Simulations and experiments of the balloon dilatation of airway stenoses: Simulationen und Experimente zur Ballondilatation von Atemwegstenosen

This article investigates the mechanics of balloon dilatation in the treatment of bronchotracheal stenosis. The ‘‘scar stricture’’-type stenosis examined in this paper is typically dilated manually, using a dilatation balloon. If indicated, this is followed by stent implantation. The selection of the stent with proper characteristics is performed empirically, based on personal experience and preference. In order to optimize the therapeutic outcome, however, it is necessary to match the stent with the stress-strain properties of the stenosis, which are not determined during manual balloon dilatation. The objective is to utilize models to experimentally and theoretically establish the correlation between the pressure/volume curve measured during the dilatation and the stressstrain properties of the stenosis, taking into account that during dilatation of scar strictures the balloon is only partially compressed, as it extends beyond both ends of the stenosis. Experiments are carried out using stenosis models with various extensibilities and lengths. As expected, more hardened stenosis resulted in steeper pressure/volume curves during the dilatation. On the other hand, the comparison between stenosis of equal extensibilities, but different length, showed an initially unexpected larger distension of the shorter stenosis, at equal pressure increases. This is caused by the fact that the margins of the stenosis are allowed more time to distend, compared to the central areas of the stenosis. The term ‘‘effect of margin expansion’’ was introduced to describe this behavior. The modeling of the dilatation process is based on the equilibrium conditions of cutfree balloon portions. The balloon/stenosis system is divided into three areas with different characteristics: (1) the proximal and distal area of the balloon outside the stenosis; (2) the area of contact between the balloon and the stenosis; and (3) the transition area between (1) and (2). Numerical simulations of the balloon dilatation confirm the conclusions from the experimental results and the theoretical considerations regarding the correlation between the pressure/volume curve of the dilatation and the stress-strain properties of the stenosis

Cone Beam Computertomography (CBCT) in Interventional Chest Medicine – High Feasibility for Endobronchial Real Time Navigation

Introduction: Currently there are several advanced guiding techniques for pathoanatomical diagnosis of incidental solitary pulmonary nodules (iSPN): Electromagnetic navigation (EMN) with or without endobronchial ultrasound (EBUS) with miniprobe, transthoracic ultrasound (TTUS) for needle approach to the pleural wall and adjacent lung and computed tomography (CT)-guidance for (seldom if ever used) endobronchial or (common) transthoracical approach. In several situations one technique is not enough for efficient diagnosis, therefore we investigated a new diagnostic technique of endobronchial guided biopsies by a Cone Beam Computertomography (CBCT) called DynaCT (SIEMENS AG Forchheim, Germany). Method and Material: In our study 33 incidental solitary pulmonary nodules (iSPNs) (28 malignant, 5 benign; mean diameter 25 +/-12mm, shortest distance to pleura 25+/-18mm) were eligible according to in- and exclusion criteria. Realtime and onsite navigation were performed according to our standard protocol.22 All iSPN were controlled with a second technique when necessary and clinical feasible in case of unspecific or unexpected histological result. In all cases common guidelines of treatment of different iSPNs were followed in a routine manner. Results: Overall navigational yield (ny) was 91% and diagnostic yield (dy) 70%, dy for all accomplished malignant cases (n=28) was 82%. In the subgroup analysis of the invisible iSPN (n=12, 11 malignant, 1 benign; mean diameter 15+/-3mm) we found an overall dy of 75%. For the first time we describe a significant difference in specifity of biopsy results in regards to the position of the forceps in the 3-dimensional volume (3DV) of the iSPN in the whole sample group. Comparing the specifity of biopsies of a 3D-uncentered but inside the outer one third of an iSPN-3DV with the specifity of biopsies of centered forceps position (meaning the inner two third of an iSPN-3DV) reveals a significant (p=0,0375 McNemar) difference for the size group (\u3e1cm) of 0,9 for centered biopsies vs. 0,3 for uncentered biopsies. Therefore only 3D-centered biopsies should be relied on especially in case of a benign result. Conclusion: The diagnostic yield of DynaCT navigation guided transbronchial biopsies (TBB) only with forceps is at least up to twofold higher than conventional TBB for iSPNs \u3c2cm. The diagnostic yield of DynaCT navigation guided forceps TBB in invisible SPNs is at least in the range of other navigation studies which were performed partly with multiple navigation tools and multiple instruments. For future diagnostic and therapeutic approaches it is so far the only onsite and realtime extrathoracic navigation approach (except for computed tomography (CT)-fluoroscopy) in the bronchoscopy suite which keeps the working channel open. The system purchase represents an important investment for hospitals but it is a multidisciplinary and multinavigational tool with possible access via bronchial airways, transthoracical or vascular approach at the same time and on the same table without the need for an expensive disposable instrument use

Towards Individualized Tracheobronchial Stents: Technical, Practical and Legal Considerations

Stent placement has been established as a standard procedure for treating airway obstructions. Other indications are localized malacias and fistulas. Though many different stents with various diameters and lengths are available, the shapes are hardly ever ideal because of the distorted anatomy in patients with diseased airways. There are technical and legal limitations for customizing purchased airway stents. Individually tailored stents would be preferable. New techniques of additive manufacturing such as 3D printing make it possible to produce optimized stents for a particular patient. Using CT data and bronchoscopic images, stents can be constructed that match a particular anatomical situation and apply the optimized expansion force. We give an overview of the currently available manufacturing techniques for polymeric stents and report about our own experience. Direct on-site printing of polyurethane stents in a hospital and printing individual extrusion molds for silicone stents in a certified cleanroom are both feasible. Furthermore, there are promising attempts of combining mechanically customized stents with surface modifications, drug-eluting features, biodegradability, and time-dependent adaptation (4D printing). Truly optimized airway stents with the potential of solving the well-known stent problems such as granulation tissue formation, remodeling, mucostasis, and infections are in reach. The technical hurdles are probably easier to overcome than the legal constraints. The legal situations are discussed from a physician's and a manufacturer's perspective

Radiation Exposure of Patients by Cone Beam CT during Endobronchial Navigation - A Phantom Study

Rationale: Cone Beam Computed Tomography imaging has become increasingly important in many fields of interventional therapies. Objective: Lung navigation study which is an uncommon soft tissue approach. Methods: As no effective organ radiation dose levels were available for this kind of Cone Beam Computed Tomography application we simulated in our DynaCT (Siemens AG, Forchheim, Germany) suite 2 measurements including 3D acquisition and again for 3D acquisition and 4 endobronchial navigation maneuvers under fluoroscopy towards a nodule after the 8th segmentation in the right upper lobe over a total period of 20 minutes (min). These figures reflect the average complexity and time in our experience. We hereby describe the first time the exact protocol of lung navigation by a Cone Beam Computed Tomography approach. Measurement: The hereby first time measured body radiation doses in that approach showed very promising numbers between 0,98-1,15mSv giving specific lung radiation doses of 0,42-0,38 mSv. Main results: These figures are comparable or even better to other lung navigation systems. Cone Beam Computed Tomography offers some unique features for lung interventionists as a realtime 1-step navigation system in an open structure feasible for endobronchial and transcutaneous approach. Conclusions: Due to this low level of radiation exposure Cone Beam Computed Tomography is expected to attract interventionists interested in using and guiding endobronchial or transcutaneous ablative procedures to peripheral endobronchial and other lung lesions

Modification of Apremilast from Pills to Aerosol a Future Concept

Background: Inhaled drugs have been available in the market for several years and for several diseases. Drugs for chronic obstructive pulmonary disease, cystic fibrosis, and diabetes have been used for several years. In the field of drug modification, these drugs range from tablets to aerosol. Methods: Milling as used to break down the tablets to powder and nebulisers are used to produce aerosol droplets. A mastersizer was used to measure the mass median aerodynamic diameter of the aerosol droplets. Results: Apremilast produced mmad diameters (2.43 μm) without any statistical difference between the different jet-nebulizers. The residual cup B contributed to greater mmad diameters as the 95% interval of mean values, based on those the ANOVA mean square clearly indicated, followed by cups C and F. The previous interval plot is much better clarified when the interaction means between drug and residual cap are plotted. The residual cups B, C and F produce mmad between (2.0–3.2). Conclusion: In the current research study we demonstrated our methodology to create apremilast powder and produce apremilast aerosol droplets with different nebulisers and residual cups

Bronchoscopic Lung Volume Reduction with Endobronchial Valves in Low-FEV1 Patients

Background: Bronchoscopic lung volume reduction (BLVR) with valves has been shown to improve lung function, exercise capacity, and quality of life in patients with emphysema, but only few patients with forced expiratory volume in 1 s (FEV1) ≤20% predicted have been included in former studies. Although the procedure can be performed safely, pneumothorax is a frequent complication, which can be critical for these very severely diseased patients. Objectives: The aim of the study was to assess the safety of BLVR in patients with a very advanced stage of emphysema, as indicated by FEV1 ≤20% predicted. Patients and Methods: Patients in whom BLVR was performed between January 2013 and August 2015 were included in this analysis if their baseline predicted FEV1 was ≤20%. BLVR, performed only if collateral ventilation was absent, achieved complete occlusion of the target lobe. All patients were closely monitored and were not discharged before the fourth day after BLVR. Results: Twenty patients with FEV1 ≤20% predicted were included in the analysis. Lung volume reduction was achieved in 65% of the cases. Pneumothorax occurred in 4 cases (20%). No patient died. Lung function and exercise tolerance improved after 1 and 3 months, respectively. Conclusions: BLVR with valves can be safely performed in patients with FEV1 ≤20% predicted when close postprocedural monitoring is provided. Improvement in lung function and exercise capacity can be achieved

Drug Eluding Stents for Malignant Airway Obstruction: A Critical Review of the Literature

Lung cancer being the most prevalent malignancy in men and the 3rd most frequent in women is still associated with dismal prognosis due to advanced disease at the time of diagnosis. Novel targeted therapies are already on the market and several others are under investigation. However non-specific cytotoxic agents still remain the cornerstone of treatment for many patients. Central airways stenosis or obstruction may often complicate and decrease quality of life and survival of these patients. Interventional pulmonology modalities (mainly debulking and stent placement) can alleviate symptoms related to airways stenosis and improve the quality of life of patients. Mitomycin C and sirolimus have been observed to assist a successful stent placement by reducing granuloma tissue formation. Additionally, these drugs enhance the normal tissue ability against cancer cell infiltration. In this mini review we will concentrate on mitomycin C and sirolimus and their use in stent placement

The structure of the nuclear stellar cluster of the Milky Way

We present high-resolution seeing limited and AO NIR imaging observations of the stellar cluster within about one parsec of Sgr A*, the massive black hole at the centre of the Milky Way. Stellar number counts and the diffuse background light density were extracted from these observations in order to examine the structure of the nuclear stellar cluster.Our findings are as follows: (a) A broken-power law provides an excellent fit to the overall structure of the GC nuclear cluster. The power-law slope of the cusp is $\Gamma=0.19\pm0.05$, the break radius is $R_{\rm break} = 6.0'' \pm 1.0''$ or $0.22\pm0.04$ pc, and the cluster density decreases with a power-law index of $\Gamma=0.75\pm0.1$ outside of $R_{\rm break}$. (b) Using the best velocity dispersion measurements from the literature, we derive higher mass estimates for the central parsec than assumed until now. The inferred density of the cluster at the break radius is $2.8\pm1.3\times 10^{6} {\rm M_{\odot} pc^{-3}}$. This high density agrees well with the small extent and flat slope of the cusp. Possibly, the mass of the stars makes up only about 50% of the total cluster mass. (c) Possible indications of mass segregation in the cusp are found (d) The cluster appears not entirely homogeneous. Several density clumps are detected that are concentrated at projected distances of $R=3''$ and $R=7''$ from Sgr A*.(e) There appears to exist an under-density of horizontal branch/red clump stars near $R=5''$, or an over-density of stars of similar brightness at $R=3''$ and $R=7''$. (f) The extinction map in combination with cometary-like features in an L'-band image may provide support for the assumption of an outflow from Sgr A*.Comment: accepted for publication by A&A; please contact first author for higher quality figure