Heavy dependent nicotine smokers--Newfound lifestyle appreciation after quitting successfully. Experiences from inpatient smoking cessation therapy.

OBJECTIVES: This is an evaluation of an ongoing inpatient smoking cessation program available in Austria and aims to show to what extent even heavy nicotine dependent smokers can benefit from a three-week inpatient therapy. STUDY DESIGN: A particular focus lies on analyzing the benefits and changes in lifestyle and sense of well-being. METHODS: 270 initially heavy nicotine dependent smokers are observed for a one year period consisting of recruitment, therapy and two post-therapy follow-up visits; post program smokers are compared to post program ex-smokers. RESULTS: 12 month post-therapy, 42.6% of participants are identified by carbon monoxide-verifications as ex-smokers, 34% as smokers and the remaining did not attend follow-up visits. Significant changes in lifestyle satisfaction are reported by ex-smokers compared to still smokers. CONCLUSIONS: Convincing heavy dependent nicotine smokers that significant changes in lifestyle satisfaction can be expected as part of a successful cessation process should lead to enough motivation for these individuals to seek such inpatient smoking cessation program.

A biochemical/biophysical 3D FE intervertebral disc model.

Present research focuses on different strategies to preserve the degenerated disc. To assure long-term success of novel approaches, favorable mechanical conditions in the disc tissue are essential. To evaluate these, a model is required that can determine internal mechanical conditions which cannot be directly measured as a function of assessable biophysical characteristics. Therefore, the objective is to evaluate if constitutive and material laws acquired on isolated samples of nucleus and annulus tissue can be used directly in a whole-organ 3D FE model to describe intervertebral disc behavior. The 3D osmo-poro-visco-hyper-elastic disc (OVED) model describes disc behavior as a function of annulus and nucleus tissue biochemical composition, organization and specific constituent properties. The description of the 3D collagen network was enhanced to account for smaller fibril structures. Tissue mechanical behavior tests on isolated nucleus and annulus samples were simulated with models incorporating tissue composition to calculate the constituent parameter values. The obtained constitutive laws were incorporated into the whole-organ model. The overall behavior and disc properties of the model were corroborated against in vitro creep experiments of human L4/L5 discs. The OVED model simulated isolated tissue experiments on confined compression and uniaxial tensile test and whole-organ disc behavior. This was possible, provided that secondary fiber structures were accounted for. The fair agreement (radial bulge, axial creep deformation and intradiscal pressure) between model and experiment was obtained using constitutive properties that are the same for annulus and nucleus. Both tissue models differed in the 3D OVED model only by composition. The composition-based modeling presents the advantage of reducing the numbers of material parameters to a minimum and to use tissue composition directly as input. Hence, this approach provides the possibility to describe internal mechanical conditions of the disc as a function of assessable biophysical characteristics.

Experimental and model determination of human intervertebral disc osmoviscoelasticity.

Finite element (FE) models have become an important tool to study load distribution in the healthy and degenerated disc. However, model predictions require accurate constitutive laws and material properties. As the mechanical properties of the intervertebral disc are regulated by its biochemical composition and fiber-reinforced structure, the relationship between the constitutive behavior of the tissue and its composition requires careful consideration. While numerous studies have investigated the annulus fibrosus compressive and tensile properties, specific conditions required to determine model parameters for the osmoviscoelastic model are unavailable. Therefore, the objectives of this study were (1) to complement the existing material testing in the literature with confined compression and tensile tests on human annulus fibrosus and (2) to use these data, together with existing nucleus pulposus compression data to tune a composition-based, osmoviscoelastic material constitutive law. The osmoviscoelastic material constitutive law and the experimental data were used to describe the fiber and nonfiber properties of the human disc. The compressive material properties of normal disc tissue were G(m) = 1.23 MPa, M = 1.57, and alpha = 1.964 x 10(-16) m(4)/Ns; the tensile fiber material parameters were E(0) = 77.0 MPa; E(epsilon) = 500 MPa, and eta = 1.8 x 10(3) MPa(-s). The goodness of fit ranged from 0.88 to 0.96 for the four experimental conditions evaluated. The constitutive law emphasized the interdependency of the strong swelling ability of the tissue and the viscoelastic nature of the collagen fibers. This is especially important for numerical models to further study the load sharing behavior with regard to disc degeneration and regeneration.