Tobacco smoking is the first cause of avoidable death in industrialised countries [1
]. It has been known for many years that the negative effects of tobacco smoking on health are numerous [2
]. Tobacco smoking is involved in the appearance of different types of cancer. It is also the main risk factor for cardiovascular disease, the most common known cause of chronic obstructive pulmonary disease, and many other health problems. Despite wide knowledge on the subject, the prevalence of tobacco smoking is still high. According to the 2006 National Health Survey, 31.56% of adult men and 21.51% of women are daily smokers, of whom 79% of men and 70% of women smoke more than 10 cigarettes per day.
Smoking cessation is beneficial for health at any point in life, both in healthy people and in people already suffering from a smoking-related disease [4
]. However, smoking cessation is not an easy task, given that nicotine is a drug that generates great addiction [5
According to article 12 of the Spanish Act 28/2005 (art. 12 Ley 28/2005) based on health measures for tobacco smoking and the regulation of its sale, supply, consumption and the advertising of tobacco products, the Spanish public Administrations are to promote the development of health programmes for smoking cessation in the Spanish Health System, especially in Primary Care. Likewise, National Health System strategies for cancer, ischemic cardiopathy and chronic obstructive pulmonary disease include reducing the prevalence of tobacco smoking amongst their objectives.
Although many smokers claim to have quit smoking on their own [6
], others require specific help. Primary care doctors and nurses see most of the smokers at least once a year in their practice and have an excellent opportunity to diagnose tobacco smoking, evaluate the motivation behind it, and help them quit smoking. There is growing evidence on how healthcare professionals can help smokers end their addiction through pharmacological and non-pharmacological therapies [7
]. The latter include: brief advice given by a doctor or a nurse, the delivery of self-help materials or more complex or intensive interventions based on motivational interviews and cognitive-behavioural techniques for psychological support, sometimes combined with pharmacological therapies [8
The majority of non-pharmacological interventions for smoking cessation use the so-called transtheoretical model of change described by Prochaska and DiClemente at the beginning of the 90s [9
]. According to this model, the smoker goes through a series of phases during his/her smoking cessation process: pre-contemplative (the smoker does not contemplate quitting smoking), contemplative (the smoker begins to be unhappy with his/her addiction and starts thinking about quitting smoking within the next 6
months), preparative (the smoker is prepared to quit smoking), smoking cessation and the eventual relapses that re-start the cycle.
The brief advice given by a healthcare professional can achieve between 1–3% smoking cessations after 6
months, taking into consideration that an additional 2–3% manage to quit smoking without help. Therefore, this measure is moderately effective, although it has a great impact across the population [10
] and the percentage can be increased if the advice is not as brief and/or if it is accompanied by self-help and/or follow-up materials [11
]. In order to increase the rates of smoking cessation by means of brief advice, another strategy could be the evaluation of the physical effects of smoking using physiological measures that offer the smoker some feedback on the effects of smoking, as happens with hypertensive patients and blood pressure readings [12
These interventions are based on the hypothesis that one of the reasons why people continue smoking, in spite of knowing the harmful effects of tobacco, is that they underestimate the personal risk of becoming ill because of it. In this sense, the interventions will offer motivational feedback to promote awareness of the risk [13
]. It has been suggested that some smokers who manage to quit smoking are more aware of the adverse effects of tobacco or to have had their health seriously compromised [14
Three different types of feedback have been established: the first type analyses biomarkers of exposure to tobacco (nicotine, carbon monoxide); the second offers information regarding the risk of tobacco-related diseases (predisposition to lung cancer according to the CYP2D6 genotype); and the third describes the harmful effects of smoking (atherosclerotic plaques or worsening of pulmonary function) [15
]. Isolated studies have provided mixed results regarding the effect of biomedical risk assessment as an aid for smoking cessation. A recent systematic review [16
] concludes that, due to the lack of good quality evidence, it is not possible to draw firm conclusions. The following methodological recommendations are made: use adequate sample sizes, use allocation concealment procedures, agree on a definition of “abstinence” and systematically introduce measures to biochemically confirm it and, finally, carry out analyses by intention to treat. The measurement of CO levels in exhaled air by CO-oximetry is used to evaluate the degree of smoking by the smoker given that, in general, there is a direct relationship between the levels of CO and the number of cigarettes smoked [17
]. The measurement of exhaled CO is also the preferred measurement to confirm tobacco abstinence [18
It has been observed that the measurement of CO in exhaled air in smokers could be an indicative test of immediate and future harm to their health as a consequence of smoking [19
] and this could increase their motivation to stop smoking, which could lead to smoking cessation in these patients. In the review mentioned above [16
], three studies that measured the direct effect of CO-oximetry on smoking cessation [20
] were identified. Two of them were carried out in primary care settings [20
]. No positive changes in the rate of smoking cessation were observed.
The measurement of CO levels in exhaled air by CO-oximetry is an inexpensive, non-invasive, fast technique that requires little technical training [23
] making it a technique for risk assessment in smokers that can be easily applied in primary care and, if proven effective, could serve as a reinforcement aid in smoking cessation intervention activities.
Therefore, we think it would be interesting to study its possible effect on smoking cessation to a greater extent through the design of a new study incorporating the methodological recommendations given by the experts, and by providing more robust results to determine efficacy.
The purpose of the present study is to evaluate the efficacy of the CO-oximetry technique, together with brief advice, in smoking cessation at month 12 in smokers in contemplative or pre-contemplative phase compared with brief advice alone. Furthermore, the study also aims to evaluate the efficacy of the CO-oximetry technique together with brief advice in the reduction of the number of cigarettes and in the variation of the motivation to quit smoking at month 12 in smokers in contemplative or pre-contemplative phase compared with brief advice alone.