DIALYSERS

DEFINITION: Is a part in the artificial kidney system the treatment actually takes place Blood is freed from waste products Need: Removal of waste product from plasma Regulation of the composition of blood plasma To retain the normal pH of the blood

Process: 3 process: Diffusion Osmosis ultrafiltration The rate of clearance of waste products (64 ml/minute) from the blood depend upon the rate of blood flow(200 ml/minute).

TYPES: Parallel flow dialyzers Coil hemodialyzer Hollow fibre Haemodialyzer

Parallel flow dialyzers: No need for blood pump Uses arterial blood pressure 3 polypropylene boards with dialyzing membranes laid between them Held firmly and fastened by bolds at the sides Rubber gasket: avoids leakage Longitudinal grooves are also made (increased surface area)

Contd. Not disposable ( needs technical skills) Cleaned and re-built Avoids bacterial infections higher efficiency

Contd.

Coil hemodialyzer: Tubular membrane placed between flexible support wrapped around a rigid cylindrical core Membrane: cellophane (20-30) micron or cuprophane (18-75)micron Channels for blood (1,2,4) Width of channel (38-100)mm

Hollow fibre Haemodialyzer Most commonly used 10,000 hollow de-acetylated cellulose di-acetate capillaries Covered by plastic cylinder (18 cm in length, 7cm in diameter) Dialyzing area is 9000 cm2 / unit 130ml of blood

Contd.

contd: Advantages: Drawbacks: Expensive Disposable (sterilization is eliminated) Reduction in infection risk Reduced operator set-up time Drawbacks: Expensive

Performance analysis: Clearance: Overall performance Part of the total blood flow through the dialyser which is completely cleared of solute clearance= blood flow rate / A+Bx blood flow rate A and B are constants

Contd. Dialysance curve:

Contd. Residual blood flow:

Contd. Performance capacity: = A/ RS A = surface area Rs =mass transfer resistance Priming volume: Volume of blood within the dialyzer 75 ml to 200 ml

Contd. Pyrogenicity: Pyrogen reaction KIIL dialyser Leakage rate: Blood-to-dialysis fluid leak – 3%

Dialyzer:

Dialyzer:

Heart lung machine Artificial heart-lung function During open heart surgery To maintain circulation and gas exchange Extra corporeal circulation Pumping and oxygenation

Heart lung machine

Systole/ diastole: Pressure: 130/75 mm of Hg in aorta 130/5 mm of Hg in left ventricla 9/5 mm of Hg in left atrium 25/0 mm of Hg in right ventricle 3/0 mm of Hg in right atrium 25/12 mm of Hg in pulmonary artery

Heart lung machine – a model

Process: Filter : to avoid air bubble Ventriclular fibrillation : breakdown of red blood cells Blood is rewarmed

Process:

Blood pumps: Two types: Pulsatile pump 2 chambers : inner chamber and outer chamber Non-pulsatile pump Roller is present Time extended: may produce breakdown of RBC

Characteristics of an ideal blood pump: Calibration should be perfect Automatically and manually Rate : 6 l/minute Not damages the blood cells Unwanted mechanical stress should not be there Pump must be cleaned easily Smooth parts: avoids clot

Oxygenators: Function of lungs Artificial lungs 5 litres of blood per minute

Types: Bubble Membrane Liquid-liquid Film Rotating disc film Foam Blood film screen

Bubble oxygenator: Oxygen is bubbled through the blood and the blood flows through the slanting path Beads, sponges, meshes with anti foaming agent(silicon) Bubbles are broken since silicon reduces the surface tension

Membrane oxygenator: O2 travels in the opposite direction Effective oxygenation Micro porous polyethylene

Liquid-liquid oxygenator: Blood and liquid with dissolved oxygen are travelling in the opposite direction Gaseous exchange takes place

Film oxygenator: Rotating disc type: Horizontal disc type 120 rpm Film is formed and then oxygenated and removed