The use of Design of Experiments for steady-state and transient inverse melanoma detection problems

Melanoma is one of the most fatal skin cancers; for this reason, there is a need for the development of new safe, non-invasive and efficient diagnostic techniques. Dynamic thermography is showing to be a promising technique for the early detection of skin cancers. Therefore, this paper investigates two different inverse bioheat problems using steady-state and transient skin temperature measurements. Both problems are investigated numerically to estimate how accurate blood perfusion rate, metabolic heat generation, diameter and thickness of the tumour can be estimated simultaneously under exact and noisy measurement data, based on a complex numerical model describing multilayer tissue. The inverse problems have been tested using different melanoma size, Clark II and Clark IV. The Design of Experiments (DOE) technique has been used to solve and analyse the inverse problems. A substantial number of numerical model evaluations, totalling 2,306,486 simulations, had to be undertaken as part of the full factorial DOE. The results show that it is always possible to obtain tumour parameters using exact static or dynamic measurement data. However, for noisy temperature data, the use of a dynamic approach showed an advantage over the steady-state one, which failed because of the very small temperature differences between the healthy skin and the tumour. The dynamic thermography can retrieve blood perfusion rate, thickness and diameter of the tumour as well as the metabolic heat generation despite the low sensitivity for low and high levels of measurement error; however, to detect melanoma lesions at an early stage, the measurement and model errors should be kept as low as possible

A feasibility study of awake videolaryngoscope-assisted intubation in patients with periglottic tumour using the channelled King Vision® videolaryngoscope

Airway management in patients with periglottic tumour is a high-risk procedure with potentially serious consequences. There is no consensus on how best to secure the airway in this group of patients. We conducted a feasibility study of awake tracheal intubation using a King Vision® videolaryngoscope with a channelled blade in a cohort of 25 patients, with a periglottic tumour requiring diagnostic or radical surgery. We used 10% and 4% lidocaine to topicalise the airway and midazolam and remifentanil for sedation. We recorded the success rate, number of attempts, time to obtain glottic view, time to intubation and complications. Twenty-three of the 25 patients (92%, 95%CI 75–98%) were intubated with the awake videolaryngoscope-assisted technique, with 17/23 (74%, 95%CI 54–87%) intubations achieved at the first attempt. Five patients required two and one patient, three attempts at intubation. Two patients (8%, 95%CI 2–25%) could not tolerate the procedure due to inadequate topical anaesthesia. Median (IQR [range]) times to obtain glottic view and to intubate were 19 (17–22 [10–30]) s and 49 (42–71 [33–107]) s, respectively. Traces of blood in the airway were observed in 4/25 (16%, 95%CI 6–35%) patients. Although airway management in this group of patients was expected to be difficult, successful awake intubation with the King Vision videolaryngoscope was achieved in the majority of patients within less than a minute. This study highlights a number of potential advantages of awake videolaryngoscope-assisted intubation over other awake methods of securing the airway in patients with upper airway obstruction due to periglottic mass

A paramedic study comparing the use of the Airtraq®, Airway Scope and Macintosh laryngoscopes in simulated prehospital airway scenarios

In a randomised, cross-over study, we compared the use of the Airtraq®, Airway Scope and Macintosh laryngoscopes by paramedics for tracheal intubation in three simulated prehospital scenarios. Fifty-four paramedics were invited to take part. When evaluated in a difficult airway manikin, median IQR [range] time to intubation with the Airtraq (21 (16–37 [6–80] s) and Airway Scope (16 (5–75 [12–23] s) was shorter than that with the Macintosh laryngoscope (39 (25–54 [7–120] s; p < 0.0001). The success rate within 30 s was greater with the Airtraq (61%) and Airway Scope (93%) than with the Macintosh laryngoscope (22%; p < 0.0001). When used for a standard intubation and in the sitting position, we found minimal differences among the three laryngoscopes. We conclude that the Airway Scope and Airtraq have significant advantages over the Macintosh laryngoscope and that of the two, the Airway Scope is the more effective device to use in the prehospital environment

Numerical and experimental modeling of lyophilization of lactose and mannitol water solitions in vials

The paper reports on the development of a numerical model for the simulation of a liofilization process in a vial. The lactose and mannitol-water mixtures are used as the working medium in the vial. Experimental analysis of lyofilization dynamics inside a single vial and multiple vials in a laboratory scale lyofilizer is reported, with the main focus on the primary drying phase. The key parameter measured is the temperature distribution inside the main axis of the vial filling. In the numerical model, a 1D vial approximation is used, and governing equations of heat and water vapor transport with moving front between the frozen and the porous part of the filling are solved by a dedicated finited difference method in a time stepping nonlinear iteration procedure. The comparison of numerical and experimental results show, that the developed numerical model is able to accurately capture the transition points from primary to secondary drying, accompanied by accurate capturing of the temperature levels inside the drying material. The main difference in drying of lactose and mannitol solutions lies in the fact, that the lactose shows undercooling effects during the primary drying phase, which is not the case for the mannitol solution. This effect is a consequence of shrinking behavior of lacose porous matrix, loosing contact with vial side and hence decreasing the overall heat input to the vial. The derived numerical model is able to accurately reproduce drying kinetics of mannitol, whereas for drying of lactose an upgrade of the model to axysimmetric geometry would be needed.Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .International centre for heat and mass transfer.American society of thermal and fluids engineers

Numerical and experimental modeling of lyophilization of lactose and mannitol water solutions in vials

The paper reports on the development of a numerical model for the simulation of a lyophilization process in a vial. Lactose and mannitol-water mixtures are used as the working media. Experimental analysis of the lyophilization dynamics inside a single vial in a laboratory scale lyophilizer is reported, with the main focus on the primary drying phase. In order to assess the primary drying kinetics, the temperature distribution along the vertical axis of the samples is measured. In the numerical model, a one-dimensional (1D) vial approximation is used, and governing equations of the heat and water vapor transport with moving front between the frozen and the porous part of the filling are solved by a finite difference method in a time stepping nonlinear iteration procedure. A dedicated mapping of heat transfer boundary conditions, derived for the axisymmetric vial case, is applied for the case of the 1D vial geometry approximation. The main difference in the drying of lactose and mannitol solutions lies in the fact that the lactose shows undercooling effects during the primary drying phase, which is not the case for the mannitol solution. This effect is a consequence of shrinking behavior of the lactose porous cake, leading to a loss of contact with the vial side and hence to a decrease in the overall heat input to the vial. In order to account for the shrinking process in the numerical model, a linear approximation of the decrease of the heat transfer from the vial side wall during the simulation is introduced. The comparison of the numerical and experimental results shows that the developed numerical model is able to accurately capture the movement of the sublimation front, dividing the frozen from the porous part of the filling, at typical locations inside the vial, accompanied also by an accurate capturing of the temperature levels inside the drying material, with the derived numerical model also able to reproduce the temperature drop during the primary drying of the lactose solution