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Biomedical subjects

J Allt-Graham

Publications and source records attributed to J Allt-Graham.

6 recordsLinked to original sources
PubMed1992

A comparison of the filtration properties of heat and moisture exchangers.

Heat and Moisture Exchangers are used increasingly as filters to prevent the contamination of breathing apparatus and to limit cross-infection. A series of laboratory tests has been developed to evaluate the microbial filtration and air flow resistance properties of these devices. The tests were designed to simulate the clinical situation and therefore evaluated devices in both dry and wet conditions. The devices tested (Engstrom Edith, Pall BB50T, Dar Hygrobac, Intersurgical Filtatherm and Intersurgical Filtaguard) were each representative of a particular type of construction. The simple hygroscopic device (Engstrom Edith) showed poor airborne and liquid-borne filtration efficiency, but its resistance to air flow remained low in all conditions. The composite devices (Dar Hygrobac, Intersurgical Filtatherm and Intersurgical Filtaguard), which all possessed relatively large pores, performed well in terms of dry airborne filtration efficiency, but showed substantial increases in air flow resistance and poor filtration efficiency in the presence of liquid. The pleated membrane filter (Pall BB50T), which possessed small pores, showed good airborne filtration efficiency and prevented the passage of liquid. The latter property enabled this device to prevent the passage of liquid-borne contamination and to maintain a low resistance to air flow in wet conditions. It would appear that in terms of contamination control and air flow resistance the pleated membrane filter provides a wider margin of safety than either the hygroscopic or composite devices.

Air↗
PubMed1987

Contamination control in long-term ventilation. A clinical study using a heat- and moisture-exchanging filter.

Twenty-eight patients who required periods of mechanical ventilation for up to 22 days in the intensive therapy unit were studied to evaluate the clinical use of the Pall Ultipor Breathing System Filter (BB50T) as a heat- and moisture-exchanging bacterial filter. Results in this group of patients showed that there was no longer any need to sterilise breathing systems or decontaminate ventilators if these filters were used. They also performed satisfactorily as a heat and moisture exchanger in patients in need of long-term ventilation, and their use appears to offer substantial advantages as regards cost, ease of use and patient safety.

Bacteria↗
PubMed1979

Inspired oxygen and Cape Bristol ventilators.

The Cape Bristol ventilator is a volume-preset machine which utilises oxygen from a flowmeter and air-entrainment attachment to provide a known inspired oxygen level. The level can be calculated from the oxygen flow rate and the patient's minute ventilation using a nomogram supplied by the manufacturers. Serious discrepancies between predicted and measured inspired oxygen levels delivered by these machines can occur and the advisability of using air entrainment devices in high oxygen dependent patients is questioned. Modification to the Cape Bristol ventilator to limit these errors are discussed and the more frequent use of oxygen monitors recommended.

Humans↗