Rodney G. Handy

Machining Cancellous Bone Prior to Prosthetic Implantation

The structure of cancellous bone can be described as heterogeneous, and as such, is difficult to shape by cutting tools during clinical surgical practices. The structure of bone can have a devastating effect on the performance of the cutting tool unless it is coated with a hard-wearing, thin solid film. Here, the use of diamond-coated cutting tools to prepare bone for biomedical implants are investigated. This paper describes developments in the use of coated cutting tools for machining of cancellous bone and to prepare a nanostructured surface.

Evaluation of physiological strain in hot work areas using thermal imagery

BACKGROUND Monitoring core body temperature to identify heat strain in workers engaged in hot work in heat stress environments is intrusive and expensive. Nonintrusive, inexpensive methods are needed to calculate individual Physiological Strain Index (PSI). OBJECTIVE Thermal imaging and heart rate monitoring were used in this study to calculate Physiological Strain Index (PSI) from thermal imaging temperatures of human subjects wearing thermal protective garments during recovery from hot work. METHODS Ten male subjects were evaluated for physiological strain while participating in hot work. Thermal images of the head and neck were captured with a high-resolution thermal imaging camera concomitant with measures of gastrointestinal and skin temperature. Lins concordance correlation coefficient (rho_c), Pearsons coefficient (r) and bias correction factor (C-b) were calculated to compare thermal imaging based temperatures to gastrointestinal temperatures. Calculations of PSI based thermal imaging recorded temperatures were compared to gastrointestinal based PSI. RESULTS Participants reached a peak PSI of 5.2, indicating moderate heat strain. Sagittal measurements showed low correlation (rho_c=0.133), moderate precision (r=0.496) and low accuracy (C_b=0.269) with gastrointestinal temperature. Bland-Altman plots of imaging measurements showed increasing agreement as gastrointestinal temperature rose; however, the Limits of Agreement (LoA) fell outside the ±0.25C range of clinical significance. Bland-Altman plots of PSI calculated from imaging measurements showed increasing agreement as gastrointestinal temperature rose; however, the LoA fell outside the ±0.5 range of clinical significance. CONCLUSION Results of this study confirmed previous research showing thermal imagery is not highly correlated to body core temperature during recovery from moderate heat strain in mild ambient conditions. Measurements display a trend toward increasing correlation at higher body core temperatures. Accuracy was not sufficient at mild to moderate heat strain to allow calculation of individual physiological stress.

Laboratory evaluation of a low-cost, real-time, aerosol multi-sensor

ABSTRACT Exposure to occupational aerosols are a known hazard in many industry sectors and can be a risk factor for several respiratory diseases. In this study, a laboratory evaluation of low-cost aerosol sensors, the Dylos DC1700 and a modified Dylos known as the Utah Modified Dylos Sensor (UMDS), was performed to assess the sensors’ efficiency in sampling respirable and inhalable dust at high concentrations, which are most common in occupational settings. Dust concentrations were measured in a low-speed wind tunnel with 3 UMDSs, collocated with an aerosol spectrometer (Grimm 1.109) and gravimetric respirable and inhalable samplers. A total of 10 tests consisting of 5 different concentrations and 2 test aerosols, Arizona road dust and aluminum oxide, were conducted. For the Arizona road dust, total particle count was strongly related between the spectrometer and the UMDS with a coefficient of determination (R2) between 0.86–0.92. Particle count concentrations measured with the UMDS were converted to mass and also were related with gravimetrically collected inhalable and respirable dust. The UMDS small bin (i.e., all particles) compared to the inhalable sampler yielded an R2 of 0.86–0.92, and the large bin subtracted from the small bin (i.e., only the smallest particles) compared to the respirable sampler yielded an R2 of 0.93–0.997. Tests with the aluminum oxide demonstrated a substantially lower relationship across all comparisons. Furthermore, assessment of intra-instrument variability was consistent for all instruments, but inter-instrument variability indicated that each instrument requires its own calibration equation to yield accurate exposure estimates. Overall, it appears that the UMDS can be used as a low-cost tool to estimate respirable and inhalable concentrations found in many workplaces. Future studies will focus on deployment of a UMDS network in an occupational setting.

Cardiovascular metrics and transepidermal water loss in a high heat risk environment

Heat stress is currently primarily classified by environmental factors and not physiological factors. It is already known that certain cardiovascular metrics such as heart rate, stroke volume, blood pressure and vascular compliance undergo changes as the body traverses the different classifications of heat stress from heat oedema to heat stroke. However, there is no specific metric that provides a consistent indication for the onset of heat stroke. Twenty four subjects were observed over a 30-minute time frame performing exercise where WBGT equalled 27.5°C to determine if gender, activity-level or age had a significant effect on transepidermal water loss (TEWL) rate in addition to the relationship that the cardiovascular metrics had with TEWL rate. It was determined that heart rate, elapsed time exercising in the high temperature/humidity environment and age of subject all had significant effects on TEWL rate at a 95% confidence. Preliminary results demonstrate the possible existence of a relationship between sympathetic baroreflex sensitivity, cardiovagal baroreflex sensitivity and TEWL.

Two approaches to effective ventilation system design for the biomedical device and pharmaceutical industries

This paper provides two alternative solutions to the difficult task of providing adequate ventilation to operations found in the biomedical device and pharmaceutical manufacturing industries. The first approach involves a two-tier strategy that includes an isolation chamber and an appropriately designed local exhaust hood. The second approach involves the design of modular, walk-in hood. Mechanical and electrical design and development criteria for each option are delineated, and advantages and limitations are elucidated for both systems. Future efforts will target the testing of these two approaches under laboratory conditions to assess the merits of each.

Medical Device Manufacturing: Environment, Engineering Control and Monitoring

The trend toward an aging population in the highly developed countries of the world has the demand for innovative biomedical devices and tools at record levels. The products desired in this market are typically smaller and more portable than their predecessors, and require more sophisticated components and allied manufacturing technologies and automation techniques. In essence, similar to traditional consumer products, biomedical devices such as patient monitors, drug delivery systems, therapeutic devices, and life assisting devices have all decreased in size yet still have market expectations of enhanced performance characteristics and features. This chapter focuses on medical device manufacturing from the environmental, engineering control, and monitoring perspectives.

Atomic Scale Machining of Medical Materials

Molecular dynamic simulations of machining at the atomic scale can reveal a significant amount of information regarding the behaviour of machining and grinding processes that cannot be explained easily using classical theory or experimental procedures. This chapter explains how the use of molecular dynamic simulations can be applied to the many problems associated with machining and grinding at the meso-, micro-, and nanoscales. These include: (a) mechanics of nanoscale machining of ferrous and non-ferrous materials; (b) physics of nanoscale grinding of semiconductor materials; (c) effects of simulating a variety of machining parameters in order to minimize subsurface damage; (d) modelling of exit failures experienced during machining such as burr formation and other dynamic instabilities during chip formation; (e) simulation of known defects in microstructures using molecular dynamic simulations, statistical mechanical, and Monte Carlo methods; (f) simulation of machining single crystals of known orientation; (g) extremely high-speed nanometric cutting; (h) tool wear during machining; and (i) the effects of hardness on the wear of tool and workpiece materials. The nature of wear of the material ahead of the machining and grinding process, the variation of machining forces, and the amount of specific energy induced into the workpiece material using molecular dynamic simulations is discussed in this chapter.

Cardiovascular Interventional and Implantable Devices

Cardiovascular interventional and implantable devices must be safe and efficacious, as well as biocompatible. Surface treatment is of importance to the design and function of these devices. Lubricity, wear resistance, thrombogenicity, inflammation, and infections can all be affected significantly by surface treatments. The surfaces of cardiovascular interventional and implantable devices can either be modified with active or passive coating. Devices with active coating such as drug eluting stents (DES) deliver therapeutic agents that can enhance the mechanical function and modulate long-term vascular responses. In some implantable devices such as vascular grafts, endothelial cell growth is desirable. This is achievable with the addition of a coating or a modification to the surface properties of the device. This chapter reviews some of the most commonly used cardiovascular interventional and implantable devices with an overview of the role that surface treatments have in their functionality and safety.

Sympathetic and cardiovagal baroreflex sensitivity as related to heat stroke

Heat stroke diagnosis takes place when core temperature exceeds 40.5°C. Many risk factors, environmental and non-environmental, are associated with increased occurrence of heat stroke. Early diagnosis of a heat related illness is believed to be important in the effective reduction of heat stress mortality and morbidity rates. Sympathetic and cardiovagal baroreflex sensitivity could provide metrics to aid in the early diagnosis. Data analysis took place using previous data from an experiment where 24 subjects performed 30 minutes of cardiovascular exercise in a chamber with WBGT equal to 27.5°C. The primary experimental objective was observation of a relationship between transepidermal water loss and cardiovascular metrics. Thus, the design of experiments limited the amount of valuable information able to be extracted pertaining to sympathetic and cardiovagal baroreflex sensitivity. However, a test of means demonstrated that diastolic pressure and heart rate underwent significant changes with time in the hot and humid environment.

An investigation of aerosol particle number and size generated during a drilling process with surface coated tools

The generation of aerosols has the potential to negatively impact the health of those exposed, including those of biological origin generated in the breathing zone of medical and dental workers during surface manipulations. A system capable of characterising the size and concentration of airborne particles generated during a drilling process on animal bone with surface-coated tools was recently developed and tested under controlled laboratory conditions. The effectiveness of a laminar flow ventilation unit, with an installed Ultra Low Penetration Air (ULPA) filter and ionisation bar, was evaluated for performance and particulate removal efficiency. Particles, ranging from 0.02 micron to greater than 5 micron, were monitored with both a portable laser particle counter and a Condensation Particle Counter (CPC). Future efforts will be aimed at improving the particulate removal efficiency through modifications in filter configurations and other system variables. In addition, a performance predictive algorithm will be developed and applied under both field and controlled laboratory conditions.