MEDICAL GASES
Table 1. Oxygen – Patient floors. Pipe size Pressure drop/100 Ft (PSIG)
1 ”⁄2 3 ”⁄4 1”
1.06 1.06 1.01
Capacity (LPM) 260 660
1400
Number of ventilators @55 LPM Number of ventilators @10 LPM 5
12 25
26 66
140 Note: This represents the maximum number of ventilators on a patient floor or wing served by the pipe sizes shown.
rarely require service outside of planned preventive maintenance. Scalability in some industries refers to
the pre-planned ability to add or subtract components, or quickly swap out different sized components. These methods are used to increase or decrease supply. Given the critical nature of medical oxygen, making changes to the bulk equipment or pipeline on the fly is impractical, so proper sizing instead of scalability should be considered in view of demand variability. Resiliency includes the ability to meet changes in demand over time. Average and peak consumption rates should still be calculated as these will represent regular operating conditions. Next, the desired surge capacity must be determined. Clinical input during this step is important to estimate how many additional devices could be activated and what the corresponding flow rates would be. A ventilator could add between 20 and 75 litres per minute (LPM) to the flow demand. A high flow therapy unit could add up to 65 LPM.
Caught short Numerous hospitals have projected and, in some cases, experienced actual demand increases of up to 20 times their historical average. This required significant investment for urgent upgrades of their bulk systems and pipelines. In other cases, hospitals have expanded with temporary facilities, which required separate bulk oxygen supply systems as the existing installations lacked resilience to meet the extra demand.
Resilient design impacts the overall
bulk installation including the reserve subsystem. Equipment sizing was previously based on historical facility data plus calculated increased loads from expansion. During extended periods of peak/surge usage, traditional system autonomy would decrease. Resilient reserve subsystems should be sized in accordance with the highest level of demand the facility anticipates. The need for synergy between the bulk gas equipment and medical gas pipeline system is heightened during pandemic- type demands. The entire hospital piping network including the supply piping from the bulk installation must be able to support the increased flow rates. Pipe sizing has also been calculated in
the past based on historical data and may even have been downsized to reduce construction budget. COVID-strained facilities have experienced reduced oxygen flow and/or pressure at the medical gas outlets in patient care areas served by smaller diameter piping. The further away these areas are from the source system (the bulk installation), the more pronounced the issue becomes. Resilient piping design decreases pressure losses and enhances the ability to care for the most vulnerable patients. California-based integrated managed
care consortium Kaiser Permanente provides the following tool (see Table 1
IFHE DIGEST 2022
and Table 2) to estimate the maximum flow capacity of the pipes of different diameters and how it translates to the number of ventilators or low flow respiratory devices that the pipeline can service.1
Upgrade approaches Healthcare facilities have taken different approaches to their oxygen system design. Some hospitals have decided not to upgrade the entire pipeline but just the part that supplies critical wards, such as ICU. Some decided to supply different parts of the pipeline from two bulk oxygen systems, which offers additional benefits. It increases redundancy – two complete systems instead of one, both capable of meeting the demand of the entire hospital. Two systems also mean two independent feeds to the hospital, so if the pipe from one system is damaged, the second remains intact. Upgrading the critical portion of the pipeline is also less expensive than updating the entire medical oxygen pipeline. Unfortunately, not all facilities were
able to prepare for the surge in oxygen demand during the pandemic and faced the need to stretch their existing bulk supply systems beyond their normal capacity. This part of the article describes the methods that were used and proved to be effective.
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