The Dumping Valve and its Clinical Application
An open reservoir for the collection and evacuation of anaesthetic gases permits leakage to room air. The use of a closed reservoir for the removal of overspill gas from anaesthetic circuits is described. Calibrated gas evacuation is carried out through an ejector flowmeter from the anaesthetic circuit or from a closed reservoir, where the gas is collected via a relief valve. In order to eliminate the risk of high or low pressure in the reservoir employed, a relief valve and a dumping valve is included in the system.
The negative pressure relief valve: pressure-flow relationships.
The scavenging of gases from anaesthetic circuits may present hazards to the patient. The negative pressure relief valve prevents the generation of subatmospheric pressures in the circuit as a result of a discrepancy between the fresh gas flow and the gas evacuation rate. The ideal valve will open at a small negative pressure, and immediately permit a high gas inflow. Leakage with positive pressure in the circuit and admixture of atmospheric air during spontaneous respiration must not occur. Six different valves were studied. Two membrane valves came nearest to fulfilling the ideal requirements.
Brushite-collagen composites for bone regeneration.
Brushite-based biomaterials are of special interest in bone regeneration due to their biocompatibility and biodegradability; on the other hand, collagen is a well-known osteoconductive biomaterial. In the present study a new brushite-collagen composite biomaterial is reported. This new biomaterial was prepared by combining citric acid/collagen type I solutions with a brushite cement powder. The obtained biomaterial was a cement paste, with improved handling properties. The effect of collagen on the setting reaction of brushite cement was studied, and was found to speed up the cement setting reaction. The cement paste set into a hard ceramic material within 18.5+/-2.1min and had compressive strength similar to that of spongeous bone (48.9+/-5.9MPa in dry conditions and 12.7+/-1.5MPa in humid conditions). The combination of collagen with citric acid revealed an interesting synergistic effect on the compressive strength of the composite material. Moreover, this new biomaterial had excellent cohesion properties (ninefold better than brushite cement), and high cellular adhesion capacity (threefold higher than brushite cement). The composite biomaterial described in this study combines good handling properties, compressive strength, cohesion and cell adhesion capacity, along with the osteoconductive and biodegradable properties inherent in brushite and in collagen-based biomaterials.