Eur J Appl Physiol (2003) 89: 411–426
`DOI 10.1007/s00421-003-0818-2
`
`O R I G I N A L A R T I C L E
`
`H. A. M. Daanen
`Finger cold-induced vasodilation: a review
`
`Accepted: 10 February 2003 / Published online: 24 April 2003
`Ó Springer-Verlag 2003
`
`Abstract Cold-induced vasodilation (CIVD) in the finger
`tips generally occurs 5–10 min after the start of local cold
`exposure of the extremities. This phenomenon is believed
`to reduce the risk of local cold injuries. However, CIVD
`is almost absent during hypothermia, when survival of the
`organism takes precedence over the survival of peripheral
`tissue. Subjects that are often exposed to local cold (e.g.
`fish filleters) develop an enhanced CIVD response. Also,
`differences between ethnic groups are obvious, with black
`people having the weakest CIVD response. Many other
`factors affect CIVD, such as diet, alcohol consumption,
`altitude, age and stress. CIVD is probably caused by a
`sudden decrease in the release of neurotransmitters from
`the sympathetic nerves to the muscular coat of the arte-
`rio-venous anastomoses (AVAs) due to local cold. AVAs
`are specific thermoregulatory organs that regulate blood
`flow in the cold and heat. Their relatively large diameter
`enables large amounts of blood to pass and convey heat
`to the surrounding tissue. Unfortunately, information on
`the quantity of AVAs is lacking, which makes it difficult
`to estimate the full impact on peripheral blood flow. This
`review illustrates the thermospecificity of the AVAs and
`the close link to CIVD. CIVD is influenced by many
`parameters, but controlled experiments yield information
`on how CIVD protects the extremities against cold
`injuries.
`
`Keywords Arterio-venous anastomoses Æ Cold induced
`vasodilation Æ Finger blood flow
`
`Introduction
`
`Millions of people are daily exposed to cold and
`face
`the
`challenge
`to maintain their body core
`
`H. A. M. Daanen
`TNO Human Factors, PO Box 23, 3769 ZG Soesterberg,
`The Netherlands
`E-mail: Daanen@tm.tno.nl
`Fax: +31-346-353977
`
`temperature at about 37°C. Peripheral vasoconstric-
`tion is a powerful mechanism to reduce the heat
`loss, but results in strong cooling of the extremities.
`However, the extremities possess the ability to prevent
`the occurrence of local cold extremes. About 5–10 min
`after the initiation of cold exposure of
`the hand,
`blood vessels in the finger tips suddenly vasodilate,
`which increases the peripheral blood flow and subse-
`quently the temperature of the finger tips. This cold-
`induced vasodilation (CIVD) is followed by a new
`phase of vasoconstriction. This process repeats itself
`and is called ‘the hunting reaction’
`(Lewis 1930).
`Arterio-venous anastomoses (AVAs) are thought to
`play a major role in the mechanism of CIVD, but the
`exact mechanism is still subject to debate. The CIVD
`reaction and the related blood vessels are important
`issues for thermal physiologists, since CIVD is thought
`to reduce the risk of local cold injuries (Iida 1949).
`Wilson and Goldman (1970) found in their experi-
`ments that freezing did not take place when CIVD
`occurred. It is likely that CIVD also improves the
`manual dexterity and tactile sensitivity during work in
`the cold. Since the blood flow increases substantially
`in the fingers during CIVD, this increases the blood
`circulation in the large vessels of the forearm, with the
`consequence of
`increasing the temperature of
`the
`forearm muscles (Ducharme et al. 1991), and likely
`contributes
`to improved manual performance by
`improving muscle function. The increased skin tem-
`perature due to CIVD will increase the firing rate of
`the pressure transducers in the skin and thus increase
`tactile sensitivity.
`CIVD can occur at several locations in the human
`body. The focus in this review is placed on finger CIVD,
`since the finger is a common site for local cold injuries
`and most data are available for this body part.
`It is the purpose of this article to review the current
`knowledge on finger CIVD, to describe the effects of
`several parameters such as core temperature, diet and
`acclimatization on finger CIVD and to discuss the pos-
`sible mechanisms involved.
`
`APL1109
`Apple v. Valencell
`IPR2017-00317
`
`

`

`412
`
`Definitions and terminology
`
`CIVD and hunting reaction
`
`Cold-induced vasodilation can be defined as vasodila-
`tion of cold-exposed blood vessels,
`in particular the
`small arteries. The term hunting reaction or hunting
`response (Lewis 1930) is used to describe the alternating
`periods of vasodilation and vasoconstriction during cold
`exposure. Some authors use the term Lewis reaction
`instead of hunting reaction (Kramer and Schulze 1948;
`Werner 1977).
`Purkayastha et al. (1992) argue that the hunting
`reaction is only one out of four possible reactions of
`blood vessels to extreme local cold. The other responses
`observed in the fingers after immersion in cold water are:
`(1) a continuous state of vasoconstriction, (2) slow
`steady and continuous rewarming and (3) a proportional
`control form in which the blood vessel diameter remains
`constant after an initial phase of vasoconstriction.
`The majority of the vascular responses to immersion of
`the finger in cold water can be classified as the hunting
`reaction. Daanen (2001) observed that the hunting reac-
`tion was present in 210 out of 226 investigated male sub-
`jects (93%) who immersed their finger in ice water. The
`reactions of the remaining subjects were difficult to clas-
`sify.
`
`Arterio-venous anastomoses (AVAs)
`
`AVAs are thought to play a major role in CIVD. These
`blood vessels have a thick muscular wall and a lumen,
`measuring on average 10–30 lm (Gray 2000), 35 lm
`(Roddie 1983) or even 50 lm (Sherman 1963). Under the
`influence of the sympathetic nervous system, with its rich
`supply of non-myelinated fibres on the wall of the vessel,
`they are capable of complete closure. When the AVAs are
`open, large amounts of blood can pass. Anastomoses are
`not fixed structures, but may come and go on demand:
`they can develop when necessary and disappear when they
`are no longer needed. Hale and Burch (1960) observed
`that AVAs develop if blood requirement increases at the
`finger tip. Clark and Clark (1934) estimated that the for-
`mation of new AVAs requires 2–3 days.
`In their studies, Hale and Burch (1960) and Clara
`(1939) mentioned the following sites of AVAs: the skin of
`the inside of the hand and foot, the nail bed, the elbow,
`lips, cheeks, ears and the nose. There is some discussion
`about the presence of AVAs in the skin of the head.
`Grant and Bland (1931) found 501 AVAs per cm2
`surface area in the nail bed, 236 in the finger tip, 150 on
`the palmar side of the distal phalanx, 20 on the palmar
`side of the medial phalanx and 93 on the palmar side of
`the proximal phalanx. They found no AVAs on the
`dorsal side of the hand. However, the numbers were
`derived from only one index finger from only one sub-
`ject, although they claim that similar results were found
`
`in three other subjects. Masson (1937) only counted
`three to four AVA’s per cm2 at the top of the finger and
`about ten in the nail bed. Clara (1939) argued that Grant
`and Bland (1931) counted the same AVA several times.
`AVAs are tortuous and they did not account for that in
`their counting technique.
`The limited information on the number of AVAs in
`the fingers and the disagreement in the existing studies
`necessitates new research to address this topic. More-
`over, there is a strong need for more accurate data on
`the amount of AVAs in the human body, in particular to
`improve current computer models on blood flow and
`heat transfer.
`
`Methodology
`
`Several methods are available to quantify the amount of
`vasodilation in the finger skin. Direct measurement of the
`diameter of blood vessels is extremely difficult, if not
`impossible, and therefore indirect measures are used.
`When the blood vessel diameter increases, the blood flow
`increases (if the viscosity of the blood remains the same)
`and this can be measured by laser Doppler flowmetry and
`strain gauge plethysmography. Some authors determine
`the blood flow by the wash out of a marker added to the
`blood (e.g. Coffman 1972). The increased blood flow
`raises the tissue temperature and thus the temperature at
`the finger tip. The finger skin temperature is the most
`frequently used method to determine CIVD. The in-
`creased finger skin temperature leads to a higher heat
`transfer to the environment, which can be assessed by heat
`flux sensors and calorimetry. The most common methods
`to quantify CIVD are briefly discussed below.
`
`Strain gauge plethysmography
`
`The principle of this technique is that a cuff is placed and
`inflated proximal to the measuring site in such a way
`that blood can enter, but not
`leave the measured
`extremity. During the obstruction a linear increase is
`seen in circumference due to the accumulating blood.
`The increase in circumference is an estimator of blood
`flow (Elkington 1968). Since fingers are almost free of
`skeletal muscle tissue, their volume changes mainly
`represent alterations in the blood volume in the cuta-
`neous blood vessels (Okuda 1942).
`
`Laser Doppler flowmetry
`
`Laser Doppler flowmetry is a method that yields infor-
`mation on local skin blood flow. The emitted laser light
`from a small probe on the skin is backscattered from
`moving red blood cells or static skin structures. Light
`scattered from moving objects is shifted in frequency
`(Doppler shift) in proportion to the velocity of the
`moving target. A photodetector, located close to the
`laser beam end, measures the backscattered light.
`
`

`

`The penetration depth of the laser in the skin is
`determined by the wavelength of the laser Doppler sys-
`tem, the fibre separation (Hirata et al. 1988) and local
`properties of the skin (Tenland 1982). Nagasaka et al.
`(1988) argues that only a minimal part of the AVAs can
`be ‘‘seen’’ by laser Doppler flowmetry using He-Ne la-
`sers. Wollersheim (1988), however, shows that at least
`part of the shunt flow is included in the laser Doppler
`results. This issue is not resolved, but it can be expected
`that new laser Doppler systems will have the ability to
`set the penetration depth.
`Skin nutritional blood flow through the capillaries is
`generally related to total blood flow of an extremity. For
`instance, Johnson et al. (1984) found a good relationship
`between laser Doppler flow and forearm blood flow
`(r=0.94–0.98). However, there are also situations, such as
`reflex vasodilation, in which skin perfusion is regulated
`independently from total blood flow (Hirata et al. 1988).
`
`Finger skin temperature
`
`Finger skin temperature is the most commonly used
`measure for CIVD. A small thermocouple is generally
`attached to the palmar side of the distal phalanx with
`tape. The measured temperature is a mix of the finger
`skin temperature and the temperature of the surround-
`ing cooling medium. Careful attachment of a small
`thermocouple to the skin minimizes the influence of the
`cooling medium temperature.
`The nail bed is also often used as a measuring site,
`since it is known that AVAs are abundant there. How-
`ever, Yoshimura (1966) showed that the temperature
`reaction measured on the pad of the finger is more
`sensitive and reproducible than that on the nail bed.
`
`413
`
`The measured finger skin temperature is a slow
`indicator of what occurs in the tissue underneath.
`Daanen (1997) observed that CIVD onset measured
`using the finger skin temperature occurred 90 (48) s later
`than measured using laser Doppler flowmetry.
`The changes in finger skin temperature profile during
`cold exposure are quantified using the terminology
`shown in Fig. 1.
`– The minimum temperature (Tmin) is the lowest finger
`skin temperature just before CIVD starts.
`– The maximum temperature (Tmax) is the highest
`finger skin temperature during CIVD.
`– The onset time (Dtonset) is the time from immersion
`to Tmin.
`– The amplitude is the difference between Tmin and
`Tmax.
`– The peak time (Dtpeak) is the time interval between
`Tmin and Tmax.
`– The mean finger skin temperature (Tmean) denotes the
`finger skin temperature averaged over the immer-
`sion period. As a rule, the onset time is not included,
`since during this period the heat in the hand is re-
`moved. In practice, the first 5 min data are removed.
`– The frequency of the hunting reaction is expressed as
`the number of waves (vasodilation/vasoconstriction
`period) within a certain time frame.
`
`Yoshimura and Iida (1952) quantified the magnitude
`of the CIVD reaction using the Resistance Index for
`Frostbite (RIF) in which Dtonset, Tmin and Tmean were
`included. Short onset times and high minimal or mean
`finger skin temperatures were rated by 3 points and long
`onset times and low temperatures by 1 point, leading to
`summated RIFs from 3 to 9. This RIF index is used by
`many other authors, in particular from Japan.
`
`Fig. 1 Parameters derived from
`a temperature profile of a finger
`tip immersed in cold water. The
`onset time (Dtonset) is the time
`from immersion to the
`minimum temperature (Tmin).
`The amplitude is the difference
`between Tmin and Tmax. The
`peak time (Dtpeak) is the time
`interval between Tmin and Tmax.
`The mean finger skin
`temperature (Tmean) denotes the
`finger skin temperature
`averaged over the immersion
`period, excluding onset time
`
`

`

`414
`
`General reactions observed during CIVD
`
`Reflex vasoconstriction and reflex vasodilation
`
`When one body part is cooled, vasoconstriction also
`occurs in other parts of the body. This phenomenon is
`known as reflex vasoconstriction. Similarly, if heat is
`applied to another part of the body, such as a leg, the
`vessels open up and the hand gets warm (Gibbon and
`Landis 1932). This phenomenon is called reflex vasodi-
`lation. Sensors in the skin react to the external stimulus
`and transfer information to the vasomotor centre. This
`centre integrates the information and sends an adequate
`response to the effector organs. Pickering (1932) showed
`that blood temperature also plays an important role in
`this mechanism. He found no reflex vasodilation when
`the venous return of a heated hand was blocked.
`Reflex vasodilation and vasoconstriction are also
`noted during the hunting reaction. Immersion of the feet
`in cold water during the hunting reaction in fingers re-
`duced the magnitude of the hunting reaction (Keatinge
`1957). Lewis (1930) observed that cooling the forearm
`suppressed CIVD in the fingers. Page and Brown (1953)
`and Livingstone et al. (1978) observed that Eskimos had
`less reflex vasoconstriction in the fingers upon cold water
`immersion of a foot than control subjects. Thus, Eski-
`mos are able to maintain good dexterity when the feet
`are cold. Werner (1983) showed that reflex vasodilation
`or vasoconstriction not only depends on the skin and
`core temperatures but also on the rate of change of these
`temperatures.
`
`Pain
`
`Immersion in cold water is often a painful experience.
`LeBlanc (1975) and Heus and Daanen (1993) noted that
`the most painful period occurred during vasoconstric-
`tion, and that the vasodilation phase was often felt as a
`relief. The pain during strong vasoconstriction may be
`seen as a warning signal for exceptional cooling. Kreh
`et al. (1984) found a close relationship between pain
`intensity and degree of vasoconstriction. If the cooling
`continues, the tissue temperature may decrease below
`the threshold for nerve conduction (7–8°C, Vanggaard
`1975). If that threshold is reached no information from
`the periphery can reach the central nervous system and
`the extremity feels numb. Sawada et al. (2000) observed
`that pain diminished after repeated cold water immer-
`sions.
`
`Experimental factors affecting CIVD
`
`Ambient temperature and body temperature
`
`The regulation of blood flow to the extremities is, at
`low ambient temperatures, primarily determined by the
`
`thermal state of the body as a whole. Even at air tem-
`peratures below )30°C, the skin temperature of bare
`hands can be sustained above 21°C (Rapaport et al. 1949).
`Therefore, it is rather likely that the body core tempera-
`ture influences the hunting reaction. In Table 1 results of
`relevant articles in the literature are summarized.
`In most investigations the effects of body temperature
`were investigated by putting subjects in a relatively cold or
`warm room. Unfortunately, the resulting core and mean
`body skin temperatures were often not recorded. The
`general
`image emerging from Table 1 is that a high
`ambient or core temperature leads to higher mean finger
`skin temperatures during the hunting reaction. Also, the
`onset time of CIVD was observed to be shorter. Daanen et
`al. (1997) and Daanen and Ducharme (1999) found that
`onset time was mainly related to the mean skin tempera-
`ture of the body and that mean finger skin temperatures
`were mainly related to body core temperatures.
`Ambient temperature may change body core tem-
`perature, but the core temperature is also modified by
`exposure to ambient light and changes in melatonin
`variations during the day (Burgess et al. 2001), and
`during the year (seasonal) (Yoneyama et al. 1999). The
`effects of these changes in core temperature on CIVD, as
`reported in the literature, are:
`
`–
`
`– The hunting reaction is more pronounced in the
`afternoon, than in the morning or the night (Kramer
`and Schulze 1948).
`Schulze (Kramer and Schulze 1948) measured his
`CIVD each month at room temperature with his
`hand in a cold air box and found an average max-
`imal finger skin temperature of 28°C in the summer
`and 16°C in the winter during immersion, indicating
`a vasoconstrictive state during winter.
`– Tanaka (1971b) measured CIVD during middle
`finger immersion in 0°C water during summer and
`winter under identical ambient conditions and also
`observed that the CIVD reaction was more pro-
`nounced in summer.
`
`In summary, it appears that in the afternoon and in
`the summer, when the core temperature is relatively
`elevated, the hunting reaction is more pronounced.
`
`Cooling medium
`
`To evoke CIVD, two media are commonly used: water
`and air. Immersion in cold water is used most often. The
`thermal conductivity of water is about 25 times higher
`than that of air, so cooling is rather quick.
`Kramer and Schulze (1948) cooled fingers in a cold
`air box, and compared the results with those of other
`studies in which the fingers where cooled in water. The
`frequency of the hunting response in 0°C water showed
`most similarity with that in )18°C air. Kramer and
`Schulze (1948) observed that
`the frequency of
`the
`hunting reaction decreased when the air temperature in
`
`

`

`415
`
`lower(CIVD)than15°C
`watertemp.ishigheror
`ambienttemp.andwhen
`Bloodflowhigherathigh
`
`alsolower
`lowerinHamplitude
`Meanfingerskintemp.
`
`increasedwhenwarm
`Meanfingerskintemp.
`
`bath:13%ofmax.
`5%ofmax.Cold
`65%ofmax.Cold:
`
`Fingerheatloss.Hot:
`roomtemp.increases
`
`Moreheatlosswhen
`
`whenindirectlywarmed
`
`Morebloodflow
`
`warmroom
`
`Moreheatlossin
`
`coldroom
`andheattransferin
`Reducedbloodflow
`
`magnitude
`times,smallCIVD
`
`Coldbody:longonset
`
`huntingmagnitude
`frequencyandsmall
`
`Coldbody:lowhunting
`
`amplitude
`infrequencyand
`temp.),nodifferences
`7.8°Cat28°Croom
`chilled(3.8°Cversus
`Tminlowerwhen
`onambienttemp.
`waterorair)but
`onlocaltemp.(cold
`
`Bloodflownotdependent
`
`coolsubjects
`Dtonsetincreasedin
`Results
`
`plethysmography
`venousocclusion
`
`Bloodflowby
`
`waterof2to35°C
`Handsfor3hin
`
`Fingerskintemp
`
`4°Cwater
`Rightmiddlefingerin
`
`Fingerskintemp
`
`of)18to10°C
`Handsincoldair
`
`Calorimetry
`
`Indexfingerinice
`
`water
`
`Calorimetry
`
`plethysmography
`Venousocclusion
`
`Toesinwater0–6°C
`Handsinicewater
`
`Calorimetry
`
`calorimetry
`
`Plethysmography,
`
`(laserDoppler)
`skinperfusion
`
`Fingerskintemp,
`
`Fingerskintemp
`
`waterof5°C
`Handfor30minin
`
`Fingerinicewater
`
`waterof5°C
`Handfor40minin
`
`waterof8°C
`Handfor30minin
`
`andplethysmography
`Fingernailbedtemp.
`
`15°Cair
`Handin0,5,10and
`
`andplethysmography
`
`Fingerskintemp.
`
`Fingerskintemp
`
`Variables
`
`icewateror0°Cair
`Terminalphalanxin
`20minin0°C
`Indexfingerfor
`
`Measurement
`
`Induction
`
`Huntingreaction
`
`–
`
`–
`
`–
`
`Tre:36.29°C
`37.02°C;H:Tes:36.18°C;
`N:Tes:36.85°C;Tre:
`
`Tes,Tre
`
`24and32°Cfor3h
`Roomtemp.16,
`20°Cwater(H)
`air(N),60minin
`30minin27°C
`variations
`dailyandseasonal
`
`Spealman(1945)
`
`Leeetal.(1996)
`
`(1948)
`
`–
`
`–
`
`–
`
`–
`
`–
`
`–
`
`Roomtemp,hotdrinks,
`
`KramerandSchulze
`
`–
`
`–
`
`–
`
`–
`
`–
`
`clothingandexercise
`and17–18°Cwith
`temp.5–6°C(1h)
`6°Cwaterbath;Room
`20.5°Cand22.5°C
`Roomtemp.14.5°C,
`andcooling
`Indirectwarming
`22°Cclothed
`unclothedand
`Roomtemp.18°C
`and9–17°C
`Roomtemp.‘‘neutral’’
`waterperfusedsuit
`immersion;hot
`
`Keatinge(1957)
`
`Greenfieldetal.(1951)
`
`Folkowetal.(1963)
`
`Elsneretal.(1960)
`
`(1960)
`
`EdwardsandBurton
`
`(2000)
`
`Tes,TreandTskTes36.1and38.0°C
`
`Wholebodycoldwater
`
`DaanenandDucharme
`
`Tre,TskandTearTear36.5and37.1°C
`
`43°Cbeverages
`Drinking0°Cand
`
`Daanenetal.(1997)
`
`roomtemp.:25°C
`33.1°C.Tskatother
`roomtemp.Tskat28°C:
`Trenotdifferentbetween
`
`Tre,Tsk
`
`15and12°Cfor2–3h
`Roomtemp.28,25,
`
`Blaisdell(1951)
`
`–
`
`–
`
`–
`
`–
`
`Results
`
`Variables
`
`BaderandMead(1949)Roomtemp.13and
`
`AdamsandSmith(1962)Roomtemp.7and
`
`32°C
`22°Cfor1h
`
`minimumtemperatureoffingerskinduringimmersion(°C),DtonsettimefromimmersiontoTmininminutes]
`Table1Influenceofbodytemperaturesonthehuntingreaction.[TreRectaltemperature(°C),Tskmeanbodyskintemperature(°C),Tmeanmeanfingerskintemperature(°C),Tmin
`
`Measurement
`
`Induction
`
`Bodytemperatures
`
`Author(s)
`
`

`

`the cooling box around the hand increased: four to six
`hunting periods were observed in 2 h at an air temper-
`ature of )18°C and only one at 10°C air temperature.
`There is no agreement in the literature concerning the
`water temperatures at which CIVD occurs. The lowest
`temperature in the studies equals 0°C, the temperature
`of stirred water with ice. Lewis (1930) and Yoshimura
`(1960) performed their experiments at this temperature,
`since they wanted a maximal response. Lewis (1930) did
`not see a hunting reaction in water temperatures above
`18°C. Hirai et al. (1970) saw no response at 15°C and
`advised an optimal temperature for investigation of 5°C,
`since the differences between two investigated popula-
`tions were optimal then.
`Havenith et al. (1992) and Chen et al. (1994) observed
`CIVD when subjects were touching cold materials, but
`decided not to use and process the data for their cooling
`models. Chen et al. (1994) observed CIVD in 14% of the
`recordings. This low percentage is probably due to two
`factors. First, a part of the thermocouple was in direct
`contact with the aluminium bar, thus underestimating
`the finger tip temperature. Second, the cold stress was
`not severe enough: the aluminium surface was –7, 0 or
`7°C in a climatic chamber of 10 or 30°C.
`
`Surface area cooled
`
`Sendowski et al. (1997) investigated the differences in
`finger CIVD response between immersing a finger, hand
`or forearm in 5°C water. The finger CIVD was more
`pronounced (faster onset and higher amplitude) after
`finger immersion than after hand or forearm immersion.
`Two main explanations were given. The first explanation
`was that the arterial blood was cooler in the finger after
`hand/forearm immersion due to pre-cooling in the hand
`or forearm. This explanation was recently confirmed by
`Ducharme et al. (2001), who observed reduced CIVD
`when the forearm tissue was cooled. The second expla-
`nation was that sympathetic activity was higher during
`hand/forearm immersion, which was illustrated by higher
`scores for pain sensation. Moreover, cardiovascular
`changes were found during hand/forearm immersion and
`not during finger immersion. To investigate the sympa-
`thetic influence in more detail, Sendowski et al. (2000)
`co-immersed the left hand with the right middle finger.
`Increased plasma norepinephrine during co-immersion
`showed that sympathetic activity was elevated. The CIVD
`amplitude reduced during co-immersion, and this is likely
`to be attributed to increased sympathetic activity. On the
`other hand, blood cooling due to the left hand immersion
`cannot be completely ruled out.
`
`Altitude
`
`A significant reduction in the hunting reaction is found
`during exposure to high altitude, where cold co-exists
`with systemic hypoxia (Mathew et al. 1977). Takeoka
`
`roomtemp.
`decreaseswith
`roomtemp.Dtonset
`increaseswith
`roomtemp.Tmean
`Tminincreaseswith
`45°Cambienttemp.
`offluctuationsat
`temp.increaseNo.
`ambientandhand
`Tmeanhigherwhen
`TmeanandshorterDtonset
`temp:higherTminand
`Withincreasingroom
`
`Fingerskintemp
`
`Fingerskintemp
`
`Fingerskintemp
`
`30minin0°C
`Middlefingerfor
`
`0and5°C
`0.5m°s-1at)5,
`Handsinairat
`
`30minin0°C
`Middlefingerfor
`
`–
`
`–
`
`–
`
`–
`
`Tre
`
`–
`
`4–36°C
`Roomtemp.
`
`(1950)
`
`YoshimuraandIida
`
`30and45°C
`(for0.5h),
`Roomtemp.15
`
`and35°C
`Roomtemp.)25,30
`
`Werner(1977)
`
`Tanaka(1971b)
`
`Results
`
`Variables
`
`Results
`
`Variables
`
`Measurement
`
`Induction
`
`Measurement
`
`Induction
`
`416
`
`Huntingreaction
`
`Bodytemperatures
`
`Author(s)
`
`Table1(Contd.)
`
`

`

`et al. (1993) showed that Tmean during the hunting
`reaction was lower in seven Japanese men at an altitude
`of 4860 m (ambient temperature 9°C) as compared to
`2260 m (ambient temperature 12°C). Recently, Daanen
`and Van Ruiten (2000) observed that CIVD was reduced
`in magnitude at an altitude of 5000 m, even when the
`body core was warmer than at sea level. Therefore, it
`seems that systemic hypoxia reduces the magnitude of
`the hunting reaction. During prolonged stay at altitude,
`the CIVD reaction gradually improves (Daanen and
`Van Ruiten 2000).
`
`Individual factors affecting CIVD
`
`Age
`
`In the elderly, the CIVD reaction occurs later and is less
`pronounced (Sawada 1996; Spurr et al. 1955). Also, Tan
`and Tregenza (2002) observed that the CIVD responses
`of a group of 18-year old students was more pronounced
`than that of their parents (40–50 years old). The reduced
`CIVD reaction is attributed to the diminished sympa-
`thetic vasoconstrictor responses with the advancing age
`(Khan et al. 2002) which is in line with the observations
`that the onset time and peak time are considerably de-
`layed by age and the finger skin temperatures are only
`slightly changed. Also, an age-related decrease in core
`temperature due to a decreased basal metabolic rate and
`reduced physical activity (Van Someren et al. 2002) will
`likely affect the CIVD response.
`For younger people, the results are less consistent.
`Yoshimura and Iida (1952) observed that children had
`lower RIF values than adults, but higher values than in
`puberty. In contrast, Miller and Irving (1962) found that
`the finger temperature of Eskimo children dropped more
`than that of adults during cold exposure. However, this
`may be attributed to their drop in body temperature,
`which was not controlled for.
`
`Gender
`
`417
`
`role here. Cooke et al. (1990) found no relation between
`female hand blood flow and levels of serum oestrogen or
`progesterone.
`Miller and Irving (1962) observed no differences in
`finger temperature response to cold air between three
`Eskimo women and eight Eskimo men and between
`eight Eskimo boys and four Eskimo girls. Also,
`Yoshimura and Iida (1952), Tanaka (1971b) and
`Yoshimura et al. (1958) found no sex differences in the
`hunting reaction. Reading et al. (1997) observed higher
`finger skin temperatures for males than for females
`during a 2-h exposure to 0°C air, during which hunting
`occurred.
`In summary, females tend to have lower hand blood
`flows when exposed to cold due to increased vascular
`reactivity, but the limited amount of available studies
`showed no indication that the temperature profiles of the
`hunting reaction differed between males and females. It
`was expected that the reduced vascular reactivity to cold
`of males as compared to females would be reflected in a
`delayed CIVD reaction, similar to the observations of
`CIVD with age. This, however, was not the case and
`further research is needed to elucidate this point.
`
`Physical fitness and fatigue
`
`Moriya and Nakagawa (1990) observed in 14 females
`that the RIF was not related to the maximum oxygen
`uptake divided by body weight. The latter variable is
`considered to be a good estimator of physical fitness.
`They found a significant correlation between absolute
`maximum oxygen uptake in l/min and RIF, but this was
`only in one subject and insufficient to draw conclusions.
`More research is needed to establish the effect of phys-
`ical fitness on CIVD.
`O’Brien et al. (1999) observed that the onset time was
`reduced in subjects after 5 days of repeated strenuous
`physical exertion with insufficient recovery. This effect
`was attributed to increased circulating norepinephrine
`levels that reduce the sensitivity to sympathetic stimu-
`lation.
`
`Hand and finger blood flow in thermoneutral conditions
`is higher for men than for women as measured by laser
`Doppler flowmetry and plethysmography, due to in-
`creased vasomotor tone in women (Cooke et al. 1990).
`By contrast, after total body warming of both genders,
`the blood flow was greater in females than in males.
`When warm hands (about 32°C) are exposed to cold,
`women show an enhanced vascular reactivity as com-
`pared to men, which causes a more pronounced decrease
`in peripheral blood flow and skin temperatures in fe-
`males (Bartelink et al. 1993; Pollock et al. 1993). The
`reactivity is most pronounced in women using oral
`contraceptives, followed by premenopausal women and
`postmenopausal women (Bartelink et al. 1993). These
`three different hormonal conditions thus have a strong
`impact on vascular reactivity, but age may also play a
`
`Mental stress
`
`Meehan (1957) showed that the hunting reaction was
`abolished in a stressed subject who had just completed
`an exam, in contrast to three previous experiments in
`which the hunting reaction had been clearly present.
`This finding was confirmed by Adams and Smith (1962).
`They showed that a strong emotional stress given during
`the vasodilation phase led to an immediate strong
`vasoconstriction. This demonstrates
`the
`functional
`integrity of efferent vasomotor nerves and receptors
`during CIVD. Mental stress increases the activity of the
`vasomotor centre which increases the intensity of vaso-
`constriction in the skin (Marriott et al. 1990). When the
`sympathetic vascular tone is high, however, mental tasks
`
`

`

`418
`
`may lead to paradoxical vasodilation (Cooke et al. 1990;
`Halperin et al. 1983). Also, humans are able to volun-
`tary vasodilate the blood vessels in the finger pad, and
`thus increase their finger temperature (Carter 1978).
`
`Acclimatization to cold
`
`Acclimatization refers to physiological or behavioural
`changes occurring within an organism that reduce the
`strain or enhance the endurance of strain caused by
`stressful changes, in particular climatic factors (IUPS
`Thermal Commission 2001). People working with their
`hands in a cold environment (e.g. fish-filleters) have in-
`creased blood flow through their hands in the cold as
`compared to unacclimatized subjects (Krog et al. 1960;
`LeBlanc et al. 1960). CIVD occurs at an earlier stage of
`cold exposure in the acclimatized subjects (Nelms and
`Soper 1962). Tanaka (1971a) found that ice chamber
`workers had a higher mean finger skin temperature, a
`higher minimal finger temperature and shorter onset
`time of CIVD than cool room workers. Purkayastha
`et al. (1992, 1993) showed that tropical residents deve-
`loped a more pronounced hunting reaction 7 weeks after
`an airlift to an arctic region and that the response was
`indistinguishable from the response of arctic residents.
`Table 2 summarizes the findings on the effects of local
`cold acclimatization on CIVD.
`
`Adaptation to cold
`
`The term genotypic adaptation refers to ‘‘a genetically
`fixed condition of a species or subspecies, or its evolu-
`tion, which favours survival in a particular total envi-
`ronment’’ (IUPS Thermal Commission 2001). This type
`of adaptation for cold is generally deduced from a
`comparison between populations who inhabit different
`locations. Studies on cold adaptation are included in
`Table 2.
`The results of the studies depend on the method that
`is used to measure the changes in finger circulation.
`The results were unambiguous when finger skin
`temperatures were measured. It was generally found that
`the cold adapted/acclimatized (CA) subjects had a
`shorter onset time and a higher minimal and mean
`temperature (Table 2). Only a few publications were not
`consistent with this statement. Takeoka et al. (1993)
`found that the cold-adapted Tibetans had a lower Tmean
`than the Japanese controls. In this case however, hy-
`poxia coexists with cold, which may alter the response.
`Bridgman (1991) found no differences between divers
`and non-divers, probably due to an insufficient stimulus
`for acclimatization. The other publications in which
`finger temperatures were measured were in general
`agreement. Meehan (1955) found that the mean skin
`temperature of the fingers during ice water immersion
`was highest for Alaskan natives, followed by Caucasians
`and Negroes respectively. Elsner et al. (1960) showed
`
`an earlier onset of vasodilation in arctic Indians as
`compared to a control group. Itoh et al. (1970) showed
`that natives of the colder Hokkaido island had a more
`pronounced hunting reaction (earlier onset, higher mean
`finger skin temperature and higher minima) than sub-
`jects born on the main island. Iampietro et al. (1959)
`showed that Negroes and Caucasi