e d in t h e r o o m air, so t h a t t h e elect r o d e surface is c o a t e d w i t h a t h i n coating (5 ~zm thick), w h i c h serves as a saline c o n t a i n e r w h e n p l a c e d on t h e skin surface. The electrode so t r e a t e d is p a s s e d t h r o u g h a c y l i n d r i c a l w a t e r b a t h , so t h a t t h e e l e c t r o d e t i p is s i t u a t e d flush w i t h t h e b o t t o m of t h e b a t h . The skin Po2 was 0 to 2.5 m m H g d u r i n g b o t h air a n d o x y g e n b r e a t h i n g w h e n t h e t e m p e r a t u r e of t h e w a t e r b a t h was a t r o o m t e m p e r a t u r e . An e x a m p l e of a r e c o r d i n g u n d e r v a r i o u s c o n d i t i o n s is s h o w n in figure 3. The results were : l. W h e n t h e t e m p e r a t u r e was raised to 46~ t h e skin Po2 increased to 48 m m Hg. 2. A f t e r blood flow was s t o p p e d b y an i n f l a t e d cuff p l a c e d a r o u n d t h e arm, t h e skin Po2 fell to n e a r l y zero. 3. On releasing t h e cuff, t h e Po2 r e c o v e r e d to t h e original value. 4. A f t e r t h e gas for b r e a t h i n g was c h a n g e d f r o m air to oxygen, t h e Po2 rose r a p i d l y to 230 m m H g in 150 sec, 5. A t this p o i n t t h e cuff was i n f l a t e d again a n d t h e Poa d e c r e a s e d t o n e a r l y zero. 6. On releasing t h e cuff a n d c h a n g i n g t h e gas from o x y g e n to air t h e Po2 a t t a i n e d a level n e a r t h e initial value. Since t h e o x y g e n diffusion layer on t h e e l e c t r o d e is e s t i m a t e d t o be only 2 v m a n d t h e e p i d e r m i s of t h i s area is a b o u t 80 ~m thick, t h e p r e s e n t electrode m e a s u r e s t h e Po2 of t h e epidermis. A c c o r d i n g to H u c h et al. 6, T h e skin o x y g e n c o n s u m p t i o n can be e s t i m a t e d b y t h e following e q u a t i o n w h e n skin Po2 is sufficiently h i g h a n d blood s u p p l y to t h e skin is i n t e r r u p t e d b y cuff i n f l a t i o n ; Vo=
19.98 a
Fig. 2. Iso-Pos line in a region close to the gold paste surface. 6
R. Huch, D. W. Lfibbers and A. Hueh, Pfltigers Arch. 337, 185 (1972). Air
I
2so
0
7 K. Ohara, Jap. J. Physiol. 2, 1 (1951). 8 N.T.S. Evans and R. F. D. Naylor, Resp. Physiol. 2, 61 (1966/67).
Occlusion
I
PO2:rnmHg
=/760 9AP/At,
w h e r e = is t h e o x y g e n a b s o r p t i o n coefficient of skin tissue ( = 0.0169 a t 46~ I n figure 3 t h e linear decrease of Po2 is 184 m m H g over t h e t i m e r a n g e of 1.75 rain. P u t t i n g t h e s e values into t h e a b o v e e q u a t i o n gives a XTozof 0.00233 m l O2/ml tissue - min. This value is slightly h i g h e r t h a n 0.002 b y O h a r a 7 a n d 0.00t8 b y E v a n s a n d Naylor s. T h i s d i f f e r e n c e is p r o b a b l y due t o t h e h i g h t e m p e r a t u r e a t w h i c h t h e p r e s e n t m e a s u r e m e n t was carried out. These results i n d i c a t e a wide a p p l i c a b i l i t y of t h e p r e s e n t elect r o d e to t h e i n v e s t i g a t i o n of tissue o x y g e n tension.
Date= July-81976 Subj.SM. :
l
/
T/ 6
lm••
2 ReleaslCii"ill
5
4
3
2
1
Fig. 3. An example of skin Po~ recording during several experimental conditions. The numbers below the recording refer to successive experimental conditions. Read right to left.
Specialia
d e g e n e r a t i o n in t h e n u c l e u s r e t i c u l a r i s p o n t i s oralis of split b r a i n s t e m cats. T h e increase of W a n d D a n d t h e d e c r e a s e of SS d i d n o t r e a c h s t a t i s t i c a l l y s i g n i f i c a n t values. O u r e x p e r i m e n t s , t h e r e f o r e , s u p p o r t t h e h y p o t h esis t h a t t h e v e n t r o l a t e r a l p o r t i o n of n u c l e u s r e t i c u l a r i s p o n t i s oralis h a s a h y p n o g e n i c f u n c t i o n and, as w a s p r e v i o u s l y r e p o r t e d 2,8, t h i s n u c l e u s h a s a n a c t i v a t i h g function on EEG. R e s u l t s s h o w t h e i m p o r t a n c e of c o n t r o l l i n g e x a c t l y t h e lesions p l a c e d a t t h e level of t h e pons, b e c a u s e little c h a n g e s in t h e l o c a t i o n a n d e x t e n t of lesions p r o d u c e q u i t e d i f f e r e n t m o d i f i c a t i o n s of S~VC. V a r i a t i o n s of S W C d u e to lesions in t h e v e n t r o l a t e r a l a r e a of n u c l e u s r e t i c u -
EXPERIENTIA 34/1
laris p o n t i s oralis are d i f f e r e n t f r o m m o d i f i c a t i o n s f o u n d a f t e r d e s t r u c t i o n of its d o r s o m e d i a l p a r t 10; also m o d i f i c a t i o n s are d i f f e r e n t f r o m t h o s e "found w h e n t h e n u c l e u s r e t i c u l a r i s p o n t i s c a u d a l i s is a f f e c t e d n or w h e n t h e r e are w i d e r lesions a t t h i s level *. I t is imprecise, t h e r e f o r e , t o s p e a k of f i n d i n g s a f t e r lesion in t h e p o n t i n e t e g m e n t u m w i t h o u t d e t e r m i n i n g t h e s t r u c t u r e s i n v o l v e d in t h e lesion.
10 F. Reinoso-Sugrez, Revta esp. Oto-neuro-oftal. Neurocirug. 29, 111 (1971). 11 J. o~. Zarranz and F. Reinso-Su~rez, in: Proc. 25th Int. Cong. Physiol. Sei., vol. 8, p. 315. German Physiol. Soc., Munich 1971.
C o n s t r u c t i o n of a thin f i l m Po2-electrode u s i n g gold paste S. M a k i n o d a 1, S. M i u r a 2 a n d T. K o y a m a
Division o/Physiology, Research Institute o/Applied Electricity, Hokkaido University, Sapporo (Japan), 24 January 1977 Summary. A t h i n film gold e l e c t r o d e for biological o x y g e n m e a s u r e m e n t was c o n s t r u c t e d u s i n g gold paste. T h i s elect r o d e is e a s y t o c o n s t r u c t , h a s h i g h s e n s i t i v i t y a n d is d i s t u r b e d o n l y s l i g h t l y b y b u b b l i n g of t h e s u r r o u n d i n g fluid. As a n a p p l i c a t i o n , t h e e l e c t r o d e was used to m e a s u r e o x y g e n c o n s u m p t i o n of t h e skin a n d yielded a r e a s o n a b l e value. I n t h e m e a s u r e m e n t of biological o x y g e n t e n s i o n , 3 f u n d a m e n t a l p e r f o r m a n c e s are r e q u i r e d for t h e polarog r a p h i c o x y g e n e l e c t r o d e ; i.e. h i g h s e n s i t i v i t y , r a p i d res p o n s e a n d r e s i s t a n c e t o t h e effects b y m o v e m e n t s of s u r r o u n d i n g fluid. T h e s e r e q u i r e m e n t s oppose one a n o t h e r a n d c a n h a r d l y b e r e a l i z e d in 1 electrode : H i g h s e n s i t i v i t y n e e d s a large surface a r e a of t h e a c t i v e electrode, r a p i d r e s p o n s e a n d r e s i s t a n c e t o fluid m o v e m e n t s r e q u i r e a s m a l l e l e c t r o d e surface. T o effect a c o m p r o m i s e of t h e s e r e q u i r e m e n t s , S a i t o a n d M o c h i z u k i 3, Saito 9 i n t r o d u c e d a u l t r a - t h i n film r i n g e l e c t r o d e of s p u t t e r e d p l a t i n u m . T h e c o n s t r u c t i o n of t h i s electrode n e e d s careful c o n t r o l of t h e s p u t t e r i n g a p p a r a t u s , b u t t h e e l a b o r a t e l y constructed electrode often becomes unstable, probably b e c a u s e t h e h e a t e x p a n s i o n of i n s u l a t e d p l a t i n u m film is m a r k e d l y l a r g e r t h a n t h a t of t h e i n s u l a t i n g glass. To a v o i d s u c h difficulties, K i m m i c h a n d K r e u z e r 5 r e c o m -
A
B t"
~u-poste
m e n d e d t o i n s u l a t e a r i n g of a p l a t i n u m foil of a b o u t 3 ~xm t h i c k b y m e a n s of p o l y v i n y l chloride. T h e o x y g e n c u r r e n t of t h e i r electrode, h o w e v e r , is still a f f e c t e d b y fluid m o v e m e n t s , w h e n u t i l i z e d w i t h o u t covering. Therefore, i t seems w o r t h w h i l e t o e x a m i n e a n o t h e r m e t h o d of c o n s t r u c t i o n of t h e t h i n n e r film r i n g electrode. I n t h e p r e s e n t s t u d y , we i n v e s t i g a t e d t h e a p p l i c a b i l i t y of gold p a s t e , w h i c h is used for t h e p a i n t i n g of china, t o t h e c o n s t r u c t i o n of o x y g e n electrode. Construction of the electrode. T h e s t r u c t u r e of t h e e l e c t r o d e is s c h e m a t i c a l l y s h o w n in figure 1, A. A t h i n glass t u b e (OD 2 m m ) is p a i n t e d w i t h d i l u t e d gold p a s t e a n d h e a t e d for 60 m i n a t a t e m p e r a t u r e of 400~ T h i s t u b e is t h e n i n s e r t e d in a n o t h e r glass t u b e w h i c h serves as i n s u l a t i o n . A i r is t h e n r e m o v e d f r o m t h e t u b e s w i t h a v a c u u m p u m p . T h e t u b e is h e a t e d while t h e v a c u u m p u m p is still r u n n i n g , w h i c h causes t h e o u t e r t u b e t o m e l t a n d s h r i n k o n t o t h e i n n e r glass t u b e a n d i n s u l a t e t h e gold film. T h e t i p of t h i s glass t u b e , h a v i n g a n i n s u l a t e d gold film in it, is c u t off a n d p o l i s h e d g e n t l y on artificial l e a t h e r w i t h c e r i u m o x i d e powder, so t h a t a s m o o t h t h i n r i n g of gold film is e x p o s e d o n t h e surface flush w i t h t h e p o l i s h e d c u t e n d of t h e glass t u b e . T h e n a silver wire c o a t e d w i t h silver c h l o r i d e is i n s e r t e d i n t o t h e glass t u b e a n d m o u n t e d in a s u i t a b l e p o s i t i o n a t t h e c u t e n d b y m e a n s of epoxiresin. T h i s Ag-AgC1 wire serves as t h e reference electrode a g a i n s t t h e gold film, w h i c h is c h a r g e d a t -0.7 V. Characteristics and testing o[ the electrode. T h e s e n s i t i v i t y a n d r e p r o d u c i b i l i t y of o x y g e n c u r r e n t of t h i s electrode was t e s t e d in a saline s o l u t i o n b u b b l e d w i t h air a n d n i t r o g e n . T h e o x y g e n c u r r e n t is of t h e o r d e r of 10 -11 A / T o r r a n d its r e s p o n s e t o a l t e r n a t e b u b b l i n g w i t h air a n d n i t r o g e n was r e p r o d u c i b l e w i t h i n a r e l a t i v e e r r o r of 6 % o v e r 7 h. W h e n air b u b b l i n g w a s s t o p p e d , t h e o x y g e n c u r r e n t q u i c k l y d e c r e a s e d b y 5 % of t o t a l c u r r e n t a n d r e m a i n e d a t t h a t level. T h i s m e a n s t h a t t h e d i s t u r b a n c e
I~' Fig. 1, A Schematic illustration of the gold paste electrode. B A microscopic photograph of a part of the gold paste active surface immersed in oil (n= 1.515) and illuminated with a light beam having a suitable incident angle. Olympus oil objective Hi M 100 • and oecular 10 • were used.
1 With leave from the department of gynecology, School of Medicine, Hokkaido University. 2 Glass laboratory. 3 Y. Saito and M. Moehizuki. 6th Int. Conf. med. electro-biol. Engng Tokyo, 600 (1965). 4 Y. Saito, J. appl. Physiol. 23, 979 (1967). 5 H . P . Kimmieh and F. Kreuzer, Prog. Resp. Res. 3, 100 (1969).
15. 1. 1978
of t h e diffusion layer b y t h e w a t e r m o v e m e n t is v e r y small. T h e C-V c u r v e s h o w s a p l a t e a u o v e r t h e r a n g e of - 0 . 3 to - 0 . 8 V. T h e t e m p e r a t u r e d e p e n d e n c y of t h e c u r r e n t was 4 • 10 -14 A / T o r r . ~ o v e r t h e t e m p e r a t u r e r a n g e of 30 to 45~ w h i c h was a r e a s o n a b l e c h a n g e in v i e w of t h e c h a n g e s of 0 2 a b s o r p t i o n a n d diffusion coefficients of saline solution. F i g u r e 1, B s h o w s a p a r t of t h e electrode surface a t a high m a g n i f i c a t i o n b y m e a n s of a m i c r o s c o p e . T h e exp o s e d gold-ring can safely be r e g a r d e d as a s t r a i g h t n a r r o w b a n d h a v i n g t h e w i d t h of 0.2 txm. The 0 2 diffusion l a y e r w h i c h d e v e l o p s on t h i s e l e c t r o d e surface can be expressed by a 2 dimensional partial derivative equation h a v i n g its X a n d Y axes a t r i g h t angles to t h e gold film surface as s h o w n in figure 2. T h e n t h e final solution for t h e o x y g e n diffusion l a y e r a t infinite t i m e is given b y ; P = Po'(1-k), where k = tan
63
Specialia
--1 ( X
+ a ) / Y -- t a n
--1 ( X - -
a)/Y a n d 2a is t h e
w i d t h of n a r r o w b a n d of t h e gold film ring. I3y p u t t i n g k ' = t a n - l k , t h e iso-Po2 line is given b y t h e e q u a t i o n ; X 2 + ( Y - a / k ' ) 2 = (1 + l/k '2)-a s.
I 21a
~A~
The n u m e r i c a l p l o t t i n g of t h i s solution is given in figure 2. T h e f a r t h e s t p o i n t f r o m t h e e l e c t r o d e surface for P = 0.9 9 Po is 19.98 9 a, w h i c h for t h e p r e s e n t elect r o d e is 2 [zm. Application. This electrode m a y be used to m e a s u r e t h e o x y g e n t e n s i o n of t h e skin. T h e e l e c t r o d e t i p is d i p p e d in a s o l u t i o n (10% in acetone) of c e m e d i n e - C | (cellulose solved in a c e t o n e - e t h a n o l - i s o p r o p a n o l m i x t u r e , C e m e d i n e Co, Tokyo) a n d is d r i e d in t h e r o o m air, so t h a t t h e elect r o d e surface is c o a t e d w i t h a t h i n coating (5 ~zm thick), w h i c h serves as a saline c o n t a i n e r w h e n p l a c e d on t h e skin surface. The electrode so t r e a t e d is p a s s e d t h r o u g h a c y l i n d r i c a l w a t e r b a t h , so t h a t t h e e l e c t r o d e t i p is s i t u a t e d flush w i t h t h e b o t t o m of t h e b a t h . The skin Po2 was 0 to 2.5 m m H g d u r i n g b o t h air a n d o x y g e n b r e a t h i n g w h e n t h e t e m p e r a t u r e of t h e w a t e r b a t h was a t r o o m t e m p e r a t u r e . An e x a m p l e of a r e c o r d i n g u n d e r v a r i o u s c o n d i t i o n s is s h o w n in figure 3. The results were : l. W h e n t h e t e m p e r a t u r e was raised to 46~ t h e skin Po2 increased to 48 m m Hg. 2. A f t e r blood flow was s t o p p e d b y an i n f l a t e d cuff p l a c e d a r o u n d t h e arm, t h e skin Po2 fell to n e a r l y zero. 3. On releasing t h e cuff, t h e Po2 r e c o v e r e d to t h e original value. 4. A f t e r t h e gas for b r e a t h i n g was c h a n g e d f r o m air to oxygen, t h e Po2 rose r a p i d l y to 230 m m H g in 150 sec, 5. A t this p o i n t t h e cuff was i n f l a t e d again a n d t h e Poa d e c r e a s e d t o n e a r l y zero. 6. On releasing t h e cuff a n d c h a n g i n g t h e gas from o x y g e n to air t h e Po2 a t t a i n e d a level n e a r t h e initial value. Since t h e o x y g e n diffusion layer on t h e e l e c t r o d e is e s t i m a t e d t o be only 2 v m a n d t h e e p i d e r m i s of t h i s area is a b o u t 80 ~m thick, t h e p r e s e n t electrode m e a s u r e s t h e Po2 of t h e epidermis. A c c o r d i n g to H u c h et al. 6, T h e skin o x y g e n c o n s u m p t i o n can be e s t i m a t e d b y t h e following e q u a t i o n w h e n skin Po2 is sufficiently h i g h a n d blood s u p p l y to t h e skin is i n t e r r u p t e d b y cuff i n f l a t i o n ; Vo=
19.98 a
Fig. 2. Iso-Pos line in a region close to the gold paste surface. 6
R. Huch, D. W. Lfibbers and A. Hueh, Pfltigers Arch. 337, 185 (1972). Air
I
2so
0
7 K. Ohara, Jap. J. Physiol. 2, 1 (1951). 8 N.T.S. Evans and R. F. D. Naylor, Resp. Physiol. 2, 61 (1966/67).
Occlusion
I
PO2:rnmHg
=/760 9AP/At,
w h e r e = is t h e o x y g e n a b s o r p t i o n coefficient of skin tissue ( = 0.0169 a t 46~ I n figure 3 t h e linear decrease of Po2 is 184 m m H g over t h e t i m e r a n g e of 1.75 rain. P u t t i n g t h e s e values into t h e a b o v e e q u a t i o n gives a XTozof 0.00233 m l O2/ml tissue - min. This value is slightly h i g h e r t h a n 0.002 b y O h a r a 7 a n d 0.00t8 b y E v a n s a n d Naylor s. T h i s d i f f e r e n c e is p r o b a b l y due t o t h e h i g h t e m p e r a t u r e a t w h i c h t h e p r e s e n t m e a s u r e m e n t was carried out. These results i n d i c a t e a wide a p p l i c a b i l i t y of t h e p r e s e n t elect r o d e to t h e i n v e s t i g a t i o n of tissue o x y g e n tension.
Date= July-81976 Subj.SM. :
l
/
T/ 6
lm••
2 ReleaslCii"ill
5
4
3
2
1
Fig. 3. An example of skin Po~ recording during several experimental conditions. The numbers below the recording refer to successive experimental conditions. Read right to left.
