Medical gas systems rank high on the list of resources necessary for a hospital to function. Oxygen, medical air, vacuum, and other systems support all manner of life-saving and life-sustaining procedures, from providing oxygen therapy for a COVID-19 patient to providing vacuum during a heart transplant.
Proper medical gas design requires both a clear understanding of system requirements and the ability to anticipate how those systems may be called upon under changing clinical conditions. The sections below cover key considerations related to designer qualifications, system capacity, oxygen and medical air demand, and preparedness:
- Medical Gas Design Qualifications
- Evaluating Medical Gas System Capacity
- How Respiratory Treatment Changed Medical Gas Demand
- Preparedness and Planning Ahead
Medical Gas Design Qualifications
In 1987, the American Society of Sanitary Engineering (ASSE) began planning for a document that would outline the minimum standard of qualification for the design and installation of medical gas systems. By 1997, the organization had developed Series 6000, Professional Qualifications Standard for Medical Gas Systems Personnel. Since that year, this standard has been revised on the same schedule as the National Fire Protection Agency (NFPA) Standard 99, Healthcare Facilities Code.
ASSE Series 6000-2021 covers ten separate qualifications, from generalists and installers to inspectors and designers. Standard 6060 – Designers requires, among other things, at least two years of documented experience in the mechanical and plumbing systems industry and at least 32 hours of training covering ASSE 6060, NFPA 99, NFPA 55, and the FGI Guidelines for certification. This training is required to be a recognized third-party training provider.
Designers must show proficiency in designing space requirements, placement of outlets, inlets, valves, alarms, sizing and layout of piping systems, and calculations for piping, intakes, exhausts, and source equipment.
At Barton Associates, we strive to maintain or exceed industry-standard training and certifications for our employee-owner staff. In keeping with this goal, two of our plumbing designers are now certified as ASSE Series 6000, Standard 6060 Medical Gas System Designers. Stephen Soltis Jr., CPD, LEED AP has decades of experience, yet he continues to stay at the forefront of design and certification standards by challenging himself to provide the highest quality solutions for our clients.
Beyond meeting design and certification standards, medical gas planning requires an accurate picture of how a facility uses these systems and how demand may change under different clinical conditions. Evaluating system capacity is a key part of that process.
Evaluating Medical Gas System Capacity
Evaluating an existing medical gas system requires more than comparing pipe sizes and equipment capacities against theoretical maximum demand. Patient population, clinical practices, equipment types, simultaneous use, and expected treatment methods can all influence actual system demand.
A hospital assessment conducted during the COVID-19 pandemic illustrates why these factors matter.
A Hospital Oxygen Capacity Assessment During COVID-19
When the novel coronavirus (COVID-19) became a reality for this country and the quarantine began, we did not know what to expect. Pandemic updates from Washington, DC by the President of the United States and his lead physicians became a daily routine. Just a few hours away, COVID-19 cases in New York City were overwhelming the hospitals. Oxygen and medical gas systems were overtaxed by patients requiring ventilators, and many existing piping infrastructures proved to be inadequately sized for such a high demand. The facilities and engineering community was scrambling to help their healthcare clients bolster their systems for the worst.
A prominent, regional hospital approached Barton Associates while they monitored the tragedies in the New York City hospitals and watched COVID-19 death tolls rise. They wanted to stay ahead of the curve and be prepared when the spread of COVID-19 cases reached their patient population.
The hospital’s clinical team had prepared a Pandemic Response Plan for intake and treatment of up to 200 critically ill COVID-19 patients. The Director of Facilities needed to verify that the existing oxygen piping system would be able to support ventilated patients. In this case, the director was not concerned about the medical gas system, so the analysis was focused on the oxygen delivery systems.
Based on initial demand and friction loss calculations using industry standards for designing new systems as the guide (an expected oxygen demand of 10 liters per minute (LPM) per patient bed and 30 LPM per ventilator), it appeared that the existing oxygen piping system would not be adequate to meet the needs of the hospital’s Pandemic Response Plan.
With this realization, we decided to interview the hospital’s respiratory therapy team to compare the recommended theoretical oxygen demand against what they projected from a clinical perspective.
Their expected consumption of oxygen was far lower than what is recommended in the various engineering and design manuals deemed as best practice in the industry. The respiratory team anticipated each patient on a ventilator would consume a maximum of 10 LPM and the general non-COVID-19 patient population was expected to consume approximately 2-4 LPM per bed at a diversity (predicted simultaneous use) of 25%.
When using these figures, our calculations showed that the oxygen piping system would be expected to perform safely under the predicted conditions. Thankfully, the hospital did not have to rewrite the Pandemic Response Plan or make emergency changes to their system.
When we finished the first round of calculations, our collective hearts sank. “What will we do now?”, was the immediate response. Thankfully, the final rounds of calculations revealed a much better result.
The main lesson learned was the importance of including the clinical team and respiratory therapists in engineering discussions and reviews, particularly when planning for atypical response plans. When planning new facilities, industry standards remain appropriate. In this case, we needed real values from the front line to validate the system and give our client confidence that the existing oxygen infrastructure could support the anticipated surge of critical care patients.
The assessment showed that the hospital’s existing oxygen infrastructure could support the projected demand. It reinforced a broader lesson as well: the best time to assess system capacity is before ICU beds are filling during an emergency. Continued research and discussions with respiratory therapists would soon demonstrate another factor: facilities need to account for changes in clinical treatment methods that can significantly alter medical air and oxygen demand.
How Respiratory Treatment Changed Medical Gas Demand
As the COVID-19 pandemic continued, hospitals located in critical, high-population centers used medical gases and mechanical ventilators in record numbers.
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 them.
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.
Following the initial hospital assessment, we continued our research and spoke 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.
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 on 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 for the regional hospital, their invasive mechanical ventilators listed peak flow rates of 30 LPM. As noted above, however, that hospital expected to treat its invasively ventilated COVID-19 patients at lower oxygen consumption levels of 10 LPM or less.
Continued 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.
Changes in Respiratory Therapy and Flow Rates
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 increased, was:
- 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.
As treatment protocols have evolved, the equipment often used to treat COVID-19 patients effectively consumes 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.
These findings reinforce why medical gas system evaluations need to account for actual clinical practice rather than relying solely on the sum of theoretical equipment loads.
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 adequate during one period of demand may not be capable of meeting demand during a future critical surge.
Healthcare facilities should inventory the equipment required for connecting medical air and oxygen to equipment and patients, based on their region’s demographics and Department of Health projections to inform planning.
Facilities should plan and store adequate quantities of these items on-site, 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.
Rather than assuming the worst about a facility’s oxygen and medical air source equipment and distribution systems, communicate with physicians, clinical professionals, and respiratory therapists and determine how patients are being treated and what they expect treatment methods to require.
Let their experience inform 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 piped medical gas system infrastructure, medical air compressors, and liquid oxygen storage system equipment.
A professional engineer can help develop projected oxygen and air demands and evaluate piped medical air and oxygen systems and main source equipment to confirm that the systems are appropriately sized.
Facilities can also work with bulk liquid oxygen and storage equipment suppliers and medical air source equipment vendors, using calculated expected demand to evaluate source equipment infrastructure. Those evaluations may identify the need for adjustments or additional piping and equipment to meet expected demand.
The experience of healthcare facilities during the COVID-19 pandemic demonstrated that medical gas design extends beyond sizing piping and source equipment based on standard assumptions. Qualified system design, accurate demand calculations, input from clinical teams, and proactive evaluation of existing infrastructure all contribute to preparing healthcare facilities for both routine operations and periods of unusually high demand.
There may be circumstances in the future when medical air and oxygen systems are called upon in ways that were not anticipated during their original design. Evaluating existing systems and equipment before those conditions occur gives facility teams more time to identify limitations, understand actual clinical demand, and plan appropriate improvements.
For more information about medical gas system design, capacity planning, or evaluating existing medical gas systems and equipment, contact us to discuss the needs of your healthcare facility.