plethysmographic methods that when the subject was pinched on the upper

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1 24 J. Physiol. (I95I) II2, 24-2I 6I2.I5.6II.976 THE DECREASE IN HAND BLOOD FLOW FOLLOWING INFLATION OF AN ARTERIAL OCCLUSION CUFF ON THE OPPOSITE ARM BY IAN C. RODDIE From the Department of Physiology, The Queen's University of Belfast (Received 27 March 195) It is well known that many sensory stimuli have a pronounced effect on the blood flow through the hand, provided that the subject is neither cold nor very hot. Stewart (1911) found that the immersion of one hand in water at 6 C. reduced the heat elimination in the opposite hand, and Capps (1936) showed by plethysmographic methods that when the subject was pinched on the upper arm there followed a diminution in blood flow into the hand on the same side. Goetz (1946) has found a decrease in toe volume in response to the rapid inflation of an arterial occlusion cuff on the arm. In many types of investigation ithe blood flow in the hand is measured while procedures are carried out which involve repetitive inflation of arterial occlusion cuffs on the opposite arm. Examples of these are: (1) measurement of arterial blood pressure at fixed intervals; (2) forearm plethysmography, where a cuff is inflated distal to the plethysmograph to stop the hand circulation during blood-flow measurement (Grant & Pearson, 1938). Having regard to the unstable nature of hand blood flows and the extent of their variation in response even to trivial stimuli, experiments were carried out to see if the inflation of a cuff to 2 mm. Hg pressure on the opposite arm caused any significant change in hand flow and if so, whether constant repetition of this stimulus was followed by adaptation. METHODS Observations were made on healthy male students aged 17 to 22 years. Before each experiment the subject rested at the selected room temperature for 1 hr. The room temperature varied in different experiments from 19-5 to 29 C., but in any one experiment was kept as constant as possible, usually varying by not more than 1-2 C. Hand blood flows were recorded by means of a venous occlusion plethysmograph (Barcroft & Edholm, 1945), filled with water at 32 C., the principle being that described by Brodie & Russell (195). The plethysmograph was placed on the right hand half an hour before observations were commenced.

2 HAND BLOOD FLOWS 25 A pneumatic cuff, connected to an air reservoir and a mercury manometer, was applied at this time in some experiments to the left arm, and in others to the wrist. It was inflated to 2 mm. Hg pressure at fixed intervals during all observations. In different experiments different cuffs whose widths varied from 5 to 1 cm. were used. The rate of increase and decrease of pressure in the cuff was recorded, by means of a tambour, simultaneously with the hand blood flow. This rate was varied by adjusting a screw clip on the tubing connecting the reservoir and cuff. During each series of observations the occlusion cuff was inflated at intervals of 6 sec. in some experiments and 9 sec. in others. It was maintained at full pressure for 1 sec. In recording the hand blood flow the collecting pressure of 7 mm. Hg was applied for 6 sec. in every 1 sec. The first of these recordings was commenced in some experiments simultaneously with, and in others 4 sec. after, inflation of the occluding cuff. In yet further experiments the collecting pressure was applied continuously for 15-2 sec. following cuff inflation. For the analysis of the results the observations were divided into either six 1 min. or five 18 min. runs. By these methods it was hoped to see whether there was adaptation to the constant repetition of the stimulus. In three experiments observations were made on subjects in a vasodilated condition, the subject, wrapped in blankets, immersing his feet in a stirred water-bath at 43.5 C. (Gibbon & Landis, 1932). RESULTS The effect of inflating a blood-pressure cuff on the hand blood flow When the cuff was rapidly inflated on the opposite arm a sigmoid blood inflow curve was obtained as shown in Fig. 1, tracings A and C. It was not a smooth curve, but could be divided into three more or less distinct parts. Immediately Fig. 1. Effect on the hand blood flow of inflation of a cuff on the opposite arm to 2 mm. Hg. At A and C the plethysmograph collecting cuff and the occluding cuff on the opposite arm were inflated. At B and D the collecting cuff only was inflated. X and Y are recording correlation marks. Time in sec. following the inflation was a latent phase during which the hand blood flow was maintained at about its previous level. This was followed in turn by a reduced flow phase and a recovery phase. Tracings B and D in Fig. 1 are control observations in which, when the tap to the blood-pressure cuff was turned, air was prevented from entering the cuff by means of a device of which the subject was unaware. The aggregate analysis of results from all the relevant experiments is presented in Fig. 2 and is based on 28 observations on ten individuals. Each point represents the averaged results of twelve to fifteen observations. The hand

3 26 IAN C. RODDIE blood-flow values have been plotted as coincident with the point where the plethysmograph collecting cuff was inflated, but they are also pertinent to the subsequent few seconds. Since the inflow following inflation of the bloodpressure cuff could be divided into three phases, the results are considered from this standpoint. (1) Blood flow during the latent phase (duration sec.). During this period the inflow appeared to be about 1% below the resting level but it was not clear whether this difference was significant. It might conceivably be a psychological effect caused by anticipation of the cuff inflation. 12 O 1 DO 8 C -,; 6 E C "'54 * * II 3.~~~~~~~~ i I * I._ - 1.1P--:~. Is i ~~. r,.i F 3 I p Is I I I I I I ' Fig. 2. Aggregate analysis of all observations excepting only those in which the subject was in a state of vasodilatation due to indirect heating. The figure includes experiments in which the arm cuff was inflated to 2 mm. Hg at 6 or 9 sec. intervals. Hand blood flows are expressed as a percentage of the resting flow, this flow being taken as the mean flow 4 and 5 sec. following the inflation of the cuff. Each dot represents the average of twelve to fifteen observations and has been plotted as coincident with the time of inflation of the collecting cuff. although it also refers to the blood flow during the subsequent few seconds. Time in seconds. Cuff inflated from 4-5 sec. (2) Bloodflow during the reducedflow phase (duration l sec.). In this phase the hand blood flow fell to an average of 33 % of the latent phase value and in some cases even fell to zero. This mean percentage includes those observations where no alteration in blood flow was elicited by inflation of the cuff. The large variation in the degree of fall produced will be seen from Fig. 2. (3) Blood flow during the recovery phase (duration 1-2 sec.). Whereas the rate of inflow remained fairly steady throughout each of the first two phases, in the recovery phase the inflow returned progressively and fairly rapidly to the

4 HAND BLOOD FLOWS 27 resting level. The durations of the latter two phases were much less constant than that of the latent phase as can be seen from the standard deviations of the individual responses from the means. At the lower room temperatures, C. recovery was rather slower, the resting level not being regained for 3-4 sec. At all temperatures there was no regular increase in flow above the resting level following the period of reduced flow. These three phases constituted the typical response to the inflation of the blood-pressure cuff to 2 mm. Hg pressure on the opposite arm. This response was elicited by about nine out of ten cuff stimuli. There was no evidence from the shape of the blood inflow curves that the inflation of the plethysmograph collecting cuff was itself responsible for a similar or smaller response. E Fig. 3. Effect of prolonged repetitive contralateral cuff inflation on hand blood flow. Curves 1-5 represent the averaged results of five consecutive runs of 12 cycles. Time in seconds. Cuff inflated from 4-S5 sec. Individual variation Though the subjects varied to some extent in their response to the stimulus they all gave a high proportion of positive results. In no subject was the average fall in hand blood flow following cuff inflation less than 25% of the normal flow in any one experiment. Since the averages from different individuals were in such good agreement a statistical analysis was thought to be unnecessary. Adaptation. The results of a typical experiment are shown in Fig. 3. This lasted for 1 min. and was conducted in five consecutive 18 min. runs separated by 2 min. intervals. The average results of each of these consecutive runs have been graphed separately, and are numbered 1-5 in Fig. 3. The decrease in hand blood flow following cuff inflation, if the previous resting levels are borne in mind, will be seen to be of much the same order throughout the experiment..2 o 3 ' 4 5

5 28 IAN C. RODDIE Results from all the relevant experiments showed that the hand blood flow fell to an average of 29% of its resting value in the initial half of the experiments and to 32-5% in the latter half. No subject experienced pain as a result of inflation to 2 mm. Hg for 1 sec., and warning the subject that the cuff was about to be inflated had no effect on the response. The element of surprise was largely eliminated by the repetition of the stimulus at constant intervals over long periods. There was no obvious alteration in the proportion of stimuli, about one in ten, which failed to elicit a response at the start and finish of each experiment. These results show that there was no important adaptation to the cuffinflation stimulus over experimental periods of 1-2 hr. 2 Fig. 4. Sec. Effect of rate of cuff inflation. Thickened lines represent the pressure in the occluding cuff. The plethysmograph collecting cuff and the occluding cuff on the opposite arm were inflated simultaneously. Tracings 1, 2 and 3 show the effect of progressively slower rates of inflation of the occluding cuff. Rate of cuff inflation The more rapid the inflation of the occluding cuff the greater were the effects produced (Fig. 4). In most experiments the cuff was inflated so that it exerted the maximum pressure in -6 sec. By means of the screw clip resistance this time could be lengthened to over 1 sec. When inflation occupied between 1 and 5 sec., the fall in blood flow was not so marked and recovery was more rapid than when the cuff was inflated in -6 sec. No change in the blood flow was found when the cuff was slowly and evenly inflated to 2 mm. Hg over 1 sec. (Table 1).

6 HAND BLOOD FLOWS TABLE 1. Effect of rate of cuff inflation. Hand blood flow expressed as percentage inflow in latent phase Hand blood flow Time in sec. for Latent Reduced flow Initial recovery inflation of cuff to phase phase phase 2 mm. Hg presure (-3-5 sec.) ( sec.) (8)-12- sec.) Under Over Room temperature Though, when the room was hot (26-29 C.) and the hand blood-flow level high, cuff inflation caused a greater absolute fall in flow, the relative fall in flow was not significantly different from that found at moderate room temperatures. When the room was colder (19-23 C.) the recovery phase was about 1 sec. longer than at higher temperatures. In experiments where the subjects underwent vasodilatation by means of indirect heating, the fall in blood flow into the hand following cuff inflation became less marked and finally, after about 15 min. of indirect heating, no fall was observed. In one subject a 15% rise in inflow followed by a sharp fall to the resting inflow value was observed. These experiments have not been included in the aggregate analysis of results (Fig. 2). DISCUSSION Goetz (1946) observed a decrease in toe volume in response to the inflation of an arterial occlusion cuff on the arm. In the experiments now described, it was found that the rapid inflation of a cuff to 2 mm. Hg pressure on the arm was followed by a marked fall in blood flow in the opposite hand. This decrease in flow was measured in ten subjects. The hand blood flow fell after a 3-4 sec. latent period to an average of 33 % of its resting value and only regained the normal level about sec. later. No important adaptation to this stimulus occurred during periods of observation of up to 1 min. duration. It follows that in experiments in which an arterial occlusion cuff is inflated while the hand blood flow is being measured on the opposite arm, misleading results may be obtained. This can, however, be avoided in experimental work of this kind if simple precautions are taken. The results showed that the fall in hand blood flow in response to contralateral cuff inflation was roughly proportional to the rate of pressure increase in the cuff. No decrease occurred when the cuff was slowly and steadily inflated over a period of 1 sec. The cuff may be filled in this manner if the tubing connecting reservoir and cuff is provided with a suitable constriction. Alternatively, undisturbed readings may be obtained 3 sec. after rapid inflation of an occluding cuff. 29 PH. CXII. 14

7 21 IAN C. RODDIE SUMMARY 1. Following the rapid inflation of a blood-pressure cuff to 2 mm. Hg pressure on one arm the hand blood flow on the opposite side fell to an average of 33 % of its mean resting value and regained this value about sec. later. 2. No important adaptation to this stimulus occurred during experimental periods lasting up to 1 min., the cuff being inflated every 9 sec. 3. The fall in flow was not observed when the subjects were in a vasodilated condition. 4. The possibility of obtaining misleadingly low hand blood-flow measurements when a blood-pressure cuff is being periodically and simultaneously inflated is discussed. 5. This disturbance of the hand blood flow can be avoided if the cuff is slowly and evenly inflated over a period of about 1 sec. I wish to thank the students of The Queen's University, Belfast, for acting as subjects, and Prof. A. D. M. Greenfield, at whose suggestion this work was carried out, for his advice and criticism. REFERENCES Barcroft, H. & Edholm,. G. (1945). J. Phy8i. 14, 161. Brodie, T. G. & Russell, A. E. (195). J. Physiol. 32, xlvii. Capps, R. B. (1936). J. din. Inve8t. 15, 229. Gibbon, J. H. & Landis, E. M. (1932). J. dlin. Invest. il, 119. Goetz, R. H. (1946). Amer. Heart J. 31, 146. Grant, R. T. & Pearson, R. S. B. (1938). Clin. Sci. 3, 119. Stewart, G. N. (1911). Heart, 3, 76.