Effect Of Lung Hyperinflation On The Breathing Pattern And Exercise Capacity In Patients With Chronic Obstructive Pulmonary Disease

Part Ⅰ Breathing Pattern and Gas Exchange in COPD Patients with LungHyperinflation[Objective] To study the influence of lung hyperinflation on breathing pattern andgas exchange at cardiopulmonary exercise testing (CPET) in stable moderate to severechronic obstructive pulmonary disease (COPD) patients.[Methods] Pulmonary function test (PFT) and CPET were tested in fifty-fourpatients with stable moderate to severe COPD. Then, Patients who had anemphysematous profile with the percentage of thoracic gas volume predicted value (Vtg%pred)<150%pred and the percentage of diffusing lung capacity for carbon monoxidepredicted value (DLco%pred)≥80%pred (low lung hyperinflation, Group A), versuspatients with Vtg%pred≥150%pred and DLco%pred <80%pred (high lunghyperinflation, Group B). The parameters of ventilation, breathing pattern and gasexchange between the two groups were measured and analyzed.[Results]1. At rest, there was no significant difference in tidal volume (VT) and breathingfrequency (BF) between these two groups, at peak exercise, VT and minute volume (VE)in Group A were significant higher than Group B (p<0.001).2. Between the two groups， the ratio of inspiratory time (tI) to expiratory time (tE),VT/tI and VT/tE had significant difference at peak exercise (p<0.01). The dyspnea ofGroup B was more severe than Group A (p<0.001). 3. At peak exercise, the peak load, peak oxygen consumption (VO2), the efficiencyof gas exchange and peak oxygen pulse (O2pulse) in Gropu B were lower than Group A(p<0.05). The reason for stopping exercise was significantly different between the twogroups.4. Peak V.O2%pred was significant associated with Vtg%pred and DLco%pred(r=-0.55and0.68, p<0.001), peak V.O2was significant associated with peak VT (r=0.77,p<0.001), moreover, peak VT was significant associated with inspiratory capacity (IC)(r=0.63, p<0.001).[Conclusion] COPD patients who with the higher lung hyperinflation had the lessexercise capacity, less ventilation function, reduced efficiency of gas exchange, andworse dyspnea. Part Ⅱ Inspiratory Fraction is Correlated with Exercise Capacity of Patients withStable Moderate to Severe Chronic Obstructive Pulmonary Disease[Objective] To investigate the association between inspiratory fraction (IF) and theexercise capacity of patients with stable moderate to severe COPD.[Methods] Fifty patients and thirty-four healthy volunteers constituted the studycohort. PFT and CPET were performed, parameters of lung ventilation and gas exchangewere measured.[Results]1. IF was significantly correlated with peak VO2%pred of patients with stablemoderate to severe COPD (r=0.52, p<0.001). IF was an independent factor inpredicting a reduced exercise capacity of COPD patients, and was more sensitive andspecific than forced expiratory volume in one second (FEV1%pred). Statistical analysis generated the final model as: peak VO2%pred=65.9IF+0.45FEV1%pred+35.8(RC~2=0.39, p<0.001).2. Patients with IF lower than0.23had more severe lung hyperinflation and lessexercise capacity than the patients with IF higher than0.23. At peak exercise, BF of twogroups was similar, whereas low IF patients had reduced peak minute ventilation andpeak tidal volume relative to the patients with high IF.[Conclusion] IF is a robust factor to reflect lung hyperinflation and to predict theexercise capacity of patients with stable moderate to severe COPD compared to FEV1.