Effectiveness of surgical face masks

The application of medical face masks is associated with severe healthcare and it is very profoundly ingrained that to challenge it will were unheard of until recently. Nevertheless, in certain practices the usage of masks was abandoned over recent years, for instance when dressing wounds. Both the usage and withdrawal of medical face masks has happened in an ad hoc fashion which is incompatible with evidence based practice. This content is going to discuss the available evidence.

The hierarchy of evidence

Evidence could be categorised based on a hierarchy. At top of the end of the hierarchy (Type Ia) the research offers a far more dependable foundation for practice. Nevertheless, a lot of the literature on medical masks is Type IV proof (at probably the lowest end of the hierarchy), this includes anecdotal accounts or maybe summaries of earlier studies (Belkin, 1996).

Sackett et al (1996) call for the’ conscientious, judicious and explicit application of present greatest evidence in making choices around the proper care of specific patients’. Such an undertaking may guarantee the process of wearing medical masks can be taken, based on conditions and as time passes, in line with the newest proof.

In an earlier characterization of evidence based medicine, Sackett and Bennett (1987) developed a benchmark of’ doing much more good than harm’ to determine whether training is highly effective. It was previously presumed that medical masks do’ more good compared to harm’; though it’s likewise been recommended that masks could do’ more damage than good’. For instance, carrying out a very small lab analysis, Schweizer (1976) reported that mask wiggling caused dropping of your skin scales and pollution of a space underneath the masked subjects.
Present devices

A medical grade face mask uk typically constitute 3 layers – a screen layer (such as polypropylene) usually separates the outer and inner layer. Probably the most frequent European design is pleated and flat with horizontal ties along with a metal strip formed over the nasal bridge.

Masks don’t filter all of particulates from the fresh air inhaled and also exhaled by the wearer. Much of the environment is pulled in and escapes where there’s minimum resistance to course, typically around the sides of the mask (venting). The masks don’t create a total seal against the face and are thus not classified as respirators and personal protective equipment (Stull, 1998).

In practice various other equipment might be used rather than face masks based on the circumstances. For instance, respirators are highly recommended reducing the danger of exposure by the wearer to destructive materials. The respirator could be’ valved’ providing safeguards to the person, or’ non-valved’ providing protection to both the individual as well as the wearer. Different standards of respirator provide proper protection in certain circumstances.

Face shields are tiny plastic sheets which often deal with the whole of the face rather than a face mask, and are installed to the pinnacle of the facial skin mask with an antifogging device between them to minimize water exhalation. Approved goggles or even eye protectors can also be worn to augment the mask to stay away from eye splashes.

Absolutely no individual product look available today fits virtually all particular performance and preferences requirements so it’s vital that the nurse constitutes a judgement based on the circumstances.

Calculating the cost effectiveness of any treatment is an adjunct to evidence based practice. Nevertheless, it’s tough to put a value on distress, additional treatment, and the pain that, for instance, a medical site infection is able to cause. The expenses are able to escalate both in private and in financial terms. The expense of wearing medical masks in theatre in a teaching hospital was believed to be around £10,000 per year (Leyland and 1993), McCloy. This’s a relatively tiny cost, though it is able to just be justified if the training is highly effective.
Length of effectiveness

A mask wet with exhaled moisture has greater resistance to airflow, is much less effective at filtering germs and also has grown venting. Current suggestions are that a brand new surgical mask is utilized for every medical situation and which they must be transformed when wet (National Association of Theatre Nurses, 1998). Some respirators are reported to be helpful for a complete change, though storage to stay away from contamination between cases will be tricky (Anon, 1999).
Questioning the rationale

Initially, the explanation for donning masks was centred on patient protection. Much more recently, the problem has shifted to defense of the wearer. For instance, a recently available post in Nursing Times exhibits a nurse practitioner performing minor surgery using a visor but virtually no mask (Gallagher, 2002).
Defending the patient

The majority of the proof on the usefulness of surgical masks pertains to the defense of the affected person, though the endpoint measured varies. Many research studies measure surgical site infection (SSI) fees among others possibly measure contamination of the medical site or even settle plates at the surgical site. Contamination studies might be performed in the lab or even the operating theatre. Distinguishing the endpoint is crucial, as a few experiments have reported that toxic contamination will undoubtedly result in illness and this particular can’t be established unless infection rates are assessed.
Calculating contamination

In the lab analysis of theirs on medical masks McLure et al (2000) discovered that bacterial shedding from individuals with beards was increased. They propose that bearded men must stay away from mask wiggling and also suggest the removal of beards. Just like the research by Schweizer (1976), this’s a good example of contamination being extrapolated to infection without measuring the endpoint of an infection.

A report which measured nasal and oral contamination of settle plates inside a forced ventilation theatre was limited to 5 things. Despite contamination, the article cites dated and speculative studies to say that the regular wearing of masks must be abandoned (Hunt and Mitchell, 1991). This study displays the faults of quite similar studies in that sizable claims develop from an extremely little sample studied under lab conditions.

Alwitry et al’s (2002) study on contamination in cataract surgery keeps that masks must still be used. The researchers mix the 2 failures associated with a tiny sample size and also extrapolation from contamination to infection’ despite the unproven link between bacterial load and also endopthalmitis rate’ (Alwitry et al, 2002).
Calculating infection

A far more solid indication of whether medical masks are more likely to trigger an SSI is measuring the infection rate. In support of discarding medical masks for the defense of the affected person, research by Orr (1981) examined more than 1,000 patients having a bunch of surgery over a period of 6 weeks. Based on Orr there was a major reduction in the infection rate during the time when masks weren’t used. Even though this research is deficient in scientific rigour, it’s caused the abandonment of the usage of surgical masks.

A colleague and the author have performed a systematic overview of the usage of surgical masks via the Cochrane Wound Group (Edwards and Lipp, 2002). In an attempt to obtain a definitive solution on mask effectiveness, this particular research focused on healthy surgery. Despite retrieving ninety seven papers for examination, just thirteen had potential relevance. 2 studies met the requirements for inclusion (Tunevall, 1991; Houang and Chamberlain, 1984). As these were quasi randomised controlled trials, it’s recognized neither was with no flaws, but a judgement was made they had been adequately valid for inclusion.’ From the small benefits it’s not clear whether wearing medical face masks leads to benefit or harm on the affected person having unpolluted surgery’ (Edwards and Lipp, 2002).

A critique of Tunevall’s study cites it as lacking’ control’ and also lists the’ five Ds of medical infection control’ (Laufman, 1992) as:

Defence mechanisms;

This requires nearly hundred variables as different as duration of aseptic barriers, ventilation, prophylactic antibiotics, patient age, and operation, like masks, respectively (Laufman, 1992).

Laufman (1992) recommends the usage of in vitro tests to exclude several of these variables. This will undoubtedly shift the end point from disease to contamination, that wasn’t the target of Tunevall’s study. If the independent variables can’t be excluded then a controlled trial should make sure they’re equally distributed via baseline comparability (Sanderson et al, 2001). Tunevall (1991) assured this was true in regards to age, elective and acute surgery, though not for comorbidity. He enlisted a big sample, that is more symbolic of the overall public of individuals undergoing surgery as well as may thus be more quickly applied to many other similar situations. Having created his argument primarily based on variables plus sample size, Laufman (1992) then changes tack and recommends wearing masks for the shelter of healthcare personnel, if not the individual.

Specialist surgery, like orthopaedics and transplantation, is usually cited as a unique situation, just where using a mask to defend the individual is essential to stay away from infection that is heavy. In these surgery types, illness is much more apt to have grave consequences. The risks of not using a mask are arguably also great. Crucially, there aren’t any randomised controlled trials which show a link between donning or perhaps not using a mask and also SSIs in these specialisms. The main proof in this particular area is founded on contamination (Friberg et al, 2001; Hubble et al, 1996; Ha’eri and Wiley, 1980). The argument for use a surgical mask in this particular sphere of surgery may much more rationally be according to staff help, as sub-micron-sized particles will probably be present.

In protecting the affected person, it’s essential to ascertain who should use a surgical mask. Should it be restricted to the individual performing the process, or even to other personnel present? Mitchell and Hunt’s (1991) laboratory analysis found no contamination of settle plates when personnel spoke at a distance of 1m. This indicates that employees within the vicinity of a process needn’t wear masks. Nevertheless, due to the tiny sample size of 5 and a loss of validity, it’s tough to have trust in these findings.

Immunocompromised people might be advised to use surgical masks. This practice might provide reassurance for each staff and patient, but it can’t be justified unless it’s dependent on evidence. To date we have seen no randomised controlled trials which establish this exercise to be efficient.
Defense for the wearer

Operating techniques and clinical circumstances that produce aerosolised hazardous agents pose a possible risk to staff. In order to evaluate mask effectiveness against aerosolised dangerous agents, Weber et al (1993) tested 8 kinds of masks for aerosol particle penetration either through the mask or perhaps via a leak (venting). In this particular lab study, they anticipate that the medical masks offer inadequate protection against potentially dangerous submicron sized particles (Weber et al, 1993).

The requirement to defend staff from contamination by individuals is now much more important. A recently available research of forty hospital staff members that contracted severe acute respiratory syndrome (SARS) in Hong Kong discovered that most employees had used masks with a minimum bacterial filtration efficiency of ninety five per cent. Personnel didn’t use respirators and just twenty eight per cent had used eye shields. The inference from these results is the fact that medical masks solely don’t give adequate protection against SARS (Ho et al, 2003). It’s inescapable because of the acute circumstances that this particular research just rates as a well designed, non experimental study (level lll within the hierarchy). To date this’s the single study which links protection of staff on the usage of the danger and medical masks of illness.

Professional companies in the USA plus the UK recognise which the link between defense of the individual and donning a medical mask is tenuous. Nevertheless, they offer careful tips on the usage of medical face masks, respirators and also eye shields if the wearer is vulnerable to contamination (Mangram et al, 1999; Association of Operating Room Nurses, 1998; National Association of Theatre Nurses, 1998).
Potential research

A useful term to keep in mind is that’ not enough proof of benefit doesn’t equate to proof of insufficient benefit’. Staff protection is a fairly robust analysis and recent concern still has to be undertaken. Only one might argue that randomising team members into masked and non masked groups results in ethical issues. Because it can’t but be ascertained whether donning a surgical mask affects infection rates this will make an ethical dilemma equivalent to randomising people into such groups.

In order to establish the efficacy of masks, a randomised controlled trial will need to be big enough to present a statistically significant result. It will need to specify the target as either patient or maybe staff protection. Controlling the independent variables would suggest setting up a balance between choosing unpolluted situations with very little comorbidity and also getting much more legitimate results by incorporating subjects with varying comorbidity, reflecting the overall public.

The explanation for using medical face masks has shifted from defense of the individual to defense of the expert. Despite this there is still a need to base the determination to use a mask on top out there evidence (Sackett et al, 1996). Regrettably, there’s a loss of strong evidence for protecting patient and nurse.

Presently there’s very little proof that wearing a medical mask provides adequate shelter from all the risks encountered in an acute healthcare environment. Because of this, the usage of any respirator and face shield must be considered based on the circumstances.