Tietz's Clinical Guide to Laboratory Tests gives a reference range of 4-5%
for COHb in smokers who smoke 1-2 packs/day and 8-9% for >2 packs/day, so
11% does seem somewhat high for this patient. [This is assuming of course
that the COHb result of 11% is accurate and also that the patient is
accurately reporting how much she smokes!] Since it's probably unlikely
that the GP is going to get her to stop smoking abruptly, you could try
measuring COHb or CO directly if you have access to a gas chromatograph) on
blood samples obtained right after she leaves work and immediately before
she returns to work to see if the carboxyhemoglobin level changes
appreciably when she is removed from her work environment. The half-life of
COHb when breathing room air at atmospheric pressure is 5-6 hours, so it
would be best to do this before and after a weekend (assuming she works
Mon-Fri), or perhaps the next time she takes a one-week vacation.
Although less likely in light of this patient's history, one should also
consider the presence of hemolytic anemia, which can elevate COHb by about
3%.
Sal Sena
Salvador F. Sena, Ph.D., DABCC
Associate Director, Clinical Chemistry
Department of Pathology and Laboratory Medicine
Danbury Hospital
Danbury, CT 06810 USA
[log in to unmask]
> -----Original Message-----
> From: Robert Forrest [SMTP:[log in to unmask]]
> Sent: Wednesday, December 20, 2000 11:40 AM
> To: [log in to unmask]
> Subject: Re: Carbon monoxide and multi-storey car parks
>
> How did you measure HbCO? Might be worth measuring exhaled CO after a
> shift.
>
> Robert Forrest
>
> > -----Original Message-----
> > From: This list is an open discussion list for the academic community
> > working in [mailto:[log in to unmask]]On Behalf Of Dr
> > David G Williams
> > Sent: 20 December 2000 16:20
> > To: [log in to unmask]
> > Subject: Re: Carbon monoxide and multi-storey car parks
> >
> >
> > Is the car park enclosed or open?
> >
> >
> > > A local GP has a patient (female) who works in a multi-storey
> > car park. She
> > > smokes 15 to 20 per day.
> > >
> > > Her carboxyhaemoglobin is consistent around 11% which seems to me
> higher
> > > than I would expect from her smoking history.
> > >
> > > Her home has been checked.
> > >
> > > Any comments would be appreciated.
> > >
> > > Trevor Tickner
>
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