Published online before print May 29, 2003, doi: 10.1161/01.STR.0000077014.47422.DB
(Stroke. 2003;34:1736.)
© 2003 American Heart Association, Inc.
Original Contributions |
Neither Arm nor Face Warming Reduces the Shivering Threshold in Unanesthetized Humans
From the Outcomes Research Institute (A.G.D., A.W., C.-M.L., Y.M.S., D.I.S.), Department of Anesthesiology (A.G.D., A.W., C.-M.L., Y.M.S., D.I.S.), and School of Medicine (K.H.), University of Louisville, Louisville, Ky; Department of Anesthesiology, Chang Gung Memorial Hospital (C.M.L.), Taipei, Taiwan; and Ludwig Boltzmann Institute, University of Vienna, Vienna, Austria (D.I.S.).
Correspondence to Dr A.G. Doufas, Department of Anesthesiology, University of Louisville Hospital, 530 S Jackson St, Louisville, KY 40202. E-mail agdoufas{at}louisville.edu
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Abstract |
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Background and Purpose— Hand warming and face warming, combined with inhalation of heated air, are reported to suppress shivering. However, hand or face temperature contributes only a few percent to control of shivering. Thus, it seems unlikely that manipulating hand or facial skin temperature alone would be sufficient to permit induction of therapeutic hypothermia. We tested the hypothesis that focal arm (forearm and hand) warming or lower facial warming, combined with inhalation of heated and humidified gas, only minimally reduces the shivering threshold (triggering core temperature).
Methods— We studied 8 healthy male volunteers (18 to 40 years of age) on 3 days: (1) control (no warming), (2) arm warming with forced air at 
43°C, and (3) face warming with 21 L/min of air at 42°C at a relative humidity of 100%. Fluid at 4°C was infused via a central venous catheter to decrease tympanic membrane temperature 1°C/h to 2°C/h; mean skin temperature was maintained at 31°C. A sustained increase in oxygen consumption quantified the shivering threshold.
Results— Shivering thresholds did not differ significantly between the control (36.7±0.1°C), arm-warming (36.5±0.3°C), or face-warming (36.5±0.3°C; analysis of variance, P=0.34) day. The study was powered to have a 95% probability of detecting a difference of 0.5±0.5°C (mean±SD) between control and either of the 2 treatments at 
=0.05.
Conclusions— Focal arm or face warming did not substantially reduce the shivering threshold in unanesthetized volunteers. It thus seems unlikely that these nonpharmacological modalities will substantially facilitate induction of therapeutic hypothermia.
Key Words: body temperature regulation • shivering
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Introduction |
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Overwhelming evidence in animals indicates that even mild hypothermia provides substantial protection against cerebral1,2 and myocardial ischemia.3 Mild hypothermia has been shown to improve outcome after cardiac arrest in humans,4,5 and major randomized outcome trials are in progress to evaluate the potential benefits of mild hypothermia during aneurysm clipping and after stroke or acute myocardial infarction. Many of these studies target core temperatures between 33°C and 34°C.
Induction of hypothermia during surgery is relatively easy because anesthetics profoundly impair thermoregulatory responses.6 However, use of therapeutic hypothermia in stroke patients may be compromised because tiny reductions in core temperature trigger aggressive thermoregulatory defenses,7 even in stroke victims.8 Shivering is the most powerful autonomic cold defense in humans.9 This has led to a search for treatments that impair shivering without causing excessive toxicity. Many drugs inhibit shivering, but most are general anesthetics10,11 or major sedatives.12 For example, the combination of buspirone and meperidine significantly reduces the shivering threshold (triggering core temperature)13; however, meperidine doses sufficient to reduce core temperature to 33°C may be associated with respiratory toxicity.
An alternative to pharmacological treatment of shivering is surface warming. For example, Sweney et al14 recently reported that focal hand warming suppresses shivering in mildly hypothermic volunteers. The same group also reported that shivering can be suppressed by warming of the lower face, combined with inhalation of heated and humidified air.15 Others have also reported that facial warming reduces shivering,16 as does radiant heating of the face and upper chest.17–19
The difficulty with these observations is that treatments reducing the shivering threshold only a couple tenths of a degree centigrade may be sufficient to attenuate shivering. Treatments that only slightly reduce the shivering threshold20,21 may appear to be effective in volunteers or postoperative patients22,23 but may be completely inadequate for induction of therapeutic hypothermia. Skin temperature contributes 20% to autonomic control of shivering, with the remainder being derived from core temperature.24,25 However, the arms and face are a small portion of the total skin surface. It thus seems unlikely that manipulating hand or facial skin temperature alone would impair thermoregulatory responses sufficiently to permit induction of therapeutic hypothermia. Therefore, we tested the hypothesis that focal arm warming or lower facial warming, combined with inhalation of heated and humidified gas, only minimally reduces the shivering threshold.
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Methods |
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With approval of the Human Studies Committee at the University of Louisville and informed consent, we studied 8 healthy male volunteers. None was obese, was taking medication, or had a history of thyroid disease, dysautonomia, or Raynaud’s syndrome.
Protocol
The volunteers fasted 8 hours before each study day. They were minimally clothed and rested supine on a standard operating room table. Ambient temperature was maintained at 22°C. Each volunteer was studied on 3 days: (1) control (no warming), (2) lower-arm warming (forearm and hand), and (3) face warming. Each study day was separated by at least 48 hours.
The arm warming apparatus consisted of 2 forced-air warming units (Bair Hugger, Augustine Medical, Inc) set to high (43°C), each attached to an upper-body coverlet that was wrapped into a muff surrounding each forearm and hand. Face warming was achieved by injection of 21 L/min air at 42°C at a relative humidity of 100% into a continuous positive airway pressure mask, which was tightly fitted around the volunteer’s face (Respironics). Air was warmed and humidified with a Vapotherm (Vapotherm, Inc).
A central catheter was introduced into the superior vena cava via an antecubital vein and used for cold-fluid infusion. Throughout the study period, mean skin temperature was maintained at 31°C, excluding the warming sites, by adjusting the temperature of circulating-water (Cincinnati Sub-Zero) and forced-air warmers. Furthermore, the back, upper body, and lower body were individually maintained at the designated skin temperature. On each day of the experiment, core cooling started 20 minutes after arteriovenous shunt vasoconstriction was documented (defined below).
Lactated Ringer’s solution, cooled to 4°C, was infused at rates sufficient to decrease tympanic membrane temperature 1°C/h to 2°C/h because these rates are not associated with induction of dynamic thermoregulatory responses.7 Fluid was given until the shivering threshold was identified.
Measurements
Heart rate was measured continuously with an ECG; blood pressure was determined oscillometrically at 5-minute intervals at the left ankle. A pulse oximeter continuously determined arterial oxygen saturation.
All temperatures were recorded with Mon-a-therm thermocouples (Mallinckrodt Anesthesiology Products, Inc). Core temperature was recorded from the tympanic membrane. Volunteers inserted the aural probe until they felt the thermocouple touch the tympanic membrane; appropriate placement was confirmed when volunteers easily detected gentle rubbing of the attached wire. The aural canal was occluded with cotton; the probe was securely taped in place; and a gauze bandage was positioned over the external ear.
Mean skin surface temperature was determined from 15 area-weighted sites.26,27 On the arm-warming day, lower-arm and hand temperatures were excluded from the calculation of mean skin temperature; similarly, facial temperature was excluded from the calculation of mean skin temperature on the face-warming day. Air temperature inside the mask was measured by a thermocouple hanging freely within the mask space, whereas facial skin temperature was measured by a thermocouple attached to the volunteer’s cheek.
Temperatures were recorded from thermocouples connected to calibrated Iso-Thermex 16-channel electronic thermometers having an accuracy of 0.1°C and a precision of 0.01°C (Columbus Instruments International, Corp). Individual and mean skin temperatures were computed by a data acquisition system, displayed at 1-second intervals, and recorded at 1-minute intervals.
Arteriovenous shunt vasomotor tone was evaluated with forearm-minus-fingertip and calf-minus-toe skin temperature gradients. There is excellent correlation between skin temperature gradients and volume plethysmography.28 Vasoconstriction was defined by a forearm-fingertip skin temperature gradient >0°C.
Shivering was quantified by oxygen consumption measured by a DeltaTrac (SensorMedics Corp) metabolic monitor; the system was used in canopy mode.29 Measurements were averaged over 1-minute intervals and recorded every minute. End-tidal PCO2 was measured with an Ultima monitor (Datex), and exhaust gases from this monitor were returned to the oxygen consumption monitor.
Data Analysis
On each study day, hemodynamic, respiratory, ambient temperature, and relative humidity data were averaged for each volunteer across the cooling period; these values were then averaged for all volunteers. A sustained increase in oxygen consumption (O2) of 
30%, as determined by a blinded investigator, identified the shivering threshold. The baseline for this analysis was the steady-state value (
5% variation in O2) before core cooling had started.
Results on the 3 study days were compared by use of repeated-measures analysis of variance (ANOVA) and Dunnett’s posthoc tests. Results are expressed as mean±SD; differences were considered statistically significant at P<0.05.
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Results |
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The volunteers were 28±3 years old, weighed 81±10 kg, and were 175±7 cm tall. One volunteer dropped out of the study after the control and arm-warming days.
Ambient temperature, relative humidity, mean arterial pressure, heart rate, respiratory rate, average end-tidal PCO2, and SpO2 were similar on each study day (Table 1). Mean skin temperature was maintained at 31°°C. Per protocol, all volunteers were vasoconstricted before the cold-fluid infusion started. Air temperature inside the continuous positive airway pressure mask on the face-warming day averaged 38.6±1.4°C (Table 2).
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Arm warming reduced the shivering threshold by 0.2±0.3°C, from 36.7±0.1°C to 36.5±0.3°C. Face warming reduced the shivering threshold by 0.1±0.3°C, from 36.7±0.1°C to 36.5±0.3°C (the Figure). The value for ANOVA across all 3 treatments was P=0.34, so posthoc comparisons were not undertaken. This study achieved a 95% power to detect a 0.5°C difference between the control threshold and either of the treatment thresholds at =0.05.
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) for shivering thresholds on the 3 experimental days. Mean±SD (
) for each day is also indicated. Thresholds did not differ significantly on the 3 treatment days. |
Discussion |
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The extent to which induction of core hypothermia will prove therapeutic in stroke victims remains unknown. Results in animals, though, are overwhelmingly positive and indicate that 3°C to 4°C of hypothermia provides better protection than existing pharmacological treatments.1,2 Uncontrolled human studies are also encouraging.30
Arm or face warming reduced shivering thresholds by only 0.2°C. Neither of these decreases was statistically significant (although we had 95% power to detect 0.5°C changes), and neither decrease was clinically important. Our data thus fail to support the proposal of Iaizzo et al15 that "this cooling paradigm holds promise as a means for the induction of mild hypothermia which may enhance cerebral protection in individuals at risk of brain injury."
The theory behind using cutaneous warming to treat shivering is that both skin and core temperatures contribute to control of thermoregulatory responses. Warming the skin surface reduces the core temperature that triggers shivering. However, skin temperature contributes only 20% to steady-state control of shivering.24,25 Furthermore, the extremities are relatively insensitive to thermal manipulation.31,32 Hand temperature was not reported by Sweney et al,14 but they also used a Bair Hugger forced-air warmer as the heat source. Thus, hand temperature in the 2 studies was presumably similar. However, we warmed both the hands and forearms rather than the hands alone. The forearm and hands constitute 10% of the total skin surface area and were warmed 6°C. We would thus expect that hand warming would reduce the shivering threshold only 0.1°C, which is entirely consistent with our results.
Thermal sensitivity of the upper chest and face is greater than that of the remaining skin surface.31,32 Furthermore, there are substantial regional differences within the face.33 We warmed the face and airway by injecting 21 L/min air at 42°C at a relative humidity of 100% into a tightly fitted mask. This increased facial temperature by 2.6°C. In contrast, Iaizzo et al15 used air at 32°C with 55% humidity and failed to report facial skin temperature. The difficulty with using facial warming to ablate shivering is that the surface area of the face is tiny, perhaps only 4.5% of the total skin area. It thus seems unlikely that facial warming alone would markedly reduce the shivering threshold. The extent to which oropharyngeal and airway thermal receptors contribute to control of shivering remains unknown. However, our results do not suggest that warming facial skin and airway receptors produces clinically important inhibition of shivering.
A critical difference between our study and previous similar ones14,15 is that we quantified the shivering threshold rather than simply observing a short-term reduction in shivering intensity. Thus, although Sweney et al14 and Iaizzo et al15 found that acute application of hand or face warming reduced shivering in nearly normothermic volunteers, we observed only trivial reductions in the steady-state shivering threshold. The most likely explanation is that unlike sustained warming, rapid increases in skin temperature provoke powerful dynamic responses.34 Thermoregulatory response thresholds35,36 and thermal sensation37–39 depend not only on static temperatures but also on the rate at which temperatures change. For example, rapid changes in skin temperature markedly augment cutaneous contribution to the sweating threshold35,36 and improve thermal sensation during hyperthermia.38 The magnitude of dynamic thermoregulatory response to facial warming remains unknown but may be even greater than for the skin surface as a whole.
Rapid increases in skin temperature ameliorate shivering.17–19 A brief reduction in shivering intensity might well facilitate performing a neurological examination, as proposed by Sweney et al.14 Nonetheless, therapeutic hypothermia must be maintained for hours or days and thus represents a thermal steady state. Therefore, the steady-state conditions of our study may best represent the typical clinical situation. Our results suggest that neither lower-arm nor face warming will prevent shivering over the period needed for therapeutic hypothermia.
Our volunteers were much younger and healthier than stroke victims, and temperature sensitivity is linearly dependent on age,40 with older people having a reduced cutaneous thermal sensitivity and a reduced thermal perception during cooling.32,41 Furthermore, the shivering threshold is reduced a full degree centigrade in the elderly.42 Inducing tolerance to therapeutic hypothermia is thus likely to be easier in elderly stroke victims than in young volunteers. Nonetheless, our results suggest that cutaneous warming alone will be insufficient and that pharmacological intervention13 will be required.
Because skin temperature contributes 20% to control of vasoconstriction and shivering,24 each 1°C decrease in mean skin temperature increases the shivering threshold 0.2°C. Mean skin temperature was kept constant at a low value throughout our study to increase the threshold, thereby minimizing risk from infusion of large amounts of cold fluid.
A limitation of our study is the use of tympanic membrane temperature as an indicator of core body temperature during face warming. Previous work suggests that tympanic membrane temperatures can be artifactually elevated during head43,44 or facial15,45,46 skin warming. However, the observed differences between tympanic and esophageal temperatures were tiny. Even small inaccuracies in our temperature measurements would not obviate our major finding that physical warming fails to induce useful amounts of thermoregulatory tolerance.
In summary, we found that neither lower-arm nor facial warming substantially reduces the shivering threshold in unanesthetized volunteers. It thus seems unlikely that either nonpharmacological intervention will contribute meaningfully to induction of therapeutic hypothermia.
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Acknowledgments |
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Funding was received from the Outcomes Research Institute and Departments of Anesthesiology and Pharmacology, University of Louisville, Louisville, Ky; Department of Anesthesiology, Chang Gung Memorial Hospital, Taipei, Taiwan; and the Ludwig Boltzmann Institute, University of Vienna, Vienna, Austria. This work was supported by Augustine Medical, Inc (Eden Prairie, Minn), NIH grant GM 58273 (Bethesda, Md), and the Commonwealth of Kentucky Research Challenge Trust Fund (Louisville). Mon-a-therm thermocouples were kindly provided by Tyco-Mallinckrodt Anesthesiology Products, Inc (St Louis, Mo). The facial and airway heating system was generously donated by Vapotherm, Inc (Annapolis, Md). We thank Gilbert S. Haugh, MS, and Nancy L. Alsip, PhD, for statistical and editorial assistance.
Received December 11, 2002; revision received January 29, 2003; accepted February 5, 2003.
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References |
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TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
1. Popovic R, Liniger R, Bickler PE. Anesthetics and mild hypothermia similarly prevent hippocampal neuron death in an in vitro model of cerebral ischemia. Anesthesiology. 2000; 92: 1343–1349.[CrossRef][Medline] [Order article via Infotrieve]
2. Sakai F, Amaha K. The effects of hypothermia on a cloned human brain glutamate transporter (hGLT-1) expressed in Chinese hamster ovary cells: -[3H]L-glutamate uptake study. Anesth Analg. 1999; 89: 1546–1550.
3. Dae MW, Gao DW, Sessler DI, Chair K, Stillson CA. Effect of endovascular cooling on myocardial temperature, infarct size, and cardiac output in human-sized pigs. Am J Physiol. 2002; 282: H1584–H1591.
4. Bernard SA, Gray TW, Buist MD, Jones BM, Silvester W, Gutteridge G, Smith K. Treatment of comatose survivors of out-of-hospital cardiac arrest with induced hypothermia. N Engl J Med. 2002; 346: 557–563.
5. Group THACAS. Mild therapeutic hypothermia to improve the neurologic outcome after cardiac arrest. N Engl J Med. 2002; 346: 549–556.
6. Sessler DI. Perioperative hypothermia. N Engl J Med. 1997; 336: 1730–1737.
7. Lopez M, Sessler DI, Walter K, Emerick T, Ozaki M. Rate and gender dependence of the sweating, vasoconstriction, and shivering thresholds in humans. Anesthesiology. 1994; 80: 780–788.[CrossRef][Medline] [Order article via Infotrieve]
8. Zweifler RM, Sessler DI, Zivin JA. Thermoregulatory vasoconstriction and shivering impede therapeutic hypothermia in acute ischemic stroke victims. J Stroke Cerebrovasc Dis. 1997; 6: 100–104.
9. De Witte J, Sessler DI. Perioperative shivering: physiology and pharmacology. Anesthesiology. 2002; 96: 467–484.[CrossRef][Medline] [Order article via Infotrieve]
10. Annadata RS, Sessler DI, Tayefeh F, Kurz A, Dechert M. Desflurane slightly increases the sweating threshold, but produces marked, non-linear decreases in the vasoconstriction and shivering thresholds. Anesthesiology. 1995; 83: 1205–1211.[CrossRef][Medline] [Order article via Infotrieve]
11. Matsukawa T, Sessler DI, Sessler AM, Schroeder M, Ozaki M, Kurz A, Cheng C. Heat flow and distribution during induction of general anesthesia. Anesthesiology. 1995; 82: 662–673.[Medline] [Order article via Infotrieve]
12. Kurz A, Ikeda T, Sessler DI, Larson M, Bjorksten AR, Dechert M, Christensen R. Meperidine decreases the shivering threshold twice as much as the vasoconstriction threshold. Anesthesiology. 1997; 86: 1046–1054.[CrossRef][Medline] [Order article via Infotrieve]
13. Mokhtarani M, Mahgob AN, Morioka N, Doufas AG, Sessler DI. Buspirone and meperidine synergistically reduce the shivering threshold. Anesth Analg. 2001; 93: 1233–1239.
14. Sweney MT, Sigg DC, Tahvildari S, Iaizzo PA. Shiver suppression using focal hand warming in unanesthetized normal subjects. Anesthesiology. 2001; 95: 1089–1095.[CrossRef][Medline] [Order article via Infotrieve]
15. Iaizzo PA, Jeon YM, Sigg DC. Facial warming increases the threshold for shivering. J Neurosurg Anesthesiol. 1999; 11: 231–239.[Medline] [Order article via Infotrieve]
16. Mekjavic IB, Eiken O. Inhibition of shivering in man by thermal stimulation of the facial area. Acta Physiol Scand. 1985; 125: 633–637.[Medline] [Order article via Infotrieve]
17. Murphy MT, Lipton JM, Loughran P, Giesecke AH Jr. Postanesthetic shivering in primates: inhibition by peripheral heating and by taurine. Anesthesiology. 1985; 63: 161–165.[CrossRef][Medline] [Order article via Infotrieve]
18. Sharkey A, Lipton JM, Murphy MT, Giesecke AH. Inhibition of postanesthetic shivering with radiant heat. Anesthesiology. 1987; 66: 249–252.[CrossRef][Medline] [Order article via Infotrieve]
19. Sharkey A, Gulden RH, Lipton JM, Giesecke AH. Effect of radiant heat on the metabolic cost of postoperative shivering. Br J Anaesth. 1993; 70: 449–450.
20. Delaunay L, Bonnet F, Liu N, Beydon L, Catoire P, Sessler DI. Clonidine comparably decreases the thermoregulatory thresholds for vasoconstriction and shivering in humans. Anesthesiology. 1993; 79: 470–474.[CrossRef][Medline] [Order article via Infotrieve]
21. Talke P, Tayefeh F, Sessler DI, Jeffrey R, Noursalehi M, Richardson C. Dexmedetomidine does not alter the sweating threshold, but comparably and linearly reduces the vasoconstriction and shivering thresholds. Anesthesiology. 1997; 87: 835–841.[CrossRef][Medline] [Order article via Infotrieve]
22. Delaunay L, Bonnet F, Duvaldestin P. Clonidine decreases postoperative oxygen consumption in patients recovering from general anaesthesia. Br J Anaesth. 1991; 67: 397–401.
23. Horn E-P, Standl T, Sessler DI, von Knobelsdorff G, Büchs C, Schulte am Esch J. Physostigmine prevents postanesthetic shivering as does meperidine or clonidine. Anesthesiology. 1998; 88: 108–113.[CrossRef][Medline] [Order article via Infotrieve]
24. Cheng C, Matsukawa T, Sessler DI, Kurz A, Merrifield B, Lin H, Olofsson P. Increasing mean skin temperature linearly reduces the core-temperature thresholds for vasoconstriction and shivering in humans. Anesthesiology. 1995; 82: 1160–1168.[CrossRef][Medline] [Order article via Infotrieve]
25. Lenhardt R, Greif R, Sessler DI, Laciny S, Rajek A, Bastanmehr H. Relative contribution of skin and core temperatures to vasoconstriction and shivering thresholds during isoflurane anesthesia. Anesthesiology. 1999; 91: 422–429.[CrossRef][Medline] [Order article via Infotrieve]
26. DuBois D, DuBois EF. A formula to estimate the approximate surface area if height and weight be known. Arch Intern Med. 1916; 17: 863–871.
27. Sessler DI, McGuire J, Moayeri A, Hynson J. Isoflurane-induced vasodilation minimally increases cutaneous heat loss. Anesthesiology. 1991; 74: 226–232.[CrossRef][Medline] [Order article via Infotrieve]
28. Rubinstein EH, Sessler DI. Skin-surface temperature gradients correlate with fingertip blood flow in humans. Anesthesiology. 1990; 73: 541–545.[Medline] [Order article via Infotrieve]
29. Tissot S, Delafosse B, Bertrand O, Bouffard Y, Viale JP, Annat G. Clinical validation of the Deltatrac monitoring system in mechanically ventilated patients. Int Care Med. 1995; 21: 149–153.[CrossRef][Medline] [Order article via Infotrieve]
30. Schwab S, Schwarz S, Spranger M, Keller E, Bertram M, Hacke W. Moderate hypothermia in the treatment of patients with severe middle cerebral artery infarction. Stroke. 1998; 29: 2461–2466.
31. Burke WEA, Mekjavic IB. Estimation of regional cutaneous cold sensitivity by analysis of the gasping response. J Appl Physiol. 1991; 71: 1933–1940.
32. Stevens JC, Choo KK. Temperature sensitivity of the body surface over the life span. Somatosens Mot Res. 1998; 15: 13–28.[CrossRef][Medline] [Order article via Infotrieve]
33. Green BG, Gelhard B. Perception of temperature on oral and facial skin. Somatosens Mot Res. 1987; 4: 191–200.
34. Hensel H. Thermoreception and Temperature Regulation. London, UK: Academic Press; 1981.
35. Wyss CR, Brengelmann GL, Johnson JM, Rowell LB, Silverstein D. Altered control of skin blood flow at high skin and core temperatures. J Appl Physiol. 1975; 38: 839–845.
36. Brengelmann GL, Wyss C, Rowell LB. Control of forearm skin blood flow during periods of steadily increasing skin temperature. J Appl Physiol. 1973; 35: 77–84.
37. Hensel H; Zotterman Y, ed. Correlations of Neutral Activity and Thermal Sensations in Man: Sensory Functions of the Skin. Oxford, UK: Pergamon; 1981: 331–353.
38. Kato M, Sugenoya J, Matsumoto T, Nishiyama T, Nishimura N, Inukai Y, Okagawa T, Yonezawa H. The effects of facial fanning on thermal comfort sensation during hyperthermia. Pflugers Arch. 2001; 443: 175–179.[CrossRef][Medline] [Order article via Infotrieve]
39. Herrmann C, Candas V, Hoeft A, Garreaud I. Humans under showers: thermal sensitivity, thermoneutral sensations, and comfort estimates. Physiol Behav. 1994; 56: 1003–1008.[CrossRef][Medline] [Order article via Infotrieve]
40. Meh D, Denislic M. Quantitative assessment of thermal and pain sensitivity. J Neurol Sci. 1994; 127: 164–169.[CrossRef][Medline] [Order article via Infotrieve]
41. Smolander J. Effect of cold exposure on older humans. Int J Sports Med. 2002; 23: 86–92.[CrossRef][Medline] [Order article via Infotrieve]
42. Vassilieff N, Rosencher N, Sessler DI, Conseiller C. The shivering threshold during spinal anesthesia is reduced in the elderly. Anesthesiology. 1995; 83: 1162–1166.[CrossRef][Medline] [Order article via Infotrieve]
43. McCaffrey TV, McCook RD, Wurster RD. Effect of head skin temperature on tympanic and oral temperature in man. J Appl Physiol. 1975; 39: 114–118.
44. McCaffrey TV, Geis GS, Chung JM, Wurster RD. Effect of isolated head heating and cooling on sweating in man. Aviat Space Environ Med. 1975; 46: 1353–1357.[Medline] [Order article via Infotrieve]
45. Thomas KA, Savage MV, Brengelmann GL. Effect of facial cooling on tympanic temperature. Am J Crit Care. 1997; 6: 46–51.[Abstract]
46. Cabanac M, Germain M, Brinnel H. Tympanic temperatures during hemiface cooling. Eur J Appl Physiol Occup Physiol. 1987; 56: 534–539.[CrossRef][Medline] [Order article via Infotrieve]
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