Peripheral airways function and nonspecific airways reactivity in cigarette smokers

Area of Science:

• Pulmonary Medicine
• Respiratory Physiology

Background:

• Cigarette smoking is a major cause of peripheral airways dysfunction.
• Identifying distinct mechanisms of this dysfunction is crucial for targeted interventions.

Purpose of the Study:

• To investigate the relationship between airway hyperresponsiveness to histamine and peripheral airways dysfunction in heavy smokers.
• To differentiate between smokers with histamine-induced airway changes and those with other causes of dysfunction.

Main Methods:

• Administered increasing concentrations of inhaled histamine acid phosphate to 31 heavy smokers.
• Measured forced expired volume in one second (FEV1) to determine histamine responsiveness (responders vs. nonresponders).
• Assessed maximal expiratory flow-volume curves (air vs. HeO2) and single-breath oxygen test (slope of phase III) to evaluate peripheral airways function.

Main Results:

• Twelve smokers (responders) showed a determined PC10 (provocation concentration for 10% FEV1 reduction), while 19 (nonresponders) did not.
• Responders exhibited a significant positive correlation between PC10 and delta Vmax50 (increase in maximal flow at 50% vital capacity with HeO2).
• A significant negative correlation was found between PC10 and delta N2/L (slope of phase III). No differences in lung function, allergy tests, or symptoms were observed between responders and nonresponders.

Conclusions:

• Heavy smokers may represent two distinct groups with peripheral airways dysfunction.
• One group's dysfunction is linked to airway reactivity (histamine response), while the other's is related to different factors.
• This suggests distinct pathophysiological pathways contributing to lung disease in smokers.