Biomedical subjects

K Littlewood

Publications and source records attributed to K Littlewood.

5 recordsLinked to original sources

PubMed2005

Forces on sanitary solids in small sewers.

An experimental and modelling study has been carried out to investigate the movement mechanisms and behaviour of large sanitary solids in small sewers. The overall performance of the model has already been verified in terms of limiting solids transport distance, but in this paper the wave profile across the solid is also shown to fit model predictions well when compared visually. Further insight into how solids behave is also explored in this paper by plotting the interplay of the main horizontal and vertical forces acting on the solid. These results illustrate the dynamics of movement initiation, transport and deposition and indicate the most important forces. Model predictions of movement 'time per hop' have also been experimentally verified, giving further credence to the model. Experimental verification of the magnitude of the forces involved is planned.

Drainage, Sanitary↗

PubMed2005

A model for the movement of large solids in small sewers.

An extensive series of experiments has been carried out to investigate the movement mechanisms and behaviour of large solids in small sewers. This paper describes the development, calibration and verification of a model (SOLID) based on data obtained from the experimental rig. It is used to predict solid movement with respect to 'limiting solid transport distance'. Key model parameters are the coefficients of static and dynamic friction, the shape factor of amorphous solids and the flow bypass coefficient. The model is shown to successfully represent the movement of a large solid down a small pipe, where the solid is moving as a sliding, leaking dam, particularly the first 'hop'. Limitations of the model include a limited facility to well represent multiple hops and the need for closely spaced computational nodes leading to small time steps, and long run times.

Calibration↗

PubMed2003

Movement mechanisms of gross solids in intermittent flow.

Gross solids, such as used tampons, sanitary towels and faecal stools, are introduced into the sewer network via the WC. Although small diameter pipes (< or = 150mm diameter) make up a large proportion of most sewer networks, the transport behaviour of gross solids in these smaller pipes is not fully established. In particular, there are concerns about the effect of water conservation measures on the transport of gross solids in the intermittent flow regime prevalent in small pipes. This paper introduces a study carried out on the movement of solids in this flow regime. An extensive series of experiments has been carried out to investigate the movement mechanisms and behaviour in detail. It was found that there are three different mechanisms of movement, and photographic evidence is provided in the paper. The concept and implications of the "limiting solid transport distance" is also introduced. It is argued that solid movement is dependent on factors other than just WC flush volume and that increased blockage potential is not inevitable.

Environmental Monitoring↗

PubMed2001

Evidenced-based airway management.

The increased polarity of evidenced-based medicine has changed the approach to evaluation of medical interventions and treatments, either placing them on firm scientific foundations or suggesting that evidence is inadequate to strongly support current or innovative practices. Airway management devices and techniques are essential and common components of clinical care. It is the purpose of this review to identify the levels of evidence that support common and novel techniques in airway management. Very few airway management techniques are supported by large, prospective randomized trials. In resuscitation, defibrillation should take priority over airway management. This is supported by animal studies and several reported series of patient experiences and will never be subjected to a prospective randomized trial. Substantial evidence supports the use of noninvasive ventilation, subglottic endotracheal tube secretion removal, changing ventilator circuits no more frequently than every 7 days, and the use of selective digestive decontamination with systemic antibiotics to reduce the incidence of ventilator-associated pneumonia. Little evidence supports using other measures such as elevating the head of the bed to 30% (but this costs nothing and is intrinsically attractive), use of heat and moisture exchangers, kinetic bed therapy, early tracheotomy, or lung secretion removal techniques to reduce ventilator-associated pneumonia. Percutaneous tracheotomy currently can only be recommended over open surgical tracheotomy based on cost, convenience and late stomal complications; it may be associated with a slightly higher morbidity and mortality.

Emergency Medical Services↗

PubMed1998

Anesthetic considerations for hepatic cryotherapy.

The evolution of hepatic cryotherapy as an accepted treatment for patients with non-resectable hepatic malignancy has required concurrent evaluation and development of perioperative anesthetic management of these cases. Review of published and institutional experience demonstrates that hepatic cryotherapy presents the anesthesiologist with an array of challenges, all of which are not intuitively apparent. Specifically, such issues as management of coexisting physiologic perturbations of the oncology patient, heat conservation during the procedure, and readiness for a more extensive procedure would be readily anticipated by most clinicians. Description and reasonable management of problems ranging from mild or moderate postoperative thrombocytopenia to the so-called cryoshock syndrome with the possibility of severe postoperative coagulopathy, renal dysfunction, and pulmonary complications, however, could emerge only with the education of experience. The goal of this article is to address the key issues faced by anesthesiologists consulted in the perioperative care of patients undergoing hepatic cryotherapy.

Anesthesia, Inhalation↗