Pumping mechanism, infusion pumps

Mechanical complications of PN are related to catheter placement and the system and equipment used to administer PN. A central venous catheter must be placed by a trained professional, and risks associated with placement include pneumothorax, arterial puncture, bleeding, hematoma formation, venous thrombosis, and air embolism.1,20 Over time, the catheter may require replacement. Problems with the equipment include malfunctions of the infusion pump, intravenous tubing sets, and filters. 

The mechanical pump approach employs miniature mechanical devices, such as implantable and portable infusion pumps and percutaneous infusion catheters, to deliver drugs into appro priate blood vessels or to a discrete site in the body. When compared with the... 

Their pumping mechanism is the roller peristaltic action which is also used for flow control. But the power consumption is high and the battery in some of these pumps needs to be replaced practically every day (6). The clinical infusion devices aforementioned are much too expensive for research purposes in laboratory animals, which are used because their inbreeding helps to avoid variations in pharmacological action due to genetic factors. Thus, there is a need to devise a simple and low cost infusion pump that can readily be modified in size or flow rate to accommodate different research requirements. 

Mechanically driven pumps are common tools for the intravenous administration of drags in the hospital setting. They allow physicians and patients to precisely control the infusion rate of a drag. Externally programmable pumps can facilitate ... 

Drug delivery from this pump is powered by the Freon propellant. When the Arrow pump is implanted subcutaneously, it is warmed by the patient s body temperature so that the propellant-containing chamber expands and exerts pressure on the movable bellows. Infusate is thus forced out of the reservoir chamber to an attached catheter through a filter and flow restrictor. This mechanism allows the delivery of infusate at a fairly constant rate to surrounding tissues or blood vessels. It should be noted, however, that the vapour pressure exerted by the outer chamber can be affected by changes in altitude/elevation or body temperature. 

An infusion control device (ICD) is a device that maintains a constant infusion rate in a gravity flow system (controller) or via a positive pressure pump. A positive pressure pump is a device that provides mechanical pressure (2-12 psi) to overcome the resistance to flow in the vessels. The types of positive pressure pumps are categorized according to how they deliver the solution and their degree of precision in the flow rate. Positive pressure pumps include peristaltic pumps, cassette pumps, syringe pumps, non-electiic or disposable pumps, and patient-controlled analgesic... 

Drugs may require i.v. administration as continuous infusions or at intervals (q4h, q6h, ql2h, etc.). Manual methods require the administration of the drug into the i.v. system at an injection site (Y-site, T-connector, stopcock, etc.), added to the i.v. solution in a mixing chamber, or added to an i.v. bag to be administered via gravity. A syringe pump or another mechanical device may be used for drug administration. 

Mechanical pumps are usually miniature devices such as implantable infusion pumps and percutaneous infusion catheters which deliver drugs into appropriate vessels or other sites in the body. Several pumps, implantable catheters, and infusion devices are available commercially. Examples of applications of these devices are as follows ... 

Mechanical or technical comphcations include malfunctions in the system used for intravenous dehvery of the solution. Examples of such malfunctions include infusion pump failure, problems with administration sets or tubing, and problems with the catheter. Catheter-related comphcations are potentially life-threatening. 

Active pumping infusion devices combine electronics with a mechanism to generate flow. These devices have higher performance standards than simple gravity flow regulators. The Association for the... 

FIGURE 25.6 Impact of five variables on flow rate accuracy in four different infusion pumps. Variables tested included solution Distilled water and 25% dextrose in water, back pressure -100 and 300 mm Hg, pumping segment filling pressure -30 inches of water and -1-30 inches of water, temperature 10°C and 40°C, and infusion rate 5 mL/h and 500 mL/h. Note First and second peristaltic mechanism qualified for low-risk patients, while the third peristaltic device qualified for high-risk patients. 

Infusion pumps deliver the infusion fluid by pressure at a constant rate. They are electrically or mechanically driven. The different types of pumps used are ... 

There are various ways to classify today s infusion devices based upon their functionality, driving mechanism, size, or ability to be disconnected periodically from the infusion apparatus. In order to simplify the classification, we have chosen to differentiate only between stationary and portable devices. Stationary devices are used for patients who remain in bed during the treatment, either at home or in a hospital environment. In general, these devices are large, programmable systems that remain near the bedside and require close supervision by medical personnel. Portable infusion pumps, on the other hand, are used by patients who can freely move during then-therapy. They include implantable and externally worn pumps, which range from somewhat bulky forms to small and concealable devices as shown in Fig.l. 

Today s stationary infusion pumps are highly sophisticated electromechanical devices that allow the user to program the desired flow rate and infusion volume for one or more i.v. lines. They are equipped with several alarm features to indicate potentially hazardous conditions such as changes in the flow rate, air in the hne, or occlusion of the catheter. The pump mechanism is either a peristaltic compression and release of the administration line or motor-controlled piston movement. The price of these devices ranges from 2,000 to 8,000, which excludes the disposable i.v. sets. The majority of these pumps are used in a hospital setting, where they are operated and supervised during operation by the medical staff. Health-care providers also lease stationary infosion pumps to chronically ill patients for home use. A flow-rate accuracy of 3 10% makes these pumps highly desirable for administration of proteins with a narrow therapeutic-index. 

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