regulators and flowmeters ret 2274 respiratory care theory 1 module 3.0

Regulators and Flowmeters

RET 2274

Respiratory Care Theory 1

Module 3.0


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


High-Pressure Reducing Valves Two types

Single Stage Multiple Stage

Available as preset or adjustable


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


High-Pressure Reducing Valves Preset Reducing Valve

(H) High-Pressure gas inlet

(G) Valve stem

(B) Pressure gauge

(E) Flexible diaphragm

(D) Ambient-pressure chamber(F) Spring

(C) High-pressure chamber

(A) High-pressure inlet

(I) Gas outlet


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



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


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


Low-Pressure Gas Flowmeters Three categories of flowmeters

Flow restrictor

Bourdon gage

Thorpe tube


Low-Pressure Gas Flowmeters Flow restrictor

Consists of a fixed orifice calibrated to deliver a specific flow at a constant pressure (50 psig)


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


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


Bourdon Gage Hollow tube

straightens as gas pressure increases – increasing flow through the fixed orifice

Will work in any position – ideal for transport


Bourdon Gage Not back-pressure

compensated

As resistance to flow increases, the indicated flow reading becomes inaccurate


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



Thorpe Tube Two types

Pressure uncompensated vs. Pressure compensated


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


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


Ranges of Flowmeters High-range

0 – 75 L/min (5-L/min intervals) CPAP and high-flow

oxygen delivery devices


Ranges of Flowmeters Low-range

0 – 3 L/min (1/4-L/min intervals) Pediatric and COPD

patients


Ranges of Flowmeters Standard

0 – 15 L/min (1-L/min interval) Most oxygen delivery

devices


Correctly Reading a Flowmeter Ball-float flowmeter

Read from the middle of the ball

6 L/min

2 L/min


Correctly Reading a Flowmeter Bobbin flowmeter

Read from the top of the bobbin

2 L/min

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)


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 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.



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 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



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:


Attaching a Regulator to a Gas Cylinder1. Select the proper gas cylinder

Ensure content of cylinder by checking the label


Attaching a Regulator to a Gas Cylinder2. Remove protective covering from cylinder

outlet


Attaching a Regulator to a Gas Cylinder3. “Crack” the cylinder to remove dust, debris

and moisture


Attaching a Regulator to a Gas Cylinder4. Select the appropriate gas regulator

Ensure that a plastic washer is in place


Attaching a Regulator to a Gas Cylinder5. Attach the gas regulator to the cylinder valve

It should fit into place easily - DO NOT FORCE IT!!!


Attaching a Regulator to a Gas Cylinder6. Tighten the fittings in place


Attaching a Regulator to a Gas Cylinder7. Open the cylinder valve SLOWLY and

pressurize the regulator, note the amount of gas pressure in tank – listen for leaks

Cylinder Wrenches


Attaching a Regulator to a Gas Cylinder8. Set the flowmeter to the prescribed flow rate

and attach the oxygen delivery device


Attaching a Regulator to a Gas Cylinder9. Place the oxygen delivery device on the

patient and monitor vital signs

regulators and flowmeters ret 2274 respiratory care theory 1 module 3.0

Documents

outlet pressure

adjustable pressure

constant pressure

high pressure

adjustablereduces pressure

psigsecond stage pressure

stepsfirst stage pressure

rate of gas flow