The study has been postponed indefinitely. It is likely to be carried out in 2026-27

Low-intervention clinical trial. The thermal and hemodynamic effects of different cryotherapy devices are evaluated. This study is included in the doctoral thesis of the principal investigator.

Investigators:

Principal Investigator: Julio Alberto Mateos Arroyo (RN, MSc, PhD student) Directors: Ignacio Zaragoza García (RN, PhD), Ismael Ortuño Soriano (RN, PhD), Paloma Posada Moreno (PhD).

Setting: Faculty of Nursing, Physiotherapy and Podiatry of the Universidad Complutense de Madrid.

The three interventions to be evaluated are:

• Applying crushed ice.
• Apply frozen peas.
• Apply comparator.

Hypothesis: There are differences in the reduction of temperature, dimensions of the internal lumen of the radial artery and blood flow inside it depending on the different modalities of cryotherapy (crushed ice or bag of frozen peas) applied in the anatomical area of the wrist, point of arterial puncture for blood gas analysis.

Main objective: To analyze the effect of 3 cryotherapy devices on the radial artery area.

Secondary objectives

• To analyze the thermal behavior of the superficial tissue under study according to the cryotherapy device used.
• To analyze the differences in the radial artery caliber before and after the application of cold in the different experimental modalities under study.
• To analyze the differences in radial artery blood flow before and after the application of cold in the different experimental modalities under study.
• To identify the safety pattern of the use of the different cryotherapy devices (adverse events).

Design: Randomized controlled clinical trial. This is a crossover clinical trial in which all participants will receive all interventions and will be randomized in the order in which they receive them.

Population: Adults with a good general state of health, who specifically do not have factors that could affect their thermoregulation or vascular pathologies.

Main variables:

• Skin surface temperature.
• Radial artery size.
• Radial artery blood flow.

Pain caused by arterial puncture for blood gas analysis is one of the most common problems with this procedure. The low utilization rates of effective methods by healthcare providers for pain reduction, such as subcutaneous infiltration of anesthetics, make it necessary to search for effective and simple methods. The use of cryotherapy devices has proven effective for this purpose because the decrease in temperature increases pain threshold and tolerance due to a reduction in nerve conduction velocity and inhibition of nociceptors. In order to standardize these devices, it is necessary to understand the specific thermodynamic and hemodynamic effects of these devices. At the hemodynamic level, the reduction in temperature can produce arterial vasoconstriction. This effect may decrease the palpation of the radial artery, a necessary step for the identification of the optimal point of arterial puncture. Our hypothesis is that there are differences in temperature reduction, radial artery internal lumen dimensions and blood flow inside the radial artery depending on the different cryotherapy modalities applied in the anatomical area of the wrist, the point of arterial puncture for blood gas analysis. In order to obtain an answer to this hypothesis, we will propose a randomized controlled clinical trial with a sham comparator and two active interventions: crushed ice and frozen peas. In addition, this trial has a crossover design with the aim of minimizing the differences that may arise due to individual particularities (within-group variability), and thus increase the possible effect of the interventions (between-group variability). This choice has its justification in that the application of cryotherapy, according to some studies, has a thermal reducing effect with high individual variability. In this study, adults with a good general state of health, who specifically do not have factors that could affect their thermoregulation or vascular pathologies, will be recruited.

Inclusion Criteria:

• Good general health.
• Conscientious, with full cognitive and communicative capacity.
• Signed informed consent for this randomized clinical trial.

Exclusion Criteria:

• Active smoker.
• Cardiovascular disease.
• Peripheral vascular disease.
• Cyanosis of hands and fingers, Raynaud's Syndrome, Scleroderma and/or CREST Syndrome.
• Diabetes.
• Surgery, recent wounds or any type of major injury affecting the neck, shoulder girdle, upper limbs and/or hands.
• Carrier of an arterio-venous fistula.
• Lack of sensitivity to cold.
• Alcohol or caffeine intake in the last 24 hours.
• Intense physical exercise in the last 24 hours.

This study uses a single-blind masking. The 2 interventions and the comparator are contained in opaque bags, that prevents participants from having visual knowledge of the contents of the bags.