Testing protective attire


  • Health
  • Wednesday, 15 Oct 2003

EVIDENCE-based nursing practice has spurred a hospital in Hong Kong to put Severe Acute Respiratory Syndrome (SARS) protective wear to the test and it was found that the best has its flaws and the most basic can be the most practical.  

During the frantic moments of the SARS outbreak earlier this year, health workers, especially in SARS-affected countries, tried to get hold of the best protective attire that could shield them from the deadly virus.  

There were many types of protective wear in the market and many claimed that theirs was the best. Pushed to find evidence of the effectiveness of the various protective wear, a team of more than 20 medical and non-medical staff at Hong Kong Polytechnic University decided to carry out laboratory tests on these apparels since April. 

Mask risks 

One of the most highly-recommended masks for health workers and patients during the SARS outbreak was the N95 respirator mask, the same kind worn by those dealing with tuberculosis patients. Unfortunately, the mask did not fit the Chinese facial curvature and as such, it leaked, said Dr Thomas Wong, head of the nursing school at the Hong Kong Polytechnic University.  

Laboratory tests on the functional properties of the mask showed that the innermost layer of the four-layered N95 mask had no water repelling ability, said Wong who gave a talk on Nursing Outcomes: Do We Really Care Enough? during the recent Asian Regional Conference on Evidence-Based Nursing in Kuala Lumpur. 

“As such, it is water absorbent, indicating that the droplets contaminated with viruses can be absorbed and spread in the inner layer through capillary effects,” he said.  

“If the viral load is normal, there is no capillary action. If the viral load is so heavy that the first three layers cannot filter out the virus and the droplets, the mask will suck in the droplets together with the virus. So we are saying that there is a risk. We are not saying that it is not effective,” said Wong. 

Since N95 is not suitable for high viral load exposure, medical staff should not expose themselves to too much virus and for too long, and the mask should be disposed of after a procedure and hands and face washed, he said.  

The test results showed that the N95 had slightly higher filtration efficiency than the three-layered surgical masks that were also used during the SARS outbreak. The N95 mask does 97.5% of the filtering job while a three-layered surgical mask filters out 95%. The first layer of the N95 mask can filter out 85%-90% of the simulated solution used in the laboratory while surgical masks can filter out 80%-82%, said Wong. 

As such, the three-layered mask is sufficient for regular use with frequent change and hand washing, without resorting to the N95, while N95 can be used in carrying out high-risk procedures such as putting a tube in a patient’s lung, said Wong. 

However, 2%-5% of the simulation solution can penetrate both types of masks, which may become critical when viral loading is high, he said. 

The second stage of the test is currently being carried out. A simulated patient is used in the laboratory and the mask is being tested with attenuated phage bacteria that is harmless but is similar in size with the corona virus, he said. 

Protective clothing 

The Barrier Man, a one-piece overall suit that covers a person from head to toe seems like the ideal protective garment because it repels water and does not allow liquid penetration. It thus works as a good barrier against contaminated droplets. 

“However, air permeability for Barrier Man is low and wearers feel hot and stuffy and they tend to wipe the sweat on their faces with their hands. That can contaminate their faces,” said Wong.  

The zipper in the front part of the clothing also poses a risk.  

“In medicine, the front part of the body is the dirtiest because that’s the part facing the patient. When you unzip the suit, you contaminate yourself and you can get infected,” he said. 

He said other types of clothing are tied at the back of the body so the chances of contamination are minimal.  

“For us, the Barrier Man is not the best coat to wear in a SARS infection unit. Depending on the circumstances, disposable protective gown that is water resistant and water repellent can be a good choice,” said Wong. 

For normal care (non-high risk), surgical gowns can also be used as it is reusable. However, if a heavy splash is expected, then a plastic apron should also be worn on the top of the surgical gown, he said.  

He said disposable personal protective clothing cost only HK$2 (RM1) and the Barrier Man costs HK$70 (RM35) or HK$80 (RM40) for a piece. 

Gloves 

During the later part of the SARS outbreak, doctors and nurses resorted to wearing two layers of gloves thinking that it would provide double protection. “While it gives a false sense of security, it may also pose higher risk of infection,” said Wong. 

Doctors and nurses only remove the outer layer glove and put on a new glove over the inner glove. There is higher chance of cross infection because they tend not to wash their hands, he said.  

“After doing documentation, washing hands is just as effective as wearing gloves. When you wear gloves, you tend to touch things and you tend not to wash the gloves and you spread infection from one place to another. With your hands, when you touch something, you will remember to wash your hands. So the chance of cross contamination is lower,” he said. 

Air curtain 

Transporting a SARS patient from one part of the hospital to another poses a problem. As such, Wong’s team came up with an idea – create an air curtain on four sides of the patient’s bed, which works as a barrier that prevents the virus from travelling out. 

The air curtain works by having air blown from the top to the bottom and sucked into an ultraviolet box underneath the bed. “Blowing the air is to prevent virus from getting out from the bed area. Air, together with bacteria and virus, are sucked into the box and the UV rays kill the virus and bacteria and clean air is released back into the bed area,” said Wong who came up with the idea. “This is a complete system,” he said. 

However, the cost factor is now being worked out. “The air curtain may not be as cheap as we thought. If it is only one bed, then it’s cheap but if you need to build a thousand beds, that is expensive,” he said.  

“The government wants to build this infectious disease unit not just for SARS but also for other infectious disease,” he said.  

A model of the bed is now being built. “If it is proven to be effective and safe, it goes to the hospital. We hope to get this done by the end of October,” said Wong. 

Other research 

Currently, at Wong’s hospital, data mining and compilation of the experiences of SARS patients and nurses who looked after SARS patients has also been completed.  

For the first stage of data mining, the histories of more than 700 SARS patients’ records were looked into for the purpose of observing critical patterns. 

Besides the medical record, parameters such as the patients’ lifestyle, what they ate, what they were like before they fell ill, stress level and blood chemistry were taken into account, said Wong.  

“We set up a template to put in all these and then we used the statistics to identify the major variables that contributed to either 100% recovery or 30% recovery. So we hope to find out all these variables. It’s going to be multi- factorial,” he said.  

“It took a long time to set up the template because we had to go through more than 700 SARS patients’ records. We have fed the information into the computer and now we are going to tabulate it. We want to finalise the template so that other countries can use it. If we have a common template, then we can pull the data together and do the analysis,” he said. 

The template on the experience of SARS patients and nurses who cared for SARS patients has just been published. The study looked into factors such as how nurses felt, what they saw and how things could be done differently. 

“For example, they realised that the working environment is so stressful and yet they still have to remember to talk to the patients so that the patients don’t suffer from being isolated. They also realised that there is a need to revise the procedures. For instance, when they feed the patient and if the patient vomits or regurgitates, there is a large volume of virus. So they will need full protective gear, face mask, goggles and N95,” he said. 

“They also realised that feeding has to be much slower and the patient has to be aware that he or she is being fed. If not, if he or she would choke and there is a chance of vomiting,” said Wong. 

“It’s important to supply scientific evidence so that people will not be panicky,” he said. 

“The battle against SARS has made our community more aware of the importance of basic and applied research in health care. We have paid an enormous price for being ignorant and unscientific,” said Wong. – By Loh Foon Fong 

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