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27 Cards in this Set

  • Front
  • Back
Examples of volume collection equipment
1)Water Seal
2)Dry Rolling Seal
Volume collection characteristics
1)Indicates change in volume by change in its dimension
2)The chamber must be sealed from the atmosphere
3)Data transfer involves pen to kymograph paper, or potentiometer output to microprocessor or computer
Types of Water Seal Devices
1)COllins, in which a metal bell is attached to a pulley and chain counterweight
2)Steadwell,which has a light plastic bell
Water Seal Advantages
2)Little calibration is necessary
3)Quality assurance
4)Can be used with all types of rebreathing tests
Water Seal disadvantages
1)Difficult to transport
2)difficult to clean
3)Water seal itself
4)Malposition of the bell
5)leaks in the system
6)May require I and E circuitry and CO2 absorber
Dry Rolling Seal
1)Can be mounted horizontally or vertically
2)Uses a piston supported by a rod connected to a frictionless bearing
3)Seal is maintained by a flexible plastic sheath that folds on itself as the piston moves in the cylinder
Dry Rolling Seal advantages
1)No water
2)Decreased risk for contamination
Dry Rolling Seal Disadvantages
1)Sticking of the rolling seal
2)Leaks in the seals
3)Increased mechanical resistance
Bellows spirometer
1)Collapsible bellows fold and unfold in response to volume change
2)May be mounted horizontally or vertically
3)Wedge design contracts and epxands like a fan
Bellows Spirometere Advantages
1)No water
2)Decreased risk of contamination
Bellows spirometer disadvantages
1)Bellow sticking
2)Leaks in the bellows
Flow Sensing Devices
Pneumotachometers-a device that measures flow using different physical principles. The flow is then integrated electrically into a volume or physically converted into a volume.
Flow Sensing Pneumotachometers
1)Pressure differential
3)Heated Wire
Pressure differential Flow sensors
1)Generally refferred to as pneumotachs
2)Tube that contains a resistive element
3)Flow through the resitive element causes a pressure drop proportional to laminar flow
4)Pressure difference is measured by a pressure transducer
Types of resistive elements
1)Fleisch--bundle of capillary tubes
3)Porous paper
Pressure differential advantages
1)small size
2)relatively easy to clean
3)Less problem with leaks
4)Direct connection to analog/signal
5)Can measure small tidal volumes
Pressure differential advantages
1)Frequent calibration required
2)Values affected by gas composition
3)no volume displacement values for quality control
4)Damage or contamination of the resistive element can alter pressure differential
5)Nonlinear at extremes of flows
Wright Respirometer
1)Flow is converted into gas mechanically by directing a flow of gaas against a vane or turbine capable of movement. The rotating vanes turn a series of gears connected to an indicator on the dial.
Range of Wright Respirometer
.1 liters-100 liters
Advantages of the wright Respirometer
1)Small and easily portable
Heated Wire Flow Sensor
1)Based on the cooling effect of gas flow
2)heated element is located in a laminar flow tube
3)Gas flow decreases temperature
4)Current to the termistor is increased to maintain temperature
5)The change in current is proportional to the flow
Ultrasonic flow sensor
1)Turbulent vortices form when a gas flows over struts in the air stream
2)Each vortex is a pulse proportional to a specific volume that is counted as it passes through an ultrasonic beam.
Advantages of the ultrasonic flow sensor
No mmoving parts
Equation for volume
Flow X Time
Equation for Pressure
FlowX Resistance=Pressure
Contamination of the resistive element would create______
1)HIgher pressure, and therefore flows would be abnormally high
In the Wright respirometer___
Both one way valves go in the same direction