In order to discuss a PD modality it is important to define the methods and techniques that characterize the modality. A PD regimen is a systematic plan of therapy that is generally characterized as intermittent or continuous when referring to the duration of dialysis, and supine or ambulatory when referring to the position of the patient. An intermittent regimen is performed periodically or several times weekly. Examples of intermittent regimens are intermittent peritoneal dialysis, as in the case of nightly (NIPD) or daytime PD (DIPD). A continuous regimen denotes the continuous presence of peritoneal dialysate in the peritoneal cavity 24-hours a day and seven days a week. Short interruptions required for the exchanges do not disqualify the regimen as continuous. A supine regimen infers that the patient is in the supine position while dialyzing and an ambulatory regimen means that the patient can be ambulatory while dialyzing.
The PD technique is the procedure by which a regimen is accomplished. These definitions can be confusing since similar terms are applied to the regimen and the technique. The continuous flow technique maintains a simultaneous and continuous inflow and outflow of dialysate by means of two catheters or a double-lumen catheter.
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The intermittent flow technique utilizes a single catheter and uses discrete inflow, dwell, and outflow phases. The flow of dialysate is totally interrupted during dwell and at the completion of inflow and outflow. Most conventional PD modalities use the intermittent flow technique (i.e. CAPD, IPD, CCPD).
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The tidal technique uses an initial fill followed by a partial drain and replacement by fresh dialysate with each cycle. This leaves a portion of the dialysate constantly in contact with the peritoneal membrane (reservoir volume) and a wave or tide created by the inflow and outflow of the tidal volume.
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