COVID-19 Ventilators & the Systems Used to Administer the Oxygen
Sarah Jane Madole, BSN, RN
Senior Associate, Technology Internal Information Consultant
Brian Hageman, LEED AP
Associate Principal, Plumbing Discipline Lead
Ventilators and ventilation practices have maintained the spotlight in COVID-19 conversations. As ventilators have been used as a primary treatment for COVID-19 patients, particularly to combat acute respiratory distress syndrome, the demand (in certain regions) has escalated beyond the available supply. As of this article, New York Governor Cuomo and New York City Mayor Blasio are still seeking additional ventilators and “rebalancing resources” to attempt to meet the greatest need now.
Receiving less publicity are the systems used to administer the oxygen. With the significant uptick in ventilator use, typical medical oxygen and compressed air systems are being taxed in ways our healthcare facilities have never experienced. Worst case, if these systems are not properly managed (and modified in some cases), this critical, “invisible” treatment could be jeopardized.
VENTILATORS: WHAT, HOW, WHEN, FOR WHOM
Mechanical ventilation is used when a patient can’t adequately breathe on his/her own. This process involves inserting a flexible tube down a patient’s airway to provide oxygen (intubation), decreasing the work of breathing until the patient no longer needs respiratory support (i.e. patient can breathe on his own). Mechanical ventilation is not a cure for COVID-19, but rather, can provide rest for respiratory muscles, better oxygenation and clearing of CO2, and allow more time for the patient’s body to recover. It is a last resort measure for critical COVID-19 patients.
Most ventilators use oxygen and medical air provided by a connection to a wall outlet. Some ventilators pull in room air and filter it, instead of requiring a medical air connection. The oxygen and medical air or room air is then blended at a level chosen by the care team to adequately support each patient’s needs. Healthcare providers have reported that critical COVID-19 patients have been requiring higher levels of oxygen to achieve adequate oxygenation. The higher levels of oxygen consumption paired with the deployment of more ventilators to support the surge of critical patients with COVID-19 could equate to problems for facilities if accommodations are not made.
NOTE: It is our understanding that oxygen systems are more critical to ventilator use and are more likely to have issues with system capacity than air systems, thus, this article is focusing on oxygen.
QUICK BACKGROUND FOR THOSE LESS FAMILIAR WITH OXYGEN STORAGE
Although patients need oxygen in its gaseous state, most healthcare facilities store it in its liquid state which requires far less space. When transitioning to a vapor, liquid oxygen will dramatically expand—approximately 860 times. Thus, liquid storage is most efficient (and practical).
Before oxygen can enter the building piping, the liquid state must pass through vaporizers, absorbing ambient heat from the outside air, transforming the liquid into a vapor. At this point, the oxygen is at too high of a pressure for “normal” use, so it is passed through pressure regulators, then into the piping systems, providing oxygen to outlets at patient bedsides.
POTENTIAL PROBLEMS ACCOMMODATING THE INCREASED USE OF VENTILATORS:
Vaporizers icing – Vaporizers are comprised of piping with metal fins to aid in the process of warming the very cold liquid. Ice forms on the fins as moisture from the outside air condenses on them. Some ice formation on the vaporizer fins is to be expected, but if excessive ice forms, the ice acts as an insulator and the vaporizers become less efficient at converting the liquid oxygen to vapor. In extreme cases, this can reduce the flow of oxygen available for treating patients.
Inadequate pressure – Undersized pressure regulators on the main oxygen line and/or undersized distribution piping within the building, can cause “pinch points’ that result in inadequate pressure for proper ventilator function.
Inadequate oxygen storage – With the increase in ventilator deployment, a surge in oxygen use can be expected. Typically, the liquid oxygen system has a primary tank that stores enough oxygen to last anywhere from several days up to several weeks at normal (non-health crisis) use rates. Additionally, a hospital must have a code-required reserve tank, sized to hold a minimum of a 24-hour supply. The reserve tank is often sized to hold a few days’ supply, to be safe. Ventilators use far more oxygen than most other treatments – so, as a very broad rule of thumb, if you double the ventilators, you nearly double the oxygen needed for the healthcare facility. Inadequate storage could result in needing deliveries more often than feasible.
OXYGEN SYSTEM ALARMS:
Another issue, though seemingly less critical, is the operation of required alarms. All critical care areas are required to have oxygen system pressure alarms. Typically, these are near the Nurse Stations for each critical care area. The normal parameters for oxygen system pressures are 55 psi entering the building and 50 psi (average) at outlets. NFPA Standards call for a low-pressure alarm to sound at 20% below regular system pressure and a high-pressure alarm to sound at 20% above regular pressure. The 20% +/- is somewhat arbitrarily set, as a reasonable operating range typically might be 40 psi (low end) and 60 psi (high end). If an increased oxygen demand causes a dip in pressure, outside of that range, the system has not necessarily “failed”. While alarms sounding may be quite stressful for clinicians and patients, most ventilators can operate at lower oxygen inlet pressures, lower than the “low-pressure” alarm. During these low-pressure events, ventilators typically pull in filtered room air or medical air (depending on the device) to supplement the pressure loss. Under these circumstances, the accuracy of O2 being delivered may be affected.
Given the unrealistic ability to redesign and construct piping systems during the midst of the COVID-19 pandemic, what can a healthcare facility do in the short term? A few recommendations for the SHORT-TERM:
Place simple 3’ or 4’ diameter portable fans to move more air over vaporizers to help prevent over-icing.
Replace undersized regulators with larger alternatives. These regulators are required to be sized to be fully redundant. The oxygen supplier who maintains the source equipment can replace these one at a time without interrupting the supply.
Increase pressure in the oxygen distribution system by adjusting the outlet pressure of the main regulators.
Adjust the system pressure alarm range to prevent “nuisance” alarms. In many cases, the medical gas system pressure alarms are internally adjustable. Of course, decisions like this need to be made carefully and should have input from staff, building engineers, oxygen source equipment vendors, and licensed medical gas system certifiers who are familiar with the system.
For extreme cases of inadequate O2 supply, employ oxygen suppliers to provide trailer-mounted oxygen systems. These systems include liquid oxygen storage, vaporizers, and regulators, supplementing the oxygen supply by connecting to the building’s Emergency Oxygen Supply Connection (EOSC). NOTE: The National Fire Protection Standards adopted by most authorities- call for every hospital oxygen system to have an EOSC. To date, these trailer systems are in limited supply too, but more are being readied.
In the LONG-TERM, resizing source equipment and some sections of these piping systems may be necessary to better equip hospitals and intensive care units. If/when a second wave of COVID comes to fruition and ventilators are still considered to be the best treatment option, more ventilators will likely be in circulation with more trained staff (compared to our current state). The gas systems serving them need to be ready.
BeaconMedeas, a leading specialist in the design, education, supply and installation of piped medical gas distribution systems, published additional, useful information on this topic of sizing medical gas systems for COVID-19. Mark Allen, VP Standards Development & Education led the development of this educational piece available here.