The term “chemo ball” is a common nickname for a medical device formally known as an elastomeric pump. This portable, disposable infusion system delivers medication outside of a formal clinical setting. It allows patients to receive a continuous, timed infusion of chemotherapy drugs while remaining ambulatory, increasing mobility and comfort compared to traditional stationary intravenous (IV) poles and pumps. The primary goal is to transition the continuous administration of medication from the hospital to the patient’s home, supporting protocols that require slow, steady drug delivery. The device is filled by a specialized pharmacy before being connected to the patient by a healthcare provider.
The Elastomeric Pump Mechanism
The elastomeric pump functions based on a precise physical principle, requiring no electricity, batteries, or complex programming. The device has a hard plastic outer shell protecting an internal, flexible drug reservoir, often called the “balloon” or elastomer. Filling the reservoir with the chemotherapy solution stretches the elastomer, creating stored pressure similar to a tightly inflated balloon.
The elastic contraction of the stretched reservoir provides the constant, non-electric force needed to push the medication out. The solution is channeled through tubing containing a flow restrictor, typically a thin capillary tube. This restrictor governs the infusion rate, ensuring the drug is delivered at a fixed, predefined speed as the pressure is slowly released. The accuracy of the flow rate is determined by the restrictor’s physical properties and the viscosity of the drug solution.
Pressure-Driven System
This pressure-driven system is a distinct departure from electric volumetric pumps, which rely on mechanical or computer-controlled components. The self-contained design allows for near-silent operation and simplifies the infusion process. Once connected, the pump immediately begins delivering medication and continues until the internal reservoir is completely empty, indicated by the balloon visibly deflating.
Clinical Application and Infusion Schedules
Elastomeric pumps are used for chemotherapy drugs that require continuous infusion to maintain a steady concentration in the bloodstream for maximum therapeutic effect. For example, continuous delivery of 5-Fluorouracil (5-FU) is often preferred over a rapid bolus injection because it may improve efficacy and reduce certain toxicities. The slow, sustained exposure helps ensure that cancer cells are consistently targeted during their most vulnerable growth phases.
The pump connects to the patient’s bloodstream through a central venous access device (CVAD), such as a peripherally inserted central catheter (PICC line), a central line, or an implanted port. These access points provide a reliable pathway for the medication to enter the circulatory system safely. The typical duration of these infusions is predetermined by the oncology protocol, often running for periods like 46 or 96 hours.
A nurse or trained healthcare professional connects the pump to the CVAD before the patient leaves the clinic. Once the scheduled time has elapsed and the balloon is fully deflated, the device is disconnected. This disconnection is performed by a visiting nurse, the patient or a trained caregiver, or back at the hospital, allowing the patient to manage treatment at home.
Care and Safety Guidelines
Patients using an elastomeric pump must adhere to specific handling and safety guidelines.
Temperature Sensitivity
The flow restrictor component, often taped directly to the skin, is highly sensitive to temperature changes. The pump must be kept at a consistent room temperature. Extreme cold can slow the flow rate, while heat from electric blankets or direct sunlight can cause the medication to infuse too quickly.
For hygiene, patients are advised to take sponge baths while the pump is connected, as the device is water-resistant but not fully waterproof. If showering is necessary, the access site and the pump must be protected with waterproof coverings to prevent damage or infection. Activities involving jarring, contact, or significant changes in body temperature, such as intense exercise, should be avoided.
Patients and caregivers should regularly check the pump and the infusion site for potential issues. Signs of a problem include the pump emptying much faster or slower than the expected timeframe, kinking in the tubing, or leakage of fluid near the pump or the access site. If any of these issues occur, the patient should immediately clamp the line to stop the flow and contact their oncology care team. Once the infusion is complete, the entire single-use device is treated as medical waste and disposed of according to hazardous material guidelines.