The scope and influence of the COVID-19 pandemic continues to grow. Cases are on the rise again. The number of hospitalizations and ventilated patients is growing. Hospitals located in critical, high population centers overrun with COVID-19 patients used medical gases and mechanical ventilators in record numbers this past spring. In fact, some facilities did not have enough medical gas tubing and hoses, connectors, medical gas wall outlets, quick-connects, and other consumables required to connect COVID-19 patients to the life-saving equipment needed to treat their patients. Oxygen consumption was so high at some hospitals that the vaporizers and evaporators at the liquid oxygen storage systems were over capacity and became ice-laden, rendering them ineffective at delivering adequate quantities of gaseous oxygen to the piped infrastructure.
Since our last article was published on our website, we have been doing continued research and have spoken with licensed respiratory therapists from various hospitals. We also spent some time with a long-time colleague and fellow medical gas systems and equipment expert, Phil Hober (of The Sherman Engineering Company, a supplier of medical gas equipment and devices) to glean insights from their lessons-learned from the front lines in city hospitals in New York, New Jersey, and Philadelphia. As our society is facing what could be another significant surge nationwide, we want to share a few things we have learned.
Medical Gas and Oxygen Demand During COVID-19
When the COVID-19 pandemic reached the United States early this year and hospitalized COVID-19 patients needed respiratory therapy beyond a simple nasal cannula, treatment moved to invasive mechanical ventilation. The flow rates required for invasive mechanical ventilators, depending on the type, could range in gas flow rates from 12-80 liters per minute (LPM) of a blend of air and oxygen, depending upon the fraction of inspired oxygen, FiO2. (Room air is 21% oxygen, which corresponds to a FiO2 of 0.21. Oxygen enriched air can be delivered at varying concentration levels to a FiO2 of 1.0 or, 100% oxygen.) During our study early this spring for a prominent regional hospital, their invasive mechanical ventilators listed peak flow rates of 30 LPM but, as we noted in our earlier article, that hospital expected to treat their invasively ventilated COVID-19 patients at lower oxygen consumption levels of 10 LPM or less.
Our latest research, study of information from manufacturers of patient ventilating equipment, and recent discussions with licensed respiratory therapists in our region indicate that many COVID-19 patients respond to and recover with treatment from high flow nasal cannulas and BiPAP, often never requiring invasive ventilation. Thus, the treatment approach has shifted, and invasive mechanical ventilation has become the last resort rather than the first step in treatment. We have been informed that the general order of respiratory therapies employed for COVID-19 patients, as acuity increases are:
- Simple nasal cannulas at flows of 2-8 LPM of oxygen;
- High flow nasal cannulas (HFNC), which use a blend of air and oxygen at flow rates ranging from 50-60 LPM;
- Bilevel positive airway pressure machines (BiPAP) also use a blend of air and oxygen, which can consume as much as 60-120 LPM depending on the equipment’s particular manufacturer; and, finally
- Invasive mechanical ventilation, 12-80 LPM of combined air and oxygen.
Now that treatment protocols have evolved, the equipment often used to treat COVID-19 patients effectively is consuming 50-120 LPM. Contributing factors to the increase in medical air and oxygen consumption include the unavoidable leakage around the high flow nasal cannula at the nose and from the BiPAP mask over the face. Excess air and oxygen used to clear away exhaled carbon dioxide gas from patients’ lungs also contribute to the high flow rates.
The flow rates of air and oxygen and information regarding “FiO2” referenced above, and notes regarding the reasons for high ventilation flow rates are based in combination upon equipment research, discussions with various respiratory therapists, and a paper by Mark Allen, April 2020.
Preparedness and Planning Ahead
Depending on the population of patients receiving respiratory therapy and the range of equipment being used within any given hospital, piped medical air and oxygen infrastructures that proved to be adequate in the spring of 2020 may not be capable of meeting the demand if another critical surge of hospitalizations becomes a reality in the winter months this year.
Healthcare facilities should inventory the equipment required for connecting medical air and oxygen to equipment and patients, assuming the worst based on their region’s demographics and Department of Health projections. Facilities should plan and store adequate quantities of these items on-site at the ready to serve not only the stock of equipment currently on site but also the additional equipment that may be purchased or borrowed if/when patient numbers increase.
Adding the absolute value of total peak flow rates for each of the various pieces of equipment used by your respiratory therapists would almost certainly reveal a total connected load that is greater than your system can provide. This approach does not necessarily provide accurate information and could lead to potentially unnecessary upgrades to your medical air and oxygen infrastructure. Do not panic or assume the worst about your facility’s oxygen and medical air source equipment and distribution systems. Instead, please communicate with the physicians, clinical professionals, and respiratory therapists at your hospital and determine how they treat COVID-19 patients today and ask them to explain what they expect in treatment methods for the immediate future. Let their experience inform your planning concerning medical air and oxygen consumption. Use this data to develop a projected demand for oxygen and medical air when evaluating or re-evaluating your piped medical gas system infrastructure, medical air compressors, and liquid oxygen storage systems equipment.
You may also want to contact a professional engineer to help you develop projected oxygen and air demands, evaluate your piped medical air and oxygen piping system, and main source equipment to help you confirm that your systems are sized appropriately. You can also contact your supplier of bulk liquid oxygen and storage equipment and medical air source equipment vendor with the calculated demands you expect and ask for assistance in evaluating your source equipment infrastructure. They may ultimately find that you need to make adjustments or install additional piping and equipment to meet the expected demands.
Whether the current COVID-19 pandemic produces another surge of patients in record numbers or not, there will likely be a time in the future when your medical air and oxygen systems will be called to task in an unprecedented manner. Do not delay in evaluating your existing systems and equipment so you are prepared when that time comes.
If you would like more information on this subject or need assistance in evaluating your medical gas systems and equipment, please contact Robert J. Allen, P.E. CPD, at firstname.lastname@example.org.