hc_k29000_hcen12208_09_2007_10

Chapter 3AK 96 - Technical description

Contents

General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3: 3Extracorporeal Blood unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3: 3Fluid unit - the hydraulic system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3: 4Power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3: 4Operator’s panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3: 4

Product decription . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3: 6Blood unit - exterior parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3: 6Blood unit - interior parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3: 8Fluid unit - exterior front parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:10Fluid unit - exterior rear parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:12Fluid unit - interior parts 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:14Fluid unit - interior parts 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:16Fluid unit - interior parts 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:18Fluid unit - valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:20

Hydraulic description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:22Subsystems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:22Hydraulic flow diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:23FM Flow path description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:24The water intake and heating system . . . . . . . . . . . . . . . . . . . . . . . . 3:24The Temperature Control and Protective System . . . . . . . . . . . 3:26

Chemical disinfectants intake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:28Mixing and conductivity regulation . . . . . . . . . . . . . . . . . . . . . . . . . 3:29Conductivity Control System, acetate . . . . . . . . . . . . . . . . . . . . 3:31Conductivity Control System, bicarbonate . . . . . . . . . . . . . . . . . 3:32Composition supervision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:33

Degassing/flow pump system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:34Preset of the degassing pressure . . . . . . . . . . . . . . . . . . . . . . . . 3:35Degassing Pressure Control System . . . . . . . . . . . . . . . . . . . . . . 3:35Adjustable dialysis fluid flow (option) . . . . . . . . . . . . . . . . . . . . 3:36Conductivity guard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:36

Fluid output - UF control system . . . . . . . . . . . . . . . . . . . . . . . . . . 3:37TMP calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:37Safety Guard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:38Deairating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:38UF regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:39The UF Control System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:40UF-cell taration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:41Diascan - Conductivity cell C (option) . . . . . . . . . . . . . . . . . . . . 3:44Blood leak detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:47

FM component description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:48Pressure regulator, PR 1 & PR 2 . . . . . . . . . . . . . . . . . . . . . . . . 3:48Heat exchanger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:48Pressure switch: SAGS & INPS . . . . . . . . . . . . . . . . . . . . . . . . . 3:48Flow Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:48Heater unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:48Feeding pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:48Mixing chambers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:49Conductivity cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:49

HCEN12208 Revision.09.2007 AK 96 - Technical description 3:1

BiCart-holder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:49pH-sensor (optional) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:49Flow pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:49Degassing chamber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:49UF measuring unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:50UFD (optional) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:50Deairating chamber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:50Blood leak detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:50Pressure transducers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:50

Extracorporeal blood circuit description . . . . . . . . . . . . . . . . . . . . . . . . . . 3:51Product description - Blood unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:51Treatment modes and disposables . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:52

Double needle treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:52Single needle treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:53

Blood flow diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:54Blood flow description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:55BPM - blood pressure module . . . . . . . . . . . . . . . . . . . . . . . . . . 3:56Single needle treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:57

BM component description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:58Power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:61Operator’s panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:62

Button description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:63

3:2 AK 96 - Technical description HCEN12208 Revision.09.2007

General information

The AK 96 is designed to be used as a single patient machine to performhemodialysis treatments upon prescription by a physician. Patientcounselling and teaching of treatment techniques are directly under thesupervision and discretion of the physician.

The AK 96 can be divided into following parts:• Extracorporeal Blood unit

• Hydraulics - Fluid unit

• Power supply

• Operator’s panel

Extracorporeal Blood unitThe blood unit is designed to control and supervise the extracorporealblood circuit. Single needle treatment can be performed with one pump(double clamp function). To prevent coagulation, anticoagulantia may beadministered by means of the syringe pump.

Disposable blood lines are used for the blood flow. The blood unitincludes following main functions:• Arterial and venous line clamps control

• Arterial blood pressure monitoring

• Blood flow regulation

• Administration of anticoagulantia (e.g. Heparin)

• Venous blood pressure monitoring

• Air detection

• Priming detection


Fluid unit - the hydraulic systemThe fluid unit is used to produce the dialysis fluid (with correcttemperature and correct composition) from reverse osmosis water andconcentrate, and to transport the dialysis fluid through the dialyzer.

The fluid unit maintains the dialysis fluid flow through the dialyzer withcontrolled ultrafiltration. If a fault occurs, the fluid unit bypasses thedialyzer.

AK 96 fluid unit includes the following main functions:

• Inlet pressure monitoring and regulation

• Temperature monitoring and regulation

• Concentrate/disinfectants intake

• Conductivity monitoring and regulation

• pH measurement of the fluid, optional

• Degassing pressure and flow regulation

• High pressure monitoring

• UF measuring and regulation

• TMP monitoring

• Clearance measurement, optional

• Blood leak detection

Power supplyThe mains voltage is fed to an AC/DC converter which generatesdifferent DC supplies to the monitor.

Operator’s panelBoth the blood unit and the fluid unit are controlled and supervisedfrom the operator’s panel. The panel consists of a number of buttons,flow paths, a time display and an information display. The buttons arelanguage independent. The information in the display can be set todifferent languages.

Detailed information about the functionality of the operator’s panel isavailable in AK 96 Operator’s Manual, HCEN12239.


This page is intentionally left blank


Product decription

Blood unit - exterior parts

19

1

2

3

4

5

7

6

8

9 11

10

12

13

14

15

16

17

18


Part list

1. Top tray

2. Operator’s panel

3. Level detector

4. Venous pressure transducer connector

5. Arterial pressure transducer connector

6. Blood pump

7. Syringe pump (option)

8. Priming detector

9. Arterial blood line clamp (option)

10. Potential equalization connection

11. Venous blood line clamp

12. Arm for dialyzer holder

13. Blood line guides

14. Expansion chamber holder

15. BPM connector (option)

16. Level adjustment knob

17. BPM cuff holder (option)

18. Infusion pole

19. Infusion/Alarm pole (option)


Blood unit - interior parts

12

3

4

5

6

7

8

9

10


Part list

1. Level regulation

2. BiCart holder (part of the hydraulic flow path; option)

3. BPM (blood pressure module; option)

4. BPM board (option)

5. BM I/O board

6. Blood pump bearing

7. Tubings to/from BiCart cartridge holder

8. Syringe pump (option)

9. Blood pump

10. Operator’s panel


Fluid unit - exterior front parts

1

3

2

14

12

15

13

11

9

9

10

4

5

6

7

8


Part list

1. Safety couplings for the dialysis fluid tubes

2. Machine outlet dialysis fluid tube;from the machine to the dialyzer (blue)

3. Machine inlet dialysis fluid tube;to the machine from the dialyzer (red)

4. Yellow: right female disinfectant connector marked P.Always use this position except during chemical disinfection.

5. Yellow: left female disinfectant connector C (not marked on themachine).Only to be used if chemical disinfectants is to be taken in via thedisinfectant inlet tube on the rear of the machine.

6. Yellow: disinfectant male connector

7. Blue: concentrate connector with white tube marking

8. Red: concentrate connector

9. Lockable wheel

10. Concentrate pick-up tube

11. Ground plate

12. Soft Pac hook (option)

13. Stand-by port for red concentrate connector

14. Stand-by port for blue concentrate connector

15. BiCart holder (option)


Fluid unit - exterior rear parts

2

1 17

16

15

14

12

13

3

4

5

6

7

8

9

10

10

11


Part list

1. Transportation handle

2. Air filter

3. Halt button

4. Battery connect indicator (green)

5. Battery charge indicator (yellow)

6. Outlet tube (Drain)

7. Inlet water tube

8. Disinfectant inlet tube

9. Dialysis fluid filter (option)

10. Wheels

11. Attachment for future implementation

12. External communication port

13. Attachment for service table

14. Mains connection

15. Fuses (12 AT)

16. Blood leak detector

17. Main switch


Fluid unit - interior parts 1

1

2

3

4

56

7

8

9

10

11 12 13 14


Part list

1. Feeding pump B

2. Feeding pump A

3. Flow pump

4. Pressure transducer, degassing pressure

5. Pressostate, INPS

6. Degassing chamber

7. Expansion chamber

8. Pressure regulator, PR2

9. Heater

10. Flow switch

11. Fan

12. Concentrate filter

13. Mixing chamber A

14. Mixing chamber B



1

2

3456

7

8

9

10

11

12

13

14

15

16


Part list

1. Temperature transducer, Cond. cell B

2. Conductivity cell B

3. Conductivity cell C (Diascan), optional

4. Conductivity cell P

5. Pressure transducer, HPG (high pressure guard)

6. Temperature transducer, Heater (outlet)

7. Temperature transducer, Cond. cell P

8. Conductivity cell A

9. Temperature transducer, Cond. cell A

10. FM I/O board

11. UF-measuring cell

12. Pressure transducer, PD

13. Blood leak detector

14. Pressostate, SAGS

15. Suction pump

16. Deairating chamber



1

2

3

4

3

1

5

6


Part list

1. Heat exchangers

2. FIVA (option)

3. Pressure regulator, PR 1

4. Back-up battery (option)

5. Battery-holder for 9V battery

6. Dialysis fluid filter holder (option)


Fluid unit - valves

AIVAREVA

FLVA

ZEVA

INVA

RIVA

DRVA

DIVA

BYVA

TAVA EVVA

FIVA

CHVA

CBVA


Valve description

AIVA Air inlet valveBYVA Bypass valveCBVA Chemical bypass valveCHVA Chemical valveDIVA Direct valveDRVA Degass restrictor valveEVVA Evacuation valveFIVA Filter valve - (option for UFD)FLVA Flush (BCH) valveINVA Inlet valveREVA Recirculation valveRIVA Rinse valveTAVA Taration (UF) valveZEVA Zero (UF) valve


Hydraulic description

SubsystemsThe AK 96 fluid unit can be divided into following main subsystems:

• The water intake and heating system

• Chemical disinfectants intake

• Mixing and conductivity regulation system

• Degassing/flow pump system

• Fluid output - UF control system

The hydraulic description of the AK 96 is based on the hydraulic flowdiagram on the next page.


Hydraulic flow diagram

P

P

M

T

T

T

T

12

T

P

P

BiCart

Dia

lysi

s flu

idfil

ter (

U80

00S

)*

FIVA

*

A co

ncen

trate

B c

once

ntra

teD

ialy

sis

fluid

Pur

e w

ater

Dia

lysa

te*=

optio

nal

CP

Flui

d co

nnec

tor

dete

ctio

nD

ialy

zer

Dea

iratin

gch

ambe

r

EV

VA

BY

VA

DIV

A

TAVA

PD

Blo

od le

akde

tect

or

Dra

inin

gre

stric

tor

Con

d.ce

ll C

*

ZEVA

HP

G

UF-

mea

surin

gce

ll

Con

d.C

ell P

Deg

assi

ngpr

essu

re

Flow

pum

p

Exp

ansi

onch

ambe

rD

RVA

*pH

Cel

l(u

pgra

de k

it)

Flow

rest

ricto

r

Hea

ter

AIV

AIN

VA

Flow

sw

itch

PR

1P

R 2

INP

S

Hea

t ex

chan

gers

RE

VA

Con

d.ce

ll A

Con

d.ce

ll B

B p

ump

A pu

mp

FLVA

Mix

ing

cham

ber

Mix

ing

cham

ber

CH

VA

CB

VA

AB

Suc

tion

pum

p

SA

GS

Deg

assi

ngch

ambe

r

RIV

A

BiC

art

hold

er*

Figure 3:9 AK 96 - Hydraulic flow path


FM Flow path description

The water intake and heating systemBefore entering the machine, the water passes a pressure regulator(PR1) which lowers the water supply’s pressure of 5–6 Bar to 0.8 Bar(600 mmHg).

A heat exchanger using the outgoing water raises the incoming watertemperature several degrees, to ensure that machines at clinics with verycold water can still reach the correct heat disinfection temperature.

T

Fluid connectordetection

Heater

AIVA

INVA

Flow switch

PR 1 PR 2INPS

Heat exchangers REVA

SAGS

Pure waterinlet

Drain

Figure 3:10 AK 96 - water intake and heating system

In the machine the water passes a second pressure regulator which lowersthe pressure to about +130 mmHg – and INVA – Inlet Valve. Theinlet pressure is monitored with a pressostate – INPS – which alarms ifpressure drops below 99 ±20 mmHg and the alarm is disabled when thepressure reach above 150 ±20 mmHg again.

AIVA – Air Inlet Valve – facilitates draining of the fluid system (it opensduring Drain). REVA – Recirculation Valve – is used during disinfectionand rinsing (water is circulating).

Water is heated as it passes through the heating element in the heater. Theflow switch in the inlet is used for overheat protection (No flow = heateroff). The PT-100 transducer “Regulator Temperature” at the heater’soutlet is one of the two temperature transducers used for regulation –the other is placed in cond cell B.


The heating element is controlled through a solid state relay, which isdriven by a TTL-level duty cycle signal (which can be monitored as avalue from 0 to 100%).


The Temperature Control and Protective System

Example:

37.5˚ CFlowswitch

TX RX

Heating

element

PT-100

Waterinlet

SetTemperature

Set point:

Feedback 2:

Temperature, cond B

Feedback 1:

–

+ Power drive(duty cyclecontrol)

–

SRI(13)

SRI(11)

+

Cond B

PT-100

SRI(15)

+

– Estimatedtemperature drop(0 - 2.0 ˚C)

Temperature atheating elementoutput

37.8 ˚C

37.5 ˚C

0.3 ˚C

Temperature is set to 37.5˚Dialyzer temperature: 37.2˚

Figure 3:11 Temperature control loop

The temperature of the dialysis fluid is controlled by two temperaturetransducers, one immediately after the heating element and the one inconductivity cell B.

The temperature drop from conductivity cell B to the dialyzer can beestimated by measuring the (stabilized) temperature in the fluid tubeswith a reference instrument and comparing it to the temperature inconductivity cell B. The drop can then be entered in “Calibration”,“Others”, “ESTIM. TEMP. DROP.” The temperature at the dialyzer willthen achieve the SET temperature.

The regulation is handled by two feedback loops. The feedback fromthe heating element outlet – where temperature changes are largeand fast – goes to a fast reacting loop. The temperature transducersin the conductivity cell A and in the conductivity cell P are usedfor compensation of the conductivity measurements only – not fortemperature regulation.

Overheat protection is achieved by monitoring the out flow from theelement with a flow switch: If the flow stops, power to the heater elementis cut off.


The heater element is driven by an opto relay, in series with the “KACO”relay which is controlled by the Protective System.

CPU C CPU P

CPU W

Control system Protective system

Watchdog

I2CMains

KACOrelay

Cond cell Ptemperature

Flow switch status

Heated water

Flow switch

Cold water

I2CI2C

Mainssupplysensor

Parallel comm.

OPTOrelay

&

Controltemperature

Cond cell Btemperature

Dutycycle

Figure 3:12 Temperature control and protective system


Chemical disinfectants intakeAn intake for chemical disinfectants is placed on the rear of the machine.The machine is for safety reasons equipped with two valves, CHVA andCBVA.

These valves are controlled separately. CHVA is controlled by theprotective system and CBVA is controlled by the control system.

C P

CHVA

CBVA

B

Figure 3:13 AK 96 - disinfectants intake

The machine is equipped with two yellow female connectors, C (chem)and P(park). The yellow male connector shall only be placed in the femaleC-connector if chemical disinfectants is to be taken in via the disinfectantinlet tube on the rear of the machine.

The yellow male connector shall be connected to the yellow disinfectantpick-up tube when chemical disinfectants is to be taken in from thefront of AK 96.

NoteRefer to AK 96 Operator’s manual for detailed information aboutdisinfection of the machine.

Note


Mixing and conductivity regulationThe heated water now passes through the concentrate pick-up tubeconnectors. If a concentrate connector is pulled out, the connector willseal and there will be a suction from the respective feeding pump to thetube’s stick.

In the concentrate connector port there is Hall effect element that givesinformation to the monitor if a connector is in or out of the concentrateconnector port.

The concentrate/water mixture passes via the feeding pump A through amixing chamber. The mixing chamber separates air (if any) and bypassesconductivity cell A, since air in the conductivity cell will disturb themeasurement and leads to unstable conductivity regulation.

TT

BiC

artC P

Cond.cell A

Cond.cell BB pump

A pump

FLVA

Mixing chamberMixing chamber

CHVA

CBVA

A

B

BiCartholder*

Figure 3:14 AK 96 - Concentrate intake/mixing and conductivity regulation

The temperature transducer in Conductivity cell A has nothing to do withtemperature regulation; it is used for compensation of the conductivitymeasurement which by nature has a positive temperature coefficient of1.7%/°C.

The B regulation circuit works in the same way with the B-supply comingfrom either the bottom of the BiCart or from the “B” pick-up tube.

As mentioned above, the temperature transducer in the “B”-cell isused both as the second measurement in the temperature regulationand for temperature compensation of the conductivity measurement inconductivity cell B.

A very important feature of the conductivity regulation is the supervisionof concentrate pump speed. A parameter called relative pump speed isused. This expresses, in %, how much a pump’s actual speed deviatesfrom the theoretical speed.

The theoretical speed is calculated from the Na+ /HCO3 - settings,from the preset list of the concentrate’s chemical components and theflow in channel 1. If the actual speed moves outside predefined limits,an attention alarm is issued, and the fluid monitor goes in Bypass. Thedefault values for these limits are:

-10% 0 +10%

-40% -20% 0 +20% +40%

-10% 0 +10%

B-pump,Acetate mode

B-pump,Bicarbonate mode

A-pump,Bicarbonate mode

-30%

-30% +30%

+30%


The limits can be changed in Preset mode.

In order to optimize the dialysis treatment the concentrations of sodiumand bicarbonate in the dialysis fluid can automatically be changedfollowing a predetermined continuous decreasing or increasing lineargraph. Profiling of sodium is controlled by the A-pump and profiling ofthe Bicarbonate is controlled by the B-pump.

The valve FLVA (Flush Valve) is used during the priming of the BiCartcartridge. Priming means filling up the cartridge with warm water andwaiting for liquid bicarbonate to come out in the bottom. This is howit works:

When the priming is triggered – either by the fact that the cartridge isplaced in the holder before the machine is started, or that the holder isopened during operation – both concentrate pumps stop. The machineruns, waiting for the measured conductivity (B) to drop below 2.0 mS/cm.

TT

BiC

artC P

Cond.cell A

Cond.cell BB pump

A pump

FLVA

Mixing chamberMixing chamber

CHVA

CBVA

A

B

BiCartholder*

The priming starts by opening the FLVA, connecting the flow pumpssuction side to the bottom of the BiCart, and running the B-concentratepump at full speed. The machine now waits for the B-conductivity toachieve more than 5.0 mS/cm. This will normally happen within 60seconds, if it doesn’t an attention alarm appears. Otherwise, the FLVA isclosed, the B-concentrate pump is stopped and the machine waits for theB-conductivity to drop below 2.0 mS/cm. The priming is completed.

After conductivity cell B the fluid passes a pH-cell. pH-monitoring isan optional safety feature with a low and a high limit, changeable fromthe front panel.

Safety feature in the sense that some disinfection agents can give the sameconductivity but the pH value is totally of limit (differs a lot from pH 7).


Conductivity Control System, acetate

+ -

Feedback:Conductivity,cell B

Power driveto pump

Cond. cell B

Conc.pump B

Acetate

ToAK 96,cond P

Conductivitycalculation

Conc.preset

Set point

FromAK 96,heatingsystem

Relative pump speed deviation

SRI(24)

SRI(27)

SRI(28)

Set Na+

Flow, ch1Calculation of areference pumpspeed

The conductivity set point is calculated on basis off the sodium set valueand the information in the concentrate preset.

The speed of the concentrate pump is constantly monitored and relatedto calculated speed (calculated from the conc. preset, the sodium setpoint,and the flow in ch1) to ensure that it stays within limits which are ±10 %(default). If these limits are exceeded an attention is issued:

INCORRECT CONCENTRATECheck concentrate

The relative pump speed – the deviation between the actual and calculatedspeed, in percent, can be logged, of course, and should ideally be zero.On a machine, running with WRO-supply and high quality concentrates,it will normally be very close to zero.


Messi

Note

lien tuc

Conductivity Control System, bicarbonate

Set Na,HCO3 Cond.

cell B

ToAK 96,cond P

+

-

Power driveto pump

Feedback:Cond. A

FromAK 96

Conc.pump A

Acid conc.

Bicarb.conc.

Conc.preset

Conductivitycalculation

+

-

Power driveto pump

Feedback:Cond. B2 Conc.pump B

Set point

Set point

Cond.cell A

Relative pump speed

Relative pump speed

SRI(20)SRI(26)

SRI(22)

SRI(19)

SRI(23)

SRI(24)Flow,ch1 -

+

The bicarbonate mode uses two feedback loops: one for the A-pump –the acid component, and one for the B-pump – the bicarbonate. Again,the set points are calculated on the basis of the sodium and bicarbonateset values, and the concentrate preset. Both pump speeds are monitoredand related to the calculated speeds to ensure that pump speeds staywithin limits which are ±10 % for the A-pump, and ±20 % for theB-pump (default). If the limits for the respective pumps are exceeded,attentions are issued:

INCORRECT ACIDIC CONCENTRATECheck concentrate fluid

INCORRECT BICARBONATE CONC.Check concentrate fluid


Messi

Note

bom A

Messi

Note

bom B

Composition supervisionThe pump speed of each feeding pump is supervised by the controlsystem, which uses the conductivity values measured from conductivitycell A and B. The conductivity cell P measures the total conductivity of thefluid. The dialyzer is bypassed if the conductivity exceeds the alarm limits.

Despite these supervision functions there is a risk that the dialysisfluid has the correct conductivity but erroneous composition of theconcentrates A and B during treatment in bicarbonate mode.

The composition of the dialysis fluid is therefore supervised duringtreatment in bicarbonate mode, in order to detect if conductivity cell Adoes not measure correctly. An erroneous dosage of concentrate A mayotherwise result in bad fluid composition without causing a conductivityalarm.

The composition supervision can also detect if wrong concentrates areused at the same time as the conductivity is still between the alarmlimits. This can for example happen if the powder in the BiCart doesnot dissolve properly.

The composition supervision is monitoring the pump speed ratio. Thismeans that the actual pump speed is monitored. If the difference inthe pump speed between the two pumps is more than the preset value(default 15%) an attention will be issued and the fluid will be bypassed.

INCORRECT DIALYSIS FLUIDCOMPOSITION

The value that triggers the attention can be logged as SRI(056). Thevalue may vary between 850 and 1150 (default). The limits can be preset(2-22-3) as a % pump speed deviation. The default value is set to 15 %.

The variable is calculated as:

Pump speed pump A x Dose A

Pump speed pump B x Dose B= 1

Where the value 1 is the ideal value. Dose is the dilution of theconcentrate depending on the concentrate preset.

As one of the pumps deviate the value will change and if it varies morethan 15% the attention is issued.


Messi

Note

toc do bom A / toc do bom B

Degassing/flow pump systemA natural process, when mixing A- and B-concentrate is the generationof free gas, carbon dioxide. This must be removed since it will disturbboth conductivity- and flow measurements. The purpose of the bypasstube from the top of the second mixing chamber diverts the gas awayfrom the cell but doesn’t remove it.

This takes place in a degassing circuit, consisting of a restrictor, a pump,and a degassing chamber. By pulling the fluid through the restrictor anegative pressure of approx. -600 mmHg is created (default -610). Thegas expands to larger bubbles and enters the chamber:

P

M

T

PCond.Cell P

Degassingpressure

Flowpump

Expansionchamber

DRVA*pH Cell(upgrade kit)

Flow restrictor

Suctionpump

Degassingchamber

RIVA

Figure 3:20 AK 96 - Degassing system

As the gas and air builds up in the chamber, the fluid level will dropuntil the point where the floater drops. The gas then escapes the top ofchamber since there is suction here from the Suction pump. As a result,the floater jumps up again and seals the outlet, until more gas forces itthe fluid level down.

RIVA

In

Out

Air outlet

O-r ing

The seal in the top consists of a very small o-ring. It is placed in a plasticfixture which is screwed onto the top of the chamber. If it is missing,misaligned or damaged not only gas but also fluid will escape throughthe top. This will lead to reduced flow through channel 1 in the flowtransducer – the UF-cell.

The result of this will be pump speed alarms (“INCORRECTCONCENTRATE”-attentions). The reason is that the conductivitycontrol is based upon the assumption that the flow through theconductivity cells is the same as the flow in channel 1. A leakage in the top


Messi

Typewriter

of the degassing chamber will therefore lead to decreased pump speedsand the corresponding attention alarms. Or if it is big C CFF 006 003.

Preset of the degassing pressureThe Flow Pump generates the negative degassing pressure by pulling thefluid through the degassing restrictor.

The default preset value is -610 mmHg, but can be presetto other values (-500 to -620 mmHg in 5 mmHg steps) incase the AK 96 is operated at other altitudes than sea level.If the flow is set to above 500 ml/min in Acetate, the degassing pressureshould be preset to -650 mmHg. Here is the relation between pressureand altitude:

Pdegass = - - 150 , mmHg, or in table form:760

eh/7338

h, meters Pdeg, mmHg-------------------------------

3800 -3022200 -4131000 -513200 -5900 -610

The degassing restrictor has to be exchanged if the altitude is above 2800m

Degassing Pressure Control System

P

M

Feedback:Degassing pressure

Set point:

Degassing pressure,preset

Power driveto pump

+

–

Degassingpressure

Flowrestrictor

Flow Pump

DRVA

SRI(33)

SRI(34)

From condcontrol system

The Flow Pump generates the negative degassing pressure by pulling thefluid through the degassing restrictor.

The degassing pressure set point comes from the presets. The defaultvalue is -610 mmHg, but can be preset to other values (-302 to -610mmHg in 5 mmHg steps) in case the AK 96 is operated at other altitudesthan sea level. Here is the relation between pressure and altitude:

h[metres]

0 200 400 600 800 1000 1147 1400 1600 1800 2000 2200 2373

Pdegass

[mmHg]-610 -590 -570 -550 -532 -513 -500 -478 -461 -445 -429 -413 -400

3000 3800

-355 -302


Adjustable dialysis fluid flow (option)The fluid flow in the AK 96 can be adjusted between 300 ml/min to700 ml/min in 20 ml/min steps.

The regulation is done with an adjustable valve (DRVA) driven bya stepper motor with an aspheric axis connected in parallel with a200 ml/min restrictor.

To make sure that the flow is stable, the machine will postpone anadjustment of the flow 120 seconds before and 30 seconds after taration

If a flow deviation of 30 ml/min or more (compared to the set flow) isdetected continuously for 3 minutes, an automatic adjustment of the flowwill be triggered. The automatic adjustment can be activated once aftereach self calibration of the UF cell also called taration. The time neededto activate the automatic adjustment is only counted when the dialysisfluid is considered to be stable.

Conductivity guardThe third conductivity cell, cond cell P, right after degassing, is usedby the protective system as a guard. Like the two cells used by thecontrol system, it has its own temperature transducer for temperaturecompensation of the conductivity measurement.

The dialysis fluid is bypassed if the conductivity value differs more than±5% from the calculated set value and/or the temperature exceeds 40°C±0.5°C.

P

M

T

PCond.Cell P

Degassingpressure

Flowpump

Expansionchamber

DRVA*pH Cell(upgrade kit)

Flow restrictor

Suctionpump

Degassingchamber

RIVA


Fluid output - UF control systemAfter the cond cell P, the pressure is monitored by a pressure transducer,the HPG – High Pressure Guard. It protects the dialyzer if the fluid tubesare blocked after the dialyzer. If the tubes are blocked before the dialyzer,it protects the machine (from silicon connectors popping off).

T

12

P

BYVA

DIVA

TAVA

ZEVA HPG

UF-measuringcell

Cond.Cell P

The flow is then measured by channel 1 in the UF-cell (to be used for theUF regulation) and passes through the DIVA, Direct Valve, provided thetemperature and conductivity are both inside limits.

In an alarm situation, i.e. if cond and/or temp are outside limits, theDIVA will be closed, and the fluid will bypass the dialyzer through theBYVA – Bypass Valve.

The dialysis fluid is forwarded to the dialyzer via the blue dialysis fluidtube.

From the dialyzer the dialysate (dialysis fluid mixed with waste productsand excess fluid) is returned to the machine via the red dialysis fluid tube.

TMP calculationThe fluid returns to the machine through a particle filter which physicallyis placed inside the fluid tube connector. The pressure is measured by thePD transducer (Pressure Dialysis), physically mounted on the Deairatingchamber house. The PD value is used, together with the Venous Pressureto calculate the Trans Membrane Pressure – the TMP:

TMP = P venous - P dialysis

Example:P venous = +120 mmHg, P dialysis = -300 mmHgTMP = +120 -(-300) = +420 mmHg

The TMP is used as supervision of the UF regulation: It is monitoredwith alarm limits and displayed.


Messi

Typewriter

Safety GuardWhen the machine is not in treatment mode the dialyzer tubes areplaced in the safety coupling, where the pressure is monitored by theSAGS – Safety Guard Switch. It ensures that none of the hygieneprograms can be started when the tubes are removed from the coupling.The function SAGS is doubled by mechanical switches which sense thepresence of the connectors.

DeairatingIn case of worn O-rings inside the dialyzer connectors (the Hansenconnectors), an incorrectly placed tube or insufficient priming of thedialyzer, the returning fluid will – due to the negative pressure – containair-bubbles which must be removed before it reaches channel 2. Thisprocess takes place in the deairating chamber:

P

T

T

12

P

Dialyzer

Deairatingchamber

EVVA

BYVA

DIVA

TAVA

PD

Blood leakdetector

Drainingrestrictor

Cond.cell C*

ZEVA HPG

UF-measuringcell

Cond.Cell P

Suctionpump

The fluid level in the chamber is monitored by a ring-shaped floater,containing a magnet which activates a reed relay if the level drops belowapprox. 15 mm. The EVVA , the Evacuation Valve will then briefly openand let out air – the level goes up. A second reed relay is used to detecthigh level (too high level) in the chamber.

The valve, following immediately after the chamber – the TAVA, TarationValve – is used for the so-called taration or UF-cell self-calibration. It willbe described later in this document.


UF regulationThe UF rate is controlled by the Suction pump. The AK 96 has one“machine” treatment mode only: “Volume control”. In this mode theoperator is required to set two parameters:• Treatment Time

• UF volume

From these two parameters the machine calculates the correspondingset UF rate:

Set UF rate = Set UF volume /Set Treament Time

The set UF rate is displayed in the UF-display:

If UF-profiling is used, the set UF-volume is changed over time accordingto the chosen profiling curve. Three different profiling curves for theUF can be chosen: Linear, Step and Interval. More information aboutUF-profiling is available in AK 96 Operator’s manual.

During treatment the actual UF rate is constantly measured by subtractingthe channel 1 flow from the channel 2 flow.

The measured UF rate is compared to the set UF rate and the speed ofthe Suction pump is controlled by the difference between them.

Once per minute the machine will check the remaining treatment timeand the remaining UF volume and internally adjust the set UF rate. Thelimit (high limit) for the set UF rate is +20% of the rate set by “Time”and “UF Volume”.


The UF Control System

Suction Pump

Drain

Set point Power driveto pump

+12

Fromdialyzer

Time

UF volume

Set

–

UF rate lh

CH2-CH1Calculation

UF Gain(Function)

UF rate setcalculation

RemainingUF-volume

Remainingtime

SRI(55)

SRR(2)

SRR(1)

SRI(48) - Filtered UF rate

SRR(00) (Raw)

SRI(48) - (Filtered )

Two parameters are needed to set the UF rate:• Treatment time

• UF volume to be removed

The machine will once per minute calculate:

• Remaining UF volume = (UF volume set - UF Accumulated volume)

• UF rate set = (Remaining UF volume / Remaining Time)

The function “UF Gain” compensates for the tarations, i.e. 2 per hour.This is necessary, since UF volume is lost during a taration. Since it ispossible for the machine to discard a taration, and hence do anotherfive minutes later, “UF Gain” will constantly check the taration timer tosee when the next is done.


UF-cell tarationChannel 2 in the UF-cell carries the dialysate, i.e. dialysis fluid containingthe ultrafiltrate removed from the patient’s blood. This is a biologicalsubstance and it will during the treatment form a deposit on the channelwalls. This deposit is called a biofilm. The film will reduce the area of thechannel 2, thereby affecting the sensitivity of channel 2. In other words:Channel 2 will loose some of its accuracy, as the treatment progresses.

To compensate for this, channel 2 is calibrated every 30 minuteswith channel 1 used as reference. The process is called taration orself-calibration. It works as follows:

The self-calibration is divided in following three phases:1. Prepare Taration phase

2. Zero Flow phase

3. Differential Flow phase

Before the taration starts, a calibration of the UF-cell’s pre-amplifiercircuits takes place, but this is not noticeable for the user.

Prepare Taration

The Zeroing Valve (ZEVA) opens to let the fluid bypass the UF-cell.RIVA, the Rinsing Valve (normally used in disinfection), opens so thatthe degassing chamber fills up completely. The reason for this is to keepthe floater from dropping during the following phases – that woulddisturb the taration.

P

P

T

T

12

P

Dialyzer

Deairatingchamber

EVVA

BYVA

DIVA

TAVA

PD

Blood leakdetector

Drainingrestrictor

Cond.cell C*

ZEVA HPG

UF-measuringcell

Cond.Cell P

Flowpump

Suctionpump

Degassingchamber

RIVA

Figure 3:31 Phase 1: Prepare Taration


Zero Flow

RIVA closes again, ZEVA is kept open, i.e. there is no flow through anyof the channels. The machine now generates an offset value – a numbervery close to zero – for each channel. The two values are stored in RAM.

P

P

T

T

12

P

Dialyzer

Deairatingchamber

EVVA

BYVA

DIVA

TAVA

PD

Blood leakdetector

Drainingrestrictor

Cond.cell C*

ZEVA HPG

UF-measuringcell

Cond.Cell P

Flowpump

Suctionpump

Degassingchamber

RIVA

Figure 3:32 Phase 2: Zero flow

Differential Flow

ZEVA now closes. The Taration Valve (TAVA) is closed and BYVAopens. The channels are now placed in series, which means that the flowin channel 2 is the same as the flow in channel 1.

The calibration coefficient – a number very close to 1.00 – for channel 2is now changed until the difference between the channels is zero. Channel2 now has the same sensitivity as channel 1. The calibration coefficient isstored in RAM.

The taration takes place every 30 minutes. The first time five minutesafter green fluid path has been obtained or if blood is detected withinthese five minutes the counter will be cleared and the first taration willtake place five minutes after blood has been detected.

P

P

T

T

12

P

Dialyzer

Deairatingchamber

EVVA

BYVA

DIVA

TAVA

PD

Blood leakdetector

Drainingrestrictor

Cond.cell C*

ZEVA HPG

UF-measuringcell

Cond.Cell P

Flowpump

Suctionpump

Degassingchamber

RIVA

Figure 3:33 Phase 3: Differential flow


Approved/not approved

The calibration values (two offsets, one coefficient) generated duringthe first taration are compared to the corresponding values in the UFcell’s E2PROM. If they don’t differ too much, the taration is approved,the Taration Timer is set to 0 seconds, counting up to 1800 seconds (30minutes) for the next taration.

From the second taration and onwards the machine will use the lasttaration’s values as comparison. If the calibration values differ too muchthe taration is not approved. But since the taration is a sensitive processthat can be disturbed by e.g. an air bubble during the offset phase,a new taration will be performed again after 5 minutes. In case of anot-approved taration the Taration Timer will be set to 1500 seconds,starting a taration when it reaches 1800 seconds.

Prolonged taration

Before the taration starts the machine looks at the variation of the flowsignal:

If the flow is unstable, each phase (offset and differential) will take 15seconds longer: The Taration Timer counts up to 1545.

If the re-taration fails

If a re-taration is requested and this re-taration fails an error code willbe issued.


Diascan - Conductivity cell C (option)The Diascan can be used for:

• Clearance measurement (K) in order to read the current dialysisefficiency for the on going treatment.

• Dialysis dose measurement (Kt or Kt/V) in order to check that theprescribed dialysis dose is being maintained, which provides qualityassurance for the treatments.

• Kt/V target supervision , which means that the machine constantlycalculates if the desired and minimum values for Kt/V, set by theoperator for each individual patient, can be reached at treatment end.If not, the operator will immediately be notified during treatment.If Kt/V measurement is required, a distribution volume (VOLUME)has to be set before the measurement check takes place. Thedistribution volume is patient-related (based on the patients dryweight) and has to be properly calculated and set by the operator inorder to obtain a correct Kt/V value.

Hardware

The hardware is an extra conductivity cell. The conductivity cell is usedto measure the conductivity after the dialyzer. The Diascan cell hasa temperature sensor, PT-100, for temperature compensation of theconductivity value. The temperature can not be logged like the othertemperature transducers, since the conductivity value is compensated fortemperature already in the cell. The cell cannot be calibrated in the field.

The Diascan is offset, to match the B cell, as the UF cell is performingtaration. The reason for the offset is the fact that the cell is after thedialyzer. This means that it is affected by the biofilm and hence the offset.

TT

Condcell "B"

T

Diascan(Option)

Cond B Cond Diascan


Function

The Diascan measure the effectiveness of the treatment or the K. K forclearance or how many ml/min of blood that has been cleared fromurea. However the machine cannot measure urea. But the machine canmeasure sodium ions. Sodium ions has about the same size as urea.

The idea is to calculate the clearance of sodium or how the transportof sodium is done over the membrane. The calculation also takes inconsideration things that decrease the transport capacity like the actualblood flow, fluid flow, clotting, fistula recirculation and many other factorsby increasing/decreasing the sodium level in a step of 0.5 mS/cm (preset)for about 5-7 minutes and then measure the conductivity before andafter the dialyzer, the ability of the dialyzer to transport sodium can becalculated. Depending on sodium level in the blood and in the dialysisfluid, the step will either be negative or positive.

Cond B

Cond Diascan

Conductivity supervision expanded

Hydraulic delay

Actual measurement Pre step measurement

Pre measurement stability

5 minutes 3 minutes about 5 minutes

Parameters locked

How often the measurement is done is a preset (start value). Before themeasurement is done the flow condition has to be stable for 5 minutesand then the actual measurement is done for 8-10 minutes.

If stable flow conditions are not met the measurement is delayed until theconditions have been stable for 5 minutes. Then there is a measurementof the pre step condition (3 minutes) then step is added and the actualmeasurement is done. The time can be a bit flexible depending on thehydraulic delay and the preset of the step length. If a measurement ofpre step condition is disturbed by an alarm or change of blood flow, themeasurement is rescheduled to be performed again when the conditionsare stable.

The limits for conductivity are widened during the measurement and until1 minute after. Stable flow conditions:

No changes in: Blood flow, UF-rate or Fluid composition No:UF-tarations (bypass) or Bypass Alarms (bypass or blood pump stop)

Some parameters are locked during the measurement (Pre step and step)• sodium and bicarbonate (conductivity)

• temperature

• dialysis fluid flow

• UF volume

• profiling settings


The following can interrupt a measurement:• Blood flow stop or change

• UF stop

If a measurement is interrupted, the measurement will be rescheduleduntil stable flow conditions are met.

If the limit for sodium load has been reached an attention is issued.

Error codes

There are no error codes that will interrupt the treatment. If there is atechnical error with the Diascan during treatment the attention belowwill be issued.

And a silent error code will be stored in the buffer.


Blood leak detectionBlood leakage is detected by a detector situated between channel 2 (or theoptional conductivity cell C, if it is installed) and the Suction pump.

Blood leakdetector

Drainingrestrictor

The restrictor in the bottom facilitates the complete draining and fillingof the detector house, by restricting the outflow, thus forcing the house toempty slowly and fill up completely.


FM component descriptionPressure regulator, PR 1 & PR 2Two different pressure regulators, with different springs inside,are used to decrease the pressure in two steps.PR1: 0.8 Bar/600mmHgPR2: 130 mmHg

Heat exchangerThe heat exchanger is used to raise the temperature on the inlet water.Machines made for 230V are equipped with two heat exchangers whilemachines made for 115V are equipped with four heat exchangers.

Pressure switch: SAGS & INPSThe pressure switch is used to monitor if there is an inletpressure (INPS) and if the dia connectors are connected tothe machine before a disinfection program is started (SAGS).The pressure switch is switching on and off as bellow:SAGS: on = -74mmHg off = -59mmHgINPS: on = 150mmHg off = 99mmHg

Flow SwitchThe flow switch is used to check if there is flow through the heater.Containing a glass tube, a floater and an infrared sensor.

Heater unitThere are three different heater units:• one for 115V/1300W

• one for 230V/3*580W.

The Heater unit for 230V contains three windings of each 580W. Theheater unit is controlled with a duty cycle.

The heater unit is connected to the relay board, via a cable. Thetemperature transducer is connected to a transducer board, via a cable.The transducer board interfaces directly to the FM I/O board, via aboard connector.

The temperature maximum deviation from set value is 35°C to 39°C(default) the limit is wider during priming, low limit is 33°C. If thetemperature exceeds these limits a temperature alarm is issued.

Feeding pumpsThe water flushes through the ceramic house of each pump tocreate a water film which acts as a lubricant. The pumps are ceramichigh-precision units, they never wear out, and never need calibration.

This is how the pump works: The pump piston has a small cut-awayon the last 5–6 mm. By combining rotation with an up–and–downmovement, the pump volume is “sucked–lifted–moved–and–pressed”from the pump inlet to the outlet. (What is inlet and outlet is simply aquestion of which way the piston rotates).

The piston is rotated by a stepper motor – the up–and–down movementcomes from mounting the pump at an angle to the motor. The small pin


on the piston is connected to the rotating plastic arm through a spheric(ball-shaped) bearing for full freedom of movement.

Mixing chambersThe Mixing chambers is used to mix the fluid and bypass air,if any, to avoid disturbance in the conductivity measurement.It consist of a housing and a nipple in the top. The housing is sealed withtwo O-rings: one in the top and one in the bottom.

Conductivity cellsThe conductivity measuring unit is used to measure the conductivity ofdialysis fluid composition. It consists of a mechanical part, a transducerboard, two shielding carbons and a PT-100. The mechanical part consistsof plastic isolators and carbon electrodes.

The transducer board contains driver and receiver circuitry. The shieldingcarbons are used to protect the measurement from noise in the fluidpath. The conductivity of the fluid is dependent on the temperature andthe PT-100 is used to measure this.

There are four different conductivity cells in the machine:• Conductivity cell A

• Conductivity cell B

• Conductivity cell P

• Conductivity cell C (Diascan -optional)

Conductivity cell P, located right after degassing, is used by the protectivesystem as a conductivity guard.

BiCart-holderThe BiCart holder is a device to hold the BiCart column or the CleanCartcolumn. Bicarbonate concentrate is produced by mixing water withbicarbonate powder inside the disposable BiCart column.

Citric acid is produced in the similar way using the disposable CleanCartcolumn. Fluid spillage is prevented by valves. Magnet sensors indicateclosed arm position.

pH-sensor (optional)Glass electrode which measure the pH.

Flow pumpsGear pumps controlled with a duty cycle.

Degassing chamberThe chamber has four connectors, inlet, outlet, air outlet and rinse valve(RIVA). A floater is placed inside the chamber. The top of the floatconsist of a needle which seals against a very small o-ring inside the airoutlet connector. The gas escapes the top of chamber since there issuction here from the Suction pump. As a result, the floater jumps upagain and seals the outlet, until more gas forces the fluid level down.


UF measuring unitThe UF cell – is based on the electro-magnetic flow measurementprinciple (Faraday’s Law of Induction):

The voltage V, is proportional to the velocity of the fluid, the area of themeasuring channel and the magnetic field. From this follows that if thefield is kept constant the voltage will be proportional to the flow only.

For this to happen the field, the tube, and the electrodes must be aligned90° to one another, like this:

and the fluid must contain a few free ions. In practice, independence ofconductivity is achieved when conductivity is higher than 100–200mS/cm.

Another practical consideration is that the magnetic field must alternate.Otherwise the presences of free ions would lead to electrochemicaldeposits on the measuring electrodes.

UFD (optional)When the UFD kit is installed an ultrafilter U 8000 S is inserted in the fluidpath in the front of the dialyser and acts as a bacteria and endotoxin filter.

Deairating chamberPlastic chamber containing a magnetic floater which slides on a pin withtwo reed relays inside. The floater can have tree positions: high, lowand middle (not high and not low).

Blood leak detectorTransducer = Infrared LEDReceiver = Photo transistor

Pressure transducersThe pressure transducers are so called Gauge transducers which meansthat the pressure transducer use’s the atmospheric pressure as reference.The transducers are connected to the main electronic via I2C busses.


Extracorporeal blood circuit description

Product description - Blood unit

Venous pressure

transducer Air

detector

SyringepumpBlood

lineguide

Bloodline

guide

Expansionchamberholder

Dialyzerholder

Venousblood line

clamp

Primingdetector

Arterialblood line

clamp

Bloodpump

Arterialpressure

transducer

Figure 3:37 Blood unit components


Treatment modes and disposablesDouble needle treatment

Arterial blood line

Venous blood line

Figure 3:38 Arterial and venous blood lines setup in HD - double needle mode


Single needle treatment

Figure 3:39 Arterial and venous blood lines setup in HD - single needle mode


Blood flow diagram

Dialysis fluid filterU 8000 S

Arterial lineclamp

Venous lineclamp Priming detector

AK 96: HD, DN/SP (double needle - single pump)

Dialyzer

P

Arterial blood pump

Arterialpressure

Venous pressureLevel detector

Patient

P

UF-measuringcell

Water

Water

Drain

Concentrate

Simplified Fluid unit

Simplified Fluid unit

Blood unit

Blood unit

Venous drip chamber

P PD

Dialysis fluid filterU 8000 S

(Arterial phase)

Priming detector

Dialyzer

P

Arterial blood pump

Arterialpressure

Venous pressure

Arterial lineclamp

Venous lineclamp

Level detectorVenous expansionchamber

P

UF-measuringcell

Drain

Concentrate

Patient

AK 96: HD, SN/SP (single needle - single pump)

Venous drip chamber

P PD

HD - HemodialysisSN - Single needleDN- Double needleSP - Single pump

Open valve / clampClosed valve / clamp

Pure waterDialysis fluidDialysateBloodNo flow

Figure 3:40 AK 96 - Extracorporeal blood flow diagram


Blood flow descriptionArterial blood from the patient’s vascular access, passes the arterial lineclamp (option). During treatment the line clamp is open. The arterialpressure transducer is used to give an alarm if the pressure becomes toolow. For example, if the needle or the arterial blood line is blocked, analarm will be given (the blood pump is stopped). The alarm is activatedif there is an increased negative pressure between the patient and theblood pump, e.g:

• A drop in blood pressure.

• Altered positions of the arterial needle.

• A kink in the arterial line between the patient and the blood pump.

The function of the blood pump is to maintain the extra corporeal bloodflow. Blood is removed from the patient, forwarded to the dialyzer andthen returned to the patient. The blood pump can not be run whenthe pump cover is open. If necessary, the blood can be returned to thepatient manually.

The blood passes the dialyzer under controlled ultrafiltration. Refer toAK 96 Operator’s manual for more information about the treatmentconditions and operating instructions.

The purpose of the syringe pump is to add anticoagulantia (e.g. Heparin)to the blood. An alarm is issued when the syringe is empty or if the linefrom the syringe to the arterial blood line is kinked. The syringe pumpparameters can be adjusted by pressing the blood path menu button,choose syringe and press the select button.

The venous pressure transducer measures the venous blood pressure afterthe dialyzer. The lamp in the venous pressure button is lit and the buzzersounds if the alarms are activated and the venous blood pressure is outsidethe alarm limits. If the event of an alarm, the blood flow is stopped.

The AK 96 has double venous pressure transducers: one for thecontrol system, one for protective system. An out of limit value on any ofthe transducers will put the monitor in a patient safe state.

Venous pressure is used for the back filtration warning (i.e. negativeTMP) and also in the event of a leakage on the venous side of the bloodline it will stop the monitor from draining the patient on the floor.

If the venous pressure is too high, the cause may be:

• An obstruction after the venous drip chamber.

• A change in the patient’s position.

If the venous pressure is too low, the cause may be:

• A line separation.

• A drop in blood pressure.

• A change in the patient’s position.


The level detector has the following function:

If the blood level in the venous drip chamber is too low, an alarm is givenand the blood flow is stopped (the blood pump and syringe pump arestopped and the venous line clamp is closed). The venous drip chamberacts as an expansion chamber to even out pressure pulsations.

When the air detection alarm is generated, the lamp in the Air detectbutton is lit and the buzzer sounds. The lamp begins flashing when theair detector does not detect air any longer. The operator must reset theair detection alarm by pressing the Air detect button. After pressing theAir detect button for 3 seconds, the air detector alarm is bypassed for xseconds (presettable 0-120 sec.). Default it is disabled (0 seconds) and nooverride is possible.

The priming detector detects if there is blood in the venous blood line.If no blood is detected, it is not possible to start the treatment.

The priming detector is a two channel device, with both parts of theprotective system agreeing about the signal.

The purpose of the priming detector is to facilitate priming by suppressingcertain alarms when no blood is in the venous line. CPU P outputs apulse train to the transmitting side (a LED) of the priming detectorhead. The signal consists of nine pulses and a pause, nine pulses and apause, etc. Again this is a self-check procedure: CPU P and CPU Ware supposed to catch the pause.

When blood is detected for more than 20 seconds, CPU P and CPU Wdisconnect the priming detector function and keep the AK 96 in BloodMode until the end of the treament, i.e. when Time = 0:00 is confirmed.Confirmation is done by pressing the “TIME”-button for 3 secondswhen the display shows “0:00”.

When the monitor is out off blood mode it is possible to enter anothermode than treatment mode.

The blood is transported back to the patient via the venous line clamp.The clamp is normally open. But in the event of an alarm from the airdetector or the venous pressure transducer, the line clamp clamps theblood line and stops the blood flow (not during high pressure alarm).

BPM - blood pressure moduleThe BPM monitor is a passive measuring device that can issue attentionsand alarms but the alarms will not interfere with the AK 96 treatment.

The intended use for the BPM is to measure the patient’s blood pressureand to activate an alarm if the patient’s blood pressure goes under analarm limit set by the operator. This will give the nurses the possibilityto take measures before the patient suffers the ill effects of hypotension(low blood pressure).

The BPM module includes the following components; air pump, bleedvalve, dump valve, pressure transducers (control and protective) andmicroprocessor board. The module includes control and protectivesystems.


The control system measures the pressure and pulse wave to calculate thesystolic, diastolic, mean blood pressure and pulse rate. The air pump,dump and bleed valves are controlled by this system as well as externalcommunication.

The protective system supervises the maximum pressure and inflatingtime. Maximum pressure is 320 ± 10 mmHg and maximum inflating timeis 180 seconds. When these values exceed specified limits, dump andbleed valves are opened and air pump is stopped by the protective system.

A self-calibration/auto zero function is included in the module, whichmeans that the offset for the pressure transducers is calibrated/adjustedeach time the module is turned on.

The BPM measures and calculates the non-invasive blood pressure byusing the oscillometric method. This method uses the pulsation thatoccurs in the artery in the arm when it is restricted by the inflated cuff.The noise or oscillation originates from the fact that when the cuffrestricts the vessel, the flow in the vessel becomes turbulent, instead oflaminar. The pulsation causes the pressure in the cuff to oscillate whichthe pressure transducer in the BPM module measures.

The relationship between the changes of cuff pressure and its oscillationis used to determine the blood pressure. When the BPM deflates the cuffand the blood starts to pass the restriction, the oscillation incline rapidlyand the systolic (high) pressure is measured. When the oscillation haspeaked and is declining rapidly the diastolic (low) pressure is measured.The mean pressure is measured when the oscillation is peaking. Theheart rate is determined by using the pressure oscillations measuredby the pressure transducer. When to measure the diastolic pressure isdetermined by extensive experiments to establish an algorithm, whichis included in the BPM software.

In the field it is possible to perform a check of the device to determineif it works or not. The device has to be sent to Gambro for repair incase of malfunction.

Single needle treatmentWhen the AK 96 is used for single needle treatment, the arterial andvenous phases are pressure - controlled. Arterial blood is removed fromthe patient when the arterial line clamp is open and the venous line clampis closed.

The running time of the blood pump is determined by the venouspressure high limit. In this way a positive pressure is created. In thenext phase, the blood pump is stopped, the arterial line clamp is closedand the venous line clamp is opened, i.e. the blood is returned to thepatient by means of the positive pressure. The venous line clamp is thenclosed, the arterial line clamp is opened, the blood pump is started andthe procedure is repeated.

The expansion chamber evens out pressure pulsation.


BM component description

Blood line clamps The blood unit includes two line clamps:Arterial line clamp and venous line clamp.The arterial line clamp is located to theright and the venous line clamp is locatedto the left when viewed from the front.The clamp covers also have differentcolour markings: The arterial clamp coveris marked with a red dot and the venousclamp cover is marked with a blue dot.The line clamp unit consists of thefollowing:• Housing with covers (mounted on the

front plate).

• 2 solenoids (as one unit).

• Line clamp driver board.

• 2 clamp detectors.

The line clamp driver board interfaces tothe protective CPU board, via a boardconnector and a flat cable.

Blood pump unit The blood pump unit consists of thefollowing:• Tube pump (self-threading).

• 24 V bruchless DC motor with anencoder for velocity monitoring.

• Gear box (1:50).

• Cover detector.

The blood pump unit, except the tubepump, is mounted on the back of thefront plate. The motor, cover detector andposition board interface to the BM I/Oboard, via connectors and cables.


Syringe pump The syringe pump unit consists of thefollowing components:• Syringe pump. The diameter of the

syringe can range between 10 to 30mm

• Stepping motor.

• Gear box (1:120).

• Syringe pump position board.

• Syringe pump feedback potentiometer.

The stepping motor, syringe pump positionboard and syringe pump potentiometerinterface to the BM I/O board, via cables.

Venous pressuretransducer (C+P)

The blood unit is equipped with twopressure transducers connected to oneport, which are used to measure the venousblood pressure. The pressure transducersare mounted on a pressure transducerboard, which interfaces directly to the BMI/O board, via a board connector. Thepressure transducers are connected to thevenous pressure transducer nipple (locatedon the front), via a small tube.

Arterial pres-sure transducer

AK 96 is equipped with a second pressuretransducer, named Arterial PressureTransducer. This pressure will bedisplayed on the arterial bargraph. Thetransducer is used for true arterial pressuremeasurement or any other pressure.The pressure transducer is mountedon a pressure transducer board, whichinterfaces directly to the BM I/O board,via a board connector.


Air detector The air detector’s receiving side is split intotwo identical channels, leading to CPUP and CPU W respectively. The idea isthat both systems must “agree” about thesignal (that it’s OK).The transmitter is continuously sendingout 9 pulses with high amplitude and onewith low amplitude, the low amplitudepulse simulates an air bubble. Theinformation about when the low amplitudepulse is issued is sent to CPU W. If thelow amplitude pulse is not registered byCPU P and W an alarm is issued sincethe air detector is not working properly.This means that the air detector is a selfchecking device.

Priming detector The priming detector is a two channeldevice, with both parts of the protectivesystem agreeing about the signal.The purpose of the priming detector is tofacilitate priming by suppressing certainalarms when no blood is in the venousline. CPU P outputs a pulse train to thetransmitting side (a LED) of the primingdetector head. The signal consists of ninepulses and a pause, nine pulses and a pause,etc. Again this is a self-check procedure:CPU P and CPU W are supposed to catchthe pause.When blood is detected for more than 20seconds, CPU P and CPU W disconnectthe priming detector function and keepthe AK 96 in Blood Mode until the endof the treament, i.e. when Time = 0:00is confirmed. Confirmation is done bypressing the “TIME”-button for 3 secondswhen the display shows “0:00”.When the monitor is out off blood modeit is possible to enter another mode thantreatment mode.

BPM The BPM monitor is a passive measuringdevice that can issue attentions and alarmsbut the alarms will not interfere with theAK 96 treatment.The BPM module includes the followingcomponents; air pump, bleed valve, dumpvalve, pressure transducers (control andprotective) and microprocessor board. Themodule includes control and protectivesystems.


Power supplyFigure: to be inserted here!

The AC/DC is developed to work between 85V – 265V mains voltagewith a frequency of 50Hz-60Hz.

The power supply generates +24 V, +/-12 V and +5 V:• +5 V – digital electronics

• ±12 V – analog electronics (among other components the A/Dconverters)

• +24 V – LEDs and displays, blood pump, heparin pump, clamps,pump motors (flowpump, suction pump) valves, fan and heater relay.

+24 V is supplied by the AC/DC-unit and fed to an internalDC/DC-converter; the converter produces +/-12 V and +5 V.The two safety processors are fed by separate +5 V supplies.The +/-12 V supply is supervised by CPU W’s on-chip A/D-system.


Operator’s panel

Figure 3:41 AK 96 - Operator’s panel


Button description

NoteFor more information about the functionality of the buttons on theOperator’s panel, refer to AK 96 Operator’s manual.

Note

On/Off-button

Priming-button

Rinse back-button

Rinse/disinfection-button

Mute-button

Attention-button

Alarm-button

Air Detector-button

Venous Pressure-button

Fluid Bypass-button


Time-button

Arterial Pressure-button

UF Start/Stop-button

Blood path-button

BPM-button

Fluid path-button

Up-key

Blood pump-button

Down-key

Left cursor-key

Right cursor-key

Select-key


Back-key


This page is intentionally left blank


hc_k29000_hcen12208_09_2007_10

Documents

intentionally

blood leak

blood leak

module includes

venous line

hydraulic

arterial line

venous drip