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 (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

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, constant-pressure 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 high-resistance equipment such as jet nebulizers

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

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

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

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

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!!!

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

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

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

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

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