ISSN-e: 2737-6419

Period: April-June 2025

Athenea Journal

Vol.6, Issue 20, (pp. 07-18)

Type of article: bibliographic review https://doi.org/10.47460/athenea.v6i20.92

A review of ﬂow and volume sensors applications in hemodialysis

Stephanie Malav

e M

endez*

https://orcid.org/0009-0002-4336-0172

malave 164010@students.pupr.edu

Universidad Polit

ecnica de Puerto Rico

San Juan - Puerto Rico

Julio C. Mart

ınez Ocasio

https://orcid.org/0009-0008-7667-7372

martinez 123888@students.pupr.edu

Universidad Polit

ecnica de Puerto Rico

San Juan - Puerto Rico

*Correspondence author: malave 164010@students.pupr.edu

Received (25/11/2024), Accepted (04/02/2025)

Abstract. This article describes distinct types of ﬂow and volume sensors, and their respective appli-

cations used during hemodialysis. Through a review of the literature, new opportunities in the ﬁeld

of non-invasive methods are explored to optimize and develop innovative technologies in the ﬁeld of

biomedical implants and accelerate the completion of kidney disease treatment. The ﬁndings reveal that

the combination of these devices and noninvasive techniques contributes signiﬁcantly to the treatment

of kidney diseases. In addition, it helps in the development of biological models and the performance

of operational/mechanical analyses to predict more eﬀective and rapid implementation methods for

patient recovery.

Keywords: bioﬂuids, ﬂow and volume sensors, hemodialysis.

Una revisi´on de las aplicaciones de sensores de ﬂujo y volumen en

hemodi´alisis

Resumen. - Este art

ıculo describe diferentes tipos de sensores de ﬂujo y volumen, y sus respectivas

aplicaciones durante la hemodi

alisis. A trav

es de una revisi

on bibliogr

aﬁca se exploran nuevas oportu-

nidades en el campo de los m

etodos no invasivos para optimizar y desarrollar tecnolog

ıas innovadoras

en el campo de los implantes biom

edicos y acelerar la ﬁnalizaci

on del tratamiento de enfermedades re-

nales. Los hallazgos revelan que la combinaci

on de estos dispositivos y t

ecnicas no invasivas contribuye

signiﬁcativamente al tratamiento de enfermedades renales. Adem

as, facilita el desarrollo de modelos

biol

ogicos y la realizaci

on de an

alisis operativos/mec

anicos para predecir m

etodos de implementaci

as efectivos y r

apidos para la recuperaci

on del paciente.

Palabras clave: bioﬂuidos, sensores de ﬂujo y volumen, hemodi

alisis.

Malav´e S and Mart´ınez J. A review of ﬂow and volume sensors applications in hemodialysis

ISSN-e: 2737-6419

Period: April-June 2025

Athenea Journal

Vol.6, Issue 20, (pp. 07-18)

I. INTRODUCTION

Hemodialysis (HD) is a life-saving treatment for chronic kidney failure, replacing key

kidney functions by ﬁltering blood through a dialyzer to remove waste, excess ﬂuids, and

toxins. Speciﬁcally, it serves patients with chronic kidney disease (CKD) and end-stage

renal disease (ESRD), where maintaining a balance between ﬂuid removal and replace-

ment is essential. To achieve this, accurate control of blood and dialysate ﬂow rates, as

well as ultraﬁltration volume [1], is ensured through integrated ﬂow and volume sen-

sors, which play a key role in treatment efﬁcacy and patient safety. As dialysis therapies

become more complex, the demand for reliable sensor technologies continues to grow.

In addition, ESRD, one of the leading causes of reduced lifespan with a high mortality

rate, requires long-term dialysis, and by 2030, an estimated 5.4 million patients will need

this therapy. Effective dialysis depends on proper vascular access to ensure sufﬁcient

blood ﬂow [2]. Thus, epidermal blood ﬂow sensors have been introduced for real-time

monitoring.

Furthermore, access points such as arteriovenous ﬁstulas (AVF), arteriovenous grafts

(AVG) and catheters [3] can fail due to stenosis or thrombosis, making wearable thermal

anemometric ﬂow sensors crucial for early detection. In addition, ﬂow sensors measure

the movement of liquids or gases through output signals [4] or pressure changes [5], en-

hancing the precision of treatment and patient outcomes. Similarly, volume sensors are

integral to modern HD systems, providing real-time ﬂuid balance monitoring. In gen-

eral, this review highlights the role of bio-ﬂuids in medical device design, emphasizing

the importance of ﬂow and volume sensors to align with biological properties for effec-

tive patient care. According to Y

anez et al. [6], blood comprises 8% of an adult’s body

mass, while total water content ranges from 58% to 80%, distributed between organs

such as brain (73%), heart (73%), skin (65%), lungs (84%), kidneys (79%), liver (71%) and

pancreas (73%). Ultimately, as advancements in biomedical engineering continue, ﬂow

and volume sensors will play an increasingly vital role in enhancing treatment precision,

improving patient outcomes, and shaping the future of dialysis technology.

II. FIELDS OF INTEREST TO THE SUBJECT

Flow and volume sensors are crucial in biomedical devices, ensuring precise ﬂuid con-

trol in medication delivery and diagnostics. As medical technology continues to evolve,

ﬂow sensors have become essential for accurately monitoring and managing ﬂuid move-

ment in various applications. Their development, progressing from Microelectromechan-

ical Systems (MEMS) to microﬂuidic devices on a single chip [7], has allowed for in-

creasing efﬁciency and adaptability. Doppler ultrasound sensors enabled transcutaneous

blood ﬂow measurements [8], while wearable sensors expanded to track vital signs like

heart rate and oxygen levels [9]. Meanwhile, Laser Doppler ﬂowmetry provided a non-

invasive way to assess circulatory function, including retinal blood ﬂow in rabbits [10].

Alongside these advancements, volume sensors have been essential in medical applica-

tions, particularly in regulating physiological functions. Relative blood volume monitor-

ing has been used to track hematocrit changes [11] and improve blood pressure regula-

tion during hemodialysis [12]. As technology advanced, bioimpedance analysis emerged

Malav´e S and Mart´ınez J. A review of ﬂow and volume sensors applications in hemodialysis

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to estimate total body water [13], while ultrasound dilution sensors measured cardiac

output in pediatrics [14]. Additionally, portable nuclear magnetic resonance improved

disease diagnosis and tumor detection [15]. Eventually, biomarker sensors introduced

biological markers like glucose detection [16], leading to portable glucose monitors for

diabetes care. The miniaturization and non-invasive design of these sensors have en-

sured high sensitivity, precision, and low power consumption, enabling broad medical

applications. This research highlights their growing role in modern healthcare, demon-

strating how engineering advancements continue to shape the medical ﬁeld.

A. A Brief Review: Flow Sensors

Flow sensors in hemodialysis (HD) are critical for monitoring the rate at which ﬂuids,

primarily blood and dialysate, circulate through the system. Among the various types,

electromagnetic ﬂow sensors offer high accuracy by detecting voltage changes induced

by magnetic ﬁelds as blood ﬂow through the sensor, although they tend to be costly and

technically complex. Ultrasonic ﬂow sensors, in contrast, are widely used due to their

non-invasive nature; they measure ﬂuid velocity using high-frequency sound waves. Op-

tical ﬂow sensors determine ﬂow rate by analyzing changes in light transmission through

the ﬂuid, often leveraging suspended particles within the blood to enhance measurement

precision. Together, these technologies provide essential data for optimizing hemodialy-

sis treatment and ensuring patient safety.

B. Flow Sensor Types

Microelectromechanical Systems (MEMS) ﬂow sensors have been developed for intra-

venous (IV) systems to measure small ﬂow rates, such as those involved in drug deliv-

ery. One such sensor employs artiﬁcial hair cells (AHCs) on a silicon die, incorporat-

ing two differently sized AHCs designed to minimize ﬂow disturbance [7]. The sensor

is coated with a parylene ﬁlm to ensure waterprooﬁng and compatibility with various

drugs. Doppler ultrasound ﬂow sensors utilize diffraction grating transducers (DGTs)

made of ﬂexible bioﬁlm to generate low-energy optical signals, making them well-suited

for long-term implantation. These sensors enhance sensitivity by creating overlapping

ultrasonic beams [8] that detect dispersed ultrasound signals from blood ﬂow. Wearable

ﬂow sensors represent a noninvasive solution for real-time medical monitoring [9], inte-

grating ﬂexible, wireless, multipoint devices that measure pulse waves, skin color, and

tissue temperature. The system includes sensors, cables, a data transmitter, and a tablet

or smartphone for data display, with installation supported by medical ﬁlm dressings

and a polydimethylsiloxane sheet.

Laser Doppler ﬂowmetry offers a noninvasive and wearable approach, using six wire-

less sensors to detect Doppler shifts from red blood cell movement, allowing simulta-

neous monitoring of blood perfusion at multiple sites [10]. Similarly, epidermal blood

ﬂow sensors provide noninvasive, wearable monitoring of skin blood ﬂow, effectively

adapting to sensor placement variability and tissue differences. These sensors capture

weak temperature signals associated with high-volume blood ﬂow [2], offering continu-

ous surveillance valuable in managing end-stage renal disease (ESRD) patients. Lastly,

anemometric ﬂow sensors also present a wearable, noninvasive solution, designed to

Malav´e S and Mart´ınez J. A review of ﬂow and volume sensors applications in hemodialysis

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detect changes in blood ﬂow through vascular access points such as arteriovenous ﬁstu-

las (AVF) and arteriovenous grafts (AVG) [3]. These sensors deliver immediate physio-

logical feedback with high sensitivity and have demonstrated accurate performance in

vivo studies. Collectively, these technologies underscore the progress in ﬂow sensing

for hemodialysis and broader clinical applications, balancing precision, ease of use, and

patient comfort.

C. A Brief Review: Volume Sensors

Volume sensor analysis in dialysis plays a crucial role in monitoring and managing ﬂuid

volumes within the dialysis system to ensure effective treatment and optimal patient

care. By accurately measuring and tracking ﬂuid movement across various components,

such as dialysate delivery, blood ﬂow, and ultraﬁltration, these sensors help maintain

proper ﬂuid balance and prevent complications like ﬂuid overload or dehydration. Tech-

niques such as relative blood volume monitoring (RBVM) and bioimpedance analysis (BIA) are

commonly used to assess patient hydration status and guide real-time adjustments to

ultraﬁltration rates during dialysis sessions. Two main types of volume sensors are em-

ployed: cumulative volume sensors, which continuously monitor the total volume of blood

or dialysate processed, providing essential data on ﬂuid removal or replacement; and

real-time volume sensors, which offer instantaneous volume measurements to enable dy-

namic control and maintain equilibrium. Many of these devices also incorporate optical

technologies to measure hematocrit levels, serving as indicators of hemoconcentration

and aiding in the precise evaluation of blood volume changes. Together, these volume

sensing approaches enhance dialysis safety, personalization, and clinical outcomes.

D. Volume Sensor Types

Volume sensors represent a fundamental category within monitoring and automation

systems, allowing for the precise measurement of the quantity of liquid or gas contained

in each space. Their applications span multiple sectors, from the medical and food in-

dustries to automotive engineering and smart manufacturing processes. The choice of

the appropriate sensor type depends on factors such as the type of ﬂuid, the required

accuracy, the operating environment, and response speed. Below are the main types of

volume sensors, their operating principles, and their advantages in different technologi-

cal contexts.

Relative Blood Volume Monitoring (RBVM) is a key technique in dialysis that tracks

changes in hematocrit [11], the ratio of red blood cells to plasma, as ﬂuid is removed

from the patient [12]. This allows for real-time adjustments of ultraﬁltration targets,

helping to prevent complications such as intradialytic hypotension by avoiding excessive

ﬂuid removal. Bioimpedance Analysis (BIA) complements RBVM by estimating body water

compartments, including extracellular water (ECW), intracellular water (ICW), and total

body water (TBW) [13], through the measurement of the body’s electrical properties. BIA

aids in determining a patient’s dry weight and guides ﬂuid removal strategies during

dialysis. Various BIA methods exist, including single-frequency, multi-frequency, and

bioimpedance spectroscopy (BIS), and can be applied using whole-body or segmental

approaches. Ultrasound dilution sensors provide additional ﬂuid status insights by mea-

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suring blood ﬂow and cardiac output, detecting changes in ultrasound wave velocity [14]

after injecting a known volume of ﬂuid, such as saline, into the arterial line. Portable nu-

clear magnetic resonance (NMR) sensors utilize low magnetic ﬁelds [15] to quickly assess

ﬂuid status at the bedside, offering rapid differentiation between hypervolemic and eu-

volemic states, signiﬁcantly faster than conventional MRI techniques. Lastly, biomarker

sensors enable the detection and quantiﬁcation of speciﬁc biological markers [16] using

technologies such as paper-based platforms, vibrating resonators, and optical detection

systems. These sensors support early disease detection, monitoring ﬂuid overload, treat-

ment tracking, and personalized therapy, contributing to improved outcomes in dialysis

care. Collectively, these volume sensing technologies enhance the precision, safety, and

personalization of ﬂuid management in hemodialysis.

E. Integration of Flow and Volume Sensors in the Hemodialysis Process

Flow and volume sensors integrated into dialysis machines play a crucial role in deliv-

ering safe, efﬁcient, and individualized treatment by providing real-time data to moni-

tor and regulate both blood and dialysate ﬂow. These sensors enable automatic system

responses to abnormalities such as low blood ﬂow or excessive ﬂuid removal, thereby

preventing complications like dehydration or intradialytic hypotension and enhancing

overall patient safety. In clinical hemodialysis, ﬂow and volume sensors serve several

key functions. Monitoring blood ﬂow is essential to maintain optimal perfusion through

the vascular access and extracorporeal circuit [17], and ﬂow sensors help detect access

dysfunction early, ensuring treatment efﬁcacy. Dialysate ﬂow regulation is another critical

application, as dialysate ﬂow rate directly impacts solute clearance; accurate monitoring

via ﬂow sensors improves dialysis efﬁciency and clinical outcomes [18]. Ultraﬁltration

management relies on volume sensors to precisely control the amount of ﬂuid removed

during treatment, aiding in the achievement of patient-speciﬁc dry weight targets and

avoiding the risks of ﬂuid overload or hypotension. Additionally, while non-ﬂow sensors

per se, leak and air detection systems use differential ﬂow measurements between blood

inﬂow and outﬂow to identify anomalies such as tubing leaks or air ingress, prompt-

ing immediate corrective action. Together, these sensor technologies enhance the safety,

accuracy, and personalization of dialysis therapy.

F. Dialysis Machines

Dialysis machines [19] are critical medical devices used to perform renal replacement

therapy in patients with end-stage renal disease (ESRD) or acute kidney injury. These

machines mimic the ﬁltration function of healthy kidneys by removing waste products,

excess ﬂuids, and toxins from the bloodstream through a semi-permeable membrane.

Hemodialysis, the most generic form, circulates blood through an external dialyzer, while

peritoneal dialysis uses the patient’s peritoneal membrane as the ﬁltration surface. Dial-

ysis machines tightly regulate parameters such as blood ﬂow rate, dialysate composition,

temperature, and ultraﬁltration volume to ensure safe and effective treatment. Modern

systems, such as the Fresenius 5008 CorDiax and Baxter’s AK 200 ULTRA S, are equipped

with real-time monitoring, integrated sensors, and customizable treatment protocols to

improve patient outcomes. Integrated ﬂow and volume sensors within these machines

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enhance safety by implementing air detectors, pressure monitors, and blood leak de-

tectors to minimize risks of detecting air bubbles, pressure anomalies, and blood leaks,

allowing for automatic system adjustments. Peritoneal dialysis machines, such as the

Baxter Amia, use the peritoneal membrane for ﬁltration and are designed for home use,

offering patients greater ﬂexibility and autonomy. Dialysis machines also store historical

treatment data, aiding clinicians in personalizing therapy and tracking patient progress

over time. The primary goal of these machines is to maintain ﬂuid and electrolyte bal-

ance, reduce uremic symptoms, and improve survival and quality of life in patients with

compromised renal function. Continued technological advancements aim to increase ef-

ﬁciency, portability, and patient comfort, making dialysis therapy more accessible and

effective.

G. Method Calculations

Since this review serves as a collection of relevant research, it focuses on providing

information that supports and sustains the discussion. Among the key topics, ﬂow rate

is widely assessed due to its versatility and extensive applications in ﬂow and volume

sensors. Understanding this concept is essential, as equation (1) deﬁnes the relationship

between ﬂuid velocity, cross-sectional area, and the volume of ﬂuid passing through a

point over time [20]:

Q =

(1)

where Q represents the ﬂow rate (e.g., blood ﬂow), V denotes the average velocity,

and S corresponds to the cross-sectional area of the ﬂuid (e.g., blood).

Equation (2) expands upon ﬂow rate by incorporating volume ﬂow rate (Q

), which

can be modiﬁed depending on the speciﬁc application. For instance, when analyzing

laminar blood ﬂow in a rectangular channel, the volume ﬂow rate is expressed as:

4ba

3µ



−







1 −

192a

∞

∑

i=1,3,5,...

tan h



inb







(2)

where b represents the width, a is the half-height of the channel, and µ signiﬁes the

ﬂuid viscosity. The term −

refers to the pressure gradient within the channel, while

∑

∞

i=1,3,5,...

the summation term accounts for the inﬂuence of odd integers on the ﬂow be-

havior. Additionally, tan h



inb



represents the geometric characteristics of the channel.

Another essential equation used in ﬂow and volume sensors is the Doppler equation

(3), primarily utilized to measure the velocity of blood ﬂow:







(3)

where f

is denotes the Doppler frequency shift, V represents the velocity of blood

ﬂow, λ is the wavelength of the transmitted wave, and d is the distance.

In contrast to the Doppler equation, the wavelet spectrum equation (4) is applied to

evaluate signals from ﬂow and volume sensors:

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W(s, τ) =

√

∞

−∞

x(t)ψ

∗



t − τ



(4)

where W(s, τ) represents the wavelet transform of the signal, s is the scale parameter,

x(t) is the evaluated signal, τ corresponds to the time parameter, and ψ

∗

is the complex

conjugate of the wavelet function.

Additionally, the non-dimensional temperature equation (5) is implemented in ﬂow

and volume sensors to adjust temperature measurements for improved accuracy:

nondim

T − T

standard

∆T

standard

(5)

where T

nondim

represents the non-dimensional temperature, T is the measured temper-

ature, T

standard

signiﬁes the reference temperature, and ∆T

standard

is the difference between

two reference temperatures.

Finally, the ﬂow sensitivity equation (6) is incorporated into ﬂow and volume sensors

to assess their responsiveness to variations in ﬂow rate:

Sensitivity(%) =

∆T

100mL/min

− ∆T

800mL/min

∆T

800mL/min

× 100 (6)

where ∆T

100mL/min

represents the time change at a lower ﬂow rate of 100mL/min, and

∆T

800mL/min

corresponds to the time change at a higher ﬂow rate of 800mL/min.

H. Outcomes of ﬂow sensors

Experiments on ﬂow sensors provided signiﬁcant insights across various applications.

For instance, MEMS ﬂow sensors demonstrated a dynamic range of 2–200 ml/h, but

showed output saturation near 200 ml/h, while IV system testing at 0.05 ml/min con-

ﬁrmed adaptability. Additionally, Doppler ultrasound ﬂow sensors measured veloci-

ties between 110–122 cm/s with minimal variation, though estimates deviated by 5.9%

across ﬂow rates of 60–500 mL/min. Meanwhile, wearable ﬂow sensors in clinical trials

achieved physician agreement rates of 96%–99.2%, with 90% of patients recommending

future use. In addition, laser Doppler ﬂowmetry studies showed perfusion decreased

when transitioning upright, but increased in a head-down position, with forehead mea-

surements exhibiting minimal microcirculation changes. Notably, blood pressure and

heart rate were consistently higher in vertical positions. Furthermore, epidermal blood

ﬂow sensors provided precise vascular access monitoring, showing a 12.2% deviation

from Doppler ultrasound across ﬂow rates of 100–600 ml/min, with a compact design

suitable for hemodialysis. Lastly, anemometric ﬂow sensors accurately monitored blood

ﬂow in CKD patients, adapting to AVF development, vascular stenosis, thrombosis, and

access failure, while maintaining reliable performance despite minor setup imbalances.

Ultimately, in vivo studies validated their precision across different ﬂow conditions, with

benchtop models conﬁrming the impact of vessel structure on sensor sensitivity. These

ﬁndings highlight the essential role of ﬂow sensors in advancing patient monitoring and

medical technology.

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ISSN-e: 2737-6419

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I. Technological Advancements and Innovations in Sensors

Recent advancements in dialysis technology have signiﬁcantly improved the perfor-

mance and integration of ﬂow and volume sensors. Miniaturization has led to the devel-

opment of smaller, more compact sensors that can be seamlessly embedded within dial-

ysis machines, reducing the overall system size and enhancing portability. Smart sensors,

pate potential complications and automatically adjust treatment parameters to enhance

patient safety and optimize outcomes. Additionally, wireless monitoring has transformed

clinical practice by enabling real-time, remote access to sensor data, allowing healthcare

providers to oversee a patient’s dialysis session without being physically present. These

innovations are complemented by improved accuracy, achieved using advanced materi-

als and technologies such as high-precision electromagnetic and miniaturized ultrasonic

sensors, which ensure greater measurement reliability and clinical effectiveness.

J. Challenges and Limitations

Flow and volume sensors in dialysis systems, while essential for ensuring accurate and

safe treatment, are subject to several limitations. Sensor drift is a common issue, where

prolonged use leads to gradual loss of accuracy, necessitating routine recalibration to

maintain performance. Additionally, external interference, including ﬂuctuations in tem-

perature, pressure, and changes in the chemical composition of blood or dialysate, can

compromise the reliability of sensor readings. Mechanical failures also pose a signiﬁcant

risk; malfunctions can result in erroneous data that may threaten patient safety if not

promptly detected. Furthermore, these sensors demand consistent maintenance and clean-

ing to prevent blockages or clogs, ensuring continuous, unobstructed operation and ac-

curate monitoring throughout the dialysis process.

III. METHODOLOGY

This review focused on the assessment of mechanical and operational properties for ﬂow

and volume sensors using a diverse range of scientiﬁc literature and academic contribu-

tions. The primary sources included peer-reviewed journal articles, doctoral and mas-

ter’s theses, and conference presentations, all provided by researchers, and recognized

scientiﬁc organizations. The objective was to gather comprehensive, high-quality infor-

mation that reﬂects the current state of knowledge in the ﬁeld. To ensure a comprehen-

sive and inclusive literature review, an exhaustive search was conducted across Ameri-

can and European academic databases, emphasizing repositories afﬁliated with institu-

tions specializing in biomedical engineering. The primary search focused on publications

from 2021 to 2025 to capture the most recent advancements, utilizing databases such as

PubMed, Scopus, IEEE Xplore, EBSCOhost, Google Scholar, and ScienceDirect. These

platforms were selected for their broad coverage of biomedical and interdisciplinary re-

search, allowing the identiﬁcation of high-quality peer-reviewed articles, conference pro-

ceedings, and technical reports. Supplementary information from secondary sources, in-

cluding engineering textbooks, technical manuals, handbooks, internet-based resources,

and review articles, further enriched the contextual and technical depth of the review. To

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determine the most appropriate ﬂow or volume sensor for a given clinical setting, sev-

eral critical criteria must be considered according to the researched data evaluated from

collected references. These include performance characteristics such as accuracy and reli-

ability, and material properties like durability, biocompatibility, and ease of sterilization.

Cost factors compassing initial investment, maintenance, and operational expenses, are

also evaluated. Additionally, the simplicity of use, including training requirements and

the ease of integration into existing dialysis systems, plays an important role in sensor

selection. Real-time monitoring capabilities are essential for continuous assessment dur-

ing the dialysis process. A comparative analysis of these criteria for each sensor type is

presented in Table 1, with each criterion rated on a scale of Low, Medium, or High.

Tabla 1. Inclusion and Rejection Criteria.

Criteria Key Questions Rating (Low/

Medium/High)

Accuracy How accurate is the sensor?

What is the reliability of the sensor?

Material of What is the durability of the sensor?

Construction Is it biocompatible with other equipment?

Is it easy to sterilize the sensor?

What is the initial investment cost? Refer to Tables

Cost What is the cost of maintenance? 2 and 3 for a

What is the cost for operation? complete evaluation

How easy is it to use? of ﬂow and

Simplicity What training does it require? volume sensor

How hard is it to integrate with the system? criteria.

Invasiveness Does it require direct access to blood or

a vascular access point?

Real-Time Does it provide real-time monitoring

Monitoring during the dialysis process?

Clinical Is it used in clinical dialysis centers or

Maturity mostly in research settings?

IV. RESULTS

Table 2 presents the ﬂow sensor types analyzed and their distinctive characteristics,

as well as their applications in health situations based on the information collected from

the references obtained during this document’s preparation.

Table 3 presents the volume sensor types analyzed and their distinctive characteris-

tics, as well as their applications in health situations based on the information collected

from the references obtained during this document’s preparation.

According to the obtained results presented on Table 2, the best ﬂow sensor option

for hemodialysis mentioned on this paper should be Doppler Ultrasound ﬂow sensor

based on its high accuracy, real-time performance, non-invasive characteristics and clin-

ically validated use. These characteristics prove the effectiveness in dialysis clinics for

vascular access ﬂow surveillance and early detection of complications like thrombosis

and stenosis. For the other hand, MEMS ﬂow sensors and wearable devices could en-

hance monitoring, especially for continuous, home-based settings, but they need more

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Tabla 2. Flow Sensors Results.

Sensor Type

Accuracy

Durability

Cost

Ease

Invasive

Real-Time

Maturity

Clinical Application

MEMS H M H L L M L Experimental implantable blood ﬂow

monitors

Doppler

Ultrasound

H H M M L H H Vascular access blood ﬂow measure-

ment, stenosis detection

Wearable M M M–H H L L L Home/outpatient vascular monitor-

ing

Laser Doppler

Flowmetry

L H H M L M L Monitoring superﬁcial skin blood

ﬂow; not suitable for hemodialysis

circuits

Epidermal L–M H H L L H L Skin perfusion monitoring, future

vascular access checks

Anemometric M M L–M H L H M Prototypical dialysis blood ﬂow mon-

itoring

Legend: H = High, M = Medium, L = Low

Tabla 3. Volume Sensors Results

Sensor Type

Accuracy

Material Durability

Cost (USD)

Ease to Use

Invasiveness

Real-Time Monitoring

Clinical Maturity

Clinical Application

RVBM M–H H L–M H L H H Intradialytic blood volume tracking

to prevent hypotension

BIA M H L H L L H Assessment of ﬂuid overload pre-

/post-dialysis

Ultrasound

dilution

H H M–H M L M M–H Blood volume and cardiac output

monitoring during dialysis

NMR H H H L L L L Detailed body composition and hy-

dration state

Biomarker M M M–H M L M L Monitoring biochemical markers re-

lated to hydration (natriuretic pep-

tides)

Legend: H = High, M = Medium and L= Low

validation and ruggedization. Corresponding to obtained results presented on Table 3,

the best volume sensor option for hemodialysis mentioned on this paper should RBVM

(Relative Blood Volume Monitoring) volume sensor based on its real-time performance,

non-invasive characteristics, cost-effective and clinically validated use. These character-

istics prove the effectiveness for blood volume management during hemodialysis. For

the other hand, Biomarker sensors and advanced NMR techniques could enhance ﬂuid

management in the future but are not yet practical for routine use. Along the course of the

review, it was found that sensor accuracy is directly linked with sensitivity. This means

that at a higher sensitivity, it can increase the performance of the sensor. In hemodialysis

the incorporation of these sensors is crucial, because it can guarantee the well-being of

the patient and at the same time ensure treatment effectiveness.

Malav´e S and Mart´ınez J. A review of ﬂow and volume sensors applications in hemodialysis

ISSN-e: 2737-6419

Period: April-June 2025

Athenea Journal

Vol.6, Issue 20, (pp. 07-18)

CONCLUSIONS

The review covered a comprehensive range of topics centered on ﬂow and volume sen-

sors and their applications in hemodialysis treatment. Each sensor type demonstrated

speciﬁc strengths and limitations under various clinical conditions, yet all effectively ful-

ﬁlled their intended roles in accurately monitoring blood ﬂow and ﬂuid dynamics. Flow

and Volume sensors play a vital role in enhancing the precision of ﬂuid management,

thereby contributing to improved patient outcomes. The selection of an appropriate sen-

sor depends on a combination of clinical requirements, resource availability, and cost

considerations. Continued advancements in sensor technologies, especially regarding

integration with dialysis systems and real-time monitoring capabilities, offer promis-

ing prospects for further improving the safety, efﬁciency, and overall effectiveness of

hemodialysis therapy.

Moreover, interdisciplinary research efforts and collaborations between medical de-

vice manufacturers and healthcare providers are essential to accelerate innovation in this

ﬁeld. Future developments should focus on miniaturization, increased sensor sensitivity,

and seamless integration with automated control systems to facilitate personalized treat-

ment protocols. Such advancements will not only optimize hemodialysis procedures but

also enhance patient comfort and reduce long-term healthcare costs.

Additionally, emerging trends emphasize the incorporation of artiﬁcial intelligence

and machine learning algorithms into sensor technologies, enabling predictive analytics

for early detection of complications such as clot formation, vascular access dysfunction,

and ﬂuid overload. These intelligent systems, already under exploration in advanced

healthcare centers worldwide, have the potential to revolutionize hemodialysis manage-

ment by providing data-driven insights for personalized treatment adjustments in real

time. As seen in recent studies from leading institutions in the United States, Germany,

and Japan, this technological convergence is paving the way for more adaptive and re-

silient dialysis systems, ultimately aiming to improve survival rates and quality of life

for patients undergoing long-term treatment.

ACKNOWLEDGEMENT

We would like to express our sincere gratitude to the academic institution Polytechnic

University of Puerto Rico for the support and guidance throughout the development of

this review. Their assistance has been relevant in inﬂuencing the success of this work.

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Athenea Journal

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