Volume and Flow Measuring Devices

Volume Measuring Spirometers
Wedge Bellows
Collapsable bellows that folds and unfolds as patient
Will volume if cracks or holes in bellows

Dry Rolling Seal Spirometer
Volume Displacement
Consists of a within a supported by a rod resting on a frictionless bearings
Rod can be attached directly to a potentiometer or recording pen on paper
Can be used to assess pre/post bronchodilator changes

Water Seal Spirometer
Volume Displacement
AKA Collins or
Large bell - L, submerged in a column of
As pt breathes, bell moves an equally distance
Recorded with chain/pulley device connected to kymograph
For rebreathing studies: hoses and scrubber are needed
Calibration: Using 3L syringer, must be accurate - range +- %
Leak Test: Filling spirometer to 1/2 volume then applying a
Flow Cal: using 2-12 L/sec

Flow measuring Devices

Peak flow meter
Measure peak expiratory flow at
Pt inhales maximally then exhales hard and fast through deice
PEFR is read directly from
Factors that affect accuracy - Pt effort, , Debris

Turbine Device
Wright Respirometer
Rotating with gears, flow causes vanes to and displays volume
Accurate from 3-200 lpm
Assure by checking flows with 3L syringe
Can become alinear from vane , contamination or debris

Pneumotach - measures flow and converts to volume display

Ultrasonic Pneumotach
AKA Shedding or Transit Time
Consists of an emitting and recieving and a lflow tube with struts
Number of is proportional to

Pitot Tube
Flow measured by placing a series of small in a flow sensor and connecting to a pressure transducer
Condensation and secretions affect measurements

Thermal Element
Contains heated wire or small metal that as gas flows across. Amount of current needed to maintain tem is to flow
Accuracy is affected by gas

Pressure Differential
AKA Fleisch Pneumotach
Contains element that causes pressure to drop as gas flows across. Difference in pressure is to flow
Commonly used in Body Box
Heat is incorporated to reduce

CO2/Water Absorbers

CO2 Absorbers
Sodium , NaOH (SodaLime, Soda-Sorb) BaraLyme, Barium Hydroxide
Used for tests, Dilution or DLCO RB
Replace: When exhausted, when color , Weekly
Produced H20 as a byproduct. Place upstream from H20

Water Absorber
Drie-Rite (calcium sulfate, CaSO4)
Removes moisture from pt breathes through circuit
When CO2 reacts with soda lime it produces H20
Place co2 absorber and before analyzer

Permapure Tubing ()
Special tubing - conditions gas to equilibrate with humidity
Allows for accurate levels in gas samples

Valves
Directional Valves
Allows tech to switch pt into
exhaled gas through analyzers.spirometers

Calibration
3L syringe to check for
Volume should be checked at low, med and high to assure linerity
Rotameter is a good device for low flows
Sine-Wave : Biphasic, simulates flows and volumes
Automatic Syringe - Controlled motor syringe
Explosive device - simulates FVC
Alinearity can happen: Contamination, bent vanes, moisture, debris
Once volume displacement spirometer is caled it will retain linearity until it develops a