Yellow Springs Instrum ent Co., Yellow Springs, Ohio, U.S.A.

Transcription

1 THE TEMPERATURE OF REBREATHED AIR, AND THE ARTERIAL BLOOD : REBREATHED AIR ALCOHOL RATIO. Roll a N. Harger and Robert B. Forney Indiana U n iv e rs ity, U.S.A. Although most o f the present q u a n tita tiv e breath alcohol instrum ents are presumed to employ a lv e o la r a ir, the samples o f end e x p ira to ry a ir used a c tu a lly have an ethanol vapor pressure which is lower than th a t in the a lv e o li. is because the mucosa o f the upper re s p ira to ry tr a c t has a temperature which is lower than 37 C., and removes some ethanol from the pulmonary breath. This In a 1930 paper ( 1 ), L ilje s tra n d and Linde reported th a t the temperature o f breath le avin g the mouth is 31 C. A 1942 review o f published researches on th is s u b je c t, by Winslow e t a l., stated (2 ): "The temperature o f the expired a ir under normal conditions is 32 to 35 C.;." In 1950, Harqer e t a l. reported (3) breath temperature measurements during prolonged, forced e x p ira tio n, w ith re s u lts which e s s e n tia lly confirmed the values given by Winslow e t a l. I. TEMPERATURE RANGE OF REBREATHED AIR. We have re c e n tly measured the temperature o f rebreathed a ir, obtained by a procedure which we described in 1956 (4 ). The breath is c o lle c te d in a 2 L. polyethylene bag*, the open end o f which is pleated around a 12 cm. length o f r ig id p la s tic tubing w ith a diam eter o f about 1.7 cm., and the bag is held to the tube by rubber bands. P rio r to ta k in g the sample, the bag and it s mouthpiece are wanned in s id e an e le c tric a lly -h e a te d, zippered sack, w ith it s in te r io r temperature m aintained a t C. With his nose closed by lig h t pressure ju s t above the n o s t r ils, the subje ct in fla te s the warmed bag and then rebreathes th is a ir fo u r tim es, le a vin g the bag in fla te d a t the end o f the opera tion. For measuring breath temperatures in our 1950 study, we used a copper- c onstantin thermocouple o f 0.2 mm. w ire and a s u ita b le ammeter. In the present study we have employed a YSI* * Model 43 Tele-Thermometer and a YSI No. 405 Therm istor probe designed fo r a ir tem peratures. time o f th is probe is about 0.25 second. In moving a ir, the response For in s e rtin g the Therm istor probe in to the bag, a second length o f the 1.7 cm. p la s tic tube was attached to the bag through a hole made in the bottom o f the la t t e r, and held there by rubber bands. k Coldspot fre e z e r bag, Sears Roebuck & Co., U.S.A. Yellow Springs Instrum ent Co., Yellow Springs, Ohio, U.S.A.

2 With a room temperature o f about 23 C., and the bag and it s p la s tic tube connections pre-warmed as usual, the baq was q u ic k ly removed from the warming sack, the Therm istor probe was in serte d in to the bag through one o f the in le t tubes, and th a t tube was closed by a s p lit rubber stopper surrounding the lead to the probe. With an attendant holding the probe in le t tube so th a t the head o f the probe was maintained near the center o f the bag, the sub je ct then c a rrie d out the rebreathing procedure as described. The atten dan t recorded the temperature in side the bag a t the end o f the f i r s t e xh alation and a t the end o f the f i f t h e x h a la tio n. study. Twenty a d u lts, 15 men and 5 women, were used in th is The re s u lts obtained are summarized in Table I below. TABLE I. TEMPERATURE RANGE OF REBREATHED AIR. Temperature read a t: Range Average _BC "C A. End o f f i r s t exhalation B. End o f f i f t h exhalation Average o f A and B Thus, the average temperature o f the rebreathed a ir, du rin g the c o lle c tio n period was close to 34 C. With a few o f the s u b je c ts, the rebreathing experiment was repeated w ith the Therm istor probe in sid e the p la s tic mouthpiece. Here there was a marked p u lsa tio n o f temperature w ith each re s p ira to ry c y c le, the readings being about 32.5 C. a t the end o f an in s p ira tio n, and about 34.4 a t the end o f an exh alation. The 20 subjects were also asked to exhale as deeply as p o s s ib le, through a 12 cm. length o f the p la s tic tu b in g, in to which the Therm istor probe had been in s e rte d. The temperature a tta in e d a t the end o f the forced exh alation ranged from 34.4 to 35.7 C., and averaged 35.1"C. When the expired a ir was f i r s t passed through an unwarmed B reathalyzer mouthpiece, and then through the 1.7 cm. p la s tic tube contain ing the probe, the average temperature peak was only about 33.5 C. I I. IN VITRO DISTRIBUTION OF ETHANOL BETWEEN BLOOD AND AIR, AND BETWEEN WATER AND AIR. In 1950 Harger e t a l. (5) published the re s u lts o f extensive experiments to determine the e q u ilib riu m d is tr ib u tio n r a tio (Ostwald p a r titio n constant) o f ethanol between a ir as one phase, and w ater, blood o r u rin e as the o th e r. re s u lts fo r a ir : water and a ir : blood are given in Table I I below: The II. 74

3 TABLE I I. PARTITION RATIO OF ETHANOL BETWEEN WATER AND AIR, AND BLOOD AND AIR. Temp. C Wt. o f ethanol per l i t e r o f a ir Wt. o f ethanol per ml o f liq u id B lo o d :A ir Ratio Water Blood ,000 : ,150 : Q * 2,540 2, * 2, , , U ,420 In te rp o la te d from values fo r 30 and 35 Our 195u alcohol p a r titio n r a tio values fo r water and a ir agreed w e ll w ith those o f most e a r lie r in v e s tig a to rs, and were la te r confirmed by Grosskopf ( 6). For the system, blood : a ir, apparently the only published p a r titio n ra tio s are fo u r determ inations by L ilje s tra n d and Linde (1) and the much la rg e r se rie s by ourselves, lis te d in Table I I. Since these values are v it a l fo r any breath alcohol procedure, we would welcome fu r th e r in - v it r o studies o f the blood : a ir system. Reported blood plasma : a ir studies apparently comprise ju s t one determ in atio n by ourselves (5 ). Such blood plasma data are u rg e n tly needed i f one wishes to estim ate the le vel o f plasma alcohol from analysis o f breath. I I I. REBREATHED AIR - BLOOD STUDIES WITH HUMAN SUBJECTS, USING THE DRUNKOMETER. Since 1954 we have conducted many studies in v o lv in g alcohol analyses of blood and rebreathed a ir obtained sim ultaneously from d rin k in g s u b je cts. o f our subjects ingested 1.03 or 0.69 grams o f ethanol per k ilo, during a period o f 1/2 hour, which dose corresponds to 6, or 4, f lu id ounces o f 100-proof liq u o r fo r a 150 lb. person. The rebreathed a ir samples were obtained as described above, and th e ir alcohol concentration determined by the H2SO4 - permanqanate method o f Harger, w ith the volume o f rebreathed a ir used to reach the end p o in t measured w ith a qasometer made from a dry glass syringe (4 ). c a lc u la tin g the blood alcohol concentration from the concentration in the re breathed a ir, we used the 2,100 : 1 r a tio. This assumes th a t the w eiqht o f Each For II. 75

4 II. 76 ethanol present in 1 ml o f the s u b je c t's blood is present in 2.1 lit e r s o f his rebreathed a ir. Four o f these rebreathed a ir - blood studies w ill now be b r ie f ly described: Study No. 1 ; 1954 ( 4 ). F in g e rtip blood was used in th is stud y, which comprised 54 te s ts w ith 31 s u b je cts. We waited one hour a fte r the end o f d rin k in g before takin g the f i r s t sam ples.of blood and rebreathed a ir. c h ie f re s u lts obtained are given in Table I I I. Study No. 2; 1962 ( 7 ). Other d e ta ils and the This study was conducted lik e No. 1, except th a t the sampling o f fin g e r tip blood and rebreathed a ir was begun ju s t lb minutes a fte r the end o f d rin k in g. The re s u lts o f th is study are also given in Table I I I. Study No. 3; 1962 ( 7 ). a rte ry. In th is study we employed a r te r ia l blood from the ra d ia l As w ith study No. 2, sampling o f blood and breath began 15 minutes a fte r the end o f d rin k in g. Table I I I gives the re s u lts o f th is study. Study No. 4; In th is study the blood samples were drawn from the c u b ita l v e in. During the f i r s t hour a fte r the end o f d rin k in g, many o f the d ire c t analyses o f blood showed low re s u lts compared w ith the c a lcula te d re s u lt from the rebreathed a ir analyses. This is due to the marked lag in c u b ita l vein blood alcohol le vel during a ctive absorption (7 ). Table I I I gives the re breathed a ir - blood alcohol c o rre la tio n fo r the period o f 1-3 hours a fte r the end o f d rin k in g, which c o rre la tio n is q u ite s a tis fa c to ry. Study No. Blood Source 1. p** TABLE I I I. ACCURACY OF ESTIMATING BLOOD ALCOHOL LEVEL FROM ANALYSIS OF REBREATHED AIR, USING THE DRUNKOMETER. Time a fte r end o f d rin k in g No. o f Subje c ts No. o f Tests B lood-breath c o rre la tio n F ra c tio n * F ra c tio n * w ith in beyond +5% +10% + 15% +15% 1-3 hrs p** 1/4-3 hrs /4-1.5 hrs V# 1-3 hrs * F raction o f to ta l te s ts ; F = F in g e rtip ; A u = Radial a rte ry ; V = C ubital veil In study No. 3, one te s t out o f the 14 gave -16% d e v ia tio n fo r the rebreathed a ir value. As explained in our paper (7 ), we re a liz e d th a t we had passed the end p o in t in th is p a r tic u la r Drunkometer a n a ly s is, but could not repeat th is te s t because a second subje ct was due to be tested in 7 m inutes. In study No. 3 a ll rebreathed a ir re s u lts were s lig h t ly below those from d ir e c t an alysis o f the a r te r ia l blood, averaging -4%. We be lie ve th a t the re s u lts presented in Table I I I in d ic a te th a t the 2,100 : 1 fa c to r fo r estim a tin g the blood alcohol le v e l from the le v e l in the

5 rebreatlied a ir, is approxim ately c o rre c t. The re s u lts in study No. 2 are less s a tis fa c to ry than those o f the other three s tu d ie s, because the le v e l o f alcohol in fin g e r tip blood lags somewhat behind th a t o f a r te r ia l blood fo r a t le a s t 30 minutes a fte r the end o f d rin k in g. IV. COMPARISON OF THE USE OF REBREATHED AIR AND END EXPIRATORY AIR FOR BREATHALYZER ANALYSES. Two studies in v o lv in g th is type o f comparison were made: A. TESTS USING THE SAME BREATHALYZER. In th is study 31 d rin k in g subjects were given two bre a th a lyzer te s ts in rapid succession, one in the usual way and the second using the same instrum ent and rebreathed a ir. For the la t t e r te s t, the subje ct performed rebreathing w ith the warm p la s tic bag, and the closed bag was returned to the warming sack. The d e liv e ry tube o f the p la s tic bag was then connected to the breathing tube o f the B reathalyzer and pressure was applied to the warming sack to f i l l the B reathalyzer chamber and p a rtly flu s h i t o u t. The c o rre la tio n between these two te s ts made on each o f the 31 subjects is given in Figure I. A nalysis o f the data showed th a t the average d e v ia tio n o f the a lv e o la r a ir re s u lts from the rebreathed a ir re s u lts was -9%. REBREATHED AIR (mg Alcohol/2.1 L) B. TESTS USING TWO DIFFERENT BREATHALYZERS AND FINGERTIP BLOOD. With as l i t t l e delay as possible between sam plings, each o f 49 d rin kin g

6 subjects was given the usual B reathalyzer te s t using a lv e o la r a ir, a Breatha ly z e r te s t using rebreathed a ir, and a sample o f his fin g e r tip blood was H^aun fo r la te r a n a ly s is. The average d e v ia tio n o f the rebreathed a ir values from the fin g e r tip blood va-ues was %, w h ile the corresponding average d e via tio n o f the a lv e o la r a ir values from the blood values was -7%. We are presenting th is apper in the hope th a t some o f our colleagues in the chemical te s t f ie ld might be induced to tr y out rebreathed a ir vs. a r te r ia l blood w ith th e ir p a rtic u la r breath alcohol instrum ents, and miqht even be w illin g to perform the drudgery o f fu rth e r in - v it r o determ inations o f the p a r titio n r a tio o f alcohol between a ir and whole blood, o r blood plasma. REFERENCES 1. L ilje s tra n d, G., and Linde, P.: Skandinav. Arch. f. P hysiol. 60:18, J 2. Winslow, C.E.A., H errington, L.P., and Nelbach, J.H.: Am. J. Hygiene 35:27, Harger, R.N., Forney, R.B., and Barnes, H.B.: J. Lab. C lin. Med. 36:306, Harger, R.N., Forney, R.B., and Baker, R.S.: Quart. J. Stud. A le. 17:1, Harger, R.N., Raney, B.B., B rid w e ll, R.G., and K itc h e l, M.F.: J. B io l. Chem. J83:197, Grosskopf, K.: Angew. Chem. 3:306, Forney, R.B., Hughes, F.W., Harger, R.N., and Richards, A.B.: Quart. J. Stud. A le. 25:205, II. 78