Phys Ther 1987 Belitsky 1080 4

1987; 67:1080-1084.PHYS THER. Hubley-KozeyRosalind B Belitsky, Stella J Odam and Cheryland Cryogen Packs in Reducing Skin TemperatureEvaluation of the Effectiveness of Wet Ice, Dry Ice,

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Evaluation of the Effectiveness of Wet Ice, Dry Ice, and Cryogen Packs in Reducing Skin Temperature

ROSALIND B. BELITSKY, STELLA J. ODAM, and CHERYL HUBLEY-KOZEY

The purposes of this study were to evaluate and compare the ability of wet ice (WI), dry ice (DI), and cryogen packs (CGPs) to reduce and maintain the reduction of skin temperature directly under the cooling agent and to determine whether the cooling effect on skin extended beyond the surface area in contact with the cooling agent. Ten female volunteers participated in the study, and each of the three cold modalities was applied randomly to the skin overlying the right triceps surae muscle. After 15 minutes of cold application, mean skin temperatures recorded under WI, DI, and CGP decreased 12°, 9.9°, and 7.3°C, respectively. The only significant differences in cooling were between WI and DI and between WI and CGP. Fifteen minutes after removal of the cold modalities, no significant differences were found in mean skin temperature between WI, DI, and CGP. The residual mean decrease in skin temperature between the pretreatment rest interval (time 0) and 15 minutes after removal of the cold modality (time 30) was significant for WI only. No cooling was demonstrated 1 cm proximal or distal to any of the cooling agents after 15 minutes of cold application. These findings provide valuable information for the use of cryotherapy in the clinical setting.

Key Words: Cryotherapy, Physical therapy, Skin temperature.

Cryotherapy is used in the treatment of various musculoskeletal and neuro­logical disorders. Both physiological and clinical evidence suggest that cold application in various forms can be val­uable in reducing musculoskeletal pain, muscle spasm, connective tissue disten-sibility, nerve conduction velocity, hem­orrhage, edema, inflammation, and in­tramuscular temperature.1,2 Evidence also exists that cold can be used as an aid to neuromuscular facilitation.3

Despite the widespread use of cryo­therapy, a lack of quantitative data ex­ists for determining the exact specifica­tion for its use. For example, the most effective mode of a cold application, the length of time needed to cool an area, the amount of time that an area remains cool after the removal of the cold appli­

cation, and the amount of cooling that occurs beyond the area in contact with the cooling agent have not been ad­dressed fully.

Several studies have been conducted relating cold applications to the skin to decreased subcutaneous and intramus­cular temperatures.4-15 Several investi­gators have demonstrated that the tem­perature of the skin is related to the temperature of the tissue underlying it; that is, the more the skin is cooled in absolute degrees, the greater the cooling of the underlying tissues.4,6,7

A few individuals have evaluated the effectiveness of different cooling agents on deep and superficial tissues. Mc-Master et al evaluated four different modes of cooling: ice chips in a plastic bag, chemical ice envelopes, refrigerant-inflated bladders, and prefrozen gel packs.10 In their study, two dogs were anesthetized, their thighs were shaved, and their temperatures were recorded using a hypodermic thermistor probe inserted beneath the skin into the deep quadriceps muscle mass immediately adjacent to the femoral shaft. Readings were taken at 15-minute intervals for one hour. They found that chipped ice was the most efficient mode of cooling, followed by a slightly less efficient gel

pack. The other two cooling mediums were the least efficient in cooling the deep tissues.

McKeeken et al compared the effi­ciency of two cold modalities—ice and cryogen packs—by measuring their re­spective effects on skin temperature di­rectly beneath the cooling agent and on nerve conduction velocity of the under­lying motor nerve fibers.13 After 20 min­utes of cooling the upper arm, they found that ice was more effective than cold packs in cooling superficial and possibly deep tissues beneath the cooling agent.

LaVelle and Snyder evaluated the cooling of the skin using chipped ice in a plastic bag applied directly to the skin and through various barriers, including padded and unpadded elastic bandages and dry and damp washcloths.14 They found that skin temperature was re­duced significantly when ice was applied over a dry washcloth, a damp washcloth, and an unpadded elastic bandage and when applied directly to the skin; how­ever, cold was not conducted through a padded elastic bandage. No significant differences in cooling, however, were found between the use of a damp wash­cloth and direct application to the skin. Although these articles provide the cli-

Ms. Belitsky is Staff Physical Therapist, Nova Scotia Rehabilitation Centre, Physiotherapy De­partment, 1341 Summer St, Halifax, Nova Scotia, Canada B3H YK4.

Ms. Odam is a physical therapist, Bedford Sack-ville Physiotherapy Clinic, Bedford, Nova Scotia, Canada B4A 2X9.

Ms. Hubley-Kozey is Assistant Professor, School of Physiotherapy, Dalhousie University, Halifax, Nova Scotia, Canada B3H 3J5.

This article was submitted February 18, 1986; was with the authors for revision 21 weeks; and was accepted September 75, 1986. Potential Conflict of Interest: 4.

1080 PHYSICAL THERAPY

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RESEARCH nician with some information regarding the application of cold, many questions remain unanswered.

For musculoskeletal disorders, three cold modalities commonly used inter­changeably in clinical practice are wet ice (WI), dry ice (DI), and cryogen packs (CGPs).15 Clinical application time gen­erally is between 10 and 45 minutes, although the average application time is 15 minutes. No studies have used this clinical time frame to assess the effec­tiveness of these three modalities for reducing skin temperature in contact with the cooling agent, maintaining the temperature reduction, or cooling the skin surface beyond contact with the cooling agent. These factors are impor­tant for determining the effectiveness of the treatments and will provide a basis for determining more precise specifica­tions for using the three methods.

The purposes of this study were to quantify and compare the ability of WI, DI, and CGPs to reduce skin tempera­ture and to determine the magnitude of the warming that occurred after removal of the cooling agent. We also wanted to determine the effectiveness of each agent in cooling the skin surface area beyond contact with the cooling agent.

We anticipated that skin temperatures would decrease directly beneath the cooling agent and that cooling would occur beyond the area of skin surface in contact with the agent. We also expected that rapid warming of the skin would not occur after removal of the cooling agent because therapeutic techniques such as joint mobilization and muscle stretching often are tolerated subsequent to cryotherapy. Because clinicians use ice and CGPs interchangeably, we have attempted to determine their compara-biUty.

METHOD

Subjects Ten healthy female volunteers partic­

ipated in the study. Their mean age, body mass, and height were 23.3 ± 2.2 years, 58.6 ± 4.6 kg, and 165.9 ± 4.1 cm. Subjects were screened and ex­cluded from the study if they had open leg sores, cardiovascular or peripheral vascular disease, known muscular or neurological pathological conditions, or a history of smoking. Each volunteer was informed of the procedure of the study and the risks involved, and in­formed consent was obtained before participation in the study.

Various precautions were taken to prevent hypothermia, frostbite, or ice burn. These precautions were excluding fair-skinned subjects from the study; covering the subject's body, except for the lower limb being tested, with a blan­ket; monitoring the subject's skin tem­perature at 5-minute intervals proximal and distal to the site of cold application; asking the subject to report any discom­fort; and limiting the length of applica­tion to 15 minutes.

Fifteen minutes was chosen for this study because this time period com­monly is used clinically and because observations have shown that minimal patient discomfort within this time frame has resulted in high patient com­pliance.

Equipment and Materials

Skin and air temperature were re­corded to the nearest 0.1°C using a Yellow Springs Model 44TD telether-mometer* similar to that reported in the literature.5,12 A Yellow Springs Model T2630 proximal skin temperature probe* was held in place by a 0.3-kg waterproof sandbag. The distal and cen­tral measurements were taken with a Yellow Springs Model T2625 "banjo" probe* that also was held in place with a 0.3-kg sandbag. The probes used were calibrated in a water bath over the range of evaluation and checked against a lab­oratory mercury thermometer. The WI consisted of ice flakes, and the DI con­sisted of ice flakes enclosed in a plastic bag. We used a commercially available CGP.† Each modality was wrapped in a wet, uniformly sized terry-cloth towel that had been dampened with cool water. Excess water was wrung out of the towels before wrapping. The surface area of each pack was 10 x 24 cm, total weight was 0.5 kg, and the starting tem­perature on the surface of the cold me­dium was between 0° and 2°C. The flaked ice was produced by a Scotsman* ice machine, and the CGP was frozen for two hours before use, as recom­mended by the manufacturers.

Procedure

Each subject participated in three, 45-minute sessions that were conducted at least 6 hours apart. The three treatments

were assigned randomly at each of these sessions. Each session consisted of 15 minutes rest, 15 minutes of cold appli­cation, and 15 minutes without treat­ment (corresponding to times 0, 15, and 30, respectively).

The subjects were instructed to refrain from heavy exercise and ingesting caf­feine for two hours before each session. They were requested to wear shorts and long-sleeved shirts and to remove their shoes and socks during the testing ses­sion. Testing was conducted in a ther­mostatically controlled room in which the temperature ranged from 22° to 24°C. The subjects lay in the prone po­sition on a plinth with one pillow under their tested lower leg, one under their stomach, and one under their head throughout the experiment. Subjects were requested to relax and limit the movement of their legs to prevent un­necessary muscle activity that could cause temperature changes.

Rest period. During the rest period, we tested the subjects for hot and cold sensation by touching the leg to be tested with one test tube filled with hot tap water and with another filled with cold tap water. Sensation was considered in­tact if the subject could discriminate between the hot and cold tubes.15 A point on the belly of the gastrocnemius muscle one quarter of the distance be­tween the popliteal crease and the me­dial malleolus was marked with an in­delible ink marker. Two other points were marked 8 cm proximal and distal to this point. A resting skin temperature was recorded at each of the three points. Air temperature also was recorded.

Cold application. One of the three modalities described above was selected randomly and applied over the central point on the gastrocnemius muscle with its length perpendicular to the axis of the three points. Proximal- and distal-point skin temperatures were recorded at 5-minute intervals during the 15 min­utes of cold application. The cooling agent then was removed, and the central skin and air temperatures were re­corded.

Recovery. Fifteen minutes after re­moval of the cooling agent, central, proximal, and distal skin temperatures and air temperatures were recorded.

Data Analysis

A 3 x 3 analysis of variance (AN-OVA) for repeated measures was used

* YSI Co, Inc, Yellow Springs, OH 45387. † Cryogel Brand,- 3M Co, Health Care Specialties

Div, 3M Center, St. Paul, MN 55144-1000. ‡ Model AFIAW-ID, Queen Products, Div of

King-Seeley Thomas Co, 505 Front, Albert Lea, MN 56007.

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to statistically analyze the data, using a level of significance of .05. The Bonfer-roni post hoc test was used to determine the differences between all possible pairs of means with significant probability values.16

RESULTS

Central Skin Temperature Measurement

Before the application of the cooling agent, the mean central starting temper­atures on the skin were between 29.5° and 30.0°C. After 15 minutes of cold application, the skin temperatures de­creased to 17.9°, 20.1°, and 22.1°C for WI, DI, and CGP, respectively. Fifteen minutes after removal of the cold mo­dality, mean skin temperatures were be­tween 27.0° and 28.2°C for all condi­tions (Fig. 1).

The ANOVA results shown in Table 1 illustrate significant differences (p < .05) for time, treatment, and time-treat­ment interaction. The post hoc analysis showed no significant differences be­tween WI, DI, and CGP at time 0. After 15 minutes of cold application, the post hoc analysis revealed significant differ­ences between the means of WI and DI and those of WI and CGP, with WI demonstrating the greatest mean de­crease in skin temperature. The differ­ence between DI and CGP, however, was not significant.

Fifteen minutes after the removal of the cold modality, we found no signifi­cant differences between the three treat­ments. All pair-wise means over time were significantly different for the WI treatment. For DI and CGP, the mean skin temperatures at time 15 differed significantly from those at time 0 and time 30, but no significant differences were found between them at time 0 and time 30.

Proximal and Distal Skin Temperature Measurements

No significant differences were found between distal mean skin temperatures, before, during, and after cold applica­tion for the three treatments (Fig. 2, Tab. 2). For the proximal mean skin temperature, we found no significant differences between treatments at differ­ent time intervals or for time-treatment interactions, although the ANOVA did reveal a significant time effect (p < .05) (Fig. 3, Tab. 3). The post hoc analysis revealed a significant pair-wise differ­

ence for WI between time 0 and time 15 that was the result of warming.

DISCUSSION Results of this study provide support

for previous related work and informa­tion that should prove valuable for ther­apists using cold therapy in the clinical setting. The data revealed that WI was significantly more efficient in reducing skin temperature than DI and CGP. These results are consistent with those of McKeeken et al,13 who measured su­perficial cooling in the upper arm in humans, and with those of McMaster et al,10 who measured cooling deep in the quadriceps femoris muscles of dogs.

The skin temperature decreases re­corded in this study warrant further elaboration with respect to some basic research and clinical practicalities. Some studies have shown that skin tempera­tures less than 16°C are necessary for

anesthesia,2,6 analgesia,17 and relaxation sufficient to permit active and passive exercising of painful areas immediately after treatment.6 None of the three cold modalities used in our experiment pro­duced skin temperature cooling below 17°C. Further studies should investigate whether cooling times longer than 15 minutes, using the cold modalities in this study, could produce temperature decreases required for anesthesia or an­algesia.

In clinical practice, CGPs are reusable and can be applied quickly and easily, DI is the most time-consuming to pre­pare, and WI is the least desirable mo­dality because of melting and dripping. After 15 minutes of cold application, WI yielded the skin temperature de­creases closest to those necessary for anesthesia and analgesia. Unfortu­nately, although CGPs are the most con­venient medium to use, they are the least efficient in skin cooling and in our

Fig. 1. Means and standard deviations of central skin temperatures at 0, 15, and 30 minutes for wet ice (WI), dry ice (DI), and cryogen pack (CGP).

TABLE 1 Analysis of Variance for Central Skin Temperatures

Source Blocks-subjects Ice Error Time Error Ice time Error TOTAL (Residual)

df 9 2

18 2

18 4

36 89 72

SS 64.87 41.96 62.26

1605.12 36.75 59.61 43.59

1914.16 142.60

MS

20.98 3.46

802.56 2.04

14.90 1.21

F

6.06

393.02

12.31

P

.009

.001

.001

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RESEARCH

Fig. 2. Means and standard deviations of distal skin temperatures at 0, 15, and 30 minutes for wet ice (WI), dry ice (DI), and cryogen pack (CGP).

TABLE 2 Analysis of Variance for Distal Skin Temperatures

Source Blocks-subjects Ice Error Time Error Ice time Error TOTAL (Residual)

df 9 2

18 2

18 4

36 89 72

SS 91.79

1.15 82.27 3.98

16.34 3.32

18.47 217.32 117.08

MS

0.58 4.57 1.99 0.91 0.83 0.51

F

0.13

2.19

1.62

P

NS

NS

study did not produce the skin temper­ature reductions necessary for the phys­iological changes discussed previously.

Temperature readings 1 cm proximal and distal to the site of application did not change significantly throughout the cold applications. We attributed the pair-wise mean that showed a significant difference with respect to time to chance because it represented 1 pair-wise differ­ence in 36. These results suggest that no cooling of the skin occurs that is not in contact with the cold modality. We found no other literature that examined this relationship. The proximal and dis­tal skin temperature readings are impor­tant to the therapist because only the skin surface in direct contact with the cold modality is cooled, making ade­quate size and careful placement of the cold modality essential requirements for its use.

The lack of spread of skin surface cooling may be due to the excellent

insulating property of the skin and sub­cutaneous tissue and the body's homeo-static mechanism. The application of cold to the skin initiates complex phys­iological reactions aimed at conserving heat in the body's core. These reactions are brought about by peripheral venous constriction, decreased peripheral blood flow, and increased venous pressure.18

To investigate the proximal and distal spread of cold temperatures in deeper tissues, further investigations using in­vasive techniques are necessary.

Fifteen minutes after the removal of the cold modality, rewarming occurred. Waylonis,6 Lewis and Clayfield,5 and McKeeken et al13 demonstrated similar trends in rewarming of the skin. In our study, only WI demonstrated a signifi­cant temperature difference between time 0 and time 30. These findings are consistent with those of McKeeken et al,13 who demonstrated that posttreat-ment skin temperatures remained the

coldest when ice was used. They also showed that greater changes in conduc­tion velocity of nerve fibers were pro­duced by ice packs, as compared with commercially produced CGPs.

These results suggest that therapeutic exercises and mobilization techniques should be started during or as soon as possible after cryotherapy because of the rapid rewarming demonstrated in this study. Because WI provides the greatest amount of cooling immediately after treatment and because the treated tis­sues remain slightly cooler after cold removal, we considered WI to be the best modality of those tested to use for therapeutic cooling.

CONCLUSION

Although not as convenient as DI and CGPs, WI resulted in skin temperature decreases closest to those necessary for anesthesia, analgesia, and relaxation suf­ficient to permit active and passive ex­ercising of painful areas. Cooling did not extend beyond the surface area in con­tact with the cold modality. Two impor­tant considerations regarding the use of cryotherapy, therefore, are the place­ment and the size of the cold modality. Because of the rapid rewarming that occurred after removal of the cold mo­dality, therapeutic exercise and mobili­zation techniques should be imple­mented during or as soon as possible after the removal of the cold modality. Although WI provided the only signifi­cant difference between time 0 and time 30, skin temperatures for all three cool­ing agents at time 30 were higher than those required for an anesthetic or an­algesic effect.

This study provides valuable infor­mation for the use of cold modalities. It is evident from this work that research should be directed toward developing more precise specifications for the use of cold therapy to ensure optimal ther­apeutic results.

Acknowledgment. We thank the School of Physiotherapy, Dalhousie University, for the use of its facilities.

REFERENCES

1. Olson JE, Stravino VD: A review of cryother­apy. Phys Ther 52:840-853, 1972

2. Weeks VP, Travell J: How to Give Painless Injections. New York, NY, Grune & Stratton Inc, 1957, pp 318-322

3. Urbscheit N, Bishop B: Effects of cooling on the ankle jerk and H-response. Phys Ther 50:1041-1049,1970

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4. Abramson Dl: Physiological basis for the ef­fects of physical agents in peripheral vascular disorders. Arch Phys Med Rehabil 46:216-244, 1965

5. Lewis M, Clayfield J: Temperature changes following quick icing: A brief investigation. Aus­tralian Journal of Physiotherapy 27:175-178, 1981

6. Waytonis GW: The physiological effect of ice massage. Arch Phys Med Rehabil 48:37-42, 1967

7. Bierman W: Therapeutic uses of cold. JAMA 57:1189-1192,1955

8. Wolf SL: Contralateral upper extremity cooling from a specific cold stimulus. Phys Ther 51:158-165,1971

9. Wolf SL, Basmajian JV: Intramuscular temper­ature changes deep to localized cutaneous cold stimulation. Phys Ther 53:1284-1288, 1973

10. McMaster WC, Liddle S, Waugh TR: Labora­tory evaluation of various cold therapy modal­ities. Am J Sports Med 6:291-294, 1978

11. Lowden BJ, Moore RJ: Determinants and na­ture of intramuscular temperature changes during cold therapy. Am J Phys Med 54:223-233, 1975

12. Oliver RA, Johnson DJ, Wheelhouse WW, et al: Isometric muscle contraction response dur­ing recovery from reduced intramuscular tem­perature. Arch Phys Med Rehabil 60:126-129, 1979

13. McKeeken J, Lewis M, Cochs S: Effects of cooling with simulated ice on skin temperature and nerve conduction velocity. Australian Jour­nal of Physiotherapy 30:111-114, 1984

14. LaVelle BE, Snyder M: Differential conduction of cold through barriers. J Adv Nurs 10:55-61, 1985

15. Wadsworth H, Chanmugam APP: Electrophys-ical Agents in Physiotherapy, ed. 2. Marrick-vilte, Australia, Australia Science Press, 1983, pp 93-107

16. Wilks SS: Mathematical Statistics. New York, NY, John Wiley & Sons Inc, 1962

17. Bugaj R: The cooling, analgesic, and rewarm-ing effects of ice massage on localized skin. Phys Ther 55:11-19, 1975

18. Fox RH: Local cooling in man. Br Med J 17:14-18,1961

Fig. 3. Means and standard deviations of proximal skin temperatures at 0, 15, and 30 minutes for wet ice (WI), dry ice (DI), and cryogen pack (CGP).

TABLE 3 Analysis of Variance for Proximal Skin Temperatures

Source Blocks-subjects Ice Error Time Error Ice time Error TOTAL (Residual)

df 9 2

18 2

18 4

36 89 72

SS 46.55

1.80 16.44 4.57

10.78 1.81

11.23 93.19 38.45

MS

0.90 0.91 2.29 0.60 0.45 0.31

F

0.99

3.87

1.45

P

.04

NS

1084 PHYSICAL THERAPY

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1987; 67:1080-1084.PHYS THER. Hubley-KozeyRosalind B Belitsky, Stella J Odam and Cheryland Cryogen Packs in Reducing Skin TemperatureEvaluation of the Effectiveness of Wet Ice, Dry Ice,

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