Carboxyhemoglobin Levels Induced by Cigarette Smoking Outdoors in Smokers

Area of Science:

• Environmental Health
• Pulmonary Medicine
• Toxicology

Background:

• Non-invasive carboxyhemoglobin saturation (SpCO) screening is common in emergency departments for detecting occult exposure.
• The established SpCO threshold of 9% for smokers lacks robust supporting literature, and the effect of active smoking on SpCO is unclear.
• Understanding baseline SpCO in smokers is crucial for accurate exposure assessment.

Purpose of the Study:

• To characterize baseline SpCO levels in a cohort of outdoor smokers.
• To investigate the impact of active cigarette smoking on SpCO saturation.
• To compare SpCO levels between smokers and non-smokers.

Main Methods:

• Prospective cohort pilot study conducted in two urban public areas in the USA.
• Convenience sample of adult smokers and non-smoker controls.
• Non-invasive SpCO assessment using pulse CO-oximetry before, during, and 2 minutes after smoking; statistical analyses included descriptive statistics, correlations, and generalized estimating equation modeling.

Main Results:

• Mean baseline SpCO was 2.7% (SD 2.6) in 85 smokers, significantly higher than 1.3% (SD 1.3) in 15 controls.
• Active smoking was associated with an increase in mean SpCO.
• Baseline SpCO correlated with time since the last cigarette, and individual smokers maintained their SpCO levels before, during, and after smoking.

Conclusions:

• This is the first study to measure SpCO during active smoking in an uncontrolled outdoor setting.
• Findings suggest that 80% of smokers exhibit SpCO levels of 5% or lower.
• The current 9% threshold may still be relevant depending on the clinical context, but requires careful consideration.