Current event: Annual meeting of Biomechanics Society, France

XXXIIème congrès annuel de la société de Biomécanique,
Lyon,France 28-29 août 2007

XXXIIth annual meeting of French biomechanical societyLyon,France 28-29 August 2007

Medical Devices Vigilance regulations in Switzerland

Swissmedic is the central Swiss supervisory authority for therapeutic products. It is a public service organization of the federal government with headquarters in Bern.

Its core competence includes

• licensing medicines
• granting authorizations to manufacture and distribute wholesale, and inspecting facilities
• monitoring medicines and medical devices already on the market
• controlling the traffic of narcotics
• laboratory testing of medicine quality
• drafting laws and standards

Medical devices Vigilance:

In order to monitor medical devices already on the market, manufacturers and distributors placing medical devices on the Swiss market are required to report all serious incidents and recalls that are carried out for safety reasons.

• The European guidelines on vigilance to report procedure applies also in Switzerland. MEDDEV 2.12/1.
• Incidents: people responsible for the product on the market, should report incidences to Swissmed. An information sheet from Swissmedic describes the legal obligations and the reporting procedure for serious incidents.
• Recalls: In case of recall of a product from market, Swissmedic should be informed.

To get more information about Vigilance procedure in Switzerland, take a look at the following link:

Vigilance: reporting serious incidents with medical devices

A little survey

In order to adapt better my posts to those who frequent my blog, I would appreciate if you answer the following question:

MENIETT , a device from medtronic

Ménière's Disease is a complex, progressive disorder of the inner ear characterized by the feeling of dizziness or a "spinning" sensation (rotational vertigo) associated with hearing loss, fullness or pressure in the ear, and roaring or ringing in the ear (tinnitus).

The cause of Ménière's Disease is nearly always idiopathic, meaning it is unknown. Research suggests that the primary problem is in the endolymphatic sac, an organ in the inner ear, which maintains the level of fluid (endolymph) in the hearing and balance canals of the inner ear. It is possible, but unproven, that a viral infection of the sac may trigger the onset of Ménière's Disease.

It has been discovered that the endolymphatic sac contains a substance that stimulates the kidneys to get rid of water and sodium. Although the nature of this substance and how it is regulated are still unknown, it is tempting to speculate that the endolymphatic sac is involved in the body's system to regulate sodium concentration. If this were true, it would explain why a low-sodium diet helps some people with Ménière's Disease.

The Meniett device is a product of MEDTRONIC to alleviate Ménière's Disease symptoms.

The inner ear consists of the cochlea (hearing canal), endolymphatic sac, semicircular canals (balance canals), and the hearing and balance nerves.This image shows endolymphatic fluid circulating in the cochlea (1) and semicircular canals (2), as well as the endolymphatic sac (3), where the endolymph is accumulated.

In Ménière's Disease, excess endolymphatic fluid accumulates in the hearing and balance canals, causing pressure to build and the canals to swell. The swollen canals cannot function properly, which leads to problems with the hearing and balance systems of the ear.

Treatment begins after the Meniett device performs a leakage test to verify that the earpiece is properly sealed in the external ear canal . Once the leakage test is completed successfully, the device will begin sending pressure pulses that are transmitted to the middle ear through the ventilation tube.

Pressure pulses help reduce excess endolymphatic fluid and restore the balance of the inner ear's hydrodynamic system.

The ventilation tube allows the pressure pulses to reach the middle ear, where they influence the fluid system of the inner ear through two membranes, the oval window and the round window.

Although the actual mechanisms are still not fully understood, one theory is that the action of the pressure pulses on the fluid system, combined with other physiologic reactions in the ear, forces the excess endolymphatic fluid back into the endolymphatic sac.

Once the treatment is completedthe volume of endolymphatic fluid in the inner ear has been reduced. However, the body constantly produces endolymphatic fluid, thus requiring the patient to perform the Meniett treatment on a daily basis to control the symptoms of Ménière's Disease.

for more information take a look at : reference

Studies of the outer-most layer of the vascular wall, adventita as a seperate layer

A small Introduction on different vascular layers:

The walls of all blood vessels, except the very smallest, have three distinct layers, or tunics( 'covering') , that surround a central blood-containing space, the vessel lumen. The innermost tunic is the tunica intima which is in direct contact with the blood in the lumen. This tunic contains the endothelium. The middle tuinic, the tunica media is mostly contained of smooth muscle cells, elastin and collagen fibers. The outermost layer of a blood vessel wall, the tunica externa(adventitia) is composed of loosely woven collagen fibers that protect and reinforce the vessel and anchor it to surrounding structure.

Main post:

As for the biomechanical properties of the vascular tissue, there has been quite a large number of studies done. Some of these studies report inflation-extension types of experiments done on scaffold of adventitia removed from a whole vessel. Others, have just removed out the adventitia and focused on media. The question is :

Is it really possible for all type of vessels to take out adventitia out of the vessel mechanically?

To my knowledge, this seems quite a local and specie dependent property. It looks that in some arteries , such as human femoral arteries, you can easily separate the adventitia from the rest of the vessel. However, according my experiments, it is almost impossible to take it as a whole intact cylinder out from common carotid, femoral, abdominal arteries and Jagular,facial,femoral,abdominal veins of rabbits. As for common carotid of rats, I may say, it may be possible though I had never really done it.

let's consider that you have done it. Since it is a kind of bulky collagen fibers, it does not seem really impermeable to liquids. Thus, inflating of this layer, even if we can get it from the artery, seems quite a hard job.

Have you ever tried working with adventitia layer separately in inflation-extension tests? I would appreciate as you inform me on the subject.

picture taken from : reference

Single Molecule manipulations 3

As part of their infection cycle, many viruses must package their newly replicated genomes inside a protein capsid to insure its proper transport and delivery to other host cells. Bacteriophage 29 packages its 6.6mm long double-stranded DNA into a 42 nm dia. X 54 nm high capsid via a portal complex that hydrolyses ATP. This process is remarkable because entropic, electrostatic, and bending energies of the DNA must be overcome to package the DNA to near-crystalline density.

In a recent work by Dr Bustamante, optical tweezers have been used to pull on single DNA molecules as they are packaged, thus demonstrating that the portal complex is a force generating motor. They have shown that this motor can work against loads of up to ~57 picoNewtons on average, making it one of the strongest molecular motors ever reported. Interestingly, the packaging rate decreases as the prohead is filled, indicating that an internal
pressure builds up due to DNA compression. It is estimated that at the end of the packaging the capsid pressure is ~6 MegaPascals, corresponding to an internal force of ~50 pN acting on the motor.

Reference

Mathematical modeling of biomechanical properties of the venous wall

Despite the abundant literature on blood vessel mechanical properties, blood vessel constitutive models are far less common. Blood vessels are nonlinear, anisotropic and viscoelastic, heterogeneous in the unloaded state and compressible when studying macroscopic characteristic and they behave differently in different temperatures. Despite the long list of attributes, constitutive equations generally account for only a subset of these characteristics.

In general, blood vessels can be treated as pseudoelastic, randomly elastic, poroelastic or viscoelastic . Pseudoelasticity assumes that a material can be modeled using separate equations describing the loading and unloading behavior. Random elasticity, however, assumes that the strain response for a given load is rendered around a definite value that lies on a well defined curve, such that data from both the loading and unloading curves can be included simultaneously. Poroelastic formulations treat a material as a fluid-saturated porous medium and are well suited to model wall transport. Viscoelastic formulations include time-dependent responses in the constitutive equation and are useful for modeling creep, stress relaxation, and hysteresis. Useful reviews are available, concerning the biomechanics of soft biological tissues :

Vito, R.P. and S.A. Dixon, Blood vessel constitutive models-1995-2002. Annual Review Of Biomedical Engineering, 2003. 5: p. 413-439.

Humphrey, J.D., Continuum biomechanics of soft biological tissues. Proceedings: Mathematical, Physical and Engineering Sciences (Series A), 2003. 459(2029): p. 3-46.