1. Regulators and Flowmeters
RET 2274
Respiratory Care Theory 1
Module 3.0

2. Regulators and Flowmeters
Regulating Gas Pressure and Flow
Cylinder gases exert too high of a pressure for use with respiratory equipment, and must be reduced to a working pressure of 50 psig (pounds per square inch gauge)
This standard pressure can be applied to power devices such as IPPB, pneumatic precursors, ventilators, etc.
Reducing valves are used to reduce high pressure to a working pressure

3. Regulators and Flowmeters
High-Pressure Reducing Valves
Two types
Single Stage
Multiple Stage
Available as preset or adjustable

4. Regulators and Flowmeters
High-Pressure Reducing Valves
Preset Reducing Valve
Automatic adjustment of the diaphragm-spring combination keeps the pressure in the high-pressure chamber at a near-constant 50 psig; thus the name preset
Refer to Egan’s Fundamentals of Respiratory Care, Eighth Edition for a complete working description

5. Regulators and Flowmeters
High-Pressure Reducing Valves
Preset Reducing Valve
(A) High-pressure inlet
(B) Pressure gauge
(H) High-Pressure gas inlet
(C) High-pressure chamber
(I) Gas outlet
(G) Valve stem
(E) Flexible diaphragm
(D) Ambient-pressure chamber
(F) Spring

6. Regulators and Flowmeters
High-Pressure Reducing Valves
Adjustable Reducing Valve
Some devices need variable pressures
The adjustable reducing valve allows a change in outlet pressure via a threaded hand control attached to the diaphragm
Refer to Egan’s Fundamentals of Respiratory Care, Eighth Edition for a complete working description

7. Regulators and Flowmeters
High-Pressure Reducing Valves
Multiple-Stage Reducing Valve
Can be preset or adjustable
Reduces pressure in two or more steps
First stage – pressure is lowered to an intermediate level (200 – 700 psig)
Second stage – pressure is decreased to working level (50 psig)
Provide more precise and smooth flow control

8. Regulators and Flowmeters
Low-Pressure Gas Flowmeters
Flowmeters are needed to set and control the rate of gas flow to a patient, either from a station outlet or a high-pressure cylinder
When using a a high-pressure cylinder as the gas source, a regulator (reducing valve plus flowmeter) is required

9. Regulators and Flowmeters
Low-Pressure Gas Flowmeters
Three categories of flowmeters
Flow restrictor
Bourdon gage
Thorpe tube

10. Regulators and Flowmeters
Low-Pressure Gas Flowmeters
Flow restrictor
Consists of a fixed orifice calibrated to deliver a specific flow at a constant pressure (50 psig)

11. Regulators and Flowmeters
Low-Pressure Gas Flowmeters
Fixed Orifice Flowmeter
Provide specific flow rate settings by selecting or adjusting an outlet orifice size
This unit incorporates a reducing valve and fixed orifice flowmeter

12. Regulators and Flowmeters
Low-Pressure Gas Flowmeters
Bourdon Gage
A flow-metering device that is always used in conjunction with an adjustable pressure reducing valve
It is a fixed orifice, variable-pressure, flow metering device

13. Regulators and Flowmeters
Bourdon Gage
Hollow tube straightens as gas pressure increases – increasing flow through the fixed orifice
Will work in any position – ideal for transport

14. Regulators and Flowmeters
Bourdon Gage
Not back-pressure compensated
As resistance to flow increases, the indicated flow reading becomes inaccurate

15. Regulators and Flowmeters
Low-Pressure Gas Flowmeters
Thorpe Tube
Always attached to a 50 psig gas source – either a station outlet or a pressure reducing valve
It is a variable orifice, constant-pressure flow-metering device
Measures true flow
Refer to Egan’s Fundamentals of Respiratory Care, Eighth Edition for a complete working description

16. Regulators and Flowmeters
Thorpe Tube
Two types
Pressure uncompensated vs. Pressure compensated

17. Regulators and Flowmeters
Thorpe Tube
Pressure uncompensated
Uncompensated for backpressure
Needle valve is proximal to the Thorpe tube
If pressure is applied distally to the tube, e.g., kinked tubing, flow indication may be lower than delivered flow

18. Regulators and Flowmeters
Thorpe Tube
Pressure compensated
Compensated for backpressure
Needle valve is distal to the Thorpe tube
If pressure is applied distally to the tube, e.g., flow-restricted equipment or kinked tubing, it will have NO effect on the flowmeter’s performance. The float will be an actual reading of flow delivered

19. Regulators and Flowmeters
Ranges of Flowmeters
High-range
0 – 75 L/min (5-L/min intervals)
CPAP and high-flow oxygen delivery devices

20. Regulators and Flowmeters
Ranges of Flowmeters
Low-range
0 – 3 L/min (1/4-L/min intervals)
Pediatric and COPD patients

21. Regulators and Flowmeters
Ranges of Flowmeters
Standard
0 – 15 L/min (1-L/min interval)
Most oxygen delivery devices

22. Regulators and Flowmeters
Correctly Reading a Flowmeter
Ball-float flowmeter
Read from the middle of the ball
6 L/min
2 L/min

23. Regulators and Flowmeters
Correctly Reading a Flowmeter
Bobbin flowmeter
Read from the top of the bobbin
2 L/min

24. Regulators and Flowmeters
Mini Clinic – Select the Proper Device
Problem:
An RT has an order to transport a patient to radiology with oxygen. What equipment should the therapist select?
Solution:
Because the RT has to transport a patient using oxygen, they should select an E cylinder with an adjustable regulator that includes a Bourdon gauge (unaffected by gravity)

25. Regulators and Flowmeters
Mini Clinic – Select the Proper Device
Problem:
An RT has to set up a pneumatically powered ventilator with oxygen in the ambulatory clinic, where there are not oxygen outlets. What equipment should the therapist select?
Solution:
Because pneumatically powered ventilators require 50 psig and no central oxygen outlets are available, the RT needs a preset reducing valve and a large H cylinder of oxygen.

26. Regulators and Flowmeters
Mini Clinic – Select the Proper Device
Problem:
An RT has to set up oxygen therapy with a jet nebulizer for a patient in the ICU. What equipment should the RT select?
Solution:
Because moderns ICUs have central wall outlets for oxygen, The RT needs only select a flowmeter. A compensated Thorpe tube is required for metering flow through high-resistance equipment such as jet nebulizers

27. Regulators and Flowmeters
Attaching a Regulator to a Gas Cylinder
Select the proper gas cylinder
Ensure content of cylinder by checking the label

28. Regulators and Flowmeters
Attaching a Regulator to a Gas Cylinder
Remove protective covering from cylinder outlet

29. Regulators and Flowmeters
Attaching a Regulator to a Gas Cylinder
“Crack” the cylinder to remove dust, debris and moisture

30. Regulators and Flowmeters
Attaching a Regulator to a Gas Cylinder
Select the appropriate gas regulator
Ensure that a plastic washer is in place

31. Regulators and Flowmeters
Attaching a Regulator to a Gas Cylinder
Attach the gas regulator to the cylinder valve
It should fit into place easily - DO NOT FORCE IT!!!

32. Regulators and Flowmeters
Attaching a Regulator to a Gas Cylinder
Tighten the fittings in place

33. Regulators and Flowmeters
Attaching a Regulator to a Gas Cylinder
Open the cylinder valve SLOWLY and pressurize the regulator, note the amount of gas pressure in tank – listen for leaks
Cylinder Wrenches

34. Regulators and Flowmeters
Attaching a Regulator to a Gas Cylinder
Set the flowmeter to the prescribed flow rate and attach the oxygen delivery device

35. Regulators and Flowmeters
Attaching a Regulator to a Gas Cylinder
Place the oxygen delivery device on the patient and monitor vital signs

36. Regulators and Flowmeters
Attaching a Regulator to a Gas Cylinder
Place the oxygen delivery device on the patient and monitor vital signs