Goren, Gabriel

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Regarding “Variability and reliability of air plethysmographic measurements for the evaluation of chronic venous disease” 

LETTERS TO THE EDITORS 
Regarding "A randomized study on eversion versus 
standard carotid endarterectomy: Study design and 
preliminary results: The Everest Trial" 
To the Editors: 
I received the April 1998 issue of the Journal of 
Vascular Surgery and found an error in the first sentence 
of the article entitled "A randomized study on eversion 
versus standard carotid endarterectomy: Study design and 
preliminary results: The Everest Trial" by Cao et al (J Vasc 
Surg 1998;27:595-605). The statement was made in the 
article that "Eversion carotid endarterectomy (CEA) was 
introduced in 1970 by Etheredge. l " As you may observe 
from the enclosed reprint, we originally described and 
illustrated (Fig) this method of endarterectomy in an arti-
cle published in Postgraduate Medicine (1959;26:227-37) 
11 years before the article by Etheredge appeared. In his 
article (Am J Surg 1970;120:275), Etheredge also failed 
to refer to our article . That our article is not entirely 
unrecognized is evident by the fact that at the recent 
meeting of the American Surgical Association, Dr Dhiraj 
M. Shah referred to it in his presentation entitled, 
"Carotid endarterectomy by eversion technique: its safety 
and durability." 
Michael E. DeBakey, MD 
Baylor College of Medicine 
Houston, Tex 
24/41/92213 
11 
Fig. A technique of eversion carotid endarterectomy 
from Postgraduate Medicine (1959;26:227-37). 
Reply 
We read with interest the letter from Dr DeBakey 
regarding our article (J Vasc Surg 1998;27:595-605) and 
the original description of eversion carotid endarterecto-
my. We apologize for the inaccuracy of our statement that 
attributed the original description of the method to 
Etheredge (Am J Surg 1970;120:275). It is unfortunate 
that our statement was on the basis of the latter article that 
failed to refer to a previous publication, which does con-
tain a description and an illustration of the method of 
endarterectomy as outlined by Dr DeBakey. However, we 
would like to acknowledge that referral to an article in 
Postgraduate Medicine (1959;26:227-237) would have 
been more appropriate as an indication of the original 
source of information regarding this matter. 
Piergiorgio Cao, MD 
Unid Operativa di Chirurgia Vascolare 
Policlinico Monteluce 
Via Brunamonti 
06122 Perugia 
Italy 
24/41/92212 
Regarding "Variability and reliability of air plethys-
mographic measurements for the evaluation of 
chronic venous disease" 
To the Editors: 
We welcomed and read with interest the above-named 
article by Yang et al (J Vasc Surg 1997;26:638-42) that 
appeared recently in the Journal of Vascular Surgery. 
Because we are familiar with the machine and the test pro-
tocol, 1 it is our belief that there are important issues to be 
discussed before accepting the conclusion of this work. 
It is unclear to us exactly what equipment was used by 
the authors . The APG air plethysmograph Model 1000 or 
1000 C from ACI Medical (San Marcos, Calif) is the only 
commercially available model . The authors described a 
somewhat different device (possibly a modified version 
that may use certain components of the original ACI 
product) and also deviated from the published standard 
test protocols,2,3 which could explain the variability of 
their published data. 
First, the original sensing cuffs that were supplied by 
the manufacturer were made of polyurethane and not 
polyvinyl chloride. According to Ed Arkans, the President 
of ACI Medical and an engineer by trade, who was con-
sulted in this matter, cuffs that are made of polyvinyl chlo-
ride would show significant "creep" and would not pro-
duce a stable output nor repeatable results from 1 test to 
another. Therefore, they should never be used for sensing. 
Second, the calibration method that was described is 
753 
754 Letters to the Editors 
also different from the IOO-mL method that was supplied 
with the original product and that was used by other 
investigators and us. The use of the smaller 50-mL cali-
bration volume does not adequately cover the range of calf 
venous volumes that are closer to the neighborhood of 
100 mL. 
Third, the authors waited only 3 minutes between ser-
ial tests. This is far too short of time than would be neces-
sary for a patient's arterial inflow to return to resting lev-
els after the exercise protocol of the test. This short wait-
ing time will result in elevated venous volumes and 
increased venous filling indices. Indeed, after-exercise test-
ing of the author's design showed the greatest measure-
ment variability. A IO-minute to I5-minute period is more 
appropriate to remove the confounding effect of exercise 
hyperemia. 
Fourth, the authors had the patients' elastic stockings 
removed just before testing. This practice is not recom-
mended for repeatable results because the effect of the 
compression garments may last up to 24 hours after their 
removal.4 Thus, it is important to instruct patients not to 
wear their compression stockings the day of the test if one 
is to expect repeatable serial results. 
Finally, the authors chose not to perform the key tests 
for outflow obstruction and superficial collateralization 
(by finger occlusion of the long saphenous vein).5 Those 
tests, along with the protocols for reflux and calf muscle 
pump function, are all standard APG tests that provide the 
examiner with the complete hemodynamic picture of each 
patient who is examined. In summary, it is our belief that 
the authors made 2 general errors. They have modified a 
well-tested manufacturer's device without regard to prop-
er engineering considerations and have also introduced a 
personal and deviant testing protocol. Both steps resulted 
in interpretation errors. 
In our personal experience, the manufacturer has been 
quite helpful in identifYing protocol problems and in help-
ing with experimental device modifications. They should 
have been consulted before hemodynamic information 
was improperly acquired and conclusions published. 
Gabriel Goren, MD 
Vein Disorders Center 
Encino, Calif 
REFERENCES 
1. Goren G. Regarding "Venous ulcers and the superficial 
venous system. J Vase Surg 1993;17:716-8. 
2. Nicolaides AN, Sumner DS. Air plethysmography. Inves-
tigation of patients with deep vein thrombosis and chronic 
venous insufficiency. 1st ed. London: Med-Orion; 1991. p. 
43-50. 
3. Come rota AT, Harada RN, Eze AR, Katz ML. Air plethys-
mography: a clinical review. Int Angiol 1995;14:45-52. 
4. Labropoulos N, Leon M, Volteas N, Nicolaides AN. Acute 
and long term effect of elastic stockings in patients with vari-
cose veins. Int Angiol 1994;13:199-23. 
JOURNAL OF VASCULAR SURGERY 
October 1998 
5. Nicolaides AN, Sumner DS. Outflow fraction. Investigation 
of patients with deep vein thrombosis and chronic venous 
insufficiency. 1st ed. London: Med-Orion; 1991. p. 61. 
24/41/92673 
Reply 
Thank you for the opportunity to reply to the com-
ments made by Dr Goren. Dr Goren's concern appears to 
be focused on the concept that the APG air plethysmo-
graph as supplied by the manufacturer ACI Medical (San 
Marcos, Calif) may be more accurate and more repro-
ducible in the performance of repeated tests in patients 
with chronic venous disease than our study has indicated. 
Our concern from this study was not with any specific 
brand or type of air plethysmograph but rather with the 
inherent variability in the overall methodology in this spe-
cific group of patients. Such variability is almost certainly 
related to problems with this group of patients being able 
to consistently and accurately reproduce exactly the same 
degree of muscle contraction during the tiptoe move-
ments and the same leg position, degree of immobility, 
and relaxation after the tiptoe movement. Variations in 
these parameters rather than inherent inaccuracy in the 
equipment is almost certainly the cause of the variation 
that we observed in this study. 
In response to the specific points raised by Dr Goren, 
the device that we used consisted of the sensing cuff sup-
plied by the manufacturer ACI Medical (Sun Valley, Calif) 
and a pressure transducer and recorder that was described 
in the paper. The sensing cuff is constructed from Dr 
Goren's letter polyurethane and not polyvinyl chloride as 
we had reported (there is no record of the material on the 
cuff itself). The air plethysmograph that we used was con-
structed separately and was not model 1000 or 1000 C or 
a modification of one of these. The equipment that we 
used produced accurate and reproducible measures of 
alteration in cuff volume when tested before application to 
patients. The same is, I assume, almost certainly the case 
for the APG air plethysmograph. 
The testing protocol used in our study was exactly the 
same as the protocols that were reported previously, how-
ever, additional measurements were made on the tracings 
in this study, and these have not been previously reported. 
Before starting these studies, we evaluated the calibration 
volume and found a linear relationship between the 
50-mL and IOO-mL calibration volumes. Because the 
50-mL calibration is easier to perform, this calibration was 
used in our studies. Because of this linear relationship, this 
would not have accounted for the extent of the variation 
in the volume parameters that were measured. We added 
to our protocol additional interpretation and analysis of 
the tracing after the patient had performed 10 tiptoe exer-
cises. This was performed in the hope that it would pro-
vide more reproducible data, however, this was not the 


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Regarding “Variability and reliability of air plethysmographic measurements for the evaluation of chronic venous disease”

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