Circulatory System

Defibrillator

ECG Unit

Heart Pump

Hermatology Analyzer

Pulse Oximeter

Sphygmananometer

MRI

Purpose: Used in the determination of a complete blood count (CBC). The CBC counts blood cells (red blood cells, white blood cells and platelets), and also measures hemoglobin (the oxygen-carrying molecule in red blood cells), estimates the red cells' volume, and sorts the white blood cells into five subtypes. The CBC can be used to indicate the presence of blood abnormalities that may signal important medical disorders.

Usage: Blood is collected by a finger stick or a heel stick. The area from which blood is to be collected is cleaned with alcohol and then pricked with a small, sharp surgical instrument. After the skin surface is cleaned, a needle is inserted into a vein (usually in the arm) and blood is withdrawn. The sample is collected in special tubes that are treated to keep blood from clotting, and the sample is then processed by the hematology analyzer.

Portable: Usually not

Parts of Machine:

• Electrodes – to receive and detect electrical current (Coulter Principle)
• Aperture – to let cells pass through (Coulter Principle)
• Light Source – to provide a source of light (Optical Light Scatter)
• Flowcell – a channel that directs the blood sample to the stream of focused light (Optical Light Scatter)
• Dark stop – prevents light from reaching the detector directly when there are no calls In the flowcell (Optical Light Scatter)

Coulter Principle

The Coulter Principle of particle counting utilizes an electrical current that passes through an aperture between two electrodes. When a cell passes through the aperture, it blocks the electrical current and creates resistance. Resistance produces a signal or a pulse. The amount of resistance or the height of the pulse is proportional to the cell size. The smaller the particle or cell, the lower the signal or pulse height. The larger the particle or cell, the higher the signal or pulse height.

With this technology, classification of the cells was based on the size. White blood cells are the largest cell type followed by red blood cells and then platelets.

Technicon Optical Light Scatter System

In this technology, light is transmitted through a flowcell, which is a hydraulic flow channel that directs the blood sample stream into the path of focused light. If there is nothing in the flowcell, light is prevented from reaching the detector directly by a dark stop.

When a cell is introduced into the flowcell and it passes through the light, the light is scattered. The scattered light goes around the dark stop and reaches the detector. When the scattered lightis detected, a cellis counted. The amount of light scattered is directly proportional to the size of the cell. The smaller the particle or cell, less light is scattered. The larger the particle or cell, more light is scattered.

• Eliminates the tedious process of manually counting the numbers of blood cells
• Thus making the determination of CBC a quicker process

• Cells with slightly different sizes from that typical of their type may be counted as cells from another type
• Cell size is not an accurate means of identifying cells; cell volume is a better characteristic. As cell size is not directly correlated to cell size, discrepancies in identification may result.