Why would one require 20 liters per minute (lpm) of oxygen at a fraction of inspired oxygen (FiO2) of 21%?

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From the Guidelines

A flow rate of 20 liters per minute (LPM) at FiO2 21% is not typically recommended as a standard treatment according to the BTS guideline for oxygen use in adults in healthcare and emergency settings 1.

The BTS guideline recommends specific oxygen therapy targets based on the patient's condition, such as aiming for SpO2 94-98% in patients who are not at risk of hypercapnic respiratory failure, and targeting saturation at 88-92% in those who are at risk 1.

Key considerations for oxygen therapy include:

  • Assessing the patient's risk of hypercapnic respiratory failure, which may be indicated by severe or moderate COPD, or other conditions such as severe chest wall or spinal disease, neuro-muscular disease, severe obesity, cystic fibrosis, or bronchiectasis 1
  • Monitoring the patient's SpO2 levels and adjusting oxygen therapy accordingly to maintain target ranges 1
  • Considering the use of other respiratory support therapies, such as non-invasive ventilation (NIV) or invasive ventilation, in patients with respiratory acidosis or hypercapnia 1

In terms of specific oxygen delivery methods, the guideline recommends starting with 28% or 24% oxygen or 1-2 L/min nasal oxygen and obtaining blood gases, with adjustments made based on the patient's response and blood gas results 1.

Overall, while a flow rate of 20 LPM at FiO2 21% may be used in certain clinical contexts, such as high-flow nasal cannula (HFNC) therapy, it is essential to follow established guidelines and tailor oxygen therapy to the individual patient's needs and condition, prioritizing their morbidity, mortality, and quality of life outcomes.

From the Research

Oxygen Therapy

  • A patient may require 20 liters per minute (lpm) of oxygen at a fraction of inspired oxygen (FiO2) of 21% due to various respiratory conditions, such as acute respiratory distress syndrome (ARDS) or severe community-acquired pneumonia 2, 3, 4, 5.
  • The use of high-flow nasal cannula (HFNC) oxygen therapy is effective in patients with hypoxemic respiratory failure, and some studies support its use in patients with hypercapnia 4, 5.
  • Noninvasive ventilation (NIV) is also a viable option for patients with acute hypercapnic respiratory failure, and its use in hypoxemic respiratory failure is being increasingly investigated 3, 5, 6.

Respiratory Support

  • The choice of respiratory support depends on the severity of the patient's condition, with NIV and HFNC being suitable for mild-to-moderate cases, while mechanical ventilation and extracorporeal membrane oxygenation (ECMO) may be necessary for more severe cases 2, 3, 4.
  • It is essential to carefully monitor the patient's respiratory drive and effort to prevent patient self-inflicted lung injury (P-SILI) and ventilator-induced lung injury (VILI) 2, 4.
  • The optimal ventilatory strategy for hypoxemic respiratory failure is uncertain, and further research is needed to confirm the role of NIV and HFNC in this setting 3, 5.

Oxygen Administration

  • Various methods of oxygen administration are available, including HFNC, NIV, and mechanical ventilation, each with its own benefits and risks 4, 6.
  • The goal of oxygen administration is to reduce the breathing workload and improve oxygenation, while minimizing the risk of complications such as P-SILI and VILI 2, 4.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Severe hypoxemia: which strategy to choose.

Critical care (London, England), 2016

Research

Oxygen administration for patients with ARDS.

Journal of intensive care, 2021

Research

Noninvasive Ventilation and Oxygenation Strategies.

The Surgical clinics of North America, 2022

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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