EQUIPMENT BELLRINGER

Question 1

Wrights Respirometer

Answer 1

MOA: gas passes through turbine and results displayed as volume; measures slow flows

Advantages
1) compact and portable
2) measures SVC, MV, and Vt at bedside

Disadvantages
1) large flows can distort vanes
2) unable to measure fast flow rates/FVC
3) only measures flow in one direction

Question 2

Turbine Pneumotach

Answer 2

MOA: a vane is mounted in a flow tube; an LED light is on one side with a photodetector on the other side of the vane; the rate of rotations = rate of disruptions to light and is proportional to flow rate

advantages
1) accuracy not affected by turbulent flows, water vapour or gas composition
2) small and lightweight flow sensor
3) simple technology

disadvantages
1) may not measure very low flows
2) accuracy must be verified that ATS standards are being met through calibration
3) with changing airflow accuracy is affected and the signal may not be linear

Question 3

Pitot Tube

Answer 3

MOA: sensitive pressure transducers detects changes in gas velocity based on pressure against the tube; struts set at 45 degree angles create resistance

advantages
1) measures bidirectional flow
2) meets ATS criteria
3) disposable elements available

disadvantages
1) affected by different gas composition
2) must use special solution to rise/clean tubes

Question 4

Pressure Differential

Answer 4

MOA: flows are measured by the degree of pressure drop across a known resistance; uses a variable orifice as resistance

advantages
1) lightweight and durable
2) meets ATS criteria
3) heated element prevents increases in resistance

disadvantages
1) less accurate at very high or very low flows
2) sensitive to contamination
3) requires zeroing during calibration

Question 5

Silverman Pressure Differential

Answer 5

MOA: flows are measured by the degree of pressure drop across a known resistance; uses stainless steel screen as resistance element

Advantages
1) inexpensive and disposable
2) measures bidirectional flows
3) doesn’t require heating element

Disadvantages:
1) condensation on element changes resistance
2) requires zeroing during calibration
3) sensitive to contamination

Question 6

Heated Wire

Answer 6

MOA: as gas flow passes by a temperature sensitive resistance sensitive element the wire is cooled and the proportion of cooling is converted to a flow fate

advantages
1) disposable elements available
2) meets ATS criteria
3) highly accurate

disadvantages
1) frequent calibration required for accuracy
2) fragile wire
3) condensation causes sensitivity of elements

Question 7

Peak Flowmeter

Question 8

Volumetric Capnography

Answer 8

MOA: flows are measured by the degree of pressure drop across a known resistance; uses a variable orifice as resistance; volumes of co2 measured with mainstream window

advantages:
1) measures volume and flow of CO2
2) can be used to do shunt calculations
3) meets ATS criteria

disadvantages:
1) less accurate at very high or very low flows
2) sensitive to contamination
3) requires zeroing during calibration

Question 9

Dry Rolling Seal

Answer 9

MOA: patient inhales/exhales into piston, amount of movement is measured with potentiometer responding to DC; measures volumes and expiratory flow rates

advantages:
1) fairly easy to transport and operate
2) can meet ATS
3) don’t need to counterbalance horizontal

disadvantages
1) piston needs to be maintained/monitored for smooth operation
2) leaks and rebreathing
3) rolling seal prone to sticking

Question 10

Ultrasonic Vortex

Answer 10

MOA: struts placed in a tube to create cortices which are measured by a set of ultrasonic crystal transmitter and receiver

advantage
1) sits in ventilator circuit
2) meets ATS criteria
3) measures volume and flow

disadvantages
1) expensive
2)