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P289 Carboxyhaemoglobin Levels In Emergency Department Patients: An Important Tool In Validating Smoking History And Detecting “missed Smokers”
  1. RW Fowler
  1. Queen’s Hospital, Romford, UK


Introduction Blood gas analysers in emergency departments (ED) routinely report carboxyhaemoglobin (COHb) levels, but unless environmental carbon monoxide poisoning is suspected, measurements are ignored, particularly when blood gases have been performed to check acid-base status. Raised initial COHb levels are likely to indicate highly nicotine dependent smokers needing specialist support to quit.

Methods Data were obtained from 824 samples analysed in the ED in June 2013. There were 82 samples with COHb levels >2.0%, including 66 from 55 identifiable patients. Only the first measurements were used. Records were requested and checked for diagnosis and smoking history.

Results 42 records were retrieved. The highest initial COHb level was 13.5%; 15 had levels >4.5%. There were eight confirmed COPD and two possible cases. Eleven patients presented with drug and alcohol poisoning. Table 1 lists diagnoses.

28/42 (66.7%) were current tobacco smokers; in 14 (33.3%) pack-years could be estimated. There was no smoking history recorded in seven patients. Seven others were recorded as non-smokers, but in five there was evidence to contradict this. One had an explanatory blood disorder, leaving one unexplained high level. Four patients smoked cannabis; all smoked tobacco cigarettes as well.

Only 4/42 (10%) were referred to stop smoking services (SSS), though 10/42 (23.8%) were already known and one was referred subsequently. Two previous quitters had evidently relapsed. Of the remainder known to SSS, two self-referrers quit, three failed and eight missed appointments.

In the largest group, those with drug or alcohol poisoning, smoking history was of poorer quality – pack-years could only be estimated in one case. Most had underlying mental health problems. None were referred to SSS.

Conclusions 1. Patients with COHb levels >2.0% are usually tobacco smokers.

2. Multiple substance dependence is common. Most have mental health problems and are rarely referred to SSS – a missed opportunity to improve life expectancy in this vulnerable population.

3. Carboxyhaemoglobin levels must be included in a systematic approach to identify people needing intensive support to quit smoking.

Abstract P289 Table 1

Causes of raised COHb levels by diagnosis

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