Impact of supply problems of preservative-free glaucoma medications on patients and hospital staff

PURPOSE: Glaucoma is a chronic ocular disease, which is usually managed with long-term daily medical therapy, in the form of eye drops. Patients who are intolerant to preservatives in topical medicines require preservative-free versions. From early 2011 patients attending Moorfields Eye Hospital, London, UK, started to report recurring problems with the supply of the following preservative-free glaucoma medications: Timolol 0.25% (Timoptol 0.25%, MSD UK); Dorzolamide (Trusopt, MSD UK); Dorzolamide and Timolol 0.5% (Cosopt, MSD UK). This study investigates the impact of the supply problems of these medications at Moorfields Eye Hospital from a patient, administrative and clinical perspective. METHODS: Information was sought by interviewing both patients and hospital staff, and by a retrospective case note review between April 2010 and May 2013. RESULTS: Many hospital roles, both administrative and clinical, were involved in attempting to resolve the impact of the supply problems. All staff reported a considerable increase in their workload. At the peak of the problem, the glaucoma secretaries received about 150 enquiries per week. A review of 83 sets of patient notes, retrieved from a random sample of 125 patients, showed that 22% encountered a supply problem. Of these, more than one-third attended Moorfields Eye Hospital Accident & Emergency (A&E) for repeat supplies and 89% eventually had their medication changed. In telephone interviews with 39 of a random sample of 50 patients (a subset of the 83 notes retrieved), 59% of the interviewees reported a supply problem. Of these, one-third attended Moorfields Eye Hospital A&E for repeat supplies and half eventually required an alternative medication. Some patients reported going to considerable lengths to obtain ongoing supplies in the community. CONCLUSIONS: This study shows that medication supply problems can have a major impact on patients and hospital services. Supply problems occur across many fields of medicine and with increasing frequency. The findings of this study highlight the importance of early communication of impending shortages between manufacturers and the Department of Health, as recommended in the best practice guidelines. In order to minimise the impact of medicine shortages on patients, clinicians and administrative staff, hospitals need immediate notification of potential supply problems and clear updates on supply resolution. In addition, hospitals should consider nominating an individual as a contact point for patient enquiries regarding medicine supply problems

Impact-induced vibration in vehicular driveline systems: theoretical and experimental investigations

The paper investigates the conditions leading to the emergence and persistence of an acute metallic noise in light-truck drivelines. Sudden demands in torque in the presence of lash zones give rise to this phenomenon, which is onomatopoeically referred to as clonk. The study of clonk requires combined rigid multi-body dynamics and flexible body oscillations. The results show high-frequency contributions in the driveline vibrational response of certain structural modes of the driveshaft pieces, which are induced by remote impact of meshing transmission teeth through backlash. The numerically predicted spectrum of vibration shows good correlation with experimental measurements of radiated noise from a dynamic drivetrain rig

Tribo-dynamics of differential hypoid gear pairs

This paper presents a multi-body dynamics model of hypoid gear pairs, showing the interactions between gear pair dynamics, NVH and friction in the thermo-elastohydrodynamic teeth pair conjunctions during meshing. The multi-body model consists of a two-degree of freedom torsional model developed in the ADAMS environment. The coefficient of friction is calculated using an analytical formula for non-Newtonian behaviour of a thin lubricant film. Additionally, road data and aerodynamic effects are used in the form of resisting torque applied to the output side of the gear pair. Sinusoidal engine torque variation is also included to represent engine torsional response. Results are presented for a light truck in both low speed city driving condition in 2ndgear and steady state cruising in 4th gear. Transmission efficiency is obtained under both conditions.Transmission performance under both cold and hot steady state cycles within the New European Driving Cycle (NEDC) is assessed

Thermal Analysis of an Oil Jet-Dry Sump Transmission Gear under Mixed-Elastohydrodynamic Conditions

mproved fuel efficiency and reduced emissions are key drivers for modern drivetrain systems. Therefore, in recent years, dry sumps with air–oil mist lubrication have been used for efficient transmission design in order to reduce the churning losses. With dry sumps, appropriate cooling measures should be implemented to dissipate the generated contact heat in an efficient manner. This paper integrates a tribological model with three-dimensional (3D) thermofluid analysis in order to predict the heat generated in the lubricated meshing gear contacts and its dissipation rate by an impinging oil jet in air–oil mist environment. Such an approach has not hitherto been reported in literature. The results show that the generated heat under realistic conditions cannot be entirely dissipated by the impinging oil jet in the air–oil mist transmission casing. Numerical results are used to derive extrapolated regressed equations for heat transfer purposes for time-efficient analysis. These conform well with the detailed numerical results

Prediction of airborne radiated noise from lightly loaded lubricated meshing gear teeth

This paper introduces a novel analytical method for determination of gear airborne noise under lightly loaded conditions, often promoting gear rattle of loose unengaged gear pairs. The system examined comprises a single gear pair, modelled through integrated contact tribology and inertial transient dynamics. Lubricant film thickness, structural vibration and airborne gear noise are predicted and correlated with experimental measurements undertaken in a semi-anechoic environment. Good agreement is noticed between the numerical predictions and the experimental measurements. The presented model is capable of estimating the airborne radiated gear noise levels and the dynamic behaviour of gear pairs under different operating conditions, with superimposed impulsive input speed harmonics

Transient Tribo-Dynamics of Thermo-Elastic Compliant High-Performance Piston Skirts

Advanced piston technology for motorsport applications is driven through development of lightweight pistons with preferentially compliant short partial skirts. The preferential compliance is achieved through structural stiffening, such that a greater entrainment wedge is achieved at the skirt’s bottom edge through thermo-elastic deformation, whilst better conforming contact geometry at the top of the skirt. In practice, the combination of some of these conditions is intended to improve the load-carrying capacity and reduce friction. The approach is fundamental to the underlying ethos of race and high-performance engine technology. Contact loads of the order of 5 kN and contact kinematics in the range 0–35 m/s result in harsh transient tribological conditions. Therefore, piston design requires detailed transient analysis, which integrates piston dynamics, thermo-elastic distortion and transient elastohydrodynamics. The paper provides such a detailed analysis as well as verification of the same using non-invasive ultrasonic-assisted lubricant film thickness measurement from a fired engine under normal operating conditions, an approach not hitherto reported in literature. Good agreement is noted between measured film thickness and predictions

On the dynamics of a nonlinear energy harvester with multiple resonant zones

The dynamics of a nonlinear vibration energy harvester for rotating systems is investigated analytically through harmonic balance, as well as by numerical analysis. The electromagnetic harvester is attached to a spinning shaft at constant speed. Magnetic levitation is used as the system nonlinear restoring force for broadening the resonant range of the oscillator. The system is modelled as a Duffing oscillator with linear frequency variation under static, as well as harmonic excitation. Behaviour charts and backbone curves are extracted for the fundamental harmonic response and validated against frequency response curves for selected cases, using direct numerical integration. It is found that variation in stiffness, together with asymmetric forcing, gives rise to a novel structure of multiple resonant zones, incorporating mono-stable and bi-stable dynamics. Contrary to previously considered bi-stable energy harvesters, cross-well oscillations are realized through a transition from single-well potential energy to double-well with forward frequency sweep. Furthermore, in-well_oscillations present a hardening behaviour, unlike the well-known softening in-well response of bi-stable Duffing oscillators. The analysis shows that the proposed system has multiple resonant responses to a frequency sweep, influenced by consecutive interacting backbone curves similar to a multi-modal system. This combined effect of the transition to bi-stable dynamics and the hardening in-well oscillations induces resonant response of the harvester over multiple distinct frequency ranges. Thus, the system exhibits a broadened frequency response, enhancing its energy harvesting potential

Factors influencing accuracy of referral and the likelihood of false positive referral by optometrists in Bradford, United Kingdom

YesAims: Levels of false positive referral to ophthalmology departments can be high. This study aimed to evaluate commonality between false positive referrals in order to find the factors which may influence referral accuracy. Methods: In 2007/08, a sample of 431 new Ophthalmology referrals from the catchment area of Bradford Royal Infirmary were retrospectively analysed. Results: The proportion of false positive referrals generated by optometrists decreases with experience at a rate of 6.2% per year since registration (p < 0.0001). Community services which involved further investigation done by the optometrist before directly referring to the hospital were 2.7 times less likely to refer false positively than other referral formats (p = 0.007). Male optometrists were about half as likely to generate a false positive referral than females (OR = 0.51, p = 0.008) and as multiple/corporate practices in the Bradford area employ less experienced and more female staff, independent practices generate about half the number of false positive referrals (OR = 0.52, p = 0.005). Conclusions: Clinician experience has the greatest effect on referral accuracy although there is also a significant effect of gender with women tending to refer more false positives. This may be due to a different approach to patient care and possibly a greater sensitivity to litigation. The improved accuracy of community services (which often refer directly after further investigation) supports further growth of these schemes.This study was funded by the University of Bradford