The present invention concerns a device for dilating extremity blood vessels by thermal treatment. Hereinafter such device is referred to as a thermal vascular dilator.

A great part of medical research is based on collecting numerous blood samples from patients and hea ^' lthy test persons. This necessitates insertion of sampling and infusion cannulas in peripheral arm veins. Tolerance tests are carried out also in routine medical services and form the base of many endocrine analyses. Also our entire hormone diagnostics is based on venepuncture. Since not all patients have vessels perfect to puncture it has been necessary to employ specialized test nurses being well trained in puncturing and managing the insertion of test needles in a patient. Many patients w th endocrine diseases have bad vessels. Such diseases are, e.g. , Cushmg's syndrome, Addison's disease, diabetes, 'hypofysial malfunctions including a.o. obesity and so on. It has become a routine, therefore, to utilize commonly available heat pads for heating of an arm before a puncturing attempt is made. In thi3 way the circulation is increased and a better filling of the vessels is obtained which facilitates cannula insertion. The existing heat pads, however, are not adapted to this purpose. They easily slip off and the heating • efficiency is bad. For certain purposes these heat pads arequite ^■ unsuitable , e.g. when there is a need for a so arterialization of venous blood. The thermostat used in the pads periodically swithces the current off and on which results in great temperature fluctuations and consequently very uncertainly varying arterialization of the blood.

There is a need, thus, for a suiatable thermal vascular dilator having a stable temperature steplessly variable between 27°C and 50°C. Such a device would be useful within all instances of public medical care where blood sampling occurs, as well within polyclinical as institutional medical care. A vessel dilator would be a great help for all nurses who often have to make venepunctures on patients having bad vessels. It is commonly known within the medical care that this oftenly is a problem. An efficient remedy should save much time and thereby release resources needed in other areas of the medical service.

It should be particularly valuable if all acute surgeries and intensive care surgeries could be equipped with several vascular dilators. It could then be possible to decrease the number of exposals and decrease the use of nurse anaesthe ists for cannula ^' and- catheter insertions in s ck patients. By using "arterlalized" blood (i.e. increased circulation due to ^' heat, whereby a greater part of artery blood enters the vein vessel system) it is not necessary in certain cases to utilize artery punction, but it is possible to take samples from a peripheral vein. Artery punction is oftenly associated with a greater risk for ^" the patient than ordinary venepunction .

Thus, a thermal vascular dilator can be used in numerous connections within the practical medical care as well as within research. It has its place at al'l levels of medical care and in specialities, not the least within children's hospitals and psychiatric . clinics where venepuncture causes special problems.

The object of the invention, thus, is to provide a device of the kind initially stated which apart from the desirable thermal properties offers a practical and simple handling and is comfortable for the patient.

This is accomplished in that the invention has been given the characteristic features stated in the appended claims.

An exemplifying embodiment of the invention will hereinafter be described under reference to the accompanying drawing, wherein fig. 1 shows a perspective view of a thermal vascular dilator according to the invention and fig. 2 shows same with an arm of a patient received there-in.

The -thermal vascular dilator according to the ^' invention comprises an elongate support member 1 of -a relatively rigid material, such as a hard plastic (thermoplastic resin) . The support member 1 has the shape of a channel, substantially U-shaped in cross-sec ion, which is adapted to the extremity m question, in this case an arm.

Inside the support member is fastened a sleeve 2 of flexible material, such as a relatively soft plastic. Between two layers 3 and 4 are laminated electrical resistance elements 5, which are ,voltage-fed through a cable 6 and a connection

7. Insulating layers not shown may be located between the elements 5 and the layers 3 and 4. The elements 5 preferably are so called foil elements.

By means of slots 8, 9 and 10, 11 the sleeve 2 is divided in several sections 12, 13 and 14, which can be closed separately around the arm of a patient by putting opposed flaps of the sleeve portions on each other and interlocking them by cooperating so called Velcro strips 15 and 16, 17 and 18, and, 19 and 20.

In the forward end of the support member 1 there is a cross-wise extending gripping handle 21, around which a patient is supposed to grip with his hand. Hereby is achieved what is achieved in normal venepunction by the patient clenching his hand, as well as a general stabilization of the entire aggregate relative to the arm of the patient .

In its forward end the sleeve 2 also has two forwardly directed flaps 22 and 23, which can be wrapped around the hand of the patient and be fastened to the support member 1 onto Velcro strips attached thereon, only one 26 of which is shown in fig . 1.

As appears from fig. 2, after a desired heating time a certain section of the sleeve 2 , here the section 14, may be opened for exposal of the arm of the patient.