Diurnal variation in airflow obstruction in chronic bronchitis

Area of Science:

• Pulmonology
• Respiratory Medicine
• Clinical Pharmacology

Background:

• Chronic obstructive bronchitis is characterized by airflow limitation.
• Diurnal variation in respiratory function is a known phenomenon.
• Bronchodilator therapy is a cornerstone in managing obstructive lung diseases.

Purpose of the Study:

• To assess the impact of bronchodilators on diurnal variation of peak expiratory flow rates (PEFR) in chronic obstructive bronchitis.
• To compare bronchodilator-induced changes with inherent PEFR variability.
• To investigate the circadian rhythm of PEFR in this patient population.

Main Methods:

• Twelve patients with chronic obstructive bronchitis recorded PEFR five times daily for two weeks.
• Patients received ipratropium bromide and ipratropium bromide plus salbutamol.
• Cosinor analysis was used to evaluate PEFR rhythmicity.

Main Results:

• Bronchodilators (ipratropium bromide: 9.2% FEV1 improvement; combined: 11.3% FEV1 improvement) showed less impact than inherent diurnal PEFR variation (24% of mean daily value).
• Ten of twelve patients exhibited a significant PEFR rhythm (8.6% amplitude).
• PEFR variability in chronic obstructive bronchitis was not greater than in normal subjects but less than in asthma.

Conclusions:

• Standard bronchodilators provide limited improvement in PEFR variability for chronic obstructive bronchitis patients.
• The inherent diurnal variation in PEFR is a significant factor in this population.
• PEFR variability in chronic obstructive bronchitis is distinct from that observed in bronchial asthma.