During the second wave of COVID-19 the entire country has seen a shortage of beds for the treatment of moderate, severe and critical patients whose respiratory system was
predominantly affected and O2-therapy was a profound role in treating them. This situation has led us to managing the supply and resources available for continuous supply of
oxygen and various measures were implemented as conservation strategies to prevent wastage of oxygen. This review article will summarize the sources of oxygen, best practices
in planning the oxygen supply and conservation strategies like optimal O2-therapy, careful monitoring and escalation as well de-escalation of O2-therapy when indicated.
Keywords: O2-therapy, Oxygen sources, Conservation strategies, O2-supply
The corona virus has made a great impact in the history affecting more than 18 crores of people all over the world. India has its effect of around three crores of cases
so far and that is about 16% of overall cases. Corona virus has become a deadly disease as it predominantly affects the respiratory system. O2-therapy has a profound role in
the treatment of COVID-19 patients that too the demand for oxygen has been increased during the second wave attack. So, the rational use of oxygen has become mandatory and need
of the hour. This article will have a review on best practices in oxygen supply, management, conservation and economics .
There are three types of oxygen sources in the oxygen supply system
- Primary supply
- Secondary supply
- Reserve supply
- Hospital Manifold with oxygen cylinders provided by the oxygen generator/suppliers are pressurized containers used to supply oxygen.
- Oxygen concentrators are used to concentrate the oxygen from the ambient air by selectively removing nitrogen to supply oxygen enriched air.
- Oxygen generators are used to extract medical oxygen from the air.
- Liquid oxygen tanks (liquid oxygen gasification) are used for oxygen supply. Uninterrupted oxygen supply is an essential in hospital facility and that too when the
demand is high, we need to be prepared enough to meet the need with the supply and the source (Figs. 1–4].
Fig 1. Oxygen cylinders
Fig 2. Oxygen concentrator
Fig 3. Oxygen Plant
Fig 4. Liquid oxygen tank
The appropriate choice of oxygen source depends on many factors, including: the amount of oxygen needed at the treatment centre; the available infrastructure, cost,
capacity and supply chain of local production, the reliability of electricity supply and access to maintenance services and spare parts. Oxygen need has to be estimated
based on the bed facility and the severity of the patients. In specific to requirement for COVID-19 cases, 75% of the cases are classified as severe and 25% as critical.
Based on this the requirement needs to be estimated (WHO surge calculators can be utilized) [2,3].
A randomized control study was conducted among 30 hospitals in South India to assess the vulnerability of oxygen supply system to disasters. It was found that the primary
source of the oxygen supply to the hospitals was 48% by cylinder manifolds, 40% by liquid oxygen tanks and 12% by oxygen concentrators. Backup source/reserve supply was found
to be available in only 64% of hospitals among which 44% with cylinders, and 20% with liquid oxygen. Only 52% of the hospitals had a reserve supply in a different location from
the primary. Changing the source of supply was manual in 44% of hospitals and only 20% had an automatic change over system installed. There were effective zonal and central
alarms in only 12% of hospitals. Most of the hospitals rely on a single pipeline from a single location inviting mishaps during the disasters .
Best practice in oxygen supply
- Auto changeover from supply to backup to provide continuous supply of oxygen
- Double pipeline from the primary source
- Primary supply should be sufficient for 4–5 days and reserve supply for 3 days
- Reserve supply at a different location
- Manifolds and concentrators at highest level to mitigate flood and other disasters
- Cylinder manifold should not be placed at the same site as the LMO and oxygen concentrators [5,7].
Oxygen Conservation Strategies
- 90–94% of SpO2 for a patient itself is safe
- 55–70 mmHg of PaO2
- Oxygen deliver can be minimized in litres for patients with good haemoglobin and good cardiac output. Have a look at signs of hypoxia
- Prone/semi-prone positioning improves V/Q matching and decreases FiO2 requirement
- Role of sedation and paralysis reduces O2 demand, decreases lung injury and control minute ventilation
- Avoid 100% of O2 supply to treat pneumothorax/pneumomediastinum with subcutaneous emphysema
- Stopping inappropriate therapy at the earliest.
(1). Escalation and de-escalation strategy
Escalation of O2-therapy – preferable under current constraints
- Early use of positive pressure CPAP/BIPAP/NIV
- Avoid oxygen guzzlers; Minimize HFNC nebulizers
- Use 6 to 8 Lpm non breather reservoir mask instead of 40 and 60% venture devices
- Use a mask over nasal cannula/ HFNC to increase FiO2
- Nebulisations – use air for patient who are not on ventilator
- Innovative devices
- O2 consumption in ventilators – lowest baseflow settings, minimize leaks (tubing, cuff)
- Low FiO2 alarm.
(2). System level strategies
- Preventive maintenance
- Oxygen rounds/audit – checking leaks, flow meter checks, check if FiO2 can be lowered, reverting after 100% FiO2 for suction, appropriate SpO2 alarm limits
- Distribute critical care load (split)
- Have a disaster plan
- Flow-meters calibration
- We can even extract oxygen from cylinders with less bar (using till the last).
(3). Ventilator strategies to reduce oxygen consumption
- Invasive ventilation saves oxygen
- COVID lung is very prone to Ventilator induced lung injury (VILI)
- Preventing VILI helps in saving oxygen.
(4). Measures to prevent VILI
- Use low tidal volume which will reduce minute ventilation and thereby reduces oxygen Recommended TV: 4–6 ml/kg ideal body weight
- Driving pressure be less than 15 cm H2O
- Optimal PEEP helps in keeping the lung open
- Use the lowest baseflow setting possible
- Monitor and minimize leak volumes (tubings, cuff pressures)
- Operating ventilators with concentrators (low flow inlet, FiO2 alarm).
(5). NIV considerations
- Ensure good mask fit at all times
- Use appropriate sedation to avoid hyperventilation
- Use the bare minimum pressure support/IPAP
- Covid patients require PEEP and CPAP support [6,7].
Common conservation strategies
- Use liquid oxygen(LOX). The quantitative relation of LOX to gasified gas is 860:1, allowing the storage of terribly giant quantities of gas in a very smaller
- Mobile 3000-gallon LOX units can be connected to a hospital’s secondary O2 system to refill as needed
- Use an Oxymizer or similar reservoir device to conserve oxygen delivered via a nasal cannula.
- Oxygen delivery can be hampered by shortages of sterile water used for humidification. In these situations, distilled water might function a substitute.
- Regular audit should be done to check for oxygen leakage from equipment. Anesthesia machines is unplugged once not in use, as they may have been left on and have a slow
leak of oxygen. Rooms with piped-in oxygen which are left on unknowingly should be inspected, including rooms where oxygen use is less frequent, e.g., labour and delivery.
Be sure to turn off flow to manual resuscitators that are not in use.
- Hospitals should survey the pipes that feed oxygen into potential high-demand areas, such as the emergency department and intensive care units.
- A Y-connector can be used to deliver oxygen from a concentrator to two patients at a time who are on the same flow of oxygen. The FiO2 are doing to be constant
between the two patients, however flow is going to be reduced and can vary based on downstream resistance.
- It is not uncommon for patients to be switched between high-flow nasal cannula (HFNC) oxygenation and non-invasive positive pressure ventilation (NIPPV).
As a result, HFNC and NIPPV circuits can be used up as patients are started on HFNC, then NIPPV, and then subsequently intubated. To conserve circuits,
consider either HFNC or NIPPV for a given patient, and avoid both if you suspect your patient is going to require the ventilator.
- Deployable Oxygen Concentrator Systems (DOCS) can be placed in strategic areas or at large hospitals to refill H, D, and E tanks.
- Whenever possible, use evidence-based conservative oxygen saturation targets (e.g., SpO2 90–94%, rather than >98%).
- Use an O2 face mask or a surgical mask over high-flow nasal cannulae to act as a reservoir. This may allow use of lower flow to achieve the same SpO2. Surgical
masks over HFNC may have infection prevention benefits.
- Large H cylinders can be fitted with manifolds to service multiple patients at the same time instead of just one.
- If there are enough portable oxygen concentrators, two can be used on the same patient (with a simple mask plus a nasal cannula) to raise the amount of oxygen
delivered without having to use the hospital’s in-line supply or H, D, or E tanks
- Consider using warm water sprinkler systems to keep the outside vaporizers from freezing during cold temperatures, as high oxygen demand may increase the
risk of lines freezing, leading to shutdown of a facility’s in-line system .
O2 Stewardship programme
This can be introduced in the hospital for rationale use of oxygen. The measures in oxygen stewardship programme includes
- Oxygen dashboard on consumption, available sources updated on daily basis which includes he primary supply, secondary supply and reserve supply etc.
- Optimizing the use of oxygen among patients.
- Audit/ Oxygen rounds to assess the leaks of the tubing, pressure gauge, turning off the flow when not in use, monitoring saturation periodically and promptly decrease
the FiO2 once target SpO2 achieved .
Managing oxygen demand
Oxygen cut off drill – Mock drills to be conducted in all the hospital on a regular basis to manage and to face the situation when there is cut off of oxygen.
Message to be sent to all the doctors/consultants regarding the shortage of oxygen with the approximately calculated duration till when the oxygen supply is
sufficient to handle the patients.
O2-therapy is critical for the successful treatment of COVID-19 patient. It improves oxygenation and reduces mortality in COVID-19 patients. This review article focuses
on the oxygen supply and best practices of planning the oxygen source and conservation strategies in the aspect of patient, device and system wise. Oxygen is not just a small
treatment measures but it is a drug and hence should be prescribed, administered and monitored by trained staff. In the current pandemic scenario, O2 scarcity is experienced
by all health care facility irrespective of their size, optimal utilization of oxygen is the need of the hour so that a maximum number of patients can benefit from the judicious
use of O2.
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