Dear Mr Oswal

Thank you very much for your reply to my posting. It is always interesting to see your postings which are based on practical use and experience as a surgeon in comparison with those of my physicist colleagues. It was also satisfying to learn that John Haywood and Walker Filtration were able to help you and the theatre staff by producing some useful equipment. I believe John has now retired.

Your situation in 1983 sounds rather unpleasant with regard to smoke and in comparison I seem to be looking at a rather trivial situation. The laser process is conducted via an endoscope in the oesophagus and it is likely that most bacteria and DNA debris will not emerge to the room atmosphere. However, some material may escape and I have suggested that microbiological tests should be arranged as a check on this. I also understand that the measured number of room air changes per hour is 0.7 which does not sound very high to me even for a relatively well enclosed situation.

Another correspondent has suggested ten changes per hour for a more open situation (resurfacing work) so presumably I will need to advise a value somewhat lower than ten. 

Best wishes 
Mike Edwards
Principal Physicist
Medical Physics Dept.
Derbyshire Royal infirmary
Derby




>>> [log in to unmask] 07/09/2006 15:47:46 >>>
 
Way back in 1983 when the laser machines were rudimentary and  produced 
enormous amount of char and smoke, the theatre was full of smoke even  after ten 
minutes of vaporising! I am an ENT surgeon, and most of the smoke in  cases of 
tubeless anaesthesia went my airways. The smoke was like barbeque smoke  
particularly when I was working on cancer of tongue which is very muscular and  very 
vascular! There were no dedicated suction machines, and the general theatre  
filters started to get clogged up with char.
 
I asked our then physicist Dr John Haywood if the smoke was harmful  and also 
methods the extract it efficiently. The outcome was that what you  'smell' is 
not the only constituent in the plume, there are bacteria, DNA  particles etc. Smoke is heavier than the air and thus does not quite get sucked  away 
unless the suction tip is within an inch of the laser site. Even then there  is 
ambient smoke which needs to be removed. A two suction unit was built by  Walkers 
in Newcastle. One was port was high volume low pressure and the other  was low volume high pressure. This unit certainly took away the smell. Since  smoke 
generation is so variable in each case depending upon the pathology, John  said that if we measure the volume of the room and then introduce equal amount  
of clean air so many times per minute (or per hour I cannot remember) then equal  amount of contaminated air must come out! Since dedicated filters have  
efficiency of removing 0.1um particulate, the air that comes out of its vents  
should be clean enough. By measuring the output of such a filter, it may be  
possible to relate it to the size of the room - on similar principles as in the  
plane. 
 
I know I am talking to physicists, and I may be completely wrong  about my interpretation and recall of what went on some 23 years ago ....., so  take this 
sideways thinking with a pinch of salt.
 
 
Kind regards, yours sincerely, 

Vasant Oswal, MS, FRCS,  MB, DLO, DORL
Honorary Treasurer, BMLA
Far Shirby, Upleatham, Redcar,  Cleveland, TS11 8AG, UK
Tel/Fax +44 1287 622000/+44 1287 625751 

 
In a message dated 07/09/2006 14:07:12 GMT Standard Time,  
[log in to unmask] writes:

Dear  List Members

Does any one out there know of any guidelines regarding  the ventilation of rooms such as those in Day Case Units or other rooms which  may not be of Operating Theatre standard and are  used for laser  procedures? In some cases these 
may not be suitable for the  purpose.

The procedures involved may be totally enclosed such as the  oesophagus or may be more superficial and involve the use of Laservac suction.  It would be 
useful to be able to quote numbers when I am asked about the  removal of 
residual odours.

Any information either on or off list would  be appreciated.

Mike Edwards
LPA
Medical Physics  Dept.
Derbyshire Royal Infirmary
Derby        


 
 
 


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