Contamination of the central medical air supply with water leading to mass ventilator failure

Here, we present a case of mass ventilator failure due to contaminated medical air. Multiple ventilators failed routine tests, including almost all of the ventilators in our intensive care unit. A faulty air compressor had led to water contamination of our centre's supply of medical air. Water entered the pipeline supply of air and, hence the ventilators and anaesthetic machines. The disruption of the machines' proportional mixer valve resulted in unreliable delivery of fresh gas flow. This malfunction was discovered during routine pre-use checks, and backup ventilators were available to replace the faulty ventilators. A shortage of equipment was averted due to a serendipitous availability of ventilator stockpiles prepared for the COVID-19 pandemic. Ventilator shortages are commonly described in mass casualty and pandemic scenarios. While there are multiple strategies described in literature to augment and maximise equipment available for mechanical ventilation, stockpiling equipment remains an expensive but necessary component of disaster contingency planning.

A novel method for conformity assessment testing of anaesthesia machines for post-market surveillance purposes

BACKGROUND

Anaesthesia machines, as moderate to high-risk medical devices intended for use on patients during surgical procedures must be safe and reliable with traceable performance every time they are used in healthcare practice. The new Medical Device Regulation (MDR) defines medical device post-market surveillance (PMS) as performed by independent, third-party, notified bodies more strategically in hope to improve traceability of device performance. However, there is still an apparent gap in terms of standardised conformity assessment testing methods.

OBJECTIVE

This paper proposes a novel evidence-based method for conformity assessment testing of anaesthesia machines for post-market surveillance purposes.

METHOD

The novel method is developed according to the International Organisation of Legal Metrology (OIML) guidelines and is to be used for the purpose of conformity assessment testing of anaesthesia machines with respect to their technical and metrological characteristics during PMS.

RESULTS

The developed method was validated between 2018 and 2021 in healthcare institutions of all levels. The results obtained during validation suggest that conformity assessment testing of anaesthesia machines as a method used during PMS contributes to significant improvement in devices' accuracy and reliability.

CONCLUSION

A standardized approach in conformity assessment testing of anaesthesia machines during PMS, besides increasing reliability of the devices, is the first step in digital transformation of management of these devices in healthcare institutions opening possibility for use of artificial intelligence.

Environmental and economic impact of using increased fresh gas flow to reduce carbon dioxide absorbent consumption in the absence of inhalational anaesthetics

BACKGROUND

Increasing fresh gas flow (FGF) to a circle breathing system reduces carbon dioxide (CO₂) absorbent consumption. We assessed the environmental and economic impacts of this trade-off between gas flow and absorbent consumption when no inhalational anaesthetic agent is used.

METHODS

A test lung with fixed CO₂ inflow was ventilated via a circle breathing system of an anaesthetic machine (Dräger Primus or GE Aisys CS²) using an FGF of 1, 2, 4, or 6 L min^-1. We recorded the time to exhaustion of the CO₂ absorbent canister, defined as when inspired partial pressure of CO₂ exceeded 0.3 kPa. For each FGF, we calculated the economic costs and the environmental impact associated with the manufacture of the CO₂ absorbent canister and the supply of medical air and oxygen. Environmental impact was measured in 100 yr global-warming potential, analysed using a life cycle assessment 'cradle to grave' approach.

RESULTS

Increasing FGF from 1 to 6 L min^-1 was associated with up to 93% reduction in the combined running cost with minimal net change to the 100 yr global-warming potential. Most of the reduction in cost occurred between 4 and 6 L min^-1. Removing the CO₂ absorbent from the circle system, and further increasing FGF to control CO₂ rebreathing, afforded minimal further economic benefit, but more than doubled the global-warming potential.

CONCLUSIONS

In the absence of inhalational anaesthetic agents, increasing FGF to 6 L min^-1 reduces running cost compared with lower FGFs, with minimal impact to the environment.

Advances in vaporisation: A narrative review

The output of inhalational agents from modern vaporisers are both electronically and pneumatically controlled. They are designed to deliver set agent concentrations accurately with low fresh gas flows and possess enhanced safety features. The purpose of this review article is to give an overview of three modern vaporisers, namely, the Aladin cassette vaporiser, injection vaporisers and AnaConDa™. The Aladin cassette is integrated with Datex Ohmeda S/5 ADU and GE Aisys anaesthesia machines. The electronic vapour control unit is incorporated within the anaesthesia machine. The agent specific cassettes act as a detachable vaporising chamber. The system can work as a variable bypass and measured flow vaporiser but requires a power supply to function. Injection vaporisers can achieve the set end-tidal agent concentration very rapidly with even metabolic flow rates. Hence, anaesthetic depth can be rapidly altered with minimal wastage and theatre pollution. The two types of injection vaporisers, namely, Maquet and DIVA™ are customised to function with Maquet FLOW-i and the Drager Zeus anaesthesia machine, respectively. AnaConDa™ is a combination of vaporiser and humidity and moisture exchange filter which can be fitted in the ventilatory circuit. It is primarily designed for use in intensive care for sedation and out of operating room use.