Oxygen demand and supply during a COVID-19 surge

As a rule, caregivers in the United States and most of the developed world take oxygen availability for granted. Oxygen orders are placed and the patient receives the requested amount. However, as seen during the pandemic surges and in times of extreme demand, the ability of a healthcare system to supply the ordered amount of oxygen may be stressed to the point of failure.

Rethinking both demand and supply is needed to help ensure an uninterrupted flow of oxygen. The purpose of this review is not to reassess studies determining oxygen necessity, but rather to provide a "playbook" to manage oxygen shortages to balance supply and demand.

How much oxygen does a facility have?

Most hospitals in the United States store oxygen on site in liquid form. Conversion to the gaseous form is affected by several variables, including temperature, pressure and efficiency of the system. In normal circumstances, one gallon of liquid oxygen is equivalent to 115 cubic feet of gaseous oxygen, or approximately 3,300 liters of gaseous oxygen. Depending on the facility, biomedical engineering reports the amount of available oxygen as inches or gallons, with the relationship between inches and gallons of liquid oxygen dependent upon the construct and shape of the tank. It is vital for hospital operations to be aware of the total capacity of available oxygen, not only at current usage levels but also when factoring increases for surge usage. Equally important is the amount of usable oxygen, as 5-10 percent of the liquid oxygen is used to fill the piping and pressurize the system and therefore unusable for patient delivery. 

Demand

Supplemental oxygen use

One of the lessons learned from the COVID-19 pandemic is that responsible custodianship of oxygen use has not always been a top priority. It is not uncommon to enter a patient's hospital room to find a flowing nasal cannula on the floor, or even worse, finding oxygen flowing in an empty hospital or procedural room. Eliminating this waste is the lowest-hanging fruit, yet it takes an organized plan to fix. Depending on the type of device in question, the potential savings can add up. For example, a patient using three liters per minute by nasal cannula uses over 4,000 liters of oxygen in a day.

Table 1. Approximate rates of oxygen utilization per patient based upon device

Anesthesia use

The bellows of most modern anesthesia machines can be compressed using either oxygen or air. The default is set to oxygen as a safety mechanism, but there are redundancies built into the system, so changing the driving gas to air provides another measure of oxygen conservation, as long as anesthesia providers understand that this "safety net" has been removed. The savings can be as much as 12 L/min while the machine is in use. For a two-hour anesthetic, this amounts to 1,440 L, none of it for direct patient use. If 10 operating rooms ran for eight hours each, the total oxygen usage would be well over 100,000 liters (approximately 30 gallons of liquid oxygen). Conversion away from oxygen as the driving gas saves as much as 10 percent of total oxygen use for the facility under normal operating room usage and normal oxygen demand for the hospital. Intraoperative oxygen use for the patient under general anesthesia approximates 200 L/hour, which includes both induction and maintenance of anesthesia. Running 10 operating rooms for eight hours results in 16,000 L/day, or approximately five gallons of liquid oxygen in a day. Procedural areas also utilize supplemental oxygen delivered by nasal cannula or face mask, as listed above, however for brief periods of time for most patients. As long as oxygen is turned off when not in use, surgical and procedural areas contribute nominal usage of oxygen (notwithstanding postoperative oxygen requirements).

Supply

Oxygen is delivered into hospital rooms and procedural areas under high pressure via outlets. Depending on the construction of the piping systems, there is a maximum flow rate that can be achieved. As a result, in situations like a pandemic, all outlets may not be usable simultaneously. In other words, cohorting oxygen-requiring patients may not be possible based on the maximum flows needed and construction limitations at the facility.

Oxygen delivery may also be zoned within the facility, and it's possible that some zones (those with the highest demand) could remain on liquid oxygen supply, while low-demand units could be rerouted through H-cylinder manifolds. This would provide the ability to utilize different oxygen sources for some patients, increasing the total available amount.

When liquid oxygen vaporizes to the gas phase, the supporting structure cools. If the speed of vaporization exceeds the ability to keep a near-constant temperature in the supporting structure, the piping, valves and regulators could ice-over, resulting in a diminished flow or inhibiting flow altogether. Some facilities add sprinkler systems or manually chop away ice during oxygen demand surges. 

Liquid oxygen is provided by outside vendors. These vendors rely on trucks to deliver the oxygen, and because of the increased demand throughout the region, the delivery of oxygen may not be limited by the oxygen itself, but by the number of truck drivers and the limitations placed on their driving hours. Rather than trucks filling oxygen tanks at each facility to the top, they may provide just enough to last another two to three days so there is time to make other deliveries. Oxygen delivery may no longer be a weekly routine, but instead become a daily challenge. Furthermore, some companies use national dispatchers who don't recognize regional shortages, and therefore don't relay the urgency/emergency of the situation to local distributors. It is important to identify the local dispatcher when less than 24 hours of oxygen remain. On occasion, when oxygen supply was limited to hours, police may be needed to escort a truck through traffic to the final destination. Utilizing government resources becomes a matter of life and death.

Key Implications:

• Using our practical guides, hospital staff can help:
  • Improve pulse oximetry and oxygen use
  • Optimize existing oxygen supplies
  • Expand existing oxygen systems with robust equipment and smart design

Personnel

At our hospital, several groups of caregivers met on a daily call to assess the supply/demand of oxygen and discuss potential opportunities for conservation. The role of the respiratory therapist has never taken on greater prominence than in this latest surge. Despite dealing with significant staffing shortages and having to cover more patients than typical with almost no downtime, the respiratory therapists did not only manage the critically ill patients, but also greatly assisted with policies, oxygen weaning and conservation, and leadership during this surge. Also key to the success of the oxygen management are the hospital engineering and facilities management teams who have in-depth knowledge of the hospital's infrastructure and external supply chain contacts.

Critical time

When oxygen supply on hand reaches a predefined critical threshold, or when the next delivery may not be reliable, having a backup plan is crucial. In an effort to conserve oxygen for as long as possible, some or all of the following changes may be implemented:

• Tolerate a lower oxygen saturation goal as determined by local clinical leadership
• Replace high-flow nasal cannula devices to nonrebreather masks (as tolerated)
• Position e-cylinders next to all mechanical ventilators
• Establish a communication chain between respiratory therapy, nursing and affected physicians (emergency room, intensive care and hospitalists)
• Assign each ventilated patient a specific caregiver to administer bag mask ventilation, if necessary
• Stop all nonessential activities that might necessitate increased oxygen utilization (e.g., physical therapy activities)

Summary

It's more than likely that one hospital will not be the only affected facility, so it is important to share strategies regionally. Pandemics are not limited to one building, and solutions should not be limited either. Supply chain constraints are less modifiable, and efficiencies of allocation/distribution should be looked into at a regional level. As we learn more about the fragility of the supply chain, we can and should use this as an opportunity to minimize waste and learn to problem-solve, because it's quite likely the next challenge is around the corner.

Playbook

1. Use a multidisciplinary team including respiratory therapists, physicians, nursing, administrators and facility management personnel.
2. Create oxygen conservation teams: caregivers dedicated to hospital rounds looking for running oxygen sources that are not being used on patients.
3. Provide education as to the critical nature of oxygen waste to medical students, residents, staff physicians, nurses, aides, respiratory therapists; all caregivers involved with direct patient contact.
4. Reprogram anesthesia machines to run off of air as opposed to oxygen.
5. Continually reassess the need for high-flow oxygen administration

Progression strategy:

1. 1. Mid-flow (10-15 Lpm) always before HF
   2. Trial of mid-flow for all lower FIO2 HF, effective immediately  
   3. May trial BiPAP or move to ventilator if failing mid- or high-flow
   4. HF only 48 hours or less, then move to ventilator (extreme shortage)

1. Learn the facility's oxygen system maximum capabilities and zone maps.
2. Plan for ice prevention and de-icing of piping.
3. Contact local oxygen delivery dispatchers.
4. Use government resources when needed.
5. Daily reporting of oxygen utilization by site.
6. Daily reporting of utilization – by HF, NIV and ventilator use.
7. Develop an emergency plan for when oxygen supplies may be exhausted.

Selected References and Resources

• Advisory Board: https://www.advisory.com/daily-briefing/2021/09/01/oxygen-shortage#:~:text=Covid%2D19%20surges%20lead%20to,struggling%20with%20low%20oxygen%20supplies.

• Becker's: https://www.beckershospitalreview.com/supply-chain/4-updates-on-the-us-medical-oxygen-supply.html

• Bloomberg Law: https://news.bloomberglaw.com/health-law-and-business/floridas-oxygen-woes-cue-coming-wave-of-covid-supply-shortages

• New York Times: https://www.nytimes.com/2021/05/04/world/oxygen-shortage-covid.html

• UF Health team: https://m.ufhealth.org/news/2021/uf-health-team-develops-technique-conserve-oxygen-during-acute-shortages

• Oxygen supply-demand calculator

https://opencriticalcare.org/oxygen-supply-demand-calculator/

• The BMJ: Oxygen provision to fight COVID-19 in sub-Saharan Africa https://gh.bmj.com/content/5/6/e002786.abstract

• The Lancet: Medical oxygen crisis: a belated COVID-19 response https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)00561-4/fulltext?hss_channel=tw-27013292

• The Lancet: Experts criticise India's complacency over COVID-19 https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)00993-4/fulltext?s=09

• SA Heart: Supplemental oxygen therapy in COVID-19. https://journals.co.za/doi/abs/10.10520/ejc-saheart-v17-n3-a12

• Anaesthesia: The use of high-flow nasal oxygen in COVID-19.https://associationofanaesthetists-publications.onlinelibrary.wiley.com/doi/full/10.1111/anae.15073

• Global Health: Science and Practice: Improving hospital oxygen systems for COVID-19 in low-resource settings: Lessons from the field https://www.ghspjournal.org/content/8/4/858.short

Acknowledgements

The oxygen shortage could not have been successfully managed without the integrated teamwork including intensivists, anesthesiologists, administration, nursing materials management and perhaps most importantly, the respiratory therapy teams of Cleveland Clinic Indian River, Tradition, Martin North and Weston Hospitals.