Transcript Document 7163345

Regulators and Flowmeters
RET 2274
Respiratory Care Theory 1
Module 3.0
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
Regulators and Flowmeters

High-Pressure Reducing Valves

Two types


Single Stage
Multiple Stage
Available as preset or adjustable
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
Regulators and Flowmeters

High-Pressure Reducing Valves

Preset Reducing Valve
(B) Pressure gauge
(A) High-pressure inlet
(H) High-Pressure gas inlet
(C) High-pressure chamber
(I) Gas outlet
(G) Valve stem
(E) Flexible diaphragm
(D) Ambient-pressure chamber
(F) Spring
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
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
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
Regulators and Flowmeters

Low-Pressure Gas Flowmeters

Three categories of flowmeters

Flow restrictor

Bourdon gage

Thorpe tube
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)
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
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
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
Regulators and Flowmeters

Bourdon Gage

Not back-pressure
compensated

As resistance to
flow increases, the
indicated flow
reading becomes
inaccurate
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, constantpressure flow-metering device
Measures true flow

Refer to Egan’s Fundamentals of
Respiratory Care, Eighth Edition for
a complete working description
Regulators and Flowmeters

Thorpe Tube

Two types

Pressure uncompensated vs. Pressure compensated
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
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
Regulators and Flowmeters

Ranges of Flowmeters

High-range
0 – 75 L/min (5-L/min intervals)

CPAP and high-flow
oxygen delivery devices
Regulators and Flowmeters

Ranges of Flowmeters

Low-range
0 – 3 L/min (1/4-L/min intervals)

Pediatric and COPD
patients
Regulators and Flowmeters

Ranges of Flowmeters

Standard
0 – 15 L/min (1-L/min interval)

Most oxygen delivery
devices
Regulators and Flowmeters

Correctly Reading a Flowmeter

Ball-float flowmeter

Read from the middle of the ball
6 L/min
2 L/min
Regulators and Flowmeters

Correctly Reading a Flowmeter

Bobbin flowmeter

Read from the top of the bobbin
2 L/min
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)
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.
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 highresistance equipment such as jet nebulizers
Regulators and Flowmeters

Attaching a Regulator to a Gas Cylinder
1.
Select the proper gas cylinder

Ensure content of cylinder by checking the label
Regulators and Flowmeters

Attaching a Regulator to a Gas Cylinder
2.
Remove protective covering from cylinder
outlet
Regulators and Flowmeters

Attaching a Regulator to a Gas Cylinder
3.
“Crack” the cylinder to remove dust, debris
and moisture
Regulators and Flowmeters

Attaching a Regulator to a Gas Cylinder
4.
Select the appropriate gas regulator

Ensure that a plastic washer is in place
Regulators and Flowmeters

Attaching a Regulator to a Gas Cylinder
5.
Attach the gas regulator to the cylinder valve

It should fit into place easily - DO NOT FORCE IT!!!
Regulators and Flowmeters

Attaching a Regulator to a Gas Cylinder
6.
Tighten the fittings in place
Regulators and Flowmeters

Attaching a Regulator to a Gas Cylinder
7.
Open the cylinder valve SLOWLY and
pressurize the regulator, note the amount of
gas pressure in tank – listen for leaks
Cylinder Wrenches
Regulators and Flowmeters

Attaching a Regulator to a Gas Cylinder
8.
Set the flowmeter to the prescribed flow rate
and attach the oxygen delivery device
Regulators and Flowmeters

Attaching a Regulator to a Gas Cylinder
9.
Place the oxygen delivery device on the
patient and monitor vital signs
Regulators and Flowmeters

Attaching a Regulator to a Gas Cylinder
9.
Place the oxygen delivery device on the
patient and monitor vital signs