How to Balance Oxygen Supply-Demand in Critical Care

Topic Progress:

Pearls for Balancing Oxygen Supply and Demand

1. Nurse the patient, not your unit routine.
2. Always assess if your patient has enough oxygen supply to meet the demand of critical care interventions.
3. Communicate with your team if the oxygen supply and demand imbalance is not fixed with your interventions; do not wait.

Basics of Improving Oxygen Supply and Decreasing Oxygen Demand

Caring for a critically ill patient can feel like a balancing act. Working with the patient to help restore equilibrium to the body’s oxygen demands and supply is the base of care for many acute patients. Below are some practical steps to increase supply and decrease demand so the body’s needs can be met. The next few pages will dive deeper into this framework 1

Oxygen Supply

The goal is to maximize oxygen supply through these mechanisms so the demands of the body can be met.

  • Oxygenation
    • O2 level – Fraction of inspired O2 (FiO2)
    • Carrying O2 – Hemoglobin & pH
  • Ventilation
    • Rate – Breaths per minute
    • Volume – Amount of air in and out
  • Cardiac output maximized
    • Pump – Blood being ejected
    • Pipes – Blood vessels with good tone
    • Tank – Volume of blood sufficient
    • Rate – Beats per minute is not too high or low
Oxygen Demand

The goal is to maximize oxygen supply through these mechanisms so the demands of the body can be met.

  • Physiologic Stressors
    • Pain/discomfort – increases demands for 02
  • Psychological Stressors
    • Anxiety – Increases the body’s demand for 02
  • Metabolic demand
    • Too cold – Shivering increases metabolic demand
    • Too hot – Temp rise increases demand for 02

Here are some examples of the differences in normal and critical care as it pertains to oxygen supply and demand for a patient with COVID-19.

Case Info

A 55 year old male is admitted to a critical care area with severe hypoxemia and hypercapnia secondary to COVID-19. He is intubated and mechanically ventilated. He is on sedation medications.

The previous nurse told you in report that the patient’s SPO2 drops from 95% to 81% with any type of passive or active movement. You notice his heels are getting red from being in the same position.

Routine Care

  • Elevate heels
  • Turn q4h or more frequently to offset pressure areas
  • You can assess the patient without disrupting oxygenation

Critical Care

  • Acquire an air mattress
  • Turn only as needed, while assessing patient’s oxygenation/ventilation response with each turn
  • In extreme cases, patients are not turned for an entire shift because of oxygenation/ventilation problems with turns
  • Cluster care where possible

Case Info – Update

While in the patient’s room clustering care to limit exposure, you notice his respiratory rate increases from 22/min to 28/min.

Routine Care

  • Listen to their lungs
  • Look at work of breathing
  • Check SPO2
  • Treat pain*
  • Call a physician

Critical Care

  • Listen to their lungs
  • Look at work of breathing
  • Check SPO2
  • Suction
  • Chest physio*
  • Increase ventilator oxygen*
  • Increase ventilator PEEP*
  • Check a blood gas
  • Check blood pressure
  • Check lactate
  • Increase sedation infusions*
  • Increase pain medication infusions*
  • Assess for appropriateness for ventilator settings

*If needed

Prone Position

Improve Oxygenation and Perfusion

Essentially, the prone position helps to improve blood flow and recruit alveoli that are typically posterior. This intervention is occurring for both intubated and non-intubated patients 2,3

How to Prone

It is a team effort. Refer to your local guidelines for more details.

In the meantime, have a look at one way they prone in Denmark.

The EMCrit Crew has Amazing Resources on Proning

The Intensive Care Society has proning guidelines found here, courtesy of EMCrit.

EMCrit Podcast 124

This is a deep dive into the intricacies and logistics of proning.

From Cardiff Critical Care

A simulation of proning courtesy of the team at Cardiff.

Other Methods

Inhaled Nitric Oxide

This method vasodilates the pulmonary blood vessels to allow more opportunity for ventilation/oxygenation. It is set up to the ventilator4.


  1. Gillespie & Shackell (2017). Exploring the oxygen supply and demand framework as a learning tool in undergraduate nursing education. Nurse Education Pract. 2017:27:107-113. doi:10.1016/jnepr.2017.08.022
  2. Farkus. (2016). PulmCrit Wee- Proning the non-intubated patient.
  3. P. Pelosi, L. Brazzi, L. Gattinoni. European Respiratory Journal Oct 2002, 20 (4) 1017-1028; DOI: 10.1183/09031936.02.00401702
  4. Karam, O., Gebistorf, F., Wetterslev, J. and Afshari, A. (2017), The effect of inhaled nitric oxide in acute respiratory distress syndrome in children and adults: a Cochrane Systematic Review with trial sequential analysis. Anaesthesia, 72: 106-117. doi:10.1111/anae.13628

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