Bourdon Flowmeter Quiz

Bourdon Flowmeter

• Lightweight and not affected by gravity.
• Flowmeter readings can be inaccurate under downstream resistance, leading to higher registered flow than actual flow.

Thorpe Tube Flowmeter

• Uncompensated: Needle valve is proximal to the tube, causing back pressure to lower actual flow readings.
• Compensated: Needle valve is distal, eliminating back pressure effects; ball position indicates flow accurately when connected to a gas source.

Flowmeter Ranges

• Common flowmeter range: 0-15 LPM.
• Low-range (0-3 LPM) used for pediatric/neonatal patients and COPD.
• High-range (0-75 LPM) applicable for CPAP and Vapotherm®.

Medical Gas Supply Equipment

• Proportioners mix air and oxygen to specific concentrations, operate at 50 psi and include built-in alarms for gas pressure detection.
• Demand Pulse Flow O2 Delivery Devices only deliver oxygen during inspiration, reducing dead space oxygenation and lacking humidity requirement.

Kinetic Theory of Gases

• Gases consist of discrete, randomly moving molecules with elastic collisions.
• Molecular activity is influenced by temperature; no physical attraction exists between gas molecules.

Gas Pressure

• Defined as the force exerted per unit area, caused by molecular collisions.
• Temperature impacts the velocity of gas molecules via kinetic energy.

Pascal’s Law

• Pressure in a fluid container is transmitted equally in all directions and to its container walls.

Measurement of Gas Pressure

• Mercury Barometer: employs mercury column to measure atmospheric pressure.
• Aneroid Barometer: utilizes an evacuated metal container with a spring and pointer.
• Mechanical Manometer: similar to an aneroid barometer, uses diaphragm or evacuated containers.

Bourdon Gauge

• Composed of a hollow coiled metal tube with an elliptical cross-section.
• Typically found on medical gas cylinders for pressure measurement.

Gas Flow Principles

• Flow results from pressure differences between two points; rate of flow depends on pressure difference and opening size.

Bernoulli’s Principle

• As gas velocity through a tube increases, lateral pressure decreases while total energy remains constant.

Viscous Shearing and Ejectors

• Viscous shearing occurs when a high-velocity jet is injected into stationary gas.
• Ejectors utilize nozzles, viscous shearing, and vorticity to enhance flow.

Venturi’s Principle

• Builds upon Bernoulli’s principle; describes changes in pressure in a constricted flow tube.

Gas Laws

• Boyle’s Law: At constant temperature, volume inversely varies with pressure (P1V1=P2V2).
• Charles’ Law: At constant pressure, volume directly varies with absolute temperature (V1/T1=V2/T2).
• Gay-Lussac’s Law: At constant volume, pressure varies directly with temperature (P1/T1=P2/T2).
• Combined Gas Law: Integrates Boyle’s and Charles’ laws for varying conditions.

Cylinder Valve Safety Features

• American Standard Safety System (ASSS): Prevents incorrect equipment attachment via different threading on larger cylinders.
• Pin Index Safety System (PISS): Prevents incorrect assembly by using pin placements on smaller cylinders.

Reducing Valves

• Single-stage: Reduces pressure to 50 psi in one step with opposing spring and gas pressure.
• Modified single-stage: Includes an additional spring for higher flow rates.
• Multistage: Combines multiple stages for more precise pressure control.

Regulators

• Combine reducing valves with flowmeters; can be Bourdon-type or Thorpe tube models.
• Safety features include pressure relief valves and Indexed inlets/outlets based on ASSS or PISS systems.

Medical Gas Supply Equipment

• Gases consist of molecules in random motion; collisions among them are elastic with no attraction.
• Gas pressure is defined as force per unit area, resulting from molecular collisions with container walls.
• Temperature affects gas molecular velocity through kinetic energy.

Key Principles of Gas Behavior

• Pascal's Law states pressure in a fluid is distributed equally in all directions within a container.
• Mercury barometers measure atmospheric pressure using a column of mercury.
• Aneroid barometers use a spring-driven evacuated metal container to measure pressure.
• Bourdon gauges measure gas pressure using a hollow coiled metal tube.

Gas Flow and Principles

• Gas flow is driven by pressure differences between two points.
• Bernoulli’s Principle highlights that as gas velocity increases, lateral pressure decreases.
• Venturi’s Principle, based on Bernoulli, describes gas flow through tubes with varying radii.

Gas Laws

• Boyle’s Law: With constant temperature, volume varies inversely with pressure (P1V1 = P2V2).
• Charles’ Law: With constant pressure, volume varies directly with temperature (V1/T1 = V2/T2).
• Gay-Lussac’s Law: With constant volume, pressure varies directly with temperature (P1/T1 = P2/T2).
• Dalton’s Law: Total pressure of a gas mixture equals the sum of the partial pressures of individual gases.

Gas Diffusion

• Fick’s Law states the diffusion rate of gas is proportional to its concentration gradient.
• Henry’s Law describes how gas diffuses into liquid proportional to its partial pressure.
• Graham’s Law indicates the diffusion rate through liquid is influenced by gas solubility and molecular weight.

Water Content in Gas

• At 37°C, gas can hold 44 mg of water per liter; water vapor pressure at 1 atm is 47 mmHg.

Flow and FiO2

• Flow (Lpm) and Fraction of Inspired Oxygen (FiO2) represent different concepts: flow measures velocity, whereas FiO2 measures oxygen percentage in gas mixture.

Compressors

• Compressors deliver oil-free compressed air mixed with oxygen, with pressure reduced to 50 psi.
• Types include piston, diaphragm, and centrifugal compressors.

Oxygen Production and Concentrators

• Fractional distillation produces 99.5% pure oxygen by separating air based on boiling points.
• Concentrators utilize molecular sieves or semipermeable membranes for oxygen enrichment.

Liquid Reservoir Systems

• Bulk systems store liquid oxygen at -183°C, converting to gas for medical use.
• Portable reservoirs have duration and capacity based on liquid weight and oxygen content.

Piping Systems and Safety

• Piping systems for medical gases must have safety features like alarms and pressure sensors to maintain continuous supply and avoid danger.
• Cylinder valves exist in direct acting and diaphragm types, depending on design.

Cylinder Specifications

• Common cylinder sizes include H (244 ft³ O2), E (22 ft³ O2), with D being the most used in ambulances.
• Color coding helps identify contents (e.g., O2 = green, CO2 = gray).

Safety Regulations

• Regular hydrostatic testing ensures cylinder integrity, typically every 5 or 10 years.
• Adherence to safety rules avoids accidents, highlighted by the danger posed by improperly managed cylinders.

Duration of Gas Flow Calculation

• Duration of flow depends on cylinder size, pressure, and needed flow rate; safety factors should be applied by considering a reserve of 500 psi.

Oxygen Regulation Devices

• Bourdon flowmeters measure gas flow accurately under normal conditions, with compensated types unaffected by back pressure.
• Low-range flowmeters (0-3 L/min) are suitable for pediatrics and COPD, while high-range (0-75 L/min) is for CPAP and Vapotherm® devices.

Demand Pulse Flow O2 Devices

• These devices deliver oxygen only during inspiration, optimizing oxygen use and minimizing wastage in anatomical dead space.

Test your knowledge of Bourdon flowmeters and their operation. This quiz covers the concepts of flow measurement and the effects of resistance on flow readings. Perfect for students learning about fluid dynamics and measurement instruments!