How do I know how much oxygen my facility is using or needs?

How do I know how much oxygen my facility is using?

There are multiple strategies to quantify oxygen consumption and need for a facility. The optimal strategy may vary by facility size, oxygen source and intended use of the data. Below are several potential strategies for quantifying oxygen consumption broken down by supply side and demand side approaches. 

Of note, if using data to forecast oxygen needs, plan for surges, or expand facility capacity, then current oxygen consumption may grossly underestimate optimal consumption (i.e. you must also account for patients and potential patients who currently do not have access to oxygen due to inadequate current supply).

Supply side indicators:

Measuring facility oxygen consumption may (in some settings) be most accurately done by measuring production of oxygen at the facility source. This may not always be feasible depending on the availability of special equipment and/or human resources to log such data.  

• Cylinders – logs (including number, pressure and size) of cylinders delivered to wards and/or delivered to the facility
• Portable oxygen concentrators – logs of use (hours of operation can be accessed from built in hour meter found on most units, though flow rates must be known or can be estimated)
• LOX – logs of cryogenic cylinders filled and emptied based on onsite biomed logs or LOX provider delivery logs; Log of changes in mass of LOX cryogenic storage tank contents may also be available 
• Oxygen PSA Plants – monitoring output of PSA plants may depend on how the plant is used – i.e. filling cylinders (in which a cylinder log may be most useful) vs directly supplying a reservoir and/or the facility via piping. Some plants may continuously display hourly flow rate of output which may be logged onsite. An alternative method for PSA plants that directly supply a facility via piping is to record flow with a mass flow meter (Example of mass flow meter) which can be configured to display and save/send such data automatically or detect flow problems. 

Quantifiable demand (patient) side indicators:

Quantifying oxygen consumption from the demand side can be challenging and time consuming. This may be the only option when supply side estimates are not available or when you sek to estimate consumption for specific locations within the hospital (e.g. the intensive care unit) or specific patient populations (e.g. COVID19 patients). 

When measuring or estimating oxygen consumption, one must attempt to account for leak in the O2 infrastructure as a common source of underestimating oxygen demand. This may occur for many reasons including: human error (e.g. inadvertently leaving an unused flow meter on), suboptimal practice patterns (e.g. titrating to too high of an SpO2 target) or inadequate equipment or maintenance (e.g. poorly fitted regulators, cracked tubing or piping). (Top 10 ways to conserve oxygen)

• Crude modeling of oxygen consumption by patients can be done by using oxygen consumption modeling tools but yields imprecise results.
• Pragmatic primary data collection can be done by recording (at the bedside or via electronic medical record) current consumption per patient in a facility. This includes oxygen delivery device type and settings. While total consumption will vary throughout each day for each patient and thus for the facility as a whole, it may be practical to sample such data once per day or less to obtain snapshots of facility oxygen consumption (Oxygen quantification tools compilation)
• Comprehensive primary data collection can be done daily or multiple times per day to provide the most accurate demand side estimates of oxygen consumption though require considerable resources or comprehensive EMRs. 

Common pitfalls in estimating O2 consumption

• Not accounting for leak on the O2 infrastructure
• Inaccurately estimating device consumption (e.g. BIPAP/CPAP leak, ventilator bias flow etc)
• Not accounting for increased flow demand due to decreased oxygen concentration (i.e. a cylinder filled by a low quality supply or a PSA being outstripped of capacity or that is poorly maintained may produced FiO2 that is much lower than expected and thus users may attempt to improve persistent hypoxemia in a patient by increasing flow. Thus, flow consumption may overestimate true demand)
• Estimating only current consumption and not accounting for future increases and decreases in need