Effects of tiotropium and formoterol on quiet breathing pattern assessed by optoelectronic plethysmography in COPD patients: a pilot study

Abstract

Introduction: Chronic obstructive pulmonary disease (COPD) is a disease characterized by an airflow limitation that is not fully reversible. β 2 -agonists and anticholinergics represent the most effective therapeutic options. Optoelectronic plethysmography (OEP) is a novel technology, which provides noninvasive steady-state measurements of chest wall kinematics, together with the assessment of the relative contribution of all different thoracic and abdominal compartments to tidal volume. Objectives: The aim of this pilot study was to investigate the changes in quiet breathing due to different long-acting bronchodilators (namely, formoterol and tiotropium) administered to COPD patients of different severity. Methods: Eight moderate-to-severe COPD patients were studied according to a randomized crossover design. All subjects received both the long-acting bronchodilators: formoterol (long-acting β 2 -agonist, 24 µg) and tiotropium (long-acting anticholinergic bronchodilator, 18 µg). The effect of bronchodilators on quiet breathing was evaluated by means of OEP at base conditions, and 2 and 7 hours after inhalation. Results: Both bronchodilators caused changes in the quiet breathing pattern in COPD patients that had previously reported only negligible changes in FEV 1 (ΔFEV 1 = 2.6% after salbutamol). The main changes were observed in increased ventilation per minute, inspiratory and expiratory flow, and decreased breath-by-breath variability. Formoterol induced its main effects during the first 2 hours after inhalation, while tiotropium caused improvements between 2 and 7 hours. Conclusion: Even though a greater cohort of COPD patients is needed in order to confirm the present results, this pilot study reports a novel piece of evidence concerning the effects of bronchodilators on quiet breathing pattern in severe and very severe COPD patients.