(379 days)
For non-invasive monitoring, in real time, of the estimated relative blood volume percent for patients undergoing hemodialysis so that technicians may make system adjustments in order to remove the maximum amount of fluid from the dialysis patient without the patient experiencing the common symptoms of dialysis which include nausea, cramping and vomiting.
The device can also provide estimated values of: (1) relative blood volume trend; (2) hematocrit; (3) hemoglobin and (4) blood water content or mass fraction of blood water in the total blood mass.
The device is ONLY to be used in conjunction with the Fresenius Dialysis System 2008H.
There are a variety of method for measuring relative blood volume (RBV), and all make use of the fact that certain constituents of blood (cells, haemoglobin, plasma protein, total protein) remain confined to the vascular compartment, whereas the plasma water can pass both the capillary membrane (into the interstitial compartment) and the dialyser membrane (into the dialysis fluid compartment). Therefore the blood volume change can be determined from the concentration change of these blood constituents.
The Fresenius Blood Volume Monitor is only to be installed in an available bay of the Fresenius Dialysis System 2008H machine. It uses ultrasound pulses from a transmitter through a polycarbonate cuvette installed into the arterial blood line and received on the opposite side. The primary signal measure is the transient time of the sound pulse through the blood sample, from which the sound velocity is calculated. Silicone rubber is used as sound coupling for the cuvette, with the blood passing through from bottom to top to avoid accumulation of air bubbles. Blood temperature is also measure, and a temperature controlled block prevents interference from ambient temperature changes.
The sound speed depends on the blood density, which in turn depends on the mass fraction of protein and the mass fraction of water or blood water content (BWC). Since the mass of blood protein is virtually unchanged during ultra filtration, the mass of blood water changes, and thereby the density changes. Changes in BWC can be detected by changes of sound velocity, and can be converted to relative blood volume changes. Since sound velocity not only depends on density, but also on temperature, a high precision temperature measurement is also required.
Here's an analysis of the acceptance criteria and supporting studies for the Fresenius Blood Monitor, based on the provided text:
Acceptance Criteria and Reported Device Performance
Although explicit "acceptance criteria" in a quantitative table format are not directly stated, the document emphasizes the device's accuracy in comparison to existing methods. The primary performance metric mentioned is agreement with the centrifuge method and correlation with hemoglobin concentration.
| Acceptance Criteria (Implied) | Reported Device Performance |
|---|---|
| Accuracy of blood volume information | Approximately ±2% (compared to predicate device) |
| Correlation with hemoglobin concentration | r = 0.98 (for relative blood volume) |
| Agreement with centrifuge method (mean difference) | 0.1% ± 1.8% |
1. Sample Size Used for the Test Set and Data Provenance
- Study 1:
- Sample Size: 45 patients
- Number of Examinations: Each patient examined three times, with six values each time.
- Data Provenance: Not explicitly stated, but the device was "developed in Europe and currently marketed outside the United States," suggesting the studies may have originated from Europe. The document refers to "6 centers," which could imply a multicenter study. It's unclear if this was retrospective or prospective, but the phrasing "examined three times" suggests a prospective collection for this specific study.
- Study 2:
- Sample Size: 9 patients
- Number of Comparisons: 104 comparisons with the centrifuge method.
- Data Provenance: Not explicitly stated, but likely from similar European sources as Study 1. The phrasing "underwent 104 comparison" suggests a prospective design for this specific comparative study.
2. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts
The document does not mention the use of experts to establish a "ground truth" for the test set in the traditional sense of clinical diagnosis or interpretation. Instead, the ground truth was established by established measurement methods:
- Standard Method (for correlation with hemoglobin concentration): This refers to a method used to determine hemoglobin concentration, which then allows for the calculation of relative blood volume. The qualifications of who performed this "standard method" are not specified.
- Centrifuge Method: This is a laboratory technique for separating blood components to determine hematocrit, which can be an input for blood volume calculations. The qualifications of the individuals performing the centrifuging are not specified, but it's a standard lab procedure.
3. Adjudication Method for the Test Set
Not applicable. The ground truth was established by direct measurement methods (e.g., centrifuge, standard hemoglobin measurement), not by expert consensus requiring adjudication.
4. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done, If So, What Was the Effect Size of How Much Human Readers Improve with AI vs. Without AI Assistance
No, an MRMC comparative effectiveness study involving human readers and AI assistance was not conducted or reported. The device is a monitor providing real-time data, not an AI diagnostic tool requiring human interpretation improvement. The document describes studies comparing the device's measurements to other physical measurement methods.
5. If a Standalone (i.e., algorithm only without human-in-the-loop performance) Was Done
Yes, the studies described are essentially "standalone" performance evaluations of the device. The device itself (the Fresenius Blood Monitor) directly measures and outputs values for relative blood volume. The reported studies evaluate the accuracy of these device-generated measurements against established "ground truth" methods (like centrifuge or hemoglobin concentration measurement) without human intervention in the interpretation of the device's primary output. The human aspect comes in subsequent clinical decision-making based on the device's output.
6. The Type of Ground Truth Used
The ground truth used was based on:
- "Standard method" for obtaining blood volume/hematocrit values (presumably laboratory-based methods) in the study correlating with hemoglobin.
- The "centrifuge method" for blood volume comparison.
These are objective, quantitative measurement methods, not expert consensus, pathology, or outcomes data in the context of diagnostic interpretation.
7. The Sample Size for the Training Set
The document does not mention a "training set" or any machine learning/AI training process. The Fresenius Blood Monitor operates based on physical principles (ultrasound sound velocity related to blood density) and algorithms derived from those principles, rather than being a machine learning model that requires a training dataset in the typical sense.
8. How the Ground Truth for the Training Set Was Established
Not applicable, as there is no mention of a training set for a machine learning model.
§ 876.5860 High permeability hemodialysis system.
(a)
Identification. A high permeability hemodialysis system is a device intended for use as an artificial kidney system for the treatment of patients with renal failure, fluid overload, or toxemic conditions by performing such therapies as hemodialysis, hemofiltration, hemoconcentration, and hemodiafiltration. Using a hemodialyzer with a semipermeable membrane that is more permeable to water than the semipermeable membrane of the conventional hemodialysis system (§ 876.5820), the high permeability hemodialysis system removes toxins or excess fluid from the patient's blood using the principles of convection (via a high ultrafiltration rate) and/or diffusion (via a concentration gradient in dialysate). During treatment, blood is circulated from the patient through the hemodialyzer's blood compartment, while the dialysate solution flows countercurrent through the dialysate compartment. In this process, toxins and/or fluid are transferred across the membrane from the blood to the dialysate compartment. The hemodialysis delivery machine controls and monitors the parameters related to this processing, including the rate at which blood and dialysate are pumped through the system, and the rate at which fluid is removed from the patient. The high permeability hemodialysis system consists of the following devices:(1) The hemodialyzer consists of a semipermeable membrane with an in vitro ultrafiltration coefficient (K
uf ) greater than 8 milliliters per hour per conventional millimeter of mercury, as measured with bovine or expired human blood, and is used with either an automated ultrafiltration controller or anther method of ultrafiltration control to prevent fluid imbalance.(2) The hemodialysis delivery machine is similar to the extracorporeal blood system and dialysate delivery system of the hemodialysis system and accessories (§ 876.5820), with the addition of an ultrafiltration controller and mechanisms that monitor and/or control such parameters as fluid balance, dialysate composition, and patient treatment parameters (e.g., blood pressure, hematocrit, urea, etc.).
(3) The high permeability hemodialysis system accessories include, but are not limited to, tubing lines and various treatment related monitors (e.g., dialysate pH, blood pressure, hematocrit, and blood recirculation monitors).
(b)
Classification. Class II. The special controls for this device are FDA's:(1) “Use of International Standard ISO 10993 ‘Biological Evaluation of Medical Device—Part I: Evaluation and Testing,’ ”
(2) “Guidance for the Content of 510(k)s for Conventional and High Permeability Hemodialyzers,”
(3) “Guidance for Industry and CDRH Reviewers on the Content of Premarket Notifications for Hemodialysis Delivery Systems,”
(4) “Guidance for the Content of Premarket Notifications for Water Purification Components and Systems for Hemodialysis,” and
(5) “Guidance for Hemodialyzer Reuse Labeling.”