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The design and conventional configuration of medical gas systems in hospital

The medical gas system is an essential safeguard for hospital medical services and one of the core support systems of the hospital. This article studies the design phase of the medical gas (mainly medical oxygen, positive pressure air, and negative pressure vacuum suction) system in hospital. By calculating the required gas usage and pipe diameter, this article aims to refine the design and conventional configuration of the medical gas system. It employs scientific methods to ensure the safe use of medical gas, thereby safeguarding the medical safety and quality of the hospital.

The COVID-19 pandemic has spread globally. Despite the hospitals being well-known domestically and their medical gas systems being designed according to industry standards, the demand for oxygen increased due to the transition from normal oxygen inhalation to high-flow oxygen inhalation for most patients, as well as the use of non-invasive ventilators, invasive ventilators, and even ECMO artificial lung systems. This led to a shortage in the original gas supply system. By learning from these issues, the design and conventional configuration of the medical gas system were fully considered in the early stages of the hospital's design. 

Medical gas refers to the gas used in hospital departments for treatment, equipment power source or anesthesia and other fields for the treatment of patients, mainly including medical oxygen, positive pressure air, negative pressure vacuum suction, carbon dioxide, nitrogen, laughing gas or other special gases, of course, the discharge of surgical anesthesia waste gas is also included in the scope of medical gas management. 

1. Design of Medical Oxygen System

During the pandemic, a hospital in Wuhan with 700 beds required oxygen for each bed, and almost all critically ill patients needed ventilators. Ventilators have specific requirements for oxygen pressure, generally above 0.4 Mpa. In extreme use cases (where the usage reaches ten times the daily peak), the pressure could not be increased, and the flow could not keep up. The vaporizers had completely frozen, and the valve groups were severely frosted. The problem was resolved by modifying the medical gas system, using medical molecular sieve oxygen generator system with PSA. With a complete product system and solutions, ETR can meet the medical oxygen demand of large, medium, small and medical and health institutions/clinics. At the same time, support oxygen cylinders filling were used daily from the backup manifold. 


Oxygen Usage Calculation: The calculation of medical oxygen usage in hospitals needs to refer to the GB50751-2012 "Medical Gas Engineering Technical Specification" Appendix B Medical Gas Source Flow Calculation Table. The table provides specific numerical values for the gas usage flow of various medical gases in different functional areas. Using these data combined with the beds in various functional areas of the rehabilitation hospital, the oxygen usage can be calculated using Formula.

oxygen count

Q——Calculated flow of gas source (L/min);

q1——Standard oxygen therapy average flow (L/min), recommended values is 5∼6L/min;

q2——High-flow oxygen delivery average flow (L/min), recommended values is 15–25L/min;

q3——Average flow per terminal of ICU bed (L/min), recommended values is 20–30L/min;

n1——Number of beds in ward;

n3——Number of oxygen terminals in ICU;

η1——Coefficient of simultaneous use of oxygen terminal in ward, recommended values of 0.7–0.9;

η3——Coefficient of simultaneous use of oxygen terminal in ICU, recommended values of 0.8–1.0;

θ——The proportion of serious patients converted into respiratory distress patients (Proportion of patients using high-flow oxygen therapy), recommended values of 0.30–0.45 for novel coronary pneumonia. For other acute respiratory infectious diseases, it is taken according to specific conditions, and the proportion of critically ill patients admitted to hospitals is the larger;

Qoth——Operating room gas, other oxygen terminal gas. It can be calculated according to the “Technical code for medical gas engineering” (GB 50751–2012), and it is recommended to use the coefficient η according to the actual value.

Medical Gas Pipeline System

In medical gas systems, the significance of gas pipe sizing cannot be overstated. Gas pipe sizing refers to determining the optimal diameter and thickness of pipes used in a medical gas system. It's a calculated choice based on various factors such as the type of gas being delivered, the flow rate required, the piping system's length, and the pressure under which the gas is supplied. 

Copper: Widely used due to its excellent corrosion resistance and ability to handle high-pressure conditions.

Stainless Steel: Known for its strength and durability, it is ideal for systems requiring high purity levels.

ALL medical gas outlets must be covered by a Zone Value Box on the same floor they serve. Copper seamless pipes with fluxless silver brazing are used which should be as per ASTM standard and Lloyd's certification. They are intercepted by the area valve service units (AVSUs) and area alarm panels (AAPs). AVSUs are placed in each clinical sector, to cutoff the gas delivery to the area beyond it during maintenance or to handle emergency. AAPs display the line pressures and have audiovisual alerts. All pipelines should be color coded with colored bands put at intervals of every 3m.

Medical Gas Zone Valve Box-01

2. Medical Central Suction System

Suction System Central Station: It is recommended to use oil-type vacuum pumps, automatic control systems, bacterial filters, exhaust gas treatment systems, vacuum tanks, etc., to make up the suction system central station. It is suggested to choose 2 to 3 vacuum pumps, each with a flow rate of not less than 300m³/h, one in use and one in reserve or two in use and one in reserve. Select 2 to 3 vacuum tanks with a volume of 2m³, which meet the GB150 standard requirements.

medical vaccum pumps

3. Medical Compressed Air System

Compressed Air Station: The design of the compressed air station uses 2 to 3 oil-free air compressors, each with a flow rate of not less than 1.5m³/min; the air after-treatment uses a heatless regenerative adsorption dryer and a 3-stage filter with a filtration precision of 0.01μm.

Oil Free Medical Compressed Air System-01

4. Medical Gas Monitoring System

Each department needs to set up a medical gas monitoring and control box to monitor the pressure of each system in real-time, and to alert users and maintenance personnel in a timely manner when abnormalities occur. Medical institutions with conditions should set up a medical gas monitoring system that can display the operating status of the machine room and each ward's equipment in real-time, and can monitor the flow and pressure of the medical gas system of each department, and can provide early warning and facilitate summary statistics within the hospital information system.

Medical Gas Monitoring And Alarming System

5. Basic Technical Requirements for Medical Gas System Design

The design of the medical gas system should meet the following six basic technical requirements, including compliance with industry standards for medical oxygen, negative pressure, and compressed air system pipelines, ensuring reliable grounding of medical gas pipelines, not allowing medical gas system pipelines to be laid on the same rack as gas pipelines, and other detailed requirements.

Due to the differences in the scale and medical technology of each hospital, the specific parameters and conventional configuration requirements of the medical gas system are not the same, but the parameters that need attention and consideration are consistent. It is hoped that this will help in the design process of medical gas systems in hospitals in the future.


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