Medical gas pipeline system as a limiting factor for hospital oxygen supply during COVID-19 outbreak.

INTRODUCTION

The coronavirus disease-2019 (COVID-19) first outbreak in India in September 2020 led to hospitals augmenting ventilator numbers and oxygen outlet enabled beds.[1] Simultaneous assessment of required increase in the supply of medical oxygen, emergency oxygen manifold, augmenting the storage capacity of liquid medical oxygen (LMO), and capacity of medical gas pipeline system (MGPS) was required.[2] The present case scenario highlights the insufficiency of hospital MGPS, consequent to augmentation of ventilator and oxygen outlet enabled beds in hospital. The anaesthesiologist can play an important role in the prevention of such incidents and measures can be taken for augmentation of MGPS.

Brief description of the incident

The MGPS was initially designed to supply oxygen to 60 intensive care unit (ICU) beds and 300 non-ICU beds of a 1000 bedded tertiary care hospital. Due to the rapid surge of COVID-19 patients, the hospital administration converted 70% of in-patient wards into ICUs and high dependency units. A total of about 200 patients were on ventilator support and about 450 patients were on oxygen supplementation by mask. Eventually, there was drop in pressure at the wall outlets to 3.4 bar and low-pressure alarm in various wards got activated. Both pressure-reducing valves of duplex system (main and reserve) in MGPS, which allowed total oxygen flow of 4000 + 4000 litres per minute (LPM), were insufficient to maintain wall outlet pressure of 4.2 bar. Despite adequate availability of LMO, these flow limiting valves were the bottlenecks in entire MGPS. Two hundred of 450 patients, who were on venturi mask and non-rebreathing mask, were shifted from MGPS supply to oxygen concentrators and portable oxygen cylinders. Fifty patients requiring less than 5 LPM oxygen were transferred to other COVID-19 care centers.

A team consisting of medical superintendent, anaesthesiologists, assistant nursing superintendent was constituted. The action plan was to augment the current capacity of pressure reducing station [Figure 1a]. A plan was chalked out and implemented [Table 1].

Figure 1

(a) Layout model for installation of additional pressure reducing station. (b) New higher capacity pressure reducing station (black arrow), T-connection (Red arrow) to direct oxygen flows to new pressure reducing station

Table 1

Formulated plan to augment the capacity of the pressure reducing valve of MGPS

Action plan
Restrict the admission of patients till the problem is resolved
Installation of duplex pressure reducing valve with flow capacity of 10,000 LPM each as proposed by the MGPS engineers [Figure 1(a)].
Augmentation of emergency manifold supply from 1700 LPM to 5100 LPM by installing two additional emergency manifolds.
Increased demand of oxygen was met by dividing the supply source between emergency manifold and bedside cylinders during planned shutdown. However, for safety reasons, patients on ventilator were kept on central emergency manifold supply as suggested by the anaesthesiologist.
Allocation of responsibility to nursing officers and anaesthesia residents to identify patients with mask and make excel sheet beforehand, so that they can be transferred to bedside cylinders when LMO supply is shut down.
Prepare a workflow chart, to be followed by team at the time of switching from LMO supply to emergency manifold and portable cylinders supply.
Stock up 1000 D type (7000 litres each), 1000 B type (1500 litres each) cylinders, 200 oxygen pressure regulators with flowmeters, 100 single stage double gauge pressure regulators to augment oxygen supply.
Creation of WhatsApp group for to and fro flow of information from wards and ICUs to manifold room.

ICUs: Intensive Care Units; LMO: Liquid Medical Oxygen; LPM: litres per minute; MGPS: Medical Gas Pipeline System

During changeover from LMO supply to emergency manifold supply, there was low pressure alarm at various wards for 2–3 min, which gradually diminished as 5000 LPM of oxygen supply was restored by three emergency manifolds. Nursing officers, supervised by anaesthesia residents, ensured safe transition from central supply to bedside cylinder supply in designated patients. As planned, higher capacity pressure reducing station was mounted in parallel to the existing pressure reducing station [Figure 1b]. The installation of new pressure reducing station took 110 min to complete and 80 D type cylinders were consumed at emergency manifold. Pressure-reducing valves were checked for any leaks. Patients on portable cylinder supply were transferred back to MGPS supply outlets. There was no incidence of hypoxia in any patient during the installation.

DISCUSSION

The MGPS of a hospital is designed by estimating the requirements of medical gases.[3] The requirement of oxygen is assessed as total oxygen flows to be supplied per square foot area or number of beds at terminal units.[3] The MGPS is built with 1.5 times surge capacity than expected load.[4] The pressure-reducing station in MGPS reduces high pressure (10.5 bar) of oxygen being received from LMO tank to delivery pressure of 4.8 bar in hospital MGPS. The delivery of reduced pressure in MGPS protects the terminal outlets from damage due to high pressure. While reducing pressure, it also limits the maximum flow through it.

To avoid such problems, assessment of average demand, future expansion of facility, any unexpected surge should be assessed at regular intervals.[256] Assessment of average consumption per ventilator may provide more accurate estimation.[3]

In a similar incident, overall oxygen demand never exceeded the capacity of MGPS. But there was failure of oxygen supply to certain areas due to diversion of oxygen flows to areas with excess demand. The grouping of patients based on clinical needs had created uneven demand on MGPS. After redistribution of patients to provide equal spread of oxygen demand, the issue was resolved and the hospital administration was able to allow admission of more patients than before without any need for upgrading the MGPS.[7]

Any exercise involving partial or complete shutdown of MGPS or switchover to alternate source of medical oxygen such as cylinder manifold and bedside oxygen cylinders is a complex task associated with risk to the life of patients. Cutting of MGPS pipeline has been considered as highly hazardous.[5]

The assigned role of the anaesthesiologist in the medical gas committee (MGC) is to check MGPS between the terminal unit and the patient to ensure safe delivery of medical gases.[89] The COVID-19 scenario is quite different and it has changed the responsibilities of the MGC and anaesthesiologist as well. No one other than the anaesthesiologist can come upto the expectations of the hospital requirement in augmenting the oxygen supply. The anaesthesiologist should be involved not only in the downstream oxygen supply but also needs to have a strong knowledge of the upstream supply system from MGPS to manifold, LMO tank and oxygen generator plants.[10] He can also advise on rational use of oxygen, bedside oxygen concentrators, avoiding wastage and also help in conducting oxygen audits.[1112] There should be a full-time dedicated biomedical engineer, trained technical supervisor in electrical or mechanical stream for maintenance operations and running of medical gas plant.[511]

A hospital should not rely on a single MGPS from the source.[11] A sudden disruption of MGPS during disasters shuts down oxygen supply to the entire hospital.[1011] Some measures can be taken to prevent oxygen supply-related issues such as having adequate cylinder manifold, establishment of oxygen generator plants and having oxygen concentrators in reserve. Oxygen flowmeters should be removed from the pipeline oxygen supply when not in use to ensure zero leak.[212] The admission of patients requiring ventilatory care in any area of the hospital should not exceed the diversified flows of MGPS to that area.[7]

CONCLUSION

Any planned shutdown of liquid oxygen supply, which is considered highly hazardous requires meticulous planning involving MGC, biomedical engineers, plant staff as well as hospital staff and anaesthesia trainees. Hospitals should periodically assess MGPS requirement of the hospital for any planned expansion of facility, future oxygen demand and any unexpected surge. Role of the anaesthesiologist is crucial in supervising operations, maintenance and running of medical gas plant and MGPS supply of the hospital. Teaching, training, and visits to the manifold should be emphasised in the anaesthesia curriculum.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.