CONCEPTS, COMPONENTS, AND CONFIGURATIONS
Noninvasive Monitoring of Vascular Compromise in Trauma Phillip J. Bendick, PhD John R. Mayer, MD John L. Glover, MD Indianapolis, Indiana
Many types of trauma may lead to vascular compromise unless treated effectively and promptly. In addition to direct trauma to a major vessel are the crushing injuries, fractures, and burn injuries which give rise to an ischemia-edema cycle and subsequent muscle necrosis and tissue loss. Objective adjuncts to clinical impressions, such as isotope clearance muscle blood flow or the ultrasound Doppler flowmeter are generally not suitable for continuous, uninterrupted monitoring of the degree of vascular compromise. A technique that appears promising in this respect is that of photoplethysmography. This technique uses a small LED infrared emitter/detector array. Blood volume changes in an illuminated vascular bed produce variations in the amount of reflected light sensed by the detector, which after appropriate electronic amplification results in pulsatile blood flow (if present) and its change with time being displayed on the monitor. This technique was used with 25 trauma patients with good results, avoiding unnecessary compartmental decompression in some cases. It has proved to be a simple technique that requires little or no training for interpretation, provides continuous monitoring, is noninvasive and atraumatic in nature, is portable for easy set-up, and is relatively inexpensive. Bendick PJ, Mayer JR, Glover JL: Noninvasive monitorin'g of vascular compromise in trauma. JACEP 8:320-322, Aug ust, 1979.
photoplethysmography, technique
INTRODUCTION
C u r r e n t l y , the m a i n c r i t e r i a for decompression of a t r a u m a t i z e d e x t r e m i t y are clinical: limb tenseness by palpation, surface t e m p e r a t u r e , c a p i l l a r y flush time, loss of p a l p a b l e pulses, and loss of sensation in v o l u n t a r y movement. 1-3 By the time m a n y of these signs are clinically evident, some m u s c u l a r or nerve d a m a g e m a y have a l r e a d y occurred. The only objective, n o n i n v a s i v e adjuncts to this d e t e r m i n a t i o n now available are the u l t r a s o u n d Doppler flowmeter or some type of occlusive p l e t h y s m o g r a p h y (eg, p n e u m o p l e t h y s m o g r a p h y or mercury-insilastic s t r a i n gauge), both of which r e q u i r e some degree of expertise in t h e i r use and evaluation.4, 5 Xenon 133 c l e a r a n c e techniques to d e t e r m i n e muscle blood flow ~ and direct c o m p a r t m e n t pressure measurementsT, s are both s o m e w h a t i n vasive in n a t u r e and, as such, m a y provide avenues for subsequent infection. They also r e q u i r e specialized e q u i p m e n t and t r a i n i n g for their clinical application. T i s s u e gas t e n s i o n m e a s u r e m e n t s also r e q u i r e v e r y s o p h i s t i c a t e d ins t r u m e n t a t i o n which has l i m i t e d a v a i l a b i l i t y in most medical c e n t e r s 2 This reFrom the Department of Surgery, Indiana University:~t3'choolof Medicine, Indianapolis, Indiana. Presented at the UniversityAssociation for Emergency Medicine Annual Meeting in San Francisco, May, 1978. Address for reprints: Phillip J. Bendick, PhD, Departmentof Surgery, Indiana UniversitySchool of " Medicine, 1001 West Tenth Street, Indianapolis, Indiana 46202. 8:8 (August) 1979
JACEP
320/47
port describes the development of a photoplethysmographic technique for m o n i t o r i n g v a s c u l a r s t a t u s following t r a u m a and s u m m a r i z e s the clinical experience with it.
, Sv
200 K
INSTRUMENTATION For t h e p h o t o p l e t h y s m o g r a p h , a small infrared e m i t t e r / d e t e c t o r a r r a y ( F a i r c h i l d F P A 104) is used to ill u m i n a t e the v a s c u l a r bed of i n t e r e s t and detect t h e reflected light. Almost always, t h i s v a s c u l a r bed is a nail bed of one of the digits of the affected extreniity. A nail bed is used because one is n o r m a l l y accessible even in a t r a u m a t i z e d or b u r n e d e x t r e m i t y ; the device is e a s i l y fixed to a n a i l with a s m a l l d r o p of c y a n o a c r y l a t e ester (so-called "super glue") a n d does not i n t e r f e r e w i t h l i m b t r e a t m e n t or d r e s s i n g in t h a t p o s i t i o n . I n f r a r e d emission a n d detection m i n i m i z e s interference from a m b i e n t room lighting, especially w i t h the a d d i t i o n of an infrared g e l a t i n filter (Kodak No 87) p e r m a n e n t l y m o u n t e d over the face of the solid state a r r a y . The e m i t t e r / d e t e c t o r a r r a y itself is v e r y s m a l l (cube-shaped, approxim a t e l y 4 m m on a side) and is light weight, w e i g h i n g less t h a n one gram. Four small, relatively short, lead wires from the a r r a y form a longer shielded cable w h i c h connects to int e r f a c e c i r c u i t r y t h a t m a y be connected to any s t a n d a r d E C G monitor or strip c h a r t recorder (Figure). The i n t e r f a c e c i r c u i t r y is c o n s t r u c t e d from standard integrated circuit amplifiers and c a n be b a t t e r y operated. The s y s t e m is inexpensive; the e m i t t e r / d e t e c t o r a r r a y , cable and interface components can be assembled for less t h a n $20. The monitor, which continuously d i s p l a y s the p u l s a t i l e flow signal (if present) from the detector, can also be easily connected to a recorder for c a l i b r a t i o n and d o c u m e n t a t i o n of the flow signal. The m o n i t o r can also be set to t r i g g e r a n a l a r m should the pulse a m p l i t u d e fall below a preset level, a l e r t i n g the clinical staff to potential vascular compromise. The p h o t o p l e t h y s m o g r a p h is left in place as a chronic c o n t i n u o u s monitor so long as t h e p a t i e n t - i s felt to be a t risk. CLINICAL EXPERIENCE The p h o t o p l e t h y s m o g r a p h i c monitor has been used on 25 t r a u m a pat i e n t s to date. The types of t r a u m a to these p a t i e n t s is s u m m a r i z e d (Table). D i r e c t v a s c u l a r t r a u m a cases i n c l u d e d two p a t i e p . t s With v e s s e l 48/321
50 K ~r=~/v~
'1
PHOTOPLETHYSMOGRAPH INTERFACECIRCUITRY F i g . Interface circuitry between photoplethysmograph emitter~detector array and monitor or recorder.
Table TYPES OF TRAUMA TO PATIENTS UNDERGOING PHOTOPLETHYSMOGRA PHIC MONITOR n = 25 Type of Trauma
No
Direct vascular trauma Crushing injuries
4 5
Circumferential burns
15
Frostbite
1
transection caused by gunshot wounds a n d two w i t h a r t e r i a l lacerations. M o n i t o r i n g was performed following surgical r e p a i r of the wounds a n d s h o w e d , in a l l f o u r cases, no p o s t o p e r a t i v e complications. Two of t h e five c r u s h i n g i n j u r i e s involved a u t o m o b i l e accidents; in both cases t h e r e was extensive soft tissue injury and contusions, t h o u g h no fractures. A t h i r d p a t i e n t h a d a leg t r a p p e d bet w e e n t w o pieces of f a r m m a c h i n e r y w i t h significant soft tissue damage, b u t a g a i n no bone fracture. The rem a i n i n g two o c c u r r e d w h e n ext r e m i t i e s were c a u g h t between rollers in m a n u f a c t u r i n g plants, resulti n g in w r i n g e r type injuries. In all five p a t i e n t s , t h e m o n i t o r s h o w e d m a i n t e n a n c e of good p u l s a t i l e flow at a l l t i m e s , a n d no d e c o m p r e s s i o n s were n e c e s s a r y in this group, even though three patients did develop t e n s e n e s s of t h e i n j u r e d e x t r e m i t y a n d a slow c a p i l l a r y flush time. F i f t e e n p a t i e n t s who s u f f e r e d t h i r d degree c i r c u m f e r e n t i a l burns of at l e a s t one e x t r e m i t y and one frostbite victim were also monitored with
JACEP
the p h o t o p l e t h y s m o g r a p h . In four of the burn patients clinical indications, particularly limb tenseness, indicated a n e s c h a r o t o m y should be p e r f o r m e d . T h e m o n i t o r , however, showed good p u l s a t i l e flow in these patients, and unnecessary escharotomies were avoided. In one patient t h e r e was no p u l s a t i l e flow signal detected prior to escharotomy. In three of the b u r n p a t i e n t s , escharotomies were performed before the photoplet h y s m o g r a p h was a t t a c h e d to the patient. The m o n i t o r showed good pulsatile flow following all these procedures and no f u r t h e r decompressions were necessary. The patient with frostbite m a i n t a i n e d good p u l s a t i l e flow at all t i m e s d u r i n g his hospitalization. DISCUSSION M a n y types of t r a u m a can lead to a n i s c h e m i a - e d e m a cycle in the ext r e m i t i e s u l t i m a t e l y r e s u l t i n g in muscle necrosis and tissue loss unless t r e a t e d promptly. Especially in this category, b u t c e r t a i n l y not limi t e d to t h e s e , a r e t h e c r u s h i n g injuries, fractures a n d d i r e c t t r a u m a to a m a j o r a r t e r y . A n o t h e r t y p e of t r a u m a , the b u r n injury, m a y also g i v e r i s e to v a s c u l a r c o m p r o m i s e . These injuries m a y r e s u l t in damage to u n d e r l y i n g n e r v e s a n d m u s c l e s w i t h s u b s e q u e n t loss of function. The a m o u n t of d a m a g e w i l l be proportional to the degree of vascular, compromise a n d the l e n g t h of t im~ over which it h a s occurred. This time factor is crucial since nerve functional abnormalities can begin within t h i r t y m i n u t e s of t h e o n s e t of ischemia, and i r r e v e r s i b l e loss of muscle f u n c t i o n can occur w i t h i n four hours. :: .
8:8 (August) 1979
Before a n advanced stage of the ischemia-edema cycle or the b u r n response cycle is reached, it is approp r i a t e to d e c o m p r e s s the a f f e c t e d area, but this opens avenues for subsequent infection and increased sus- • c e p t i b i l i t y to c o m p l i c a t i o n s d u r i n g the patient's recovery. Therefore, decompression should be reserved only for those patients in whom it is absolutely necessary. The clinical indications for decompression are very subj e c t i v e a n d t h e i n t e r p r e t a t i o n of these varies greatly from i n d i v i d u a l to i n d i v i d u a l . The u l t r a s o u n d Doppler flowmeter, occlusive photoplet h y s m o g r a p h y , isotope c l e a r a n c e muscle blood flow studies, or direct compartment pressure measurements are either invasive or require specialized e q u i p m e n t and t r a i n i n g for their clinical application. In addition, these techniques do not provide continuous m o n i t o r i n g of blood flow in a n e x t r e m i t y . As s i g n i f i c a n t ischemic c a n develop a t almost a n y time d u r i n g the first 48 to 72 hours following t r a u m a , the capability for continuous m o n i t o r i n g is i m p o r t a n t in m a n a g i n g these injuries2 ° The t e c h n i q u e of photoplethysmography appears to satisfy m a n y of the criteria for n o n i n v a s i v e , a t r a u matic a n d continuous m o n i t o r i n g i n t r a u m a t i z e d p a t i e n t s . It h a s b e e n applied previously for m e a s u r e m e n t s of skin flap blood flow 11 and for various aspects of diagnosing peripheral vascular disease.12,13 O r i g i n a l l y reported by H e r t z m a n in 1938,14 this technique m a k e s use of a light source and a light detector placed next to one a n o t h e r over a v a s c u l a r bed. Blood volume changes in the vascular bed p r o d u c e v a r i a t i o n s i n the a m o u n t of i n c i d e n t l i g h t reflected and sensed by the detector. With appropriate electronic amplification, these f l u c t u a t i o n s in the o u t p u t of the detector show the a m o u n t of pulsatile blood flow to t h a t p a r t of the vascular bed i l l u m i n a t e d by the light source. By p l a c i n g the i n s t r u m e n t distal to a region in which the circulation m a y become compromised, a significant decrease or loss of signal from the detector will indicate proximal occlusion to the extent t h a t decompression m u s t be seriously considered. For the p a t i e n t whose injuries do not i n v o l v e all four e x t r e m i t i e s , a second detector can be placed on a n u n i n j u r e d limb to serve as a control" and a comparison for the p u l s a t i l e signal from the affected limb. As the normal photoplethysmograph signal is v i r t u a l l y identical from a finger or
8:8 August) i979
toe, the control limb need not be cont r a l a t e r a l to the injury. W h e n the monitored signal is reduced in amplitude to approximately 30% or less of the control signal and exhibits pulsatile waveform damping, the proximal c i r c u l a t i o n has been significantly affected to the point of possible tissue ischemia. In only one p a t i e n t t h u s far, one w i t h c i r c u m f e r e n t i a l burns, have all four extremities been involved m a k i n g it impossible to obt a i n a suitable control signal. In such cases, very weak or absent pulsatile flow can be t a k e n to indicate proxim a l vascular compromise. Photoplethysmographic measu r e m e n t s can be made during the initial emergency d e p a r t m e n t evaluation and, perhaps more importantly, on a chronic m o n i t o r i n g basis d u r i n g hospitalization to determine improving or worsening trends in circulatory status. The development of comp a r t m e n t syndromes and tissue ischemic is a time-dependent phenome n o n which needs to be m o n i t o r e d c o n t i n u o u s l y for a d e q u a t e e a r l y d i a g n o s i s . It m u s t be e m p h a s i z e d t h a t sound clinical j u d g m e n t is the most i m p o r t a n t factor in the m a n a g e m e n t of these patients, with the p h o t o p l e t h y s m o g r a p h providing objective data i n support of t h a t judgment. I s o l a t e d c o m p a r t m e n t injuries, such as a f~acture affecting only a small a n t e r i o r compartment, are not likely to be detected by any n o n i n v a sive t e c h n i q u e c u r r e n t l y available. In more e x t e n s i v e injuries, the p h o t o p l e t h y s m o g r a p h should be of value as a m e a n s of rigid, n o n i n v a sive e v a l u a t i o n a n d may help avoid u n n e c e s s a r y decompressions or provide indications for a n early procedure before severe ischemia and necrosis have developed.
CONCLUSION The p h o t o p l e t h y s m o g r a p h has been found to be a reliable indicator of vascular s t a t u s in t r a u m a t i z e d extremities. The detector is very sensitive to small changes in flow and is well accepted by n u r s i n g personnel as a continuous monitor for detecting trends in flow pulsatility. It is easily set up by fixing the array to a nail bed and is entirely portable, allowing m o n i t o r i n g i n t h e e m e r g e n c y dep a r t m e n t as well as at the patient's bedside. C l i n i c a l l y , the device has proved valuable in p a t i e n t management, introducing objective data into the decision m a k i n ~ and t r e a t m e n t processes. F u r t h e r development, and correlation of photoplethysmographic
JACEP
data w i t h t h a t of muscle blood flow a n d the u l t r a s o u n d Doppler flowmeter measured under controlled c o n d i t i o n s , w i l l m a k e its c l i n i c a l i n p u t t h a t m u c h more objective and increase its v a l u e i n assessing the d e g r e e of v a s c u l a r c o m p r o m i s e in t r a u m a t i z e d extremities.
REFERENCES 1. Blount WP: Volkmann's ischemic contracture. S u r g Gynecol Obstet 90:244-246, 1950. 2. Holden CEA: Compartmental syndromes following trauma. Clin Orthop 113:95-102, 1975. 3. Matsen FA: Compartmental syndrome: A unified concept. Clin Orthop 113:8-14, 1975. 4. Clayton JM, Hayes AC, Barnes RW: Tissue pressure and perfusion in the comp a r t m e n t syndrome. J S u r g R e s 22: 333-339, 1977. 5. Moylan JA, Inge WW, Pruitt BA: Circulatory changes following circumferential extremity burns evaluated by the ultrasonic flowmeter. J Trauma 11:763-770, 1971. 6. Lassen NA, Lindbjerg J, Munck O: Measurement of blood flow through skeletal muscle by intramuscular injection of Xenon-133. L a n c e t 1:686-689, 1964. 7. Mubarak SJ, Hargens AR, Owen CA, et al: The wick catheter technique for measurement of intramuscular pressure. J Bone J o i n t Surg 58A:1016-1020, 1976. 8. Whitesides TE, Haney TC, Morimoto K, et al: Tissue pressure measurements as a determinant for the need of fasciotomy. Clin Orthop 113:43-51, 1975. 9. Nicholas C~, Miller SH: The anterior tibial compartment syndrome: Tissue gas tension measurement. J S u r g Res 24: 334-338, 1978. 10. Clayton JM, Russell HE, Hartford CE, et al: Sequential circulatory changes in the circumferentially burned limb. A n n Surg 185:391-396, 1977. 11. Webster MHC, Patterson J: The photoelectric plethysmograph as a monitor of microvascplar anastomes. Br J Plas Surg 29:182-185, '1976. 12. Hajjar WM, Sumner DS: Photoplethysmography: A noninvasive technique for the evaluation of carotid stenosis. Proceedings of the Association for the Advancement of Medical Instrumentation 12th Annual Meeting, 1977. 13. Thulesius O, Borgnis F, Dvorak T: Analysis of photoplethysmographic pulse curves with electronic derivation. Scan J Clin Lab Invest 31(suppl 128):159-162, 1962. 14. Hertzman AB: The blood supply of various skin areas as estimated by the photoelectric plethysmograph. A m J Physiol 124:328-340, 1938.
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Noninvasive Monitoring of Vascular Compromise in Trauma Phillip J. Bendick, PhD John R. Mayer, MD John L. Glover, MD Indianapolis, Indiana
Many types of trauma may lead to vascular compromise unless treated effectively and promptly. In addition to direct trauma to a major vessel are the crushing injuries, fractures, and burn injuries which give rise to an ischemia-edema cycle and subsequent muscle necrosis and tissue loss. Objective adjuncts to clinical impressions, such as isotope clearance muscle blood flow or the ultrasound Doppler flowmeter are generally not suitable for continuous, uninterrupted monitoring of the degree of vascular compromise. A technique that appears promising in this respect is that of photoplethysmography. This technique uses a small LED infrared emitter/detector array. Blood volume changes in an illuminated vascular bed produce variations in the amount of reflected light sensed by the detector, which after appropriate electronic amplification results in pulsatile blood flow (if present) and its change with time being displayed on the monitor. This technique was used with 25 trauma patients with good results, avoiding unnecessary compartmental decompression in some cases. It has proved to be a simple technique that requires little or no training for interpretation, provides continuous monitoring, is noninvasive and atraumatic in nature, is portable for easy set-up, and is relatively inexpensive. Bendick PJ, Mayer JR, Glover JL: Noninvasive monitorin'g of vascular compromise in trauma. JACEP 8:320-322, Aug ust, 1979.
photoplethysmography, technique
INTRODUCTION
C u r r e n t l y , the m a i n c r i t e r i a for decompression of a t r a u m a t i z e d e x t r e m i t y are clinical: limb tenseness by palpation, surface t e m p e r a t u r e , c a p i l l a r y flush time, loss of p a l p a b l e pulses, and loss of sensation in v o l u n t a r y movement. 1-3 By the time m a n y of these signs are clinically evident, some m u s c u l a r or nerve d a m a g e m a y have a l r e a d y occurred. The only objective, n o n i n v a s i v e adjuncts to this d e t e r m i n a t i o n now available are the u l t r a s o u n d Doppler flowmeter or some type of occlusive p l e t h y s m o g r a p h y (eg, p n e u m o p l e t h y s m o g r a p h y or mercury-insilastic s t r a i n gauge), both of which r e q u i r e some degree of expertise in t h e i r use and evaluation.4, 5 Xenon 133 c l e a r a n c e techniques to d e t e r m i n e muscle blood flow ~ and direct c o m p a r t m e n t pressure measurementsT, s are both s o m e w h a t i n vasive in n a t u r e and, as such, m a y provide avenues for subsequent infection. They also r e q u i r e specialized e q u i p m e n t and t r a i n i n g for their clinical application. T i s s u e gas t e n s i o n m e a s u r e m e n t s also r e q u i r e v e r y s o p h i s t i c a t e d ins t r u m e n t a t i o n which has l i m i t e d a v a i l a b i l i t y in most medical c e n t e r s 2 This reFrom the Department of Surgery, Indiana University:~t3'choolof Medicine, Indianapolis, Indiana. Presented at the UniversityAssociation for Emergency Medicine Annual Meeting in San Francisco, May, 1978. Address for reprints: Phillip J. Bendick, PhD, Departmentof Surgery, Indiana UniversitySchool of " Medicine, 1001 West Tenth Street, Indianapolis, Indiana 46202. 8:8 (August) 1979
JACEP
320/47
port describes the development of a photoplethysmographic technique for m o n i t o r i n g v a s c u l a r s t a t u s following t r a u m a and s u m m a r i z e s the clinical experience with it.
, Sv
200 K
INSTRUMENTATION For t h e p h o t o p l e t h y s m o g r a p h , a small infrared e m i t t e r / d e t e c t o r a r r a y ( F a i r c h i l d F P A 104) is used to ill u m i n a t e the v a s c u l a r bed of i n t e r e s t and detect t h e reflected light. Almost always, t h i s v a s c u l a r bed is a nail bed of one of the digits of the affected extreniity. A nail bed is used because one is n o r m a l l y accessible even in a t r a u m a t i z e d or b u r n e d e x t r e m i t y ; the device is e a s i l y fixed to a n a i l with a s m a l l d r o p of c y a n o a c r y l a t e ester (so-called "super glue") a n d does not i n t e r f e r e w i t h l i m b t r e a t m e n t or d r e s s i n g in t h a t p o s i t i o n . I n f r a r e d emission a n d detection m i n i m i z e s interference from a m b i e n t room lighting, especially w i t h the a d d i t i o n of an infrared g e l a t i n filter (Kodak No 87) p e r m a n e n t l y m o u n t e d over the face of the solid state a r r a y . The e m i t t e r / d e t e c t o r a r r a y itself is v e r y s m a l l (cube-shaped, approxim a t e l y 4 m m on a side) and is light weight, w e i g h i n g less t h a n one gram. Four small, relatively short, lead wires from the a r r a y form a longer shielded cable w h i c h connects to int e r f a c e c i r c u i t r y t h a t m a y be connected to any s t a n d a r d E C G monitor or strip c h a r t recorder (Figure). The i n t e r f a c e c i r c u i t r y is c o n s t r u c t e d from standard integrated circuit amplifiers and c a n be b a t t e r y operated. The s y s t e m is inexpensive; the e m i t t e r / d e t e c t o r a r r a y , cable and interface components can be assembled for less t h a n $20. The monitor, which continuously d i s p l a y s the p u l s a t i l e flow signal (if present) from the detector, can also be easily connected to a recorder for c a l i b r a t i o n and d o c u m e n t a t i o n of the flow signal. The m o n i t o r can also be set to t r i g g e r a n a l a r m should the pulse a m p l i t u d e fall below a preset level, a l e r t i n g the clinical staff to potential vascular compromise. The p h o t o p l e t h y s m o g r a p h is left in place as a chronic c o n t i n u o u s monitor so long as t h e p a t i e n t - i s felt to be a t risk. CLINICAL EXPERIENCE The p h o t o p l e t h y s m o g r a p h i c monitor has been used on 25 t r a u m a pat i e n t s to date. The types of t r a u m a to these p a t i e n t s is s u m m a r i z e d (Table). D i r e c t v a s c u l a r t r a u m a cases i n c l u d e d two p a t i e p . t s With v e s s e l 48/321
50 K ~r=~/v~
'1
PHOTOPLETHYSMOGRAPH INTERFACECIRCUITRY F i g . Interface circuitry between photoplethysmograph emitter~detector array and monitor or recorder.
Table TYPES OF TRAUMA TO PATIENTS UNDERGOING PHOTOPLETHYSMOGRA PHIC MONITOR n = 25 Type of Trauma
No
Direct vascular trauma Crushing injuries
4 5
Circumferential burns
15
Frostbite
1
transection caused by gunshot wounds a n d two w i t h a r t e r i a l lacerations. M o n i t o r i n g was performed following surgical r e p a i r of the wounds a n d s h o w e d , in a l l f o u r cases, no p o s t o p e r a t i v e complications. Two of t h e five c r u s h i n g i n j u r i e s involved a u t o m o b i l e accidents; in both cases t h e r e was extensive soft tissue injury and contusions, t h o u g h no fractures. A t h i r d p a t i e n t h a d a leg t r a p p e d bet w e e n t w o pieces of f a r m m a c h i n e r y w i t h significant soft tissue damage, b u t a g a i n no bone fracture. The rem a i n i n g two o c c u r r e d w h e n ext r e m i t i e s were c a u g h t between rollers in m a n u f a c t u r i n g plants, resulti n g in w r i n g e r type injuries. In all five p a t i e n t s , t h e m o n i t o r s h o w e d m a i n t e n a n c e of good p u l s a t i l e flow at a l l t i m e s , a n d no d e c o m p r e s s i o n s were n e c e s s a r y in this group, even though three patients did develop t e n s e n e s s of t h e i n j u r e d e x t r e m i t y a n d a slow c a p i l l a r y flush time. F i f t e e n p a t i e n t s who s u f f e r e d t h i r d degree c i r c u m f e r e n t i a l burns of at l e a s t one e x t r e m i t y and one frostbite victim were also monitored with
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the p h o t o p l e t h y s m o g r a p h . In four of the burn patients clinical indications, particularly limb tenseness, indicated a n e s c h a r o t o m y should be p e r f o r m e d . T h e m o n i t o r , however, showed good p u l s a t i l e flow in these patients, and unnecessary escharotomies were avoided. In one patient t h e r e was no p u l s a t i l e flow signal detected prior to escharotomy. In three of the b u r n p a t i e n t s , escharotomies were performed before the photoplet h y s m o g r a p h was a t t a c h e d to the patient. The m o n i t o r showed good pulsatile flow following all these procedures and no f u r t h e r decompressions were necessary. The patient with frostbite m a i n t a i n e d good p u l s a t i l e flow at all t i m e s d u r i n g his hospitalization. DISCUSSION M a n y types of t r a u m a can lead to a n i s c h e m i a - e d e m a cycle in the ext r e m i t i e s u l t i m a t e l y r e s u l t i n g in muscle necrosis and tissue loss unless t r e a t e d promptly. Especially in this category, b u t c e r t a i n l y not limi t e d to t h e s e , a r e t h e c r u s h i n g injuries, fractures a n d d i r e c t t r a u m a to a m a j o r a r t e r y . A n o t h e r t y p e of t r a u m a , the b u r n injury, m a y also g i v e r i s e to v a s c u l a r c o m p r o m i s e . These injuries m a y r e s u l t in damage to u n d e r l y i n g n e r v e s a n d m u s c l e s w i t h s u b s e q u e n t loss of function. The a m o u n t of d a m a g e w i l l be proportional to the degree of vascular, compromise a n d the l e n g t h of t im~ over which it h a s occurred. This time factor is crucial since nerve functional abnormalities can begin within t h i r t y m i n u t e s of t h e o n s e t of ischemia, and i r r e v e r s i b l e loss of muscle f u n c t i o n can occur w i t h i n four hours. :: .
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Before a n advanced stage of the ischemia-edema cycle or the b u r n response cycle is reached, it is approp r i a t e to d e c o m p r e s s the a f f e c t e d area, but this opens avenues for subsequent infection and increased sus- • c e p t i b i l i t y to c o m p l i c a t i o n s d u r i n g the patient's recovery. Therefore, decompression should be reserved only for those patients in whom it is absolutely necessary. The clinical indications for decompression are very subj e c t i v e a n d t h e i n t e r p r e t a t i o n of these varies greatly from i n d i v i d u a l to i n d i v i d u a l . The u l t r a s o u n d Doppler flowmeter, occlusive photoplet h y s m o g r a p h y , isotope c l e a r a n c e muscle blood flow studies, or direct compartment pressure measurements are either invasive or require specialized e q u i p m e n t and t r a i n i n g for their clinical application. In addition, these techniques do not provide continuous m o n i t o r i n g of blood flow in a n e x t r e m i t y . As s i g n i f i c a n t ischemic c a n develop a t almost a n y time d u r i n g the first 48 to 72 hours following t r a u m a , the capability for continuous m o n i t o r i n g is i m p o r t a n t in m a n a g i n g these injuries2 ° The t e c h n i q u e of photoplethysmography appears to satisfy m a n y of the criteria for n o n i n v a s i v e , a t r a u matic a n d continuous m o n i t o r i n g i n t r a u m a t i z e d p a t i e n t s . It h a s b e e n applied previously for m e a s u r e m e n t s of skin flap blood flow 11 and for various aspects of diagnosing peripheral vascular disease.12,13 O r i g i n a l l y reported by H e r t z m a n in 1938,14 this technique m a k e s use of a light source and a light detector placed next to one a n o t h e r over a v a s c u l a r bed. Blood volume changes in the vascular bed p r o d u c e v a r i a t i o n s i n the a m o u n t of i n c i d e n t l i g h t reflected and sensed by the detector. With appropriate electronic amplification, these f l u c t u a t i o n s in the o u t p u t of the detector show the a m o u n t of pulsatile blood flow to t h a t p a r t of the vascular bed i l l u m i n a t e d by the light source. By p l a c i n g the i n s t r u m e n t distal to a region in which the circulation m a y become compromised, a significant decrease or loss of signal from the detector will indicate proximal occlusion to the extent t h a t decompression m u s t be seriously considered. For the p a t i e n t whose injuries do not i n v o l v e all four e x t r e m i t i e s , a second detector can be placed on a n u n i n j u r e d limb to serve as a control" and a comparison for the p u l s a t i l e signal from the affected limb. As the normal photoplethysmograph signal is v i r t u a l l y identical from a finger or
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toe, the control limb need not be cont r a l a t e r a l to the injury. W h e n the monitored signal is reduced in amplitude to approximately 30% or less of the control signal and exhibits pulsatile waveform damping, the proximal c i r c u l a t i o n has been significantly affected to the point of possible tissue ischemia. In only one p a t i e n t t h u s far, one w i t h c i r c u m f e r e n t i a l burns, have all four extremities been involved m a k i n g it impossible to obt a i n a suitable control signal. In such cases, very weak or absent pulsatile flow can be t a k e n to indicate proxim a l vascular compromise. Photoplethysmographic measu r e m e n t s can be made during the initial emergency d e p a r t m e n t evaluation and, perhaps more importantly, on a chronic m o n i t o r i n g basis d u r i n g hospitalization to determine improving or worsening trends in circulatory status. The development of comp a r t m e n t syndromes and tissue ischemic is a time-dependent phenome n o n which needs to be m o n i t o r e d c o n t i n u o u s l y for a d e q u a t e e a r l y d i a g n o s i s . It m u s t be e m p h a s i z e d t h a t sound clinical j u d g m e n t is the most i m p o r t a n t factor in the m a n a g e m e n t of these patients, with the p h o t o p l e t h y s m o g r a p h providing objective data i n support of t h a t judgment. I s o l a t e d c o m p a r t m e n t injuries, such as a f~acture affecting only a small a n t e r i o r compartment, are not likely to be detected by any n o n i n v a sive t e c h n i q u e c u r r e n t l y available. In more e x t e n s i v e injuries, the p h o t o p l e t h y s m o g r a p h should be of value as a m e a n s of rigid, n o n i n v a sive e v a l u a t i o n a n d may help avoid u n n e c e s s a r y decompressions or provide indications for a n early procedure before severe ischemia and necrosis have developed.
CONCLUSION The p h o t o p l e t h y s m o g r a p h has been found to be a reliable indicator of vascular s t a t u s in t r a u m a t i z e d extremities. The detector is very sensitive to small changes in flow and is well accepted by n u r s i n g personnel as a continuous monitor for detecting trends in flow pulsatility. It is easily set up by fixing the array to a nail bed and is entirely portable, allowing m o n i t o r i n g i n t h e e m e r g e n c y dep a r t m e n t as well as at the patient's bedside. C l i n i c a l l y , the device has proved valuable in p a t i e n t management, introducing objective data into the decision m a k i n ~ and t r e a t m e n t processes. F u r t h e r development, and correlation of photoplethysmographic
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data w i t h t h a t of muscle blood flow a n d the u l t r a s o u n d Doppler flowmeter measured under controlled c o n d i t i o n s , w i l l m a k e its c l i n i c a l i n p u t t h a t m u c h more objective and increase its v a l u e i n assessing the d e g r e e of v a s c u l a r c o m p r o m i s e in t r a u m a t i z e d extremities.
REFERENCES 1. Blount WP: Volkmann's ischemic contracture. S u r g Gynecol Obstet 90:244-246, 1950. 2. Holden CEA: Compartmental syndromes following trauma. Clin Orthop 113:95-102, 1975. 3. Matsen FA: Compartmental syndrome: A unified concept. Clin Orthop 113:8-14, 1975. 4. Clayton JM, Hayes AC, Barnes RW: Tissue pressure and perfusion in the comp a r t m e n t syndrome. J S u r g R e s 22: 333-339, 1977. 5. Moylan JA, Inge WW, Pruitt BA: Circulatory changes following circumferential extremity burns evaluated by the ultrasonic flowmeter. J Trauma 11:763-770, 1971. 6. Lassen NA, Lindbjerg J, Munck O: Measurement of blood flow through skeletal muscle by intramuscular injection of Xenon-133. L a n c e t 1:686-689, 1964. 7. Mubarak SJ, Hargens AR, Owen CA, et al: The wick catheter technique for measurement of intramuscular pressure. J Bone J o i n t Surg 58A:1016-1020, 1976. 8. Whitesides TE, Haney TC, Morimoto K, et al: Tissue pressure measurements as a determinant for the need of fasciotomy. Clin Orthop 113:43-51, 1975. 9. Nicholas C~, Miller SH: The anterior tibial compartment syndrome: Tissue gas tension measurement. J S u r g Res 24: 334-338, 1978. 10. Clayton JM, Russell HE, Hartford CE, et al: Sequential circulatory changes in the circumferentially burned limb. A n n Surg 185:391-396, 1977. 11. Webster MHC, Patterson J: The photoelectric plethysmograph as a monitor of microvascplar anastomes. Br J Plas Surg 29:182-185, '1976. 12. Hajjar WM, Sumner DS: Photoplethysmography: A noninvasive technique for the evaluation of carotid stenosis. Proceedings of the Association for the Advancement of Medical Instrumentation 12th Annual Meeting, 1977. 13. Thulesius O, Borgnis F, Dvorak T: Analysis of photoplethysmographic pulse curves with electronic derivation. Scan J Clin Lab Invest 31(suppl 128):159-162, 1962. 14. Hertzman AB: The blood supply of various skin areas as estimated by the photoelectric plethysmograph. A m J Physiol 124:328-340, 1938.
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