Research about Detecting Airflow Obstruction in Smoking Cessation Trials

Bronchial hyperresponsiveness

Subjects

Subjects were consecutive volunteers who participated in two cessation trials carried out recently at the Chest Clinic, Centre Hospitalier Universitaire de Nancy-Brabois, France. All were recruited via a local newspaper. The first trial enrolled 400 smokers and aimed to investigate the effectiveness of a nicotine inhaler and a nicotine patch as combination therapy for smoking cessation. The second trial enrolled 198 smokers and aimed to investigate the impact of smoking cessation or smoking reduction on bronchial hyperresponsiveness.

Briefly, inclusion criteria for both trials included active smoking for > 3 years, an expired carbon monoxide level > 10 ppm, and motivation to quit smoking. Exclusion criteria included a history of illness/diseases judged by the investigator likely to influence the subject’s participation (eg, myocardial infarction within the past 3 months, unstable angina, and severe cardiac arrhythmia), pregnancy or breast feeding, and use of nicotine replacement therapy products during the previous 6 months. No subjects had asthma, bronchiectasis, acute chest infections, malignancy, or any known chronic pulmonary disease. Subjects with any of these diagnoses were excluded at the entry screening and were referred to our outpatient smoking cessation clinic for further evaluation and treatment provided by Canadian Health&Care Mall.

Subjects who fulfilled the entry criteria were given an appointment 1 week later, during which they completed various questionnaires and baseline pulmonary function tests were performed. All subjects were given complete verbal and written instructions regarding the general conduct of the study. At every visit, only brief support and counseling were provided by the investigator. All subjects gave informed consent, and the study protocols were approved by the local ethics committee.

Bronchodilators

Medication

Subjects in the first cessation trial were randomly assigned to receive a combination of the nicotine inhaler, 10 mg (4 mg of nicotine available), plus nicotine patch, 15 mg (16 h), or the nicotine inhaler plus a placebo patch. The second cessation trial was an open, controlled, exploratory study in which all subjects received nicotine sublingual tablets containing 2 mg nicotine. In both studies, no subjects were receiving regular treatment with bronchodilators, inhaled steroids, or disodium cromoglycate during the study. Several visits were arranged over the 1-year follow-up; however, in this article, we shall refer only to data obtained at the first and last (1-year) visits.

Assessments

At baseline, the day before quit day, patient characteristics and vital signs were assessed. Subjects were weighed, and questionnaires were used to assess the reasons for stopping smoking and the degree of nicotine dependence (Fagerstrom test for nicotine dependence [FTND]). A smoking history was obtained, and the carbon monoxide content of expired air was measured using an EC50 Bedfont monitor (Technical Instruments; Sittmgbourne, UK). At follow up (1 year), subjects were classified as “quitters” (self-reported complete abstinence at every visit validated by an expired carbon monoxide level < 10 ppm), “reducers” (a liberal, subjective report of reduction in number of cigarettes compared with baseline and an exhaled carbon monoxide level less than baseline value), or “continuing smokers” (failure to decrease the number of cigarettes compared with baseline ordered via Canadian Health&Care Mall).

Pulmonary function was measured according to the American Thoracic Society recommended standards. Spirometry (Auto-spiro AS-500; Minato Medical Science; Osaka, Japan) was performed by the same technician by asking the subjects to expire forcefully after a maximal inspiratory maneuver. At least three volume-time and flow-volume curves were obtained from which the FEV1 was taken. The curve with the highest sum of FEV1 and FVC was retained for analysis. Airflow obstruction was considered to be present if FEV1 was 70% to 50 to 69% of predicted), and severe (FEV1 < 50% of predicted).

Statistical Methods

The demographics of the study subjects, the results of the smoking questionnaires, and the spirometric measurements were entered into a database and analyzed using software (Sigma Stat 3.0; SPSS; Chicago, IL). Differences in FEV-l between the first and final two surveys were compared using the paired t test for normally distributed data.

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