Volume Collection Vs. Flow Sensing Equipment

Front 1

Examples of volume collection equipment

Back 1

1)Water Seal
2)Dry Rolling Seal
3)Bellows

Front 2

Volume collection characteristics

Back 2

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

Front 3

Types of Water Seal Devices

Back 3

1)COllins, in which a metal bell is attached to a pulley and chain counterweight
2)Steadwell,which has a light plastic bell

Front 4

Water Seal Advantages

Back 4

1)Accuracy
2)Little calibration is necessary
3)Quality assurance
4)Can be used with all types of rebreathing tests

Front 5

Water Seal disadvantages

Back 5

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

Front 6

Dry Rolling Seal

Back 6

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

Front 7

Dry Rolling Seal advantages

Back 7

1)No water
2)Decreased risk for contamination

Front 8

Dry Rolling Seal Disadvantages

Back 8

1)Sticking of the rolling seal
2)Leaks in the seals
3)Increased mechanical resistance

Front 9

Bellows spirometer

Back 9

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

Front 10

Bellows Spirometere Advantages

Back 10

1)No water
2)Decreased risk of contamination

Front 11

Bellows spirometer disadvantages

Back 11

1)Bellow sticking
2)Leaks in the bellows

Front 12

Flow Sensing Devices

Back 12

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.

Front 13

Flow Sensing Pneumotachometers

Back 13

1)Pressure differential
2)Respirometer
3)Heated Wire
4)Ultrasonic

Front 14

Pressure differential Flow sensors

Back 14

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

Front 15

Types of resistive elements

Back 15

1)Fleisch--bundle of capillary tubes
2)Silverman/Lily-screen
3)Porous paper

Front 16

Pressure differential advantages

Back 16

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

Front 17

Pressure differential advantages

Back 17

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

Front 18

Wright Respirometer

Back 18

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.

Front 19

Range of Wright Respirometer

Back 19

.1 liters-100 liters

Front 20

Advantages of the wright Respirometer

Back 20

1)Small and easily portable

Front 21

Heated Wire Flow Sensor

Back 21

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

Front 22

Ultrasonic flow sensor

Back 22

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.

Front 23

Advantages of the ultrasonic flow sensor

Back 23

No mmoving parts

Front 24

Equation for volume

Back 24

Flow X Time

Front 25

Equation for Pressure

Back 25

FlowX Resistance=Pressure

Front 26

Contamination of the resistive element would create______

Back 26

1)HIgher pressure, and therefore flows would be abnormally high

Front 27

In the Wright respirometer___

Back 27

Both one way valves go in the same direction