Diagnostic finger systolic blood pressure in the assessment of vasospastic reactions in the finger skin of vibration-exposed

NASUY, NOSET. Diagnosticvalueof finger systolicblood pressurein the assessment of vasospastic reactions in the finger skin of vibration-exposedsubjects after finger and body cooling. Scand J Work Environ Health 1991:17:184-9. To assessthe severityof vibration-induced white finger (VWF), finger systolicblood pressure (FSBP) after finger cooling and after combined finger and body cooling was measured by strain-gauge plethysmography for 100vibration-exposed men and 22 healthy men. The exposed men were classifiedas being without VWF (EW), with mild VWF (EM), and with severeVWF(ES) accordingto records of blanching attacks. FSBP was significantlyreduced only in the ESgroup after fingercoolingand in the ESand EMgroups after both body and fingercooling. The diag nostic sensitivityand specificityfor VWFwas 81.7 and 90.3 070, respectively. Skin temperature measure ments before and after immersion in cold water (5°C, for 10min) could not be used for the estimation of VWF severity.

nosing VWF (10)(11)(12). It remained unclear, however, whether this method is useful for assessing the severity of VWF. The aim of this study was to evaluate the diagnostic value and sensitivity of FSBP measurements after cold provocation as a method of assessing the severity of VWF, especially in comparison with skin temperature measurements after cold-water immersion.

Subjects
One hundred men who had received the annual compulsory examination for vibration syndrome at the San-in Rosai Hospital were examined. They consisted of 75 chain sawers, 9 rock drillers, 7 bush cleaners, 3 grinders, and 6 men in miscellaneous trades. All of them had stopped using vibrating tools more than one year before the examination. None of them suffered from metabolic or vascular disorders except for VWF. Twenty-two healthy men who had never worked with vibrating tools were subjected to the same measurements for comparison. A total of 122 men gave their informed consent and were examined. The subjects were classified according to the severity of VWF as judged in a medical interview. They were divided into the following four groups: (i) referents: 22 healthy men [mean age 51.5 (range 39-66) years, 11 smokers] without vibration exposure, (ii) exposed subjects without VWF (EW): 40 men [mean age 56.4 (range 48-70) years, 18 smokers] without VWF in the last year, (iii) exposed men with mild VWF (EM): 36 men [mean age 56.4 (range 24-71) years, 19 smokers) with several at-tacks of VWF in the last year, and (iv) exposed men with severe VWF (ES): 24 men [mean age 59.6 (range 49-75) year s, 12 smokers) with frequent attacks of VWF in the last year. All the subjects were examined in the winter of 1986-I987.

Measurement of finger systolic blood pressure after cold provocation
No vasoactive drugs were allowed for at least a week prior to the examination. Food intake and tobacco smoking were avoided for at least 2 h before the examination. The subjects were examined in a room with the temperature and humidity controlled at 26°C and 50 070, respectively. They were lightly dressed and rested for at least 30 min in the room before the examination.
FSBP was measured with a strain-gauge plethysmograph (SP-2, Medimatic, Copenhagen) with the subject in the supine position. An occluding cuff, 2.4 x 10 ern in size, and a double-inlet cuff, 3.0 x 10 cm in size, were placed on the proximal and middle phalanges, respectively, of the most affected finger (figure I). Only the occlud ing cuff was placed on the proximal phalan x of the thumb as a reference finger. For the subjects without symptoms, the middle finger and the thumb were used. Strain gauges were placed on each distal phalanx. Finger warming and cooling were performed with a double-inlet cuff for 5 min .
During the provocation, digital blood circulation was stopped with suprasystolic pressure by the occluding cuff. First, we measured FSBP by slowly deflating the occlusion cuff and recording the first increase in fingertip volume with a strain gauge after local heating of the finger at 35°C for 5 min . The test was repeated after only local cooling of the finger at 10°C for 5 min . After an inter val of more than 30 min, the FSBP was again mea sured after finger and body cooling at 10°C for 10 min . Downs et al (13) reported that an FSBP of less than 70 mm Hg (9.3 kPa) indicated arterial obstruction. An FSBP of less than 60 mm Hg (8.0 kPa), which is here strictly defined, may be due to a potent vasospasm. The subjects who showed an FSBP value below 60 mm Hg (8.0 kPa) after finger cooling only were excluded from the test of finger and body cooling. Body coolin g was performed by cooling the back of the body with a water pad perfused with cold water at 10°C. Arm systolic blood pressure (ASBP) was measured by mean s of the auscultatory method on the upper arm of the side oppos ite to that on which the FSBP was mea sured . The change in FSBP during cooling at 10°C was expressed as the percentage of FSBP at 35°C according to the following formula from Nielsen & Lassen (9).
where FSBPx is the pressure mea sured on the cooled finger and FSBPref is the pressure measured simulta-neously on a non cooled reference finger of the same hand. Second, in order to investigate the relationship between each finger's symptom and its FSBP % value, we selected 14 exposed men with VWF at random, and measured the FSBP after finger and body cooling of the bilateral index, middle and ring fingers of each person. A total of 82 fingers (2 defect ones) from 14 men were tested.

Cold-water immersion test
After more than 2 h after the FSBP measurement, the 100 men of the EW, EM, and ES groups were examined in the same room . They were relaxed in a sitting position, and the cold-water immersion test was performed . For each hand, the thermosensitive part of a thermometer was attached to the volar surface of the distal phalanx of the experiment finger. The finger skin temperatures were measured every minute before, during, and after the immersion. The average of the skin temperatures during the 5 min prior to the immersion was regarded as the initial finger skin temperature. The hand was then immersed up to the wrist for 10 min into well-stirred cold water at 5°C. After 10 min of immersion, the immersed hand was removed from the water and wiped dry with a towel. Recordings were continued for 10 min after the immersion . The rewarming response after 10 min of imm ersion was expressed as the recovery rat e as follo ws: Recovery rate (010) Tx-Te x 100,

Ti-Te
where Ti is the initial skin temp erature, Te is th e skin temperatu re at the end of the imm ersion , and Tx is the skin temperature of the immersed finger x minutes after remo val of the ha nd from the water. Recovery rates at 5 and 10 min were calculated .

Statistical methods
The population s from which the samples were drawn were not normally distributed in some of the groups . The existence of a difference among the gro ups was therefore checked with the Kru skal-Wallis rank test.
If the difference was found to be signi ficant , Tukey's method was used to mak e a two-gro up comparison. A P-value of 0.05 was con sidered the minim um level of statistical significa nce.

Finger systolic blood pressure and percentage of change in the finger systolic blood pressure as a diagnostic method for the severity of vibrationinduced white finger
The result s of the ASBP and FSBP me asurem ents are shown in tabl e I. Th ere were no significant differences among the gro ups with respect to the ASBP , the FSBP of the warmed finger and the FSBP of th e referen ce fin ger. The differences in FSBP after fin ger cooling were found to be significant between the ES gro up and the other groups according to Tukey's method. Ho wever, ther e were no significant differences in FSBP between an y of the other groups.
Furthermore, fo r the men who had an FSBP value above 60 mm Hg ( ""8.0 kPa) aft er finger cooling only, th e FSBP was measured after finger and body coo ling. All of th e referents and the members of th e EW group, 34 men in the EM gro up , and 14 men in th e ES group were subjected to the combined cooling test, in which the FSBP of the EM group , as well as th e FSBP of the ES group , differed significantly from that of the other two groups.
Ind ividual values for the FSBP % after local cooling of the finger is shown in figure 2. Six of the 24 men in th e ES gro up showed complete art erial closur e. No subj ects in the refe rence group or the EW gro up and only one su bject in the EM group show ed a zero pressure. If 90 070 is consid ered tentatively as th e lower limit of the normal value of the FSBP %, 16 (66.7 % ) of the 24 men in the ES group, 12 (33.3 %) of the 36 men in the EM gro up, and 5 (12.5 % ) of the 40 men in the EW gro up had abnor mal FSBP % values. Onl y one (4.5 % ) of the 22 men in the refe rence group had an FSBP % value belo w the defined limit. Severe cases were distin guished fro m the oth ers by the ir FSBP % values, although there were la rge overlap s among th e re feren ce, EW , and EM gro ups .
The individual FSBP % valu es a fter combined finger and body cooling are shown in figure 3. In finger and body cooling, the ES and EM groups differed in their FSBP % significantly from the referen ce and EW gro ups. If 90 % is used as the lower limit for the normal FSBP % value, for eith er local cooling or combin ed finger and body cooli ng, 49 of the 60 cases with VWF and 6 of the 62 cases withou t VW F had values Table 1. Systolic blood pressure of the upper arm (ASBP), fing er systol ic blood pressure (FSBP), and reference finger systol ic blood pressu re (FSBPref) of t he reference group and the three group s exposed to vibration after warm and cold provocat ion .

EW EM ES
below the limit. Therefore the diagnostic sensitivity is 81.7 % and the specificity is 90.3 % for VWF . The results of the FSB P measurements on the bilateral index, middle, and ring fingers of 14 random ly selected men with VWF are shown in table 2 gers with mild blanching showed a zero pressure. Statistical differences for the FSBP % value after finger and bod y cooling were disclosed for the fingers without blanching and the respecti ve one s with mild and severe bla nching in the 14 patients ( figure 4).

Cold-water immersion test for assessing the severity of vibration-induced white fingers
The results of the cold -water immersion test (10 min at 5°C) are shown in table 3. There were no significant differences in the skin temperatures and reco very rates of the three groups of exposed workers .

Discu ssion
A significant decrease in FSBP was observed only in the severe VWF group after finger cooling only. FSBP was significantly reduced in the EM and ES groups after combined finger and body cooling. Additional body cooling promoted vasospastic reaction . When the critical value of the FSBP % was defined to be 90 %, the diagnostic sensitivity for VWF was 81.3 0/ 0, and the corresponding specificity was 90.3 % . This sensitivity is not as high as reported earlier (1I, 12). One explanat ion for the higher sensiti vity in the earlier studies ma y be that the patients had been in more ad vanced stages of the disease. Another possible explanation is that the cited studies were performed at room temperatures (9-19°C) lower than in the present work (26°C) . The lowest air temperature at which a human can maintain its body temperature at a resting level of metabolic rate is approximately 26°C (14); below this point heat production increases in proportion to the body-to-air temperature gradient. At room temperatures of 18 to 25°C, the skin temperature in normal subjects has been shown to fall continuously (15).
All digits on both hands were not equally affected with blanching attacks . Th e number of fingers with blanching varied am ong th e patients. The amounts of decreases in the FSBP % after finger and body cooling relat ively cor related with the severity of blanching . Furthermore, the differences in the FSBP % Tabl e 3. Skin temperature and recovery rate after a cold water immersion test (5°C fo r 10 min) of the three groups of vibratlonexposed workers. (EW =exposed group without vibration-tnduced white finger, EM =expo sed group with m ild vibration-induced White fi nger, ES = exposed group wi th severe vibration-induced white finger)  (16 ) used skin temperature measurements after co ld-water immersion for 10 min at 5°C a s a screening test with high sensitivi ty for VWF. However, they did not mention whet her ski n temperature measurements a re useful for evaluating the severity of VWF. In the present study, mea surements of skin temperature after cold-water immersion we re found not to be feasible for d iscrimin ating among exposed men without VWF, those with mild VWF , and those with severe VWF .