Q4 RC 111 STORAGE AND DELIVERY OF MEDICAL GAS.pdf

Storage and Delivery of Medical Gases

Learning Objectives

• Describe how medical gases and gas mixtures are produced.

• Discuss the clinical applications for medical gases and gas mixtures.

• Distinguish between gaseous and liquid storage methods.

• Calculate the duration of remaining contents of a compressed oxygen cylinder.

• Understand the difference in calculating duration for liquid oxygen cylinders and compressed cylinders.

• Describe proper storage, transport, and use of compressed gas cylinders.

• Distinguish between gas supply systems.

• Detail steps to take if a bulk oxygen supply system fails.

• Differentiate among safety systems that apply to various equipment connections.

• Select appropriate devices to regulate gas pressure or control flow in clinical settings.

• Describe how to assemble, check function, and identify malfunctions in gas delivery equipment.

• Identify and rectify common malfunctions of gas delivery equipment.

Introduction to Medical Gases

• Medical gases are classified into three categories:

  • Laboratory Gases: For equipment calibration and diagnostic testing.

  • Therapeutic Gases: To relieve symptoms and improve oxygenation in hypoxemic patients.

  • Anesthetic Gases: Combined with oxygen for anesthesia during surgery.

Characteristics of Medical Gases

Oxygen (O2)

• Colorless, odorless, transparent, tasteless.

• At STPD: Density of 1.429 g/L (slightly heavier than air).

• Low solubility in water; only 3.3 ml dissolves in 100 ml of water at room temperature and pressure.

• Non-flammable but accelerates combustion.

Oxygen Production

• O2 production methods include:

  • Chemical methods (e.g., electrolysis of water).

  • Fractional distillation of atmospheric air (most common for large quantities).

  • Physical separation: using methods such as molecular sieves or oxygen concentrators.

Medical Air

• A colorless, odorless gas mixture consisting of:

  • 20.95% O2

  • 78.1% nitrogen

  • ~1% trace gases

• Produced by filtering and compressing atmospheric air.

Carbon Dioxide (CO2)

• Colorless, odorless gas, specific gravity of 1.52 (heavier than air).

• Produced by heating limestone with water; must meet FDA purity standards of 99%.

• Used for blood gas analyzer calibration and diagnostic purposes.

Helium (He)

• Odorless, tasteless, non-flammable; density of 0.1785 g/L (less than air).

• Commercially produced from natural gas; must be mixed with at least 20% O2 for safety.

• Therapeutic use in heliox therapy (mixtures of O2 and helium).

Nitric Oxide (NO)

• Colorless, non-flammable, toxic gas; high concentrations can cause methemoglobinemia.

• FDA approved for treating hypoxic respiratory failure in infants.

Nitrous Oxide (N2O)

• Colorless gas with a slightly sweet odor; used clinically as an anesthetic.

• Must be mixed with oxygen; produced by thermal decomposition of ammonium nitrate.

Gas Cylinder Storage

• Gas Cylinders: Store and ship compressed or liquid medical gases, regulated by federal standards.

  • Made from seamless steel, classified by DOT as Type 3A (carbon steel) or 3AA (steel alloy).

  • Markings include size, pressure, serial number, and ownership.

  • Subject to safety tests every 5 or 10 years to measure leakage and expansion.

Safety Relief Valves

• Designed to vent gas in case of overheating; can be triggered by:

  • Frangible metal disk rupturing.

  • Fusible plug melting.

  • Spring-loaded valve opening due to high pressure.

Measuring and Estimating Cylinder Gas Flow

Estimating Duration of Gas Flow

• Duration is affected by gas flow, cylinder size, and initial pressure.

• Formulas used:

  • For gas-filled cylinders: Duration of flow = Pressure (psig) × Cylinder factor / Flow (L/min)

  • For liquid-filled cylinders: Requires knowledge of liquid gas weight.

Safety Guidelines

• Store cylinders securely and away from combustibles, heat, and allow ventilation.

• Ensure liquid oxygen containers are kept cool and in well-ventilated areas.

• Maintain clear signage prohibiting smoking near storage units.

Bulk Oxygen Supply Systems

• Designed for healthcare facilities’ large oxygen needs (

  • Advantages over portable cylinders: Cost-effective, less prone to interruption, improved safety, and reduced transport hazards.

• Types of systems include:

  • Alternating supply: Primary bank transitions to reserves as pressure drops.

  • Cylinder supply: Incorporates primary, secondary, and reserve supply for efficiency.

  • Bulk gas system: Uses small volumes of liquid oxygen to provide large amounts of gas, ideal for space-saving.

Distribution and Regulation

• Central piping systems deliver oxygen/air at usable pressures throughout healthcare settings, with standardized pressure control measures and alarm systems.

Safety Indexed Connector Systems**

• Prevent misconnection of gas sources through:

  • ASSS: For large cylinders.

  • DISS: For low-pressure gas connectors.

  • PISS: For small cylinders.

Regulating Gas Pressure and Flow

• Reducing valves reduce gas pressure.

• Flowmeters control delivery to patients, including types like restrictors, Bourdon gauges, and Thorpe tubes.

Role of Respiratory Therapists

• Patient assessment and management including recommendations for medical gas use, monitoring outcomes, and addressing malfunctions.