Face mask standard on the horizon.

Work has recently begun on a new European Standard for face masks.

The scope of the standard covers face masks intended to limit the transmission of infective agents from staff to patients and vice-versa during surgical procedures in operating rooms and other medical settings with similar requirements.

It excludes masks intended solely for the personal protection of staff, which is covered by PPE standards.

Although still at a very early stage, the standard proposes performance requirements for 3 properties of face masks:


  1. Bacterial Filtration Efficiency (BFE)
  2. Breathability
  3. Splash resistance

The BFE test uses a nebulised mist of Staphylococcus aureus to challenge the face mask, and counts are taken with and without the mask, from which its filtration efficiency is calculated.

Breathability is assessed by measuring the differential pressure required to draw air through a fixed area of the mask, whilst the splash resistance test has not yet been finalised.

Using these criteria, face masks are classified into Type I (BFE ≥ 95%), Type IR (Type I mask which is splash resistant), Type II (BFE ≥98%) and Type IIR (Type II mask which is splash resistant). The breathability of the splash resistant masks is, as would be expected, lower than the non-splash resistant masks.

It is important to note that the tests in the current draft will test the mask material, but other factors such as the fit of the mask around the face will have a significant affect on the masks performance.

The standard is at a very early stage, and is likely to be subject to significant change.

P. Phillips

SMTL Websites


Just before Christmas, SMTL launched a new surgical dressings site, http://www.dressings.org/.

The intention of this new site is to act as a repository for dressings information, and the first set of data we have added are the dressings datacards, which used to reside on the main SMTL web site.

During the next 12 months, SMTL will be reviewing and updating the existing datacards, many of which are now 3-4 years old. More importantly, we will be adding new dressings to the site regularly, starting with the recent addition of Johnson and Johnson's Promogran in December (a sterile, freeze dried matrix composed of collagen and oxidised regenerated cellulose) and Smith and Nephew's Acticoat and Acticoat 7 (a silver-coated low-adherent primary wound dressing).


In March 2001, World Wide Wounds was re-launched in partnership with MEP, a medical publishing company. Working with MEP has enabled us to take on a professional editor for the journal, Suzie Calne, who was the editor of the Journal of Wound Care for a number of years.

The aims of the journal are substantially the same as before, to provide healthcare practitioners throughout the world with free access to regularly-updated high quality information on the prevention and management of wounds of all types. In order to achieve this, we aim to publish a minimum of two new articles each month. These will include review articles, case reports and practice guides, and will complement existing articles that have been published previously.

In recognition of the fact that the readership of World Wide Wounds includes individuals with widely differing experience and expertise, from students to advanced practitioners, the journal will continue to include articles at basic, intermediate and advanced levels.

An impressive and committed editorial board has been brought together that reflects the range of specialties involved in wound care. This group will select topics and commission articles that are central to everyday practice in order to drive the practice of wound management forward. The board includes Brian Gilchrist, Christine Moffatt, Peter Vowden, Diane Krasner, Liza Ovington and Kerlyn Carville, all recognised leaders in their respective fields.

In the past year, the following articles have been published:


  • ``Pain and wound healing'' by Ramon Pediani
  • ``Doppler assessment and ABPI: interpretation in the management of leg ulceration'', by Peter and Catherine Vowden.
  • ``Hyperbaric oxygen therapy for wound healing'', by James Wright.
  • ``Vacuum assisted closure (VAC) of wounds'', by Steve Thomas.
  • ``Opinion: NICE - time for review ?'', by Steve Thomas.
  • ``Understanding fungating wound management'', by Patricia Grocott.
  • ``New guidelines for pressure ulcer management'', by Martyn Butcher.
  • ``Obstetric care. Is there risk of pressure damage after epidural anaesthesia ?'' by Caroline Hughes.
  • ``The art and science of evaluating patient support surfaces'' by Shyam Rithalia and Laurence Kenney.
  • ``A review of the expert opinion on latex allergy'' by Peter Phillips.
  • ``Honey as a topical antibacterial agent for treatment of infected wounds'' by Peter Molan.
  • ``The development of a novel technique for predicting the exudate handling properties of modern wound dressings'' by Steve Thomas and Paul Fram.

If you wish to be kept informed when new articles are added to these sites, join one of the email lists managed by SMTL at: http://www.worldwidewounds.com/Common/MailingLists.html.

P. Phillips

SMTL branching into veterinary medicine!

A year or so ago, SMTL were called in to look at an elderly lady donkey (thought to be over 30 years old, although it was thought to be impudent to ask her actual age) at the Donkey Sanctuary in Sidmouth. The patient had a small suppurative skin wound, thought to have been caused by browsing in a thorny hedge. This had initially responded well to normal treatment, except for a discharge from a tract in the centre of the wound, which yielded a profuse growth of Escherichia coli and a moderate growth of Streptococcus species.

Repeated attempts by surgery failed to resolve the issue, and as the patient was becoming resentful of injections and topical wound treatments, it was decided to try treatment with sterile larvae.

A total of six treatments were applied, after which most of the wound consisted of bright red granulation tissue. Regular irrigation with saline followed, and the wound rapidly contracted and epithelialised over a few weeks.

The patient tolerated the maggots well, and in fact appeared to be unaware of their presence. Distracting the patient with food was sufficient to allow the larvae to be applied. However, the same could not be said of the hospital staff, who were repulsed by the noise and sight of the feeding larvae, and were less than enthusiastic about being involved with the day to day care of the donkey!

The patient is currently doing well, and is apparently delighted with an appearance in her preferred reading matter, ``The Veterinary Record'', in December 22/29 2001.

P. Phillips

Hydrocolloid dressings - a review.

The term 'hydrocolloid' has been adopted to describe a family of wound management products manufactured from gel-forming agents combined with other materials, such as elastomers and adhesives. Frequently based upon carboxymethylcellulose (CMC), hydrocolloids may also contain other polysaccharides and proteins. Typically, they are presented in the form of a flexible foam or film sheet, coated with a layer of the hydrocolloid base and covered with a piece of release paper.

Originally produced in small square pieces, hydrocolloid sheets are now available in a variety of shapes and sizes. In some the adhesive mass extends to the edge of the dressing but in others the mass is applied in the form of an island in the centre the so-called bordered dressings. Components of the base itself may also be available in the form of granules or paste, which can be applied to the wound in conjunction with the sheet to increase the absorbency of the system.


Method of action

As hydrocolloid dressings are applied to all types of wounds, a key performance requirement is that they be capable of coping with varying volumes of exudate. Their principal mechanism of action is simple absorption; exudate is taken up by the hydrophilic components of the dressing and retained within the adhesive matrix but a second mechanism depends upon the loss of the aqueous component of wound fluid through the back of the dressing as water vapour.

Most hydrocolloid dressings form a barrier to water vapour in their intact state and it is only when the adhesive mass is fully hydrated that the dressing becomes permeable. The amount of fluid lost by evaporation is therefore determined both by the permeability of the film or foam backing layer and the rate at which liquid is transmitted through the adhesive mass. These effects are additive and together with the absorbency of the adhesive matrix, determine the fluid handling properties of the dressing, which vary from product to product.

The different physiochemical properties of the various types of dressings may affect the immune system, the healing rate and the appearance of the wound bed upon removal. When they were first introduced to the market place, there were concerns that the occlusive nature of the dressing would tend to promote wound infection. This has not proved to be the case; in fact the reverse appears to be true. Wounds dressed with hydrocolloids are less prone to develop infections than those dressed with conventional treatments.

The oxygen tension (pO2) in wounds dressed with hydrocolloid dressings is usually very low and the pH is in the acid region, which is also thought to have an inhibiting effect on the growth of some bacterial species. Because of their impermeable nature, hydrocolloid dressings form an effective barrier to microorganisms. They can either be used to reduce the possibility of infection from external sources or alternatively they can be used to prevent the spread of infection from wounds that are already colonised with bacteria.

The undersurface of the dressing that is in contact with the wound is always maintained in a moist condition which means that it may be easily removed without causing damage to the underlying tissue. This lack of tissue trauma is in marked contrast to the epidermal stripping that frequently occurs when gauze or similar dressings are removed

Indications for use

Numerous animal studies have been published which indicate that wounds dressed with hydrocolloids show enhanced angiogenesis and re-epithelialisation compared to conventional treatments. These benefits also extend to all types of human wounds including burns, donor sites, leg ulcers and pressure sores. For all of these indications there is good evidence that the use of hydrocolloid dressings will accelerate healing compared with traditional dressings such as simple gauze packs or gauze dressings impregnated with paraffin. They are particularly useful in paediatric wound care as they reduce wound related pain and in many instances will permit bathing or washing.

Hydrocolloids also have a role in the management of surgical and traumatic wounds, and a few papers have been published that describe their use as dressings in sports injuries including those incurred during contact sports such as rugby or wrestling. In these situations their bacterial barrier properties shield the wound from exposure to infectious agents and prevent transmission of blood or serum to other competitors.

The only area where there is some dispute over the role of hydrocolloids is in the treatment of the diabetic foot. Some workers have suggested that their use in this indication may predispose the wound to infection with serious consequences for the patient. Others argue that the dressing can be safely used on wounds that are not obviously infected provided that the patient is closely monitored and the dressings are not left in place for extended periods. Further work is probably required to resolve this issue.

There is little doubt that there are many benefits to be derived from the correct use of hydrocolloid dressings. The decrease in pain and the considerable reductions in healing time associated with their use call into question the rationale for the continued use of treatments such as dry gauze and paraffin tulle for donor sites, leg ulcers, and similar applications.

This summary has been abstracted from a comprehensive literature on hydrocolloids, which will be available on the SMTL web site in due course.

S. Thomas

Luer connectors and the prevention of misconnection.


Most healthcare professionals will be aware of the recent tragic deaths of patients who received Vinca alkaloids (such as vincristine) by the spinal route instead of intravenously. Although rare, there have been 5 such incidents in the NHS in the past decade.

A number of reports were commissioned into these incidents, the most recent being from Professor Kent Woods (from the Department of Medicine at the University of Leicester) for the Chief Medical Officer in April 2001.

One of the conclusions reached was that these intrathecal errors belonged to a wider class of misconnection hazards resulting from the ubiquitous use of Luer connectors in a wide range of medical devices.

In February 2000, CEN (the European standards organisation) published CR 13825, ``Luer connectors - A report to CEN chef from the CEN forum task group `Luer fittings'. The task force (set up in 1997) were asked to review the evidence relating to real and potential problems arising from the misconnection of devices using Luer fittings, and to make recommendations regarding the application of Luer fittings to medical devices in order to reduce potential hazards arising from their misconnection.

The task force found that whilst there are many anecdotal reports of misconnection, evidence of serious incidents is scarce. Clinicians openly admit that misconnections are commonplace, but most are not reported because the the mistake was rectified in time or because no serious incident took place. They were able to substantiate a number of incidents including:


  • Enteral feeds delivered parenterally, resulting in fatal consequences;
  • Oxygen being delivered intravenously;
  • Enteral feed being delivered into the inflation cuff of a tracheal tube, resulting in the occlusion of the patient's airway;
  • Transposition of the aspiration and actuator lines of a vitrectomy handpiece, leading to a jet of gas entering the patient's eye;
  • Liquid inadvertently delivered into a breathing system, resulting in decreased oxygen saturation of the patient.

The problems appear to arise from two distinct events:


  1. the attachment of a delivery system (parenteral fluid, enteral feed or gas) to an inappropriate device, or
  2. the connection of two devices, each of which is fitted with a Luer connector, but which are not intended to be connected in normal use.

The task force performed a risk assessment of application versus delivery route, and identified 5 misconnection combinations which would result in immediate fatal risk to the patient, and three combinations which would result in risk to the patient, with fatal consequences if the condition was allowed to persist.

The delivery route with the greatest risk was the intravascular route, where the delivery of enteral feed or gas is likely to result in death. The task force noted that some misconnections, such as the inadvertent delivery of sterile fluid into a patients stomach, may not directly harm the patient (although this depends on the nature and volume of the fluid), but should still be avoided.

Discussing their findings, the task force note that we must expect users to misconnect devices which are provided with compatible connectors, and recognise that the potential for misconnection will rise as the number of devices with similar connectors increases. The fundamental problem is that a single design of connector has been applied to a number of incompatible applications.

Whilst the task force recognised that connector systems could not be designed to overcome every single chance of misconnection, or eliminate deliberate misuse, they concluded that a number of initiatives could be pursued to improve the current situation.

Colour coding of connectors was dismissed as being impractical, due to the extensive cooperation throughout industry that would be required, problems with colour blindness and lighting levels, as well as confusion with established colour codes on medical devices. The favoured approach was to make delivery systems for intravascular, enteral and respiratory routes incompatible with one another.

The recommendations of the group were that Luer connectors be restricted to devices intended to be connected to the vascular system or to a hypodermic syringe in order for the syringe to achieve its intended purpose, and that they should not be used with devices intended to be connected to the enteral or respiratory systems, or with systems intended to deliver compressed air or other gases to medical devices, or with patient connected drainage devices.

As a consequence of the report, CEN have set up a task force to develop standards for connectors suitable for use with devices intended for parenteral, enteral and respiratory applications, with special attention being given to the elimination of hazardous connections. This work has only recently started, with a number of sub groups tasked with proposing standard based solutions for:


  • Enteral feeding systems;
  • Respiratory systems (therapeutic and sampling);
  • Neuraxial application (epidural, intrathecal etc);
  • Urethral/Urinary;
  • Non-invasive blood pressure.

For any such system to work, international acceptance is vital (a European only system would clearly be impracticable), and therefore the International Standards Organisation (ISO) have agreed to take the project on once it has been sufficiently developed.

If successful, connection systems on medical devices will change radically over the next decade, but the enormity of the task should not be underestimated, as it would result in up to 4 variants of syringes being stocked in NHS hospitals, along with a completely new range of non-vascular connections.

Pete Phillips

The Medical
Disposables and
Dressings Newsletter
Vol. 2 No. 3
March 2002
Published by:
The Surgical Materials
Testing Laboratory

Edited by:
Dr Stephen Thomas
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Peter Phillips
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Contact Information
Tel: 01656-752820
Fax: 01656-752830
Princess of Wales Hospital
Coity Road
CF31 1RQ
©2002 by SMTL.
All rights reserved. No permission necessary to copy, reprint and distribute unaltered within the NHS as required. For other usage, please contact SMTL.

This file is also available from http://www.smtl.co.uk/Documents/Newsletters/

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