Table 1.

Definition of the study variables

Active smoker	Diagnosis of chronic obstructive pulmonary disease (COPD)
Any patient who smokes one or more cigarettes per day will be considered an active smoker.	The criteria for the diagnosis of COPD is a post-bronchodilator FEV1/FVC ratio of < 70% (absolute value).
Spirometry technique	Spirometric patterns
Baseline spirometry: the nurse responsible for the spirometry testing will be experienced in the technique and familiar with the ATS/ERS criteria for acceptability (correct start with back extrapolated volume of <150 ml or 5%, curve with no marks or notches and correct end, with no leaks and lasting at least 6 seconds or with a plateau > 1 second in the volume-time curve).	Spirometry results will be considered within the normal range if FEV1/FVC > 70% (absolute value) and FVC and FEV1 > 80% of the predicted values.
	The pattern is classified as obstructive if FEV1/FVC < 70% (absolute value).
To meet the criteria for repeatability, there must be three acceptable manoeuvres and the FVC and FEV1 values in the two best two must differ by no more than 100 ml.	The pattern is classified as restrictive if FEV1/FVC > 70% (absolute value) and FVC < 80% of the predicted value.
	The pattern is classified as mixed if FEV1/FVC < 70% (absolute value) and FVC < 80% of the predicted value.
Bronchial challenge: After performing the baseline test, patients will be given 400 mcg of Salbutamol (in a holding chamber) and 15–20 minutes later a further spirometry test will be conducted applying the same criteria for acceptability and reproducibility as for the baseline test.	The bronchial challenge is regarded as positive when FEV1 or FVC increase by 12% or 200 ml compared to baseline values 15–20 minutes after administering 400 mcg of Salbutamol (in a holding chamber).
Contraindications for spirometry testing	Quitting smoking
• Poor general health, old age, etc.	A year after the intervention, patients will be considered to have stopped smoking if they report abstinence (defined as no of consumption of tobacco for at least 7 days) and this is confirmed by CO-oximetry (a carbon monoxide concentration in exhaled air of < 10 ppm is considered sufficient).
• Recent pneumothorax (< 6 months)
• Unstable angina or recent acute myocardial infarction (< 6 months)
• Recent retinal detachment (< 6 months)
• Recent abdominal or thoracic surgery (< 6 months)	Co-oximetry technique
• Recent eye surgery (< 6 months)	The patient takes a deep breath and holds it for 15 seconds. They then breathe out slowly and completely (as far as they can). It is then necessary to wait for several seconds until the CO-oximeter settles and shows the exact concentration of carbon monoxide (CO) in parts per million (ppm) in the air exhaled by the patient.
• Thoracic aortic aneurysm
• Hemoptysis of unknown origin
• Active tuberculosis
• Tracheostomy
• Facial paresis