Peritoneal Dialysis Cyclers and Other Mechanical Devices

Peritoneal dialysis (PD) cyclers were initially designed for intermittent PD to perform many frequent and short dialysis exchanges within a hospital setting. Following the introduction of continuous cycling PD (CCPD) and variations thereof, the cycler underwent modifications that allowed a broad variety of prescriptions and laid the foundation for its success as a home therapy device. Further improvements in the performance, safety, and convenience of modern cyclers have increased the utilization of automated PD (APD), which in many countries has become the predominant PD modality. Although the emphasis during the early years was mainly on optimizing hydraulics and mechanical aspects, the current development goes far beyond filling and draining the dialysate. Modern cyclers are highly integrated devices that are designed to communicate and exchange data via secure cloud services from and to the patient’s home, allowing for remote patient monitoring and therapy management. Cyclers can directly interact with the caregiver by transferring patient and prescription data and actively guide the patient step by step through the treatment, enhancing the user experience and ensuring adequate use of the device. The potential characteristics of cyclers are summarized in Table 21.1 .

Table 21.1

Potential Features of a Modern Cycler

Functionality

Meets the needs of home, assisted care, and professional health care settings
Performs all prescriptions (e.g., CCPD, PD Plus, tidal PD, intermittent PD, adapted PD)
Allows adjustment of prescription parameters and limits to the individual patient needs
Ability to vary each exchange regarding volume, dwell time, and solution used
Allows extended treatment options to accommodate special patients:
- High total volume of dialysate and large number of cycles with one setup
- Maximal fill volumes (3–4 L) for large adults
- Minimal fill volumes (100 mL) and delivery of dialysis solutions in small increments for pediatric patients
Automatic priming of the patient line and flush-before-fill as part of the setup
Fast and efficient warming of solutions or timer-controlled preheating
Features optimized fill and drain logic allowing fast drainage (> 200 mL/min), intelligent end of drain detection, including established criteria to prevent overfill
Last bag option and ability to pump effluent to either bags or drain
Individualized user permission/user access configuration

User Interface

Large color touchscreen control panel that is easy to read and use
Variable voice and alarm volume or voice guidance
User-friendly menu with easy-to-follow step-by-step instructions and video tutorials in multiple languages
Integrated camera for real-time video assistance

Information Technology

Comprehensive data capture and storage of all relevant patient treatment parameters
Connectivity through Bluetooth, USB ports, WLAN, LAN with secured data communication, including a help feature with online access to cloud service
Automatic wireless data import from scale and blood pressure monitor
Interface and automatic data exchange with clinic management software
Full therapy and patient data management, including prescription modeling, automatic prescription programming, administrative module, and upgradable training courses

Mechanical

Low weight hardware with custom-made travel case for ease of portability
Small system footprint to fit in close to bed or onto average nightstand
Stability to hold a broad range of bag sizes (up to 6 L) without tipping, and with locking wheels and nonslip feet to prevent rolling and sliding
Able to withstand extreme temperatures with adequate performance at sea level and high altitudes
Constructed of material that is easily disinfected with common agents and sealed outer case to prevent trapping of foreign matter and liquids from penetrating into the unit
Silent operation with noise level < 35 dBA while running at maximum pumping speed
100 and 240 V AC power choices
UL/CSA/CE approval

Disposables

Singe-use, sterile components
Easy and quick setup, ideally one-step loading (cassette)
Advanced connectology with elimination of clamps
Organizer to facilitate safe connections and disconnections and reduce contamination and infection risk

CCPD , Continuous cycling peritoneal dialysis, LAN , local-area network; PD , peritoneal dialysis; USB , Universal Serial Bus; WLAN , wireless local-area network.

Mechanical Aspects and Hydraulics

PD cyclers are designed to automatically deliver multiple exchanges of dialysate solution. The dialysate volume and flow are regulated by a central control unit that may include pumps, weigh scales, occluders, manifolds, electronics, and other mechanical components. An integrated heating system ensures adequate dialysate temperature. A display screen and control board allow entering patient treatment parameters and monitoring treatment success. The filling and draining of the dialysate can be performed by gravity- or pump-based systems. Mechanically, cyclers can be categorized as devices that use gravity or pumps.

Gravity-Based Cyclers

This type of cycler uses gravity to deliver the solution from the dialysate bags, through sterile tubing to a volume control unit and heater module, and into the peritoneal cavity ( Fig. 21.1 A ). Alternatively, the dialysate bags may rest on a heating tray; from there, the solution is then transferred to the volume control module and then to the patient. In either case, the cycler ensures that the fluid is heated to body temperature and the exact prescribed volume of dialysate is delivered to the patient. After the prescribed dwell period, the spent dialysate flows by gravity through the patient line into a weigh bag, where the volume is measured to ensure complete drain and determine ultrafiltration. The dialysate is then either collected in an additionally attached drainage bag or disposed directly into the sewage. The transfer of dialysate into the sewage line can be accomplished by gravity or via a pump.

Fig. 21.1, Flow Diagrams for Different Types of Cyclers.

The control panel controls temperature and dwell time and monitors drain time and drainage volume. Inflow volume is determined and measured by a volume control unit or heating cabinet. Gravity cyclers often use scales for measuring drain volumes to ensure that a predetermined percentage of inflow volume is drained before a new cycle takes place and monitoring ultrafiltration. While the use of gravity-based cyclers declined due to the popularity of pump-based systems, recently, modern gravity cyclers have been developed that provide a simplistic and cost-effective alternative to pump-based systems ( Fig. 21.2 ).

Fig. 21.2, Example of a modern gravity-based cycler shown for educational purposes only and not available or approved in all countries.

Pump-Based Cyclers

Most modern cyclers today are pump based. Various systems have been designed to actively infuse and drain dialysate. The simplest and most economical is the use of two peristaltic or roller pumps (see Fig. 21.1 B). The first actively infuses warmed dialysate into the patient, and the second generates negative pressure to drain the spent dialysate.

A more ingenious alternative is the use of an integrated cassette design for easy setup of the cycler. The exact measurement of fluid volume flowing through the cassette can be used for volumetric control and eliminates the need for weigh scales. Current systems contain fluid chambers that serve as pumps and a series of channels for solution flow ( Fig. 21.3 A ).

Examples of modern pump-based cycler designs are provided in Fig. 21.4 .

Fig. 21.4, Contemporary Pump-Based Cycler Designs.

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