Oxygen Delivery Systems

Oxygen delivery systems are the devices used to administer supplemental oxygen to patients with, or at risk of, inadequate oxygenation. They range from low-flow devices such as nasal cannulae and simple masks to high-flow and reservoir systems, differing in how much oxygen they deliver and how precisely the inspired concentration can be controlled.

Definition

Oxygen delivery systems are the equipment used to increase the fraction of inspired oxygen reaching a patient's lungs, classified by flow and by whether the delivered concentration is fixed or varies with the patient's breathing pattern.

Scope

The topic covers the rationale for supplemental oxygen, the distinction between low-flow and high-flow systems, the devices in common use and their approximate delivered concentrations, and the principle of titrating oxygen to a target. It frames the nurse's monitoring role and presents the material as reference knowledge rather than prescribing instructions.

Core questions

• When is supplemental oxygen indicated, and what is being corrected?
• How do low-flow and high-flow systems differ?
• What determines the inspired oxygen concentration a device delivers?
• Why is oxygen titrated to a target rather than given maximally?

Key concepts

• Hypoxaemia and tissue oxygenation
• Low-flow devices (nasal cannula, simple mask)
• Reservoir and non-rebreather masks
• Fixed-performance (Venturi) devices
• High-flow nasal oxygen
• Fraction of inspired oxygen
• Oxygen saturation targets and titration

Mechanisms

Supplemental oxygen raises the fraction of inspired oxygen, increasing the pressure gradient that drives oxygen from alveoli into blood and correcting hypoxaemia. With low-flow devices the delivered concentration varies because the patient entrains room air around the supplied oxygen, so the effective inspired fraction depends on the breathing pattern. Fixed-performance devices use the Venturi principle to deliver a more constant concentration regardless of breathing, and high-flow nasal systems deliver heated, humidified gas at flows that meet or exceed inspiratory demand, providing a more reliable inspired fraction and modest positive airway pressure. Oxygen is titrated to a saturation target because both too little and excessive oxygen can be harmful.

Clinical relevance

Oxygen is one of the most frequently administered therapies in acute care, and nurses select, apply, and monitor delivery devices and the patient's response. This entry summarizes device categories and principles as reference material and does not provide flow rates or prescriptions for an individual patient.

History

Oxygen has been used therapeutically since the nineteenth century, but controlled delivery developed in the twentieth with the introduction of masks, the Venturi (fixed-performance) principle, and, more recently, high-flow nasal systems. Recognition that excess oxygen can also cause harm shifted practice toward titrating oxygen to defined saturation targets rather than administering it routinely at high concentrations.

Debates

How much oxygen should acutely ill patients receive?

Concern that both hypoxaemia and hyperoxaemia can be harmful has shifted guidance toward conservative, target-driven oxygen use rather than liberal administration, though optimal targets in specific conditions remain under study.

Seminal works

• frat-2015

Frequently asked questions

Why does a nasal cannula not deliver a precise oxygen concentration?

It is a low-flow device, so the patient breathes in room air alongside the supplied oxygen; the resulting inspired concentration varies with how fast and deeply the patient breathes.

What is high-flow nasal oxygen?

It delivers heated, humidified gas at flow rates that meet or exceed the patient's inspiratory demand, allowing a more reliable inspired oxygen fraction and some positive airway pressure compared with conventional low-flow devices.