dialysis machine

• dialysis machines filter the blood. has to be done regularly to keep the concentration of dissolved substances in to blood at normal levels and to remove waste substances
• in a dialysis machine, the persons blood flows between partially permeable membranes, surrounded by dialysis fluid. it is permeable to things like ions and waste substances but not big molecules like proteins.
• the dialysis fluid has the same concentration of dissolved ions and glucose as healthy foods. this means that useful dissolved ions and glucose wont be lose from the blood during dialysis. only waste substances diffuse across the barrier
• people have to have a dialysis session three times a week, 3-4 hours it takes. also may cause blood clots or infections. expensive. however, buys time for patient if donor kidney isn't available