742

the feet-down position the pulse-rate was approxi-mately the same as in the horizontal.When the subject was moved from the horizontal

to the feet-down position the blood pressure wasunaltered, but in the head-down position there wasan increase of 9 per cent. during natural breathing.Similar variations were observed as a result of the

TABLE III.-Pulse-rate

more frequent changes of position during rocking.Measurement of the amplitude of the pulse oscillationsrecorded during rocking showed that the systolicpressure was increased by about 10 per cent. whilethe subject was in the head-down position. For ithas been shown by Erlanger (1905) that changes inthe systolic blood pressure are indicated by changesin the amplitude of the pulse oscillations.

DISCUSSION

A comparison of the tidal air induced by rockingon the stretcher with that produced by Schafer’smethod indicates that the rocking method is at leastas effective as any of the manual methods. Therocking method has the advantage over the pronepressure method of requiring less exertion in perform-ing the necessary movements. Artificial respirationcan therefore be maintained more easily over longperiods. Further, the method can be applied by anuntrained operator, following simple instructionsas to timing. Warmth, a factor so important andso commonly neglected, can be adequately applied.

Investigation of the circulatory changes inducedby rocking show that their magnitude is not such asshould be of clinical importance. As to the variationsin the gaseous exchange with different rates of rocking,the figures show that at rates above 15 per minutethere is a tendency to over-ventilate, and hencewash out CO2 in amounts disproportionate to theamount of oxygen which can be absorbed. SinceCO2 is an important stimulus to the normal activityof the respiratory centre, the onset of spontaneousbreathing might be delayed if its amount in theblood should be too far reduced. Since measure-ments of the lung ventilation show that rockingthe stretcher 10 or more times a minute induces

adequate ventilation, we may conclude that formost subjects the optimum rate of rocking thestretcher lies between 10 and 15 per minute-i.e.,the normal rate of breathing.

In practice, of course, Schafer’s method must betried without an instant’s delay, and used till therocking stretcher with blankets and hot bottles canbe brought alongside and employed if resuscitationis delayed or inadequate.

Our thanks are gratefully accorded to Prof. B. A.McSwiney for his advice and criticism. Also toMr. W. Riley, of the Wakefield mines rescue station,and to Messrs. Siebe Gorman, of London, for theirhelp on the practical and manufacturing sides.

REFERENCES

Erlanger, J. : Jour. Exper. Med., 1905, vii., 676.,, ,, : Arch. Internal Med., 1912, ix., 22.

Eve, F. C. : THE LANCET, 1932, ii., 995.Opitz, R. Burton : Amer. Jour. Physiol., 1922, lxi., 562.Schafer, E. A. : Trans. Med. Chir. Soc. Lond., 1904, lxxxvii., 609.

,, ,, : Jour. Amer. Med. Assoc., 1908, li., 801.

AN ELECTRICAL METHOD

FOR USE IN THE DIAGNOSIS OF

DISEASES OF THE THYROID GLAND

BY M. A. B. BRAZIER, PH.D., B.Sc. LOND.RESEARCH WORKER AT THE CENTRAL PATHOLOGICAL LABORATORY,

LONDON COUNTY MENTAL HOSPITALS

IT has long been known that certain electrical

properties of the body are affected by diseases ofthe thyroid gland. Vigouroux made the observa.tion in 1888 that the resistance of the body to adirect current is influenced by the thyroid gland.More modern work with alternating currents hasfollowed this, and Lueg and Grassheim 2 have shownthat what they term the " Kondenser-wert

" of theskin varies in thyroid diseases in such a way as tobe of diagnostic value. The method used by theseworkers was that of Gildemeister.3

In the present research an improved method hasbeen developed for studying the impedance of thehuman body to an alternating current; this methodhas been published in full technical detail elsewhere,4together with a detailed criticism of Gildemeister’smethod, giving the reasons why it was not adoptedfor the present work.The electrical characteristic of the human body

which is under investigation in this paper is termedthe " impedance angle " ; a full discussion of thisproperty, together with its mathematical derivation,will be found in the paper cited, so that it is sufficienthere to give a short definition of this term and tooutline in brief the technique for its estimation.

In constant current work the impedance of thebody can be measured by a single factor-namely,the resistance ; but with alternating currents the

body functions not only as a resistance but also asa condenser. The ratio of these two factors is a

property of the dielectric under observation (in thiscase the body), and it is a function of this ratiowhich shows variations in thyroid disease, and whichis defined as the impedance angle.The method in brief is as follows.

The patient sits on a chair with each arm immersed tothe elbow in arm-baths containing salt solution. Eacharm-bath contains 10 litres of 1 per cent. NaCl at a

temperature of about 25° C. It has been shown thatthe results are unaffected by variation of the temperatureof the arm-baths, by slight movements on the part ofthe patient, by the emotional state of the patient, or bythe strength of the current passing through the body.No preparation of the patient by resting or fasting 4is necessary, and only a very slight degree of cooperationis required. The full test is accomplished in less thanten minutes. All these factors make it an extremelyconvenient method of investigating out-patients.When the arms have been immersed in the arm-baths,

an alternating current sufficiently low in intensity to beimperceptible to the patient is led through him into asimple bridge circuit. The impedance offered by thepatient to the current can be balanced on the bridge byadjusting a variable condenser and a variable resistance,and from these readings the impedance angle can becalculated. For the full details of this process the paperalready cited 4 should be consulted.

It may be mentioned that a new form of the apparatushas now been designed which is easily portable and hasthe advantage of being a direct reading instrument, sothat calculation is eliminated.

Study 4 of the normal subject shows that theimpedance angle remains almost constant from dayto day in the same individual, and normal groups giveonly a small standard deviation (S.D) about the mean

743

for the impedance angle (LA.). The values for menand for women fall into two well-defined groups, thewomen giving higher values* ; they are thus alwaystreated as two separate groups, the mean for eachgroup being taken as the zero for that sex. This

arbitrary system of units has proved more convenientfor clinical use than the expression of themeasured value of the impedance angle.

In the present work all the patientsexamined were women, and the resultsare therefore compared with the meanfor normal women, which has beenestablished 4 to be 0±2-3 (S.D.=10.1).Any variation from this mean is expressedas a plus or minus difference.

THE IMPEDANCE ANGLE IN THYROID

DISEASE

In order to determine whether thereis a significant departure from this meanin cases of thyroid disease, 120 patientswere examined. For facility in examiningthe great majority of these patients I amindebted to Mr. C. A. Joll, F.R.C.S.From a study of the results it imme-

diately becomes clear that in thyro-toxicosis there is a very marked deviationfrom the normal, these cases giving veryhigh values for the impedance angle-values which innearly all cases are far outside the standard deviationof the normal group.

As a preliminary comparison the means for thegroups of primary thyrotoxicosis and secondarythyrotoxicosis may be compared with that of thenormal women and with the mean of a group ofnon-toxic goitres (Table 1.).From these figures it is evident that the increase

in impedance angle in thyrotoxicosis is so great thateven the means for these two groups are greaterthan twice the standard deviation of the normals.Statistically these differences are of a significancebeyond all possible error of chance.

It is found that in general the severer the diseasethe higher the impedance angle, and in this way theimpedance angle can be correlated with the basalmetabolic rate. It may be noted here that the

impedance angle is not dependent on the basal

FIG. 2.-Basal metabolic rates. Frequency distribution curves forthyrotoxicosis and non-toxic goitres.

metabolic rate. It has been shown in another pieceof research (in collaboration with Dr. F. M. Grant)that in the absence of a thyroid factor the impedance’*’ In order to conform with Gildemeister’s practice theimpedance angle used throughout this paper is formally measuredwith respect to the vector corresponding to a pure capacitance.It thus corresponds with the dielectric loss angle 8 in the studyof dielectrics. For a discussion of this convention see thepaper cited.’ *

angle is independent of the B.M.R., but in all caseswhere the B.M.R. is raised by thyrotoxicosis, bythyroid feeding, or by thyroxine or thyroid injection,then the LA. will also be raised. In this way the

impedance angle proves a more specific test for

thyroid disturbance than does the B.M.R.

FIG. I.-Impedance angles. Frequency distribution curves for thyrotoxicosisand non-toxic goitres.

In Fig. 1 the frequency distribution curve for theimpedance angles of 84 cases of thyrotoxicosis is

compared with that of the 33 cases of non-toxic

TABLE I

goitre. A striking point in Table I. is the fact thatthe non-toxic goitres not only fail to give increasedimpedance angles, but in fact give values in generallower than normal; thus the mean for this group

is-9-8. This point is brought out evenmore clearly in the frequency distribu-tion curves in Fig. 1.

This fact of the impedance angle beingin general lower than normal in the caseof non-toxic goitres makes this test

extremely useful in the detection of

early toxic symptoms. It is also ofinterest in view of the fact that it hasbeen claimed by Kocher,5 by Dodds,Lawson, and Robertson,6 by Boothby 7and others, that the B.M.R. of thesecases is very often below normal. Thiswas not confirmed by the B.M.R.results of the non-toxic goitre cases

examined in the present research ; but asthere are only 11 cases where the B.M.R.was obtainable, no definite conclu-

sion can be drawn from them. Joll 8 quotes 30 casesof colloid goitre, giving an average B.M.R. of +8-5per cent. and 100 cases of nodular goitre with anaverage B.M.R. of - 1-7 per cent.The frequency distribution curves for the B.M.R.’s

of 46 of the same cases of thyrotoxicosis and of12 cases of non-toxic goitre are given in Fig. 2. Itwill be seen that 29 out of the 46 cases of thyrotoxicosis

744

gave B.M.R.’s above the normal range (-20 percent. to +20 per cent.), i.e., 63 per cent. Thiscan be compared with Fig. 1, where it is seen that69 out of the 84 cases of thyrotoxicosis gave impedanceangles above the normal limits (-10 to +10, thestandard deviation of the impedance angle for normalwomen being 10-1), or 82 per cent. As a singleclinical test, therefore, the impedance angle appearsto be a more reliable aid to correct diagnosis thanthe B.M.R., quite apart from the advantage of itsspecificity.

There occurred in this series an anomalous caseof primary thyrotoxicosis in which the B.M.R. wasextremely low. The impedance angle was, however,above normal. In brief the details of this case werethese :-CASEA.-B.M.R.= -15 per cent. LA.= +24. Clinical

picture : sudden onset of symptoms; breathlessness,headaches, excessive sweating, exophthalmos, exhaustion,dysphagia, tremor, and tachycardia associated with rapidfirm enlargement of the thyroid. Operative findings :moderately severe, fairly widespread hypertrophy andhyperplasia of the Graves’s type ; fibrosis moderate ;lymphorrhages few and small. Diagnosis: primarythyrotoxicosis.

This type of case in which the B.M.R. is low inspite of every other symptom indicating a toxiccondition is not really very uncommon. Troell 9

quotes 12 of his cases as giving low B.M.R.’s, allof which on operation showed the typical microscopicpicture of primary thyrotoxicosis. His explanationthat these low B.M.R.’s are due to remissions in thedisease seems scarcely adequate. Bram 10 quotes74 cases of untreated Graves’s disease, all showingno increased basal metabolic rate. In the case

detailed above the impedance angle would be a

more reliable guide than the B.M.R.The behaviour of the impedance angle in patients

after partial thyroidectomy for thyrotoxicosis is alsoof interest. During the first few months followingthe operation there is a decrease of impedance angleto below the normal level and then, as the remainingportion of the gland slowly adjusts itself to the taskof taking on the work of a normal thyroid, the

impedance angle gradually returns to the normal level.In other words, the LA. behaves after partial thyroid-ectomy in a similar way to the weight curve 11 andthe basal metabolic rate curve.ll Both these proper-ties behave as though the operation were followedby a quite temporary post-operative myxoedema,which is soon obliterated as the gland takes on itsnormal function.

TABLE II

In Table II. are given the pre- and post-operativefigures for 13 cases of thyrotoxicosis and 1 case

of non-toxic goitre (Case 14). It is interesting that

the only case (Case 14) which showed an increasein impedance angle following partial thyroidectomyis that of the non-toxic goitre, and here the result iswithin normal limits both before and after theoperation.

In concluding, it may be of interest in view of itscomparative rarity to report the findings on a caseof Riedel’s disease.

CASE B.-B.M.R.= +6 per cent. I.A.=O. Clinical

picture : marked exophthalmos, some tachycardia, finetremor ; bilateral firm enlargement of the thyroid, greateron the left side ; one or two nodules were palpable. Opera-tive findings : the right lobe contained two parenchymatousadenomata ; widespread and well-marked infiltration withplasma cells and lymphorrhages which had broken upthe acini and also collections of these cells were scatteredthroughout the gland ; considerable fibrosis. Diagnosis :the condition is an early stage of Riedel’s disease.

A single case of malignant adenoma occurred inthis series, the impedance angle being found normal.

CASE C.-LA.= -4. Clinical picture : firm localisedswelling in the lower pole of the left lobe of the thyroid;dyspnoea. Operative findings : adenoma with earlymalignant changes.A case of " masked hyperthyroidism " may be

reported here.CASED.—B.M.R.= +25 per cent. I.A.= +32. Clinical

picture : no visible or palpable goitre, severe tachycardia,auricular fibrillation, very slight exophthalmos, coarse

tremor, some oedema of feet, loss of weight.It is concluded from the series of results detailed

above that the impedance angle forms a very reliableaid to the diagnosis of toxic conditions of the thyroidgland. In this respect it is more specific and morecertain than the basal metabolic rate. The test itselfis open to less experimental error than the B.M.R.estimation and is particularly adaptable to the

investigation of out-patients.This line of research is now being extended to

include the study of myxoedema and cretinism.

This research was carried out with the aid of a

grant from the Medical Research Council, and underthe direction of Dr. F. L. Golla, to whom my thanksare due. I am especially indebted to Mr. Joll foradvice and help throughout this work, and for thegreat majority of the cases examined. For opportunityto examine the remainder of the cases I have to thankDr. Terence East, Dr. J. L. Livingstone, andDr. Edward Mapother and his staff at the MaudsleyHospital.

BIBLIOGRAPHY

1. Vigouroux, R. : Progrès Méd., 1888, xvi., 45.2. Lueg, W., and Grassheim, K. : Zeits f. Klin. Med., 1929,

cx., 531.3. Gildemeister, M. : Pflüger’s Archiv, 1919, clxxvi., 84.4. Brazier, M. A. B.: Jour. Inst. Elect. Engineers, 1933,

lxxiii., 203.5. Kocher, T. (quoted by Crile, G. W.) : Diagnosis and

Treatment of Diseases of the Thyroid Gland, Philadelphia,1932, p. 75.

6. Dodds, E. C., Lawson, W., and Robertson, J. D.: THELANCET, 1932, ii., 608.

7. Boothby, W. M. : Endocrinol., 1921, v., 12.8. Joll, C. A. : Diseases of the Thyroid Gland, London,

1932, p. 235.9. Troell, A. : Hygiea (Sweden), 1932, xciv., 45.

10. Bram, I. : Endocrinol., 1933, xvii., 23.11. Joll : Op cit (ref. 8), pp. 582 and 619.

BELFAST HARBOUR ISOLATION BASE.-It is pro-posed to utilise Purdysburn Fever Hospital as alter-native accommodation to the isolation base in Belfastharbour. The medical dep6t at the harbour has been inexistence for 25 years, but there has never been a seafaringpatient in the isolation hospital. From time to timepatients from the city and certain " contacts " have beentreated there, but from a shipping point of view it has neverbeen needed.