Use of ultrasounds for the treatment of decompression sickness Technicalfield The present invention concerns with the use of ultrasounds for the treatment of decompression sickness. Another object of the present invention is an apparatus emitting ultrasounds able to be used for the above treatment.

Background of the invention It is generally acknowledged that the decompression sickness is caused by bubbles of inert gas in the blood and tissues due to a too rapid pressure reduction in the environment.

The presence of gaseous bubbles in the body can produce mechanical effects, such as distortion or pressure in the tissues, while the presence of bubbles inside the blood circulation can determine a reduction in the blood supply for the interested organs, until to have an infarct.

Furthermore the bubbles can produce biochemical effects such as activation of coagulation, fibrinolysis or complement.

The variety and severity of symptoms depend upon bubble volume and location in the human body. The decompression sickness can be very mild in intensity and normally it is solved without interventions and it is characterized from pain in the joints, muscles spindles, periosteum, and nerve sheaths with skin spots, limphatic and symptoms as indisposition, anorexia and fatigue.

Sometime such symptoms precede a more serious sickness, which requests a rapid and intensive treatment, characterized from problems in the central or peripheral nervous system and cardiorespiratory system which if not treated can provoke serious invalidity or even death.

Animal experiments and autopsies of divers and caisson workers by L. Hill et al. (Caisson sickness and the physiology of work in compressed air. London, Arnold, 1912) and others at the beginning of the century led the conclusion that decompression sickness is caused by bubbles of inert gas in the blood and tissues.

Studies by Hills and Powell suggest that only 5 or 10 per cent of the inert gas absorbed during normal diving be released as bubbles after decompression. While this may seem. a small fraction, it agrees with both in vitro and vivo observations that bubbles formation is not widespread and is limited to discrete nucleation sites, whose number fluctuates with changing environmental and physiological conditions.

These phenomena are illustrated in observations of bubbles formation under the transparent shells of shrimps during an experiment performed by Daniels (Daniels S, Eastaugh KC, Paton WDM, Smith EB, Micronuclei and bubbles formation: a quantitative study using the common shrimps, crangon cragnon. In Bachrach AJ, Matzen MM: Underwaterphysiology VIII. Bethesda, Undersea Medical Society, 1984), who decompressed shrimp from sea level to altitude. Bubble formation rose with increasing altitude.

Besides Evans and Walder (Evans A, Walder DN. Significance of gas micronuclei in the etiology of decompression disease.

Nature, 1969 222: 251-252) found that bubbles formation increased with exercise through a mechanism known as tribonucleation.

Tribonucleation (Hayward ATJ. Tribonucleation of bubbles. Br J Appl Phys 18: 641-644,1967) causes bubbles formation as result of large negative pressures generated by viscous adhesion between surfaces separating in liquid. These negative pressures place the liquid in tension and may cause either spontaneous bubble formation or bubble formation from gas nuclei.

Bubbles created by tribonucleation can persist and act as gas nuclei for later bubble formation. The lifetime of such a nucleus is determined by the rate at which it dissolves.

Mechanisms that stabilize a nucleus against surface tension can prolong its lifetime. Proposed stabilization mechanisms include gas in hydrophobic crevices and surface-active shells around bubbles. Such shells have been observed surrounding bubbles in seawater.

While it is unclear whether stabilization mechanisms play role in decompression sickness, the evidence strongly suggests that the creation and destruction of gas nuclei be in dynamic equilibrium. Exercise shifts this equilibrium toward creation, more bubble forms and the risk of decompression sickness increase. The risk decreases, on the other hand, if pressure treatment shifts the balance toward destruction.

The actual treatment for the decompression sickness foresees as principal method the compression chamber treatment.

A major determinant of successful outcome is shortening the time from onset of symptoms to compression chamber treatment.

Many factors can extend this range of time such as a misevaluation of symptoms, the time for reaching the compression

chamber and the quality of the medical care during the transportation.

Disclosure of the invention It was surprisingly found and it is an object of the present invention that the simply application of ultrasounds give bubbles destruction and then solves the cited problems.

It is already known that the echographic examination is one of the most popular imaging techniques due to the low price and overall it is so safe to be used in pregnancy. The exposition to the ultrasounds in fact has no collateral effects even if prolonged and the unique risk is a heat feeling produced by the lost energy during the passage in the body.

We have found that the application of ultrasounds at the frequency normally used for the ecographic diagnosis (1-15 MHz) and at a mechanical index or power in the limit accepted from FDA for diagnostic ultrasound equipments can destroy the gaseous bubbles.

The ultrasounds, such as all the waves, have an own energy that can be released once in contact with the bubbles, destroying them. The oscillation produced by the resonance frequency can give a further destruction of the microbubbles, and substantially it accelerates the destruction.

In conclusion the ultrasounds can destroy the gaseous bubbles and regulating the level of the ultrasounds energy and their frequency can control such destruction.

Then, it is object of the present invention an apparatus characterized by having an ultrasound emission frequency comprised between 1 and 15 MHz and provided with a probe.

The transmission power and mechanical index of such apparatus is obviously in accordance with the pharmacopoeia requirements necessary for the humans and animals treatment.

The probe must have the characteristics of being able to be applied and transmit easily the ultrasounds in the regions interested by the sickness.

Particularly preferred is the use of the above apparatus in the diving centers. From a practical point of view any diving center could have such portable apparatus, with energy able to destroy the gaseous bubbles and to control the automatic elimination from the body.

Any diver complains decompression sickness symptoms could be exposed to ultrasound, on the target organs for an interval/s of sufficient duration to allow disappearance or reduction of the symptoms or enough to reach the compression chamber.

Obviously, the use of the apparatus can be followed by anyone, independently from his/her medical knowledge.

For instance, a diver complaining joint pain could be exposed to ultrasound beam directed on the painful joints till the disappearance of the pain.

Considering the physiopathology of the decompression sickness the ultrasounds can solve the minor symptoms without further interventions. For the more serious they could assist the usual interventions of first aid, such as fluid, oxygen and corticosteroids administration during the victim transportation

to the compression chamber, decreasing the symptoms and probably improving the prognosis.

In fact, in the first case the tissue supersaturation should be at a lower level respect to those present in subjects with more serious symptoms, then the prolonged insonation should be enough to preclude any problem until to reach the equilibrium between the inert gas concentration in the tissues, the blood and the environment.

In the more serious cases, where presumably the supersaturation in the tissues is at higher level, the use of the ultrasounds destroy the bubbles at organs level decreasing the symptoms, but it can not prevent the reconstruction. Then a dynamic process is created able to improve the subject prognosis that could be reach the compression chamber in better conditions.

The efficacy of the present invention is shown in the following example performed analogously to what previously cited.

EXAMPLE 10 living shrimps are placed in a compression chamber where a 40% pressure reduction respect to the atmospheric is done in 5 minutes. Under their shell is visible the formation of gaseous bubbles which, after sonication with the suitable apparatus, disappear.