What are the top ways to conserve oxygen?

Here are some tips on how to safely conserve oxygen depending on the local context:

1. Be cautious with high flow nasal cannula – high flow nasal cannula uses up to 60-70 LPM flow and can deplete stores quickly. This delivery device generally should not be used on cylinders unless a manifold system is present and a large cylinder pool is present. Additionally, even when supply may be ample, multiple HFNC devices in simultaneous use may cause system pressure failure or a rate of decline that causes excess freezing of liquid oxygen sources (which will decrease liquid oxygen output further). Always wean patient flows as quickly as possible and transition to alternative lower flow devices as soon as tolerated. There are some turbine and Venturi based devices which do not require a robust medical air supply, but these devices still consume O2 at high rates. 
2. Use evidence based SpO2 goals and avoid hyperoxia – Avoiding higher than necessary SpO2 goals will save vast quantities of oxygen (Read more on Optimal SpO2 Goals). The difference in SpO2 goal of 90 vs 92% in COVID19 patients can translate to 2-3x less oxygen utilized. This requires continuous or frequent pulse oximetry checks and careful, frequent titration. (see SpO2 goals). There are multiple auto-titration devices that are receiving increasing attention, but yet to see widespread use. 
3. Consider oxygen conserving devices – There are multiple types of oxygen conserving devices, which may or may not be useful depending on the use case. These devices include oxymizers (both pendant style and nasal reservoir style) as well as conserving devices that are placed on the cylinder directly (also known as ‘pulse dose’ devices). Reservoir-based devices conserve oxygen by enabling a higher FiO2 with lower flow rate as the patient is breathing some oxygen from the reservoir. These devices were designed to work in patients with chronic lung conditions, and their performance in patients with acute respiratory failure is largely unproven (i.e. if a patient has a higher minute ventilation). Pulse dose devices can be expensive. There are numerous other oxygen delivery devices that claim or prove oxygen conservation, however, for most of these devices performance and outcome data are lacking for acute respiratory failure patients.  
4. Consider liquid oxygen when possible –  this is the most efficient way to store and produce oxygen, based on size:capacity. However, liquid oxygen requires considerable infrastructure on site and regionally(e.g. roads, trucks, oxygen separating plants, etc). 
5. Utilize additional O2 storage methods – these may be mobile liquid oxygen units, additional cylinders (Size H/J), or reservoir devices.  
6. Inspect and eliminate O2 system leaks – leaks in oxygen infrastructure and delivery devices are common. Common causes to include: 
   • Using excess flow
   • Not turning off devices that not in use (e.g. anesthesia machines or flowmeters)
   • Incorrectly secured fitting from cylinders
   • Leaks in high or low pressure tubing due to lack of adequate maintenance
7. Utilize oxygen concentrators – Consider utilizing oxygen concentrators to preserve cylinders and central supply when possible. There are multiple ways to split an oxygen concentrator to maximize the benefit of its output for multiple patients.  
8. Carefully adjust intentional leak for CPAP/NIPPV – properly used NIPPV/CPAP will have a leak. Too much or too little can be problematic depending on the interface and patient. Proper titration requires close monitoring and regular adjustment
9. Account for Bias Flow & consider devices without bias flow – Some ventilators utilize continuous flow during the expiratory cycle – ‘bias flow.’ In some cases, this adds considerably to oxygen consumption (see ventilator settings in step 3 of this calculator) above and beyond minute ventilation consumption. See manufacturer specifications and account for this in planning. 
10. Consider systems that allow on-site filling of cylinder – PSA plants and deployable oxygen concentrator systems (DOCS) can be used to refill cylinders. Specifications vary widely depending on need. 
11. Frequent inspection and countermeasures to avoid liquid oxygen failure: 
    • Daily inspection to look for excess icing with increased use and colder weather, liquid oxygen evaporators may freeze – dramatically reducing O2 output. Regular inspection and countermeasures are critical (e.g. de-icing or warming systems to prevent freezing
    • Inspect daily for potential leaks
    • Maintain daily line pressure log and fill level
12. Frequent inspection and countermeasures to avoid portable oxygen concentrator failure:
    • Avoid running beyond max flow (this can cause humidity to build up in the zeolite and cause decreased efficiency and failure)
    • Inspect and clean air intake filter regularly (weekly)
    • Ensure functioning voltage stabilization unit if applicable
    • Even when not in use, be sure to periodically turn on the concentrator for 30 minutes weekly – this will flush the system and filters of humidity which can damage the device
    • Never run the unit without proper filters in place
    • Keep the air intake away from walls and curtains
13. Frequent inspection and countermeasures to avoid cylinder failure:
    • Keep regulators and valves dust free
    • Avoid (fire) ignition sources
    • Ensure cylinders are stored and secured properly to prevent falling over
    • Always open cylinder valves slowly
14. Estimate your burn rate and plan ahead – in some settings oxygen shortages can be avoided or ameliorated by planning ahead. Keeping track of daily facility consumption and modeling surge scenarios can help with planning for production and maintenance (PSA plans), cylinder numbers needed, refill frequency (liquid oxygen). There are many tools to help with planning. The online interactive tool (below) helps quickly model ward scenarios with varying levels of detail.  
15. Ensure adequate power and backup power for PSA/concentrators – power failures can be a significant and abrupt cause of oxygen supply failure. If dependent on oxygen concentrators (whether portable or PSA plant), it is imperative to:
    • Utilize voltage stabilization units where power supply voltage is variable
    • Implement and regularly test backup power supply and/or backup cylinders in the event of power failure

Additional Resources:

Oxygen supply and demand calculator by OpenCriticalCare.org 

Blakeman TC, Branson RD. Oxygen supplies in disaster management. Respir Care. 2013 Jan;58(1):173-83.

Compilation of oxygen planning tools and presentations by OpenCriticalCare.org

Frank’s Hospital Workshop Tutorials – Oxygen Concentrators – by Frank Weithoner

Oxygen conservation infographic – Branson et al, CHEST, May 2021