Abstract: Objective To investigate the effects of inhaled short-acting bronchodilators on diaphragm function and neural
respiratory drive in patients with chronic obstructive pulmonary disease (COPD) during maximal isocapnic ventilation (MIV).
Methods Forty-seven patient with moderate to severe COPD were randomized into 4 groups: placebo group (n=12),
salbutamol group (n=13), ipratropium group (n=10), and combined group (salbutamol and ipratropium, n=12). Each subject
received an initial MIV for 3 min at baseline and inhaled placebo (400 μg), salbutamol (400 μg), ipratropium (80 μg), or both
salbutamol and ipratropium, followed 30 min later by another 3 min of MIV. The parameters of diaphragm function and
neural respiratory drive were monitored continuously and calculated during MIV. Results During the initial MIV, all the
patients experienced a linear increase in root mean square (RMS) of diaphragm electromyogram with a gradual decrease in
transdiaphragmatic pressure (Pdi), minute ventilation (VE), and VE/RMS, and these parameters all improved significantly
after inhalation of the bronchodilators. Compared with the placebo group at the same time point, the 3 bronchodilator-treated
groups showed significantly decreased RMS and Borg score and increased Pdi, VE and VE/RMS; VE/RMS was the highest in
the combined treatment group (P<0.05). The △Borg was significantly correlated with △Pdi, △VE, △RMS, and △VE/RMS (P<
0.05). Conclusion In COPD patients, inhaled short-acting bronchodilators can alleviate diaphragm fatigue during MIV,
increase lung ventilation, reduce neural respiratory drive, and improve neuro-ventilatory coupling to relieve dyspnoea, and
the combination of β-2 agonists and anti-muscarinic antagonists produces a stronger efficacy.