The ‘Permox’ oxygen concentrator

The Use of Portable Oxygen Concentrators in Low-Resource Settings: A Systematic Review

INTRODUCTION

Portable oxygen concentrators (POCs) are medical devices that use physical means to separate oxygen from the atmosphere to produce concentrated, medical-grade gas. Providing oxygen to low-resources environments, such as austere locations, military combat zones, rural Emergency Medical Services (EMS), and during disasters, becomes expensive and logistically intensive. Recent advances in separation technology have promoted the development of POC systems ruggedized for austere use. This review provides a comprehensive summary of the available data regarding POCs in these challenge environments.

METHODS

PubMed, Google Scholar, and the Defense Technical Information Center were searched from inception to November 2021. Articles addressing the use of POCs in low-resource settings were selected. Three authors were independently involved in the search, review, and synthesis of the articles. Evidence was graded using Oxford Centre for Evidence-Based Medicine guidelines.

RESULTS

The initial search identified 349 articles, of which 40 articles were included in the review. A total of 724 study subjects were associated with the included articles. There were no Level I systematic reviews or randomized controlled trials.

DISCUSSION

Generally, POCs are a low-cost, light-weight tool that may fill gaps in austere, military, veterinary, EMS, and disaster medicine. They are cost-effective in low-resource areas, such as rural and high-altitude hospitals in developing nations, despite relatively high capital costs associated with initial equipment purchase. Implementation of POC in low-resource locations is limited primarily on access to electricity but can otherwise operate for thousands of hours without maintenance. They provide a unique advantage in combat operations as there is no risk of explosive if oxygen tanks are struck by high-velocity projectiles. Despite their deployment throughout the battlespace, there were no manuscripts identified during the review involving the efficacy of POCs for combat casualties or clinical outcomes in combat. Veterinary medicine and animal studies have provided the most robust data on the physiological effectiveness of POCs. The success of POCs during the coronavirus disease 2019 (COVID-19) pandemic highlights the potential for POCs during future mass-casualty events. There is emerging technology available that combines a larger oxygen concentrator with a compressor system capable of refilling small oxygen cylinders, which could transform the delivery of oxygen in austere environments if ruggedized and miniaturized. Future clinical research is needed to quantify the clinical efficacy of POCs in low-resource settings.

Oxygen concentrators performance with nitrous oxide at 50:50 volume

BACKGROUND AND OBJECTIVES

Few investigations have addressed the safety of oxygen from concentrators for use in anesthesia in association with nitrous oxide. This study evaluated the percent of oxygen from a concentrator in association with nitrous oxide in a semi-closed rebreathing circuit.

METHODS

Adult patients undergoing low risk surgery were randomly allocated into two groups, receiving a fresh gas flow of oxygen from concentrators (O293) or of oxygen from concentrators and nitrous oxide (O293N2O). The fraction of inspired oxygen and the percentage of oxygen from fresh gas flow were measured every 10 min. The ratio of FiO2/oxygen concentration delivered was compared at various time intervals and between the groups.

RESULTS

Thirty patients were studied in each group. There was no difference in oxygen from concentrators over time for both groups, but there was a significant improvement in the FiO2 (p<0.001) for O293 group while a significant decline (p<0.001) for O293N2O. The FiO2/oxygen ratio varied in both groups, reaching a plateau in the O293 group. Pulse oximetry did not fall below 98.5% in either group.

CONCLUSION

The FiO2 in the mixture of O293 and nitrous oxide fell during the observation period although oxygen saturation was higher than 98.5% throughout the study. Concentrators can be considered a stable source of oxygen for use during short anesthetic procedures, either pure or in association with nitrous oxide at 50:50 volume.

Inspired oxygen concentrations with or without an oxygen economizer during ether draw-over anaesthesia

An oxygen economizer tube is attached to draw-over vaporizers and acts as a reservoir of supplemental oxygen. The clinical importance of the presence or absence of the economizer tube (volume 130 ml) has not been adequately studied in manually ventilated patients using ether from an Ohmeda Cyprane Portable Anesthesia Complete (PAC) draw-over vaporizer. A total of sixteen patients ASA 1-2, undergoing elective surgery for peripheral orthopaedic procedures were studied with and without an economizer tube. Each patient acted as his or her own control. Standard procedures were used for anaesthetic induction with muscle relaxant, endotracheal intubation and anaesthetic maintenance. Supplemental oxygen was supplied by an oxygen concentrator. Using the draw-over vaporizer without an oxygen economizer tube, there was a slight increase in FiO2 of 20%, 23%, 27%, 30%, 33% and 33%, with increasing oxygen supplementation of 0 to 5 l/min, respectively. With an economizer tube, the FiO2 values increased to 20%, 26%, 35%, 46%, 54% and 66% at 0 to 5 l/min of oxygen respectively. The FiO2 values were significantly different at 3, 4, and 5 l/min (P < 0.05), showing the potential advantages of an oxygen economizer tube attached to a draw-over vaporizer in this setting. No significant differences were seen in the oxygen saturations of these healthy patients with or without an oxygen economizer.

Anaesthesia in Barbados

PURPOSE

To describe the anaesthesia services in Barbados: to present the major challenges confronting the Anaesthesia Department of the government-owned Queen Elizabeth Hospital (QEH): and to describe the Department's approaches to optimise safety and cost-effectiveness of anaesthesia at QEH.

SOURCE OF INFORMATION

Authors (KBS, HSLM, RAH), who collectively provided more than 50 yr of anaesthesia at QEH; the Dean (ERW) of the University of West Indies Medical School (Barbados campus); archives of Barbados; and records of QEH.

PRINCIPAL FINDINGS

The government of Barbados provides modern health care services to all of its citizens, primarily at QEH. Barbados, however, has tight financial constraints, infrastructural limitations, and a bureaucratic administration that predispose QEH's Anaesthesia Department to unexpected depletions of drugs and disposable supplies, sporadic shortages of personnel and functioning equipment, and occasional quality assurance problems. To deal with such problems, the Anaesthesia Department has implemented several pro-active measures: establishing an audit system to prevent depletion of imported drugs and supplies: training local personnel to maintain equipment: purchasing an oxygen concentrator to reduce oxygen costs: decreasing nitrous oxide use (expensive in Barbados): and initiating its own quality and safety standards.

CONCLUSION

Continuous delivery of high quality, cost-effective anaesthesia care requires thoughtful planning by administrators and judicious resource allocations. Health care administrators and clinical departments need to work together closely to establish a framework that enables departments to play a major role in determining how the institution's limited financial resources are best allocated to meet the departmental priorities.

A low-pressure portable anaesthesia system for field use: clinical trials

This is a report of our experience with a portable anaesthesia system that was developed for use under field conditions, when compressed gas supplies are limited. We first assembled and bench-tested a low-pressure plenum system, based upon the Farman entrainer. The entrainer required a low flow of compressed gas, O2 at 1-2 L.min-1, and generated a low-pressure mixture of O2 and air which was directed through an Oxford miniature vaporizer, a non-return valve, and a widebore T-piece circuit. With this system we anaesthetized 24 patients with intermittent positive pressure ventilation (IPPV) and nine patients breathing spontaneously. During IPPV, the circuit resembled a T-piece and provided effective gas exchange with a FGF of 1.2 times minute ventilation. Inspiratory and expiratory valves were arranged so that the spontaneous mode was non-rebreathing, and FGF was adjusted to equal minute ventilation. The system was very economical, using 1-2 L.min-1 O2 and 20-25 ml.hr-1 liquid halothane to produce a FGF of 6-10 L.min-1, an FIO2 of 0.33, and FIhal of 1-1.5 per cent. We have demonstrated that this is a versatile, safe, and economical system, compatible with the practice of modern inhalational anaesthesia under field conditions. It can be readily assembled from commercially available components.

A portable oxygen generator

The use of a portable generator which liberates oxygen from hydrogen peroxide solutions has been investigated in veterinary anaesthesia to assess its potential as an alternative to conventional oxygen supplies both in emergency situations and in the event of failure of cylinder systems. The reliability of the supply appears to be good and the operation of the generator simple, making it suitable for a number of potential uses. It should compare favourably with oxygen concentrator devices used for similar purposes.

The 'Mini O2' and 'Healthdyne' oxygen concentrators. Their performance and potential application

Two oxygen concentrators designed for home use, the 'Healthdyne' and the 'Mini O2', have been assessed with particular reference to their possible role in anaesthesia. Both were found to be a reliable source of oxygen enriched gas. Neither was fully capable of driving a gas powered ventilator satisfactorily, but both could potentially be very useful in normal and field anaesthetic practice.