Blood carboxyhaemoglobin changes during tobacco smoking.

Using multiple samples collected via an indwelling venous cannula changes in blood carboxyhaemoglobin (COHb) were studied in five subjects before, during and up to 24 hr after smoking. On average the smoking, with inhalation, of one cigarette in 64 min raised the % COHb by 1-6, compared with 2-2 for 24 min of inhaled cigar smoking and only 0-2 for 20 min of non-inhaled pipe smoking. It is suggested that it may be paradoxically safer to smoke high rather than low nicotine cigarettes as those with a high nicotine content will tend to be inhaled less.