RT-03 · Initiation & Modification of Therapy

Oxygen Delivery Devices

Low-flow versus high-flow logic, deliverable FiO2 ranges, and how to choose the device that matches the patient's inspiratory demand.

~20 min read5 concept sections·6 questions with rationale

What you'll be able to do

  • Separate low-flow, reservoir, and high-flow systems by whether they meet inspiratory demand
  • State the approximate FiO2 range and flow limits of each common device
  • Choose a device based on required FiO2 stability rather than on the number alone
  • Recognize when a delivered FiO2 is unreliable
Concept breakdown
01

The organizing question: does the device meet inspiratory flow demand?

An adult in distress can pull 30–60 L/min. Any device delivering less than that is diluted by entrained room air, so its FiO2 varies with the patient's breathing pattern.

  • Low-flow systems (nasal cannula, simple mask) deliver variable FiO2 — a deeper, faster breath dilutes it further.
  • Reservoir systems (partial rebreather, non-rebreather) store oxygen between breaths, raising but not stabilizing FiO2.
  • High-flow systems (air-entrainment mask, high-flow nasal cannula) exceed patient demand, so FiO2 is fixed and predictable.
At the bedside

If the question emphasizes a precise or stable FiO2, the answer is a high-flow device — regardless of how high the number is.

Practice quiz

Check yourself before you read the rationale.

Question 1 of 1

A patient with an exacerbation of COPD requires a precise FiO2 of 28%. Respiratory rate is 30/min with visible accessory muscle use. Which device best meets the requirement?

Practice questions

Answer first, then read why the distractors fail.

Question 1

A patient with an exacerbation of COPD requires a precise FiO2 of 28%. Respiratory rate is 30/min with visible accessory muscle use. Which device best meets the requirement?

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4 more concept sections, 5 more questions, and the exam-day playbook for this module.

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