HOSPITAL OXYGEN SYSTEMS


VIE telemetry data is to provide insight into tank refill timing, whereas fault monitoring and calculation of flow rate is well outside of the sensor specification, being far too noisy to determine much more than weekly average flow rate (even with significant signal processing). Where no flow meter is in place, installing invasive flow meters (Thermal Mass or Vortex) is a cost-effective option. However, as the hospital O2


be taken offline for installation, non- invasive, ultrasonic gas flow meters are a better alternative. Suitable devices are readily available and sufficiently affordable. The flow meters can be independently monitored or connected to the hospital’s centralised Building Management System (BMS). Using integrated flow meters, alarms can be configured to alert the Estates team in case of abnormal O2


flow rates. Demand side A more detailed view of the O2 usage in


different areas of the hospital can be used to calculate the maximum number of treatable COVID-19 patients. However, this calculation depends on various factors, which must be carefully examined and evaluated with clinical experts, including: n Hourly and daily O2


usage variation, and the potential temporary usage peaks.


n Different stages of bed and cohort planning, and potential ward usage peaks.


n Disease severity patterns with differing proportions of ICU/non-ICU patients. n Evolution of O2


usage patterns due to


changes in treatments (change from high to low-flow devices). n Non-COVID-19 O2


usage per demand (base load)


with changes to elective care schedules. The reported average O2


COVID-19 patient differs between hospitals. To establish a reliable number of treatable COVID-19 patients in each hospital, the electronic patient record (EPR) system provides valuable data. For patients with acute respiratory distress syndrome (ARDS), various treatments are applied depending on the severity of the illness. Whereas patients with mild symptoms are mainly treated with different facemasks (e.g. a Venturi mask) or nasal cannulas, many ICU patients require mechanical ventilation. For non- invasive treatments, the amount of O2


provided is recorded in the EPR by clinical staff and regularly updated. Most mechanical ventilators can be programmed to automatically log all ventilation parameters into the EPR.


Alignment of supply and demand data Since the manual O2


data reporting for


non-invasive treatments is often dependent on readings of the medical gas flow meter in the wards, over- or under-


Establishment of maximum capacity utilisation:


Despite the absence of flow meters for validation, preliminary calculations can provide an estimation of the number of treatable COVID-19 patients in CUH. The non-COVID-19 O2


base load significantly


decreased, from the usual 1100–1300 L/min, as the hospital was cleared from the beginning of March to the 1 April. In April, a base load of only 220-350 L/min remained (approx. a quarter of the usual)


3000


2500


2000


1500


1000


system cannot


500


n Hourly flow rate n Daily flow rate


0 January February March Month (2020) Regular flow rate – hourly and daily (excluding refill and repressurisation points). reporting of the actual O2 consumption


can occur. Furthermore, duplicate and erroneous patient entries in the EPR system can distort the data accuracy. Therefore, it is important to check the validity of the demand side flow rate by comparing it to the complementary supply data. Due to the data collection issues in the EPR system, as well as potential VIE telemetry inaccuracies, a complete alignment of both data sets was not achieved. However, the magnitude of the total flow rate and hourly/daily patterns should approximately match to confirm the validity of both data sources. The EPR data and VIE data show generally similar trends and magnitude in the period from 16 February-12 April. However, in multiple periods such as the 16-20 March, and 7-12 April, large discrepancies of up to 500 L/min occurred. At below 50% of maximum capacity, those differences may not seem important. However, with higher capacity utilisation, those differences could have a more significant impact.


in preparation for more COVID-19 patients. The following calculation parameters were provisionally estimated from the EPR data, and need to be confirmed once the flowmeter is installed and enough data is collected: n Share of COVID-19 patients in ICU of total COVID-19 patients: 25%.


n Share of COVID-19 patients in non-ICU wards of total COVID-19 patients: 75%.


n Share of COVID-19 ICU patients that receive O2 85%.


treatment on a given day:


n Share of COVID-19 non-ICU patients that receive O2 day: 30%.


n Average O2 n Average O2 patient: 12 L/min. usage per oxygenated non-ICU patient: 5 L/min.


Table 1 summarises the maximum number of treatable COVID-19 patients with varying base loads. In the second column, the normal base load of 1300 L/min and the calculation parameters are assumed. With these parameters, CUH could treat 340 COVID-19 patients before reaching the alarm level of 2550 L/min, of which, on average, 149 would require O2


treatment.


The third column summarises the maximum number of treatable COVID-19 patients – given the reduced COVID-19 base load of 350 L/min. With the lower base load, CUH could treat 598 COVID-19 patients before reaching the alarm level of 2550 L/min, of which, on average, 262 could receive O2


treatment. Table 1. No. of patients before raising capacity alarm (2550 L/min).


Normal base load COVID-19 base load (1300 L/min)


COVID-19 patients of which ICU patients of which non-ICU patients


Oxygenated COVID-19 patients of which ICU patients


of which non-ICU patients


340 85


255


148.8 72.3 76.5


(350 L/min) 598


149.5 448.5 261.6 127.1


134.6 January 2021 Health Estate Journal 47 treatment on a given usage per oxygenated ICU April May


Flow rate (L/min)


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